Question 1

Technological Performance and Application Fields of New Electronic Pressure Regulator

Accepted Answer

Introduction of KaoLu electronic pressure regulator:
The electronic pressure regulator is to adjust the cross-sectional area of the regulator core according to the size of control signal so as to achieve the process goals and requirements of adjusting the flow rate. The electronic pressure regulator of KaoLu optimizes the process performance, makes the structure compact and lightweight, and improves the requirements of stable performance and control accuracy.

Printing paper packaging industry
The contact roller is easy to slip during the process of winding the paper, which will cause some troubles for the subsequent correct cutting of paper. The main reason for this is the generation of accurate roller clamping pressure. Usually the higher the clamping pressure, the higher the tension and the tighter the roll. Different paper materials and quality require different roller clamping pressures for winding. The paper roll tightness information is transmitted to the main control system through the sensor, and the main controller compares it with the preset pressure value and outputs it to the electronic pressure regulator to adjust accordingly. The final output of suitable braking force ensures the smooth realization of paper rolling process and cutting process.

Grinding Industry
The grinding equipment usually adjusts the pressure of the grinding disc on the workpiece through a high-performance pressure control mechanism. In order to meet the ever-increasing customer demand, it is necessary to provide more precise grinding size and more efficient grinding speed, which have put forward higher requirements for the pressure controller. The electronic pressure regulator usually controls a grinding disc to repeat grinding action by outputting a stable pressure. The closed-loop control characteristics of the electronic pressure regulator provides an effective guarantee for a lower damage rate of the grinding equipment and a more accurate grinding pressure output.

Welding
In the field of automatic welding, in order to achieve high-speed, stable, and impact-free welding, the welding torch can contact the surface of the object for welding. The electronic pressure regulator can make the pressing force change steplessly according to the material and welding procedure, optimize the welding process, and ensure the final welding strength.

Machinery and equipment manufacturing industry
Stable, continuously varying pressure output is critical for equipment manufacturers such as winders and wire drawing machines. The roller must ensure that as the radius of the roller increases, the tension controlled by the swing arm decreases accordingly. The electronic pressure regulator can provide a high-precision variable pressure according to the pre-setting of the upper computer, and this pressure can control the displacement of cylinder to realize the swing arm, thereby controlling the tension change and ensuring the successful realization of uniform winding.

Rubber and plastic molding equipment industry
Forming and extrusion equipment is a common equipment in the field of rubber and plastic materials. Electronic pressure regulators are one of the key control elements in this type of equipment. In the entire thermoplastic process, the electronic pressure regulator can accurately output a continuous cut-off pressure to ensure that the forming production process is consistent, and the products are uniform and standard.

Custom measurement and control equipment
Some professional non-standard testing equipment and testing machines for airtight components can perform tests such as airtight performance testing, leak detection, dynamic response, etc., and electrical control components such as electronic pressure regulators are often required to execute the analog simulation control signal output by the controller, record the response of tested components and systems, and finally evaluate the performance of components/systems.

Spray and Lamination
For industrial sites that need spraying, such as automobile industry, sports equipment, packaging, etc., it is necessary to provide precisely controlled variable pressure to control spraying parameters such as switch, atomization, fan width, etc. to ensure uniform surface; for lamination technology, different materials are required. The end result is a consistent appearance, avoiding warping. All of this is reached because an electronic pressure regulator provides precise and constant pressure to the actuator.

Fluid Process Control
The pneumatic diaphragm pump is often used to pump the pressure of corrosive and high viscosity liquids to the pneumatic diaphragm pump, and finally achieve the purpose of infinitely controlling the pressure change of the pump port. In this way, the flow rate of liquid output from the pump port also changes accordingly, so as to reach the purpose of precise control of liquid.

Question 2

Application of Replacing Existing Electronically Controlled Pressure Regulator in Parallel Robot

Accepted Answer

The concept of parallel robot is based on the Steward platform used for flight simulation driving in 1965, and was proposed by Hunt, a well-known Australian institution professor, in 1978. At present, many experts and scholars have done a lot of theoretical and practical research in this field.

Compared with serial robots, parallel robots have the advantages of high stiffness, high load-to-weight ratio, uniform load distribution, no accumulation of position errors, and easy force feedback. It is suitable for occasions with high precision, large load and relatively small working space requirements.

At the same time, due to the great improvement in performance and function of pneumatic components, and with the development of science and technology such as electronics, materials, control theory and sensors, electronically controlled pressure regulator control technology has also been rapidly improved. The electronically controlled pressure regulator control system with proportional/servo control valve as the core can reach the high-precision control of continuous change of pressure and flow, and can meet the flexible production requirements of automation equipment. It makes the application of pneumatic drive in parallel robots possible.

The structure is composed of upper and lower flat joints, and the flat joints are connected by a set of telescopic connecting rods with ball joints at both ends, so that the upper platform can move and rotate in three-dimensional space. Most parallel robots use screw rods or electro-hydraulic servo cylinders as motion actuators. Because the motions between the drive units of the parallel robot cannot be independent of each other, they must maintain a very strict combination relationship. The motion error of any link will lead to control failure. In our study, the hydraulic controlled pressure regulator is replaced by a more tolerant electronically controlled pressure regulator as the transmission medium of the parallel robot actuator.

1. The extended position of the cylinder is obtained by the analog solver in the upper computer and transmitted to the lower computer.

2. The lower computer converts it into voltage (0~10v) through the D/A card and outputs it to the electronically controlled pressure regulator.

3. The electronically controlled pressure regulator controls size and direction of the opening according to the magnitude of voltage, and outputs the accurate gas flow to cylinder to promote the movement of the piston.

4. The moving position of piston is detected by the displacement sensor, and the feedback voltage of displacement sensor is output to the lower computer through the A/D card; the gas pressure at both ends of the piston is detected by the air pressure sensor, and the feedback voltage is output to the lower computer through A/D card.

5. The lower computer adjusts the control voltage of the electric proportional valve in real time according to the feedback value, so that the cylinder can reach the position accurately. 6. The position signal of the platform is fed back to the upper computer by position sensor, and the position of platform is further corrected by the upper computer.

In the entire control process, the focus is on single-cylinder control system. The experimental schematic diagram of the single-cylinder control system is shown in the following figure.

For the electronically controlled pressure regulator control system, the state single-cylinder control has better control characteristics; adding PI control in the optimal state feedback can significantly increase the stiffness of system and improve the tracking performance of system. It has good track tracking performance in the frequency range of 0.1Hz to 5Hz. The object of this test is the test platform model of the automobile suspension system, which does not require very high displacement accuracy, and is more sensitive to the speed and acceleration response speed. After the large cylinder is adopted, the load of whole system is greatly increased. The frequency response of system can reach 5~10Hz, which can meet the requirements of the test platform.

The 6-DOF parallel platform mainly composed of cylinder and electric proportional valve is adopted, which avoids the difficulty of control caused by the strict motion combination relationship between the six actuators required by hydraulic pressure and screw rod, and ensures the speed and acceleration response sensitivity. Simultaneous use of air cylinders and electronically controlled pressure regulator can greatly reduce costs, noise and pollution.

Question 3

Technical Scheme of Vacuum Precision Control in Lunar Soil Environment Ground Simulation Test Device

Accepted Answer

Abstract: In the lunar exploration project, it is necessary to collect lunar soil samples in the vacuum environment of the lunar surface. It is necessary to establish a ground test device to simulate the vacuum thermal environment of the lunar surface to test the performance of the sample in vacuum thermal environment. Therefore, the degree of vacuum is required and it can achieve precise control. In this article, a technical scheme for accurate vacuum control using FC series proportional flow control valve is proposed for the ground simulation test device of vacuum thermal environment.

1. Question
In the lunar exploration project, it is necessary to collect lunar soil samples in the vacuum environment of the lunar surface. Therefore, a ground test device needs to be established to simulate the vacuum thermal environment of the lunar surface to test the performance of sample in the vacuum thermal environment, and accurate vacuum control is required to reach precise control. Due to the particularity of the lunar soil, vacuum control in current lunar soil ground model test device still needs to solve the following problems:
(1) Lunar soil and simulated lunar soil samples are generally powdery particles, so the pumping rate in the initial time should be strictly controlled to avoid dust generation.
(2) The current vacuum measurement and control also uses a Pirani vacuum gauge, which makes the matching control system unable to reach precise control of the vacuum, resulting in poor repeatability of the test results.
(3) The lunar soil ground simulation test device is generally small in size, and it has always been difficult to achieve precise control within a wide range of vacuum degrees. The fluctuation of vacuum degree is large, which is also one of the reasons for the poor repeatability of test results. Aiming at the above problems existing in the lunar soil ground model test device, this article focuses on corresponding technical solutions and introduces the detailed implementation process.

2. Technical Scheme
The overall structure of vacuum density control system of lunar soil environment ground simulation test equipment is shown in Figure 1. The whole system mainly includes a vacuum gauge, two proportional flow control valve, a PID controller and a vacuum pump. In order to do the precise control of the full range of vacuum degree, three capacitance vacuum gauges are generally required, and the measurement accuracy of vacuum gauge is 0.25%. In order to match the measurement accuracy of capacitance vacuum gauge, the controller adopts a high-precision PID controller with 24-bit A/D and 16-bit D/A, and the independent dual-channel facilitates the gas flow adjustment and control of the upstream proportional flow control valve and downstream proportional flow control valve control. The precise control of vacuum degree uses dynamic control mode, that is, the downstream proportional flow control valve is adjusted under low vacuum conditions, and the upstream proportional flow control valve is adjusted under high vacuum conditions. This is a typical forward and reverse control method, which can effectively ensure the control accuracy of vacuum degree. In conclusion, with this proven accurate vacuum control scheme, a control accuracy of better than 1% vacuum over the full scale range can be achieved.

For further information on different models of proportional flow control valve, please visit https://www.genndih.com/proportional-flow-control-valve.htm

Question 4

Precision Vacuum Control to Reduce Solvent Loss in Evaporation and Concentration Process

Accepted Answer

Abstract: Aiming at the problems of precision vacuum control to reduce solvent loss in evaporation and concentration process, this article focuses on vacuum evaporation techniques, including the precise control method of vacuum degree, the simultaneous control method of vacuum degree and temperature, and the use of strong resistance of the corrosive electronic valve acts as a vacuum regulator.

1. Question
In the process of solvent extraction, the vacuum evaporation and concentration process is generally used. Since the solvent often has good volatility, the solvent is prone to loss during the vacuum extraction process, and sometimes the loss can reach 5~8%. Therefore, in order to solve the loss of solvent in the evaporation and concentration process, the following problems need to be solved:
(1) The precise control problem of vacuum degree, such as fixed-point control and program control, which is the key to reducing solvent loss.
(2) Simultaneous control problem of vacuum degree and temperature. This is because different vacuum degrees determine the boiling point of the solution. Through coordinated control of vacuum degree and temperature at the same time, the yield of the solvent can be greatly improved.
(3) In the vacuum evaporation and concentration process, many solvents and solutions are often corrosive to a certain extent, which requires the vacuum regulating valve to have good corrosion resistance. In order to solve the requirement of reducing solvent loss in the evaporation and concentration process, this article proposes a solution for precise control of vacuum degree, including the use of electronic flow control valve with strong corrosion resistance as vacuum degree control valves.

2. Solution
For the precise control of vacuum degree and temperature in the evaporation and concentration process, the overall structure of control system is shown in Figure 1.

(Figure 1 Schematic diagram of the vacuum degree and temperature control system structure of the evaporation and concentration process)

The basic principle of precise vacuum control is the dynamic control method, that is, according to the control set value and the measured value of vacuum gauge, the intake flow and exhaust flow of vacuum container are adjusted respectively, so that the flow in and out can reach a dynamic balance. If automatic control is required, PID control algorithms and corresponding controllers are required.

As shown in Figure 1, the accurate control proposal for vacuum degree control in this article adopts a dynamic control method, using an electronic flow control valve to adjust the intake flow, using an electronic ball valve or an electronic needle valve to adjust the exhaust flow, and the vacuum pump is used as a vacuum source. The automatic control of vacuum degree adopts PID controller.

In order to reach the temperature control function at the same time, this scheme adopts a dual-channel PID controller, one channel is used to control the vacuum degree, and another channel is used to control the temperature. This PID control has 24-bit A/D and 16D/A, with 47 input signal forms (thermocouple, thermal resistance, DC voltage), and can be connected to various vacuum and temperature sensors for measurement, display and control. It also has 2 independent measurement control channels, two-wire RS485, standard MODBUS RTU communication protocol.

(Figure 2 FC series electronic needle valve)

In order to reach high-precision adjustment in the vacuum degree control process, an electronic needle valve with fine adjustment by a numerically controlled stepping motor is used, as shown in Figure 2. The hysteresis of this FC series proportional needle valves is much smaller than that of solenoid valves, and has a high-speed response within 1 second, especially the use of fluorine rubber (FKM) sealing technology, which makes the valve have superior corrosion resistance. Equipped with a stepper motor drive circuit module with the numerical control proportional needle valve, it provides the required power supply (24VDC) and control signal (0~10VDC) for the numerical control needle valve, and can also provide direct control of RS485 serial communication.

For larger-diameter air-extraction pipelines, a miniature proportional needle valve is used in this scheme, as shown in Figure 2. This series of proportional needle valve is a small electronic valve. The valve opening can be adjusted continuously according to the change of control signal (0~10VDC). The fastest opening and closing time is less than 7 seconds, and the opening and closing time can also reach less than 1 second. The integrated design of the valve and the valve body reduces external volume and is low in price. It is often installed between the sealed container and the vacuum pump to adjust pumping rate.

In short, through the solution described in this article, the vacuum degree control accuracy in the evaporation and concentration process can reach 1%, and the corresponding temperature control can also be carried out. The vacuum regulating valve has super corrosion resistance, which can effectively reduce the loss of solvent concentration during the vacuum evaporation process.

Question 5

Proposal for Vacuum Precision Control in Low Pressure Carburizing (LPC) Process

Accepted Answer

Abstract: In order to meet the requirements of precise control of vacuum degree in low-pressure carburizing process (vacuum carburizing), corresponding solutions are proposed in this article, including adding a gas mixing tank for permeate gas mixing, using upstream and downstream dynamic vacuum level control methods and vacuum degree by coordinating the control method with the temperature, the rapid and precise control of the vacuum degree and temperature in the infiltration process can be reached.

1. Question
Low-pressure carburizing, also known as vacuum carburizing, is a process in which a carburizing medium is passed into a high-temperature furnace for rapid carburizing under a low-pressure vacuum state. The vacuum carburizing process can be divided into one-stage type, pulse type and swing type. Among them, the degree of vacuum, temperature and carburizing time will change according to the specific requirement, especially the degree of vacuum will change drastically with the temperature change. Therefore, in the vacuum carburizing process, the following problems need to be solved in terms of vacuum degree control:

(1) The problem of fast and accurate control of vacuum degree, such as fixed-point control, program control and fast pulse control, requires the vacuum control system to have high response speed and control accuracy. Especially to achieve precise control in the full range of vacuum, it is necessary to use different vacuum sensors and corresponding upstream and downstream control modes according to different ranges.

(2) Simultaneous control problem of vacuum degree and temperature. The carburizing is carried out in a high temperature environment, requiring simultaneous control of vacuum degree and temperature.
In order to meet the requirements of precise control of vacuum degree in low-pressure carburizing process, this article focuses on a solution for precise control of vacuum degree, and adopts dual-channel PID control to reach synchronous temperature control.

2. Solution
The overall structure of the vacuum degree and temperature control system in the low pressure carburizing process is shown in Figure 1.

Figure 1 Schematic diagram of the structure of vacuum degree and temperature control system in low pressure carburizing process

The basic principle of precise control of vacuum degree is the dynamic control method, that is, according to the control set value and the measured value of vacuum gauge, the air intake flow and exhaust flow of the carburizing chamber are adjusted respectively, so that the flow in and out can reach a dynamic balance. If automatic control is required, PID control algorithms and corresponding controllers are required.

As shown in Figure 1, the precision control solution for vacuum degree proposed in this article adopts a dynamic control method, using an electronic needle valve to adjust the air intake flow, using an electronic ball valve or an electronic needle valve to adjust the exhaust flow, and the vacuum pump is used as a vacuum source. The automatic control of vacuum degree adopts PID controller.

For different low pressure carburizing processes, the control range of the vacuum degree is 1Pa~100kPa. Therefore, in the specific process, different dynamic control modes need to be adopted for the control in different vacuum degree ranges. For the vacuum degree control in the high vacuum range of 1Pa~1kPa, the upstream control mode of fixed exhaust flow and adjustable intake flow is adopted; for the vacuum degree control in the low vacuum range of 1kPa~100kPa, fixed intake flow and adjustable exhaust downstream control mode of the flow.

As shown in Figure 1, in order to reach the adjustment and control of air intake flow, a gas mixing tank is added to the intake end of carburizing chamber, and a gas mass flow meter is used to distribute various permeated gases into the gas mixing tank. The gas flows through the electronic needle valve for flow regulation and control.

In order to reach the temperature control function at the same time, this scheme adopts a dual-channel PID controller, one channel is used to control the vacuum degree, and the other channel is used to control the temperature. This PID control has 24-bit A/D and 16-bit D/A, with 47 input signal forms (thermocouple, thermal resistance, DC voltage), and can be connected to various vacuum and temperature sensors for measurement, display and control of 2 independent measurement control channels, two-wire RS485, standard MODBUS RTU communication protocol.

Figure 2 FC series electronic needle valve

In order to reach high-precision adjustment in the vacuum degree control process, an electronic needle valve with fine adjustment by a numerically controlled stepping motor is used, as shown in Figure 2. The hysteresis of FC series of needle valves is much smaller than that of solenoid valves, and has a high-speed response within 1 second, especially the use of fluorine rubber (FKM) sealing technology, which makes the valve have superior corrosion resistance. Equipped with a stepper motor drive circuit module with the numerical control electronic needle valve, it provides the required power supply (24VDC) and control signal (0~10VDC) for the numerical control needle valve, and can also provide direct control of RS485 serial communication.

In conclusion, through the solution described in this article, the vacuum degree control accuracy in the low pressure carburizing process can reach 1% in the full scale range, and the corresponding temperature control can also be carried out.

Question 6

Ultra-Low Loss Single-Mode Optical Fiber Fused Taper Production by Accurate Vacuum Level Control Adsorption Fixture

Accepted Answer

Abstract: In the fiber fused taper system of fusion method, the fiber coupling with minimal loss corresponds to the optimal vacuum degree for adsorbing and fixing the optical fiber. Therefore, it is necessary to precisely control the adsorption vacuum degree and find the optimal vacuum degree value. In this article, focusing on the stable batch production of fiber fused taper system with minimal loss, an improvement scheme of vacuum system using FC series proportional flow control valve is proposed, which can reach precise control of vacuum degree.

1. Question
In the process of making optical fiber couplers and optical fiber cones in the optical fiber taper system, two or more optical fibers are generally positioned and clamped on the optical table by means of vacuum adsorption and special fixtures, and the two or more optical fibers are fixed in a certain way. A plurality of bare fibers are rotated and moved closer to the axis, heated and melted by a hydrogen-oxygen flame or a laser, and stretched to both sides at a certain speed, and finally a special waveguide structure in the form of a double cone is formed in the heating zone.

The current optical fiber taper technology is difficult to produce optical fiber couplers stably with a loss of less than 0.1 in batches, which is mainly due to the fact that optical fibers are fixed too tightly by vacuum adsorption. Some literatures reported that the vacuum system for adsorption and fixation fixture was improved, and the corresponding fiber couplers were fabricated under a series of different adsorption and fixation vacuum degrees, and it was proved that coupling loss in the entire vacuum degree range has a minimum area, When the vacuum degree is 120mBar, the minimum loss is 0.05dB.

The higher the vacuum degree, the tighter the fiber is fixed, and the coupling loss will be larger. It can be seen that in order to obtain an ultra-low loss fiber coupling device, it is necessary to precisely control the vacuum degree of the vacuum adsorption device.

In this article, according to the requirements for precise control of vacuum degree in the process of fabricating ultra-low loss optical fiber coupling devices by fiber taper method, a technical scheme of vacuum control system and corresponding supporting contents are proposed to reach precise and rapid control of vacuum degree.

2. Technical Scheme
In order to reach the precise control of adsorption vacuum degree in the left and right stretching fixtures, a vacuum tank is added to the original vacuum system. As long as the vacuum pressure in the vacuum tank is controlled, the adsorption vacuum degree of the left and right stretching fixtures can be controlled which shown in figure 2.

The vacuum degree control system shown in Figure 2 mainly includes an electronic needle valve, a vacuum gauge, a PID controller and a vacuum pump. The precise control of the vacuum degree adopts the dynamic control method, that is, according to the comparison between the measured value of the vacuum gauge and the set value, the PID controller adjusts the intake air flow and the exhaust air flow at the same time to quickly achieve dynamic balance and control the vacuum degree to the set value. , the control accuracy can reach ±1%.

In conclusion, through precise control of vacuum degree, stable mass production of ultra-low-loss fiber-coupled devices can be reached.

Figure 2 Schematic diagram of the vacuum degree control system of the fiber taper machine

Question 7

Electropneumatic Proportional Valve and Control Valve

Accepted Answer

Electropneumatic proportional valve is referred to as proportional valve, ordinary pneumatic valve can control the fixed value of equipment through pre-adjusted liquid flow pressure and flow. The feedback is reached by continuous changing speed of slow, fast and slow, or by simulating a good control curve with a certain precision to realize the force control. The ordinary pneumatic valve is controlled by pneumatic system of electropneumatic proportional valve.

Control valve consists of two main assemblies: valve body assembly and actuator assembly (or actuator system), which are divided into four series: single-seat series control valve, double-seat series control valve, sleeve cylinder series control valve and self-operated series control valve. Variations of four types of valves can lead to many different applicable configurations, each with its own specific applications, features, advantages and disadvantages. While some control valves are used in a wider range of applications than others, control valves are not suitable for all applications to work together to create the best solution for enhanced performance and reduced cost.

The electropneumatic valve is a pneumatic component that drives the valve core by an electromagnetic coil, while the control valve is a component that generates electromagnetic force through electromagnetic induction. The greater the current of the control valve, the greater the thrust, so will different energization currents for the common solenoid valve coils make the original on-off valve become a proportional valve?

This problem is obviously negative. Generally speaking, the internal processing of ordinary solenoid valves cannot achieve the processing accuracy of proportional valves. In addition, its internal structure does not consider too many parameters such as pneumatic pressure balance. Therefore, when the electromagnetic force is not large, the valve core cannot be stabilized in the transition position, and the electromagnetic switch valve cannot represent the proportional performance. Or the proportional performance of the solenoid switch valve is very inconspicuous. Therefore, the design and manufacturing process of proportional valves must be very different from those of on-off valves, requiring more investment in research and development.

Another question: For the same proportional valve, can the drive current of the solenoid coil be directly powered by the DC model without using the proportional amplifier? This method is possible in principle. The variable resistance signal can be used for coil control. However, it will waste a lot of energy, and at the same time, it will be accompanied by a lot of heat, and there will be no flutter and current when the valve core moves. Due to the feedback effect, the performance of the valve cannot be optimized.

In addition to the internal current feedback of the amplifier, the high-frequency dither signal is also an important function. The high-frequency flutter signal can keep the proportional spool vibrating at all times, so that it can overcome the influence of static friction and try to eliminate the influence of hysteresis on its performance.

A proportional amplifier is an electronic device used to provide a specific performance current to a proportional electromagnet, and to perform open-loop or closed-loop regulation of an electropneumatic proportional valve or electropneumatic proportional control system. So, what performance does the so-called specific performance current refer to?

To sum up, using a proportional amplifier can achieve the following functions: control the amount of current applied to the coil by the valve, set the minimum and maximum input signal of the proportional valve, set the minimum and maximum output current, and also set the ramp-up and ramp-down time, and finally set The frequency of the dither signal is obtained through the built-in current negative feedback function.
For further information about electropneumatic valve, please visit:
https://www.genndih.com/proportional-pressure-regulator.htm

Question 8

How to classify proportional valves?

Accepted Answer

1. According to the controlled parameters

The parameters controlled by a proportional valve include pressure, flow and direction, etc. There are proportional valves that control one parameter (single parameter, single function), and there are proportional valves that control two or multiple parameters.

Proportional pressure regulator including proportional pilot pressure regulator, proportional relief valve, proportional pressure reducing regulator, proportional sequence valve, etc., all are proportional valves that input electrical signals to control the pressure parameters (single parameter) of pneumatic system. There are various suppliers of proportional pressure regulator on the shelf, like the ones as Festo, SMC, Proportion-Air, Asco and many more. KaoLu is specialized in supplying high resolution, high pressure range, and high speed regulator series.

Proportional flow valve including proportional throttle valve, proportional speed control valve, proportional one-way speed control valve, etc., it is also a single parameter control valve. Also mentioned main players are Clippard, Bosch Rexroth AG, Burkert, etc. KaoLu offers stepper motor driven proportional flow control valve that features high repeatability, high resolution and low hysteresis.

Proportional directional (directional flow) valve is a multi (two) parameter control valve, which simultaneously controls the flow rate and flow direction of the liquid flow according to the magnitude and direction of the input electrical signal.

Multi-function proportional valve is a multi-parameter control valve, which is a compound valve that combines pressure compensator and pressure valve on the basis of proportional directional valve. According to the magnitude and direction of the input electrical signal, the flow of the circuit and the direction of the oil flow are simultaneously controlled, and because the pressure compensator is installed, the flow of the control circuit is not affected by the load change, regardless of the load change. In addition, due to the combination of the pressure valve, it can also be used to control the maximum working pressure of the hydraulic system to achieve a variety of control functions.

Proportional pressure regulator is also a multi-parameter proportional control valve, which combines pressure and flow control together, and through a balance valve (pressure compensation valve), the pressure at both ends of the throttle valve orifice remains unchanged.

(2) According to the control method
This mainly refers to the classification according to the electro-mechanical conversion method in the pilot control valve of the proportional valve. Its electric control part has various forms such as proportional electromagnet, torque motor (mobile and suspension type) and DC servo motor.

Electromagnetic type refers to a proportional valve that uses a proportional electromagnet as an electro-mechanical conversion element. The proportional electromagnet converts the input current signal into mechanical output, that is, output force and displacement, and then controls parameters such as pressure, flow and direction.

Electric type refers to a proportional valve that uses a DC servo motor as an electromechanical conversion element. The DC servo motor converts the input electrical signal into the rotational speed of the rotary motion, and then outputs the force and displacement through the reduction device and conversion mechanism such as screw nut, rack and pinion or cam to control the output hydraulic parameters.

The electro-pneumatic type refers to a proportional valve that uses a torque motor and a nozzle-baffle structure as the pilot control stage. Input different electrical signals to the torque motor, and output displacement or angular displacement through the baffle (sometimes the armature of the torque motor is the baffle) connected with it.

(3) According to the installation position of electronic amplifier and the proportional valve body
• Separate type (the proportional valve body is separated from the electronic amplifier);
• Type with electronic amplifier (electronic amplifier is integrated on the proportional valve body).

(4) According to sensor with and without displacement The valve with displacement sensor can reach closed-loop displacement control of the valve, and its steady-state error ( hysteresis, sensitivity) is better than that of the servo valve without displacement sensor (electrical feedback).

(5) According to the valve core structure There are spool valve type, poppet valve type and cartridge type structure. For the proportional valve with large flow, the structure of the cartridge valve is mostly used.

Question 9

The difference between proportional valve and servo valve

Accepted Answer

The proportional valve is mostly electrical feedback. When there is a signal input, the main spool drives the displacement sensor connected to it to move. When the feedback displacement signal is equal to the given signal, the main spool stops moving and the proportional valve reaches a new balance of position.

There are two types of servo valves: mechanical feedback and electrical feedback. Generally, the frequency response of the servo valve with electrical feedback is high, and the frequency response of the servo valve with mechanical feedback is slightly lower, and the action is basically the same as that of the proportional valve.

Difference: The input power of the general proportional valve is relatively large, basically ranging from several hundred mA to more than 1 amp, while the input power of the servo valve is relatively small, basically tens of mA. The control accuracy of the proportional valve is slightly lower, and the hysteresis is higher than that of the servo valve. The valve is large, and the control precision of the servo valve is high, but the requirements for the oil are also high.

From the structural understanding, the spool of the proportional valve is balanced by electromagnetic force, hydraulic pressure and spring force. While the servo valve is balanced by hydraulic pressure, so the proportional valve has no advantage in controlling large flow and high pressure. The earliest product of proportional valve is open, which should be the reason why it is called proportional valve. Otherwise, servo valve is more widely used in application, not only can be used for precise position, speed and other control, but also has a follow-up function. The power steering of car is a follow-up servo system, which is difficult to achieve with proportional valves.

The up and down movement of the oil cylinder can be reached by switching the oil circuit by the valve at different positions. This type of valve can be reached by using an ordinary reversing valve, and the function of servo or proportional valve is not only to control the direction of oil cylinder, but also to precisely control the opening of valve, so that the flow can be precisely controlled (the working state remains unchanged).

The feedback of valve can only determine whether the valve is in place accurately, but cannot control the state of system, because even if the opening of valve is accurate, the actual flow into actuator is also affected by pump pressure, pipeline consumption, load changes, etc. Therefore, to reach accurate position of speed control, another loop avoidance loop - system closed loop is required. For position and speed, there are now formed speed and position control boards to achieve. Some people say that "no matter how accurate it is, it is only a problem of the valve itself, but it is difficult for the controlled object", which is true, but the displacement of actuator does not correspond to the displacement of servo spool, because the valve core opens the oil port after the valve is opened. Even if it is not in motion, the actuator will always maintain the motion, just like the faucet at home, the water will flow continuously when you turn it on.

The proportional valve does not have the closed-loop position of spool of the servo valve. It is a simplified design form that relies on a large and precise control of the amount of current supplied to the proportional spool to control the relatively accurate spool position. The proportional valve does not need to be equipped with a fixed actuator, and the precise realization of position and speed control still requires a closed-loop system. For further information about proportional valve, please visit https://www.genndih.com/proportional-pressure-regulator/low-pressure-proportional-regulator-0-8bar.html

Do both proportional valves and servo valves need amplifiers? Is the input control signal 4-20MA or 0-10V? Is there no -10V-+10V, which means that its action direction is realized by the two coils acting respectively to change the oil circuit, not by its input control signal, is that so?

The input control signals of proportional valve and servo valve are 4-20MA, 0-10V, -10V-+10V, among which the current input signal has strong anti-interference, but the corresponding price is expensive, the internal coil can be one or two. Many three-way valve uses only one coil and controls the positions on both sides by voltage inversion. The three-way valve usually has two coils arranged on both sides of the three-way valve, but the coils can be controlled individually or in series or in parallel. In fact, it is difficult to distinguish between proportional valve and servo valve. Maybe the only difference is the driving method. The servo valve is a torque motor, the proportional valve is a proportional coil, the servo valve is a nozzle baffle, the response is high, and the proportional valve is a spool valve, but when it comes to the control accuracy of proportional valves may be higher. Especially in two-pole feedback valves, because the proportional valve feedback of the pilot is an electrical displacement sensor, and the servo valve is a mechanical feedback rod, so some parameters such as repeatability, hysteresis ring, linearity proportional valve is better than servo valve.

Question 10

LAMINATING PRESSES

Accepted Answer

Our customer is a laminating press machine equipment manufacturer. Through the design and use of an electronic air pressure regulator, the pressure control of mold press is controlled. Since the thickness of products to be pressed is different, it will be sensed through a sensor. The sensed signal is fed back to the PLC through software settings, and the command signal is sent to the electronic air pressure regulator for proper pressure adjustment and stabilization. The digitally controlled electronic air pressure regulator can be effectively used in such related equipment.

Question 11

A Precise Control Method of Temperature and Pressure in Rayleigh-Brillouin Scattering Spectrometry

Accepted Answer

A Precise Control Method of Temperature and Pressure in Rayleigh-Brillouin Scattering Spectrometry

Abstract: For the Rayleigh-Brillouin scattering (RBS) spectroscopy experimental device, users proposed to reach high-precision control of temperature and pressure of measuring gas chamber. This article introduces a specific implementation, in which high-precision temperature control is implemented using semiconductor TEC modules and proportional control flow valve. Pressure control adopts a high-precision vacuum pressure control system, which includes a high-precision pressure sensor, a precision proportional control flow valve and a 24-bit acquisition precision PID controller. This temperature and pressure control scheme has been widely used and proven.

The introduced proportional flow control valve is introduced in https://www.genndih.com/proportional-flow-control-valve.htm

1. Technique requirement
According to customer requirements, temperature and pressure in Rayleigh-Brillouin scattering (RBS) spectroscopy as shown in Figure 1(the content of the red box area) for precise control, the specific requirements are as follows:
(1) Temperature range is 300K~318K; temperature control accuracy is ±0.02K.
(2) Pressure range is 30kPa~90kPa (absolute pressure); pressure control accuracy is ±0.1kPa; atmosphere is 99.9trogen.

2. Temperature control scheme
For high-precision temperature control near room temperature, it is proposed to use semiconductor heating and cooling technology shown in Figure 2 to reach, the specific contents include:
(1) Heating refrigerator: TEC module.
(2) Sensor: platinum resistance or thermistor temperature.
(3) PID controller: high-precision 24-bit temperature and pressure controller.

3. Pressure control scheme
The absolute pressure range required for experimental device to work is 30kPa~ 90kPa, and pressure within this range is required to be accurate and constant at any set point. Using KaoLu’s proportional control flow valve is the best choice.

(1) Using a capacitance pressure gauge with a range of 1000torr for pressure measurement, its accuracy can reach ±0.2%. A vacuum pressure sensor with a higher accuracy of ±0.05% can also be used for measurement.
(2) The high-precision PID vacuum pressure controller with 24-bit A/D acquisition is used to match the measurement accuracy of high-precision vacuum pressure sensor and ensure control accuracy.
(3) Install a proportional flow control valve at air inlet and exhaust port of air chamber respectively. The proportional flow control valve is directly installed at air inlet.

https://www.genndih.com/proportional-flow-control-valve/mid-flow-proportional-valve-0-130L-min.html

(4) During the control process, the pumping speed is guaranteed to be constant after vacuum pump is turned on. First, you need to set the air intake electronic needle valve so that pressure and flow of intake port are constant, and then perform self-tuning of PID parameters. Last, realize precise control of air chamber pressure by automatically adjusting the flow rate of exhaust port.

Question 12

Vacuum Level and Temperature Control Method in Glove Box

Accepted Answer

A Detailed Tutorial on Vacuum Degree and Temperature Control Method in Glove Box

Abstract: In order to reach powerful functions of glove box for two environmental variables of vacuum and temperature in glove box. This article focuses on integrated solution for accurate measurement and control of vacuum and temperature, and describes the upstream, downstream, bi-directional methods. Also introduces the specific application of switching control mode in different vacuum degree ranges, and demonstrates the new proportional flow control valve and 24-bit ultra-high-precision PID controller used in the control.

1. Questions
Vacuum glove boxes are often used for readily oxidizable and deliquescent substances. Chemical reactions, material processing and performance testing that require manual operations in an anaerobic and anhydrous environment are very helpful. The core function of glove box is to provide a vacuum environment and easy to use, but in current practical applications most glove boxes only use anaerobic environment and manual operation functions of glove box, and do not give full capacity to the role of glove box. The more powerful application of glove box is also reflected in the following two aspects:

(1) The vacuum glove box is a hermetic environmental box, and the ultimate vacuum degree can generally reach about 10Pa, so that vacuum degree in glove box can be controlled at any set point between 10Pa and atmospheric pressure as required. Various chemical reactions, experiments and tests that are sensitive to vacuum can be carried out; also various manual operations can be carried out without changing and destroying the vacuum environment.

(2) In addition to vacuum, temperature is another important environmental variable for many reactions, experiments and tests. By placing the corresponding heating device in the glove box, various experimental studies under the combined environment of temperature and vacuum degree can be carried out. And so on, other physical quantity environmental conditions can also be configured to form multi-physical quantity coupling test conditions under various boundary conditions. In order to achieve the full performance of a vacuum glove box, it focuses on two environmental variables of vacuum degree and temperature in the glove box.

This article introduces in detail the integrated solution for accurate measurement and control of vacuum degree and temperature, and introduces the different vacuum degree ranges of upstream, downstream and bidirectional control modes in vacuum control process.

2. Vacuum control in glove box
Glove box belongs to a low vacuum environment cavity. The vacuum degree of the glove box using a mechanical pump can generally reach an absolute pressure of about 10Pa. By vacuuming and filling with inert gas, the vacuum degree of the glove box can be controlled from 10Pa to one atmosphere (absolute pressure 0.1MPa). For control in such a vacuum range spanning four orders of magnitude, vacuum sensors with different precisions will be used according to actual needs, and there will be different control modes accordingly. The following is the specific content of each control mode.

2.1 Upstream Control Mode
As shown in Figure 1, under the condition that the pumping speeds of downstream vacuum pump is kept constant. The upstream control mode is to adjust the opening of proportional flow control valve of upstream air intake port through PID vacuum pressure controller according to the measurement signal of vacuum gauge, that is, by controlling intake flow to keep pressure in glove box at the set point. Upstream mode is often used for high vacuum control.

2.2 Downstream Control Mode
As shown in Figure 2, under the condition that the pumping speed of downstream vacuum pump is kept constant, the downstream control mode is to adjust the opening of proportional flow control valve of downstream air outlet through PID vacuum pressure controller according to the measurement signal of vacuum gauge, that is, by controlling the air flow rate, the pressure in glove tank is controlled at the set value. We can see that downstream mode is often used for low vacuum control.

2.3 Bi-directional Control Mode
The above upstream and downstream control modes have their own advantages, and are rarely used alone in practical applications. Generally, the upstream and downstream modes are integrated together, which is the so-called bi-directional control mode, as shown in Figure 3. In bi-directional control mode, the vacuum pressure controller is required to have forward and reverse control functions, that is, reverse control for upstream proportional flow control valve and reverse control for downstream proportional flow control valve.

2.4 Dual sensor automatic switching mode
As mentioned above, if the accurate measurement and control of vacuum degree is carried out in the full range of 10Pa~0.1MPa, it is generally necessary to configure two high-precision diaphragm pressure gauges of 1000Torr and 10Torrswitch automatically. As shown in Figure 4, the high switching point (2-3) is the high point where low vacuum sensor works, and the low switching point (1-2) is the low point where high vacuum sensor works. The controller performs smoothing calculation between these two points. When the continuous sampling of low vacuum measurement PV1 and high vacuum measurement PV2 is below the lower switching point, switching to the rough vacuum sensor. When continuous sampling of low vacuum measured value PV1 and high vacuum measured value PV2 is above the upper switching point, the switch to high vacuum sensor is made.

3. Selection of vacuum gauge, valve and controller

3.1 Selection of vacuum sensor
Like other sensors, various vacuum sensors also have a certain measurement range and accuracy. The basic rule is that a sensor with a wide measurement range has poor accuracy; a sensor with high measurement accuracy has a narrower measurement range. For glove box, as shown in Figure 5, the used vacuum sensors generally have the following three categories:
(1) Conventional vacuum gauge: Pirani vacuum gauge, the accuracy is ±(15~50)% of the full scale, but one vacuum gauge can cover the full scale.
(2) High-precision vacuum gauge: diaphragm pressure gauge, the accuracy is ±2.5% of the full scale, if it covers the range of 10Pa~0.1MPa, two vacuum gauges of 1000Torr and 10Torr are generally required.
(3) Ultra-high precision vacuum gauge: semiconductor vacuum gauge, the accuracy is ±0.05% of the full scale, and the effective range is 50Pa ~ 0.1MPa, which cannot cover higher vacuum.

3.2 Selection of electric valve
In glove box of vacuum control, two types of valves are generally involved: one is an air intake valve that adjusts the flow at air intake, and the other is an exhaust valve that adjusts the exhaust flow. Air intake valves are mostly used for small flow regulation, so needle valves are generally selected. Exhaust valves are mostly used for vacuuming, so ball valves with larger diameters are generally required.

Due to the automatic control, both needle valves and ball valves are required to be driven by DC voltage, DC current or digital signal (RS485) which is the so-called proportional flow control valve. Proportional flow control valve selects a small-sized stepper motor-driven proportional flow control valve, as shown in Figure 6. This proportional flow control valve has high response speed (within 1s) and linearity (within 1%). For FC series proportional flow control valve, please visit https://www.genndih.com/proportional-flow-control-valve.htm

3.2 Selection of controller
From the above various control modes of vacuum degree of glove box, it can be seen that control process of vacuum degree puts forward high requirements for the controller. As shown in Figure 7, the selected controller must meet the following criteria:

(1) At least it is a PID controller, and has the function of PID parameter self-tuning.
(2) The accuracy of vacuum gauge itself is high. In order to give full play to the measurement accuracy of vacuum gauge, PID controller that needs data acquisition and control must have high accuracy. It is recommended that controller should be 24-bit A/D acquisition and 16-bit D/A output. (3) At least 2 channels are required to achieve simultaneous measurement and control of temperature and vacuum degree, also to reduce installation space.
(4) Multiple input signal access functions, which can directly connect the input signals of different types of sensors such as thermocouple, thermal resistance, DC voltage, etc., to achieve simultaneous testing, display and control of different parameters.
(5) Forward and reverse control function to reach two-way control mode.
(6) With dual sensor switching function, each channel can support dual sensor switching of high and low temperature and high and low vacuum. Two channels can form a control combination with a total of four sensors connected.
(7) Program control function, you can create and save multiple control programs by yourself, and you only need to select and call to start (program control mode).
(8) It has a communication interface to connect with computer, such as the RS485 interface of the standard MODBUS protocol.

4. Temperature control of the glove box
In addition to providing a vacuum environment, the glove box can also put a heating device in the glove box to perform various experiments and tests at different temperatures, so it is necessary to introduce temperature control function into glove box application. Temperature control is a very mature and classic technology, which is generally realized by using a PID controller in combination with a temperature sensor. In order to reduce the cost and installation volume, a multi-channel PID controller is generally used to control temperature and vacuum degree at the same time. The controller communicates with a computer to display and store measurement control data and curves. The working temperature in glove box is generally not required to be too high, but if thermal protection and cooling are done well, the working temperature range above 1000°C can also be achieved. The temperature measurement sensor generally chooses a thermocouple. If the measurement accuracy is high, the thermal resistance and the thermistor temperature sensor can also be selected. These sensors can be directly connected to the above-mentioned high-precision PID controller.

5. Conclusion
Through the introduction of above content, the various control methods of vacuum degree and temperature in glove box and the main sensors, proportional flow control valve and PID controllers involved are basically explained. In specific applications, partial improvements can be made to the specific structure and function of glove box, and the overall design, installation and integration of glove box can also be carried out according to actual requirements.
Although this article only introduces the measurement and control of vacuum degree and temperature in glove box, these methods and specific implementation contents can also be extended and applied to the control of test parameters in other fields that are more sensitive to the atmosphere environment, such as low temperature, geometric quantity, optics and acoustics.

Question 13

KaoLu's Electronic Air Flow Control Valve

Accepted Answer

KaoLu's Electronic Air Flow Control Valve

1. Overview
KaoLu's Electronic Air Flow Control Valve is actually the exact same control valve, only the OEM is different. As shown in Figure 1, this gas control valve is a needle valve driven by a stepper motor, which can convert an external control signal into a prescribed valve needle position, thereby adjusting the opening of the valve to reach gas flow control. The external control signal can be in the following three types :
(1) DC simulation voltage (0~10VDC)
(2) Interface module
(3) RS232 interface
For this gas control valve, INFICON and Pfeiffer provided matching controllers, as shown in Figure 2, the models are: INFICON: VCC500-Z; Pfeiffer: RVC 300.
This article will introduce the corresponding technical indicators for the above-mentioned control valves and controllers, and introduce the corresponding localized alternative products and their technical indicators, so as to provide cost-effective products for localized substitution.

2. Technical indicators of foreign products

2.1 Controller Technical Indicators

Operating Mode Pressure Control, Gas flow regulation Analog Output 4 channels: vacuum pressure sensor signal, valve signal(0-10VDC), valve position, +10VDC reference voltage(10mA) Number Output 8 channels: open valve, closed valve, valve position, valve error, sensor error, preparation, divergence, sensor condition Analog Input 2 channels: vacuum pressure set point (standard value),flow set point (standard value) Number Input 8 channels: flow reduction, flow addition, external closure, external open, flow mode, pressure mode, discharge open, exhausting open Characteristic After power outage, turn on output "reach the standard value", then it can adjust tolerance Display Unit mbar, Pa, Torr, mV Language English, German Communication Interface RS232C, RS485

Controller type PI automatic: it can choose control speed step 1-99
PID: Users can define parameters Control Accuracy ±5% FS sensor Display Accuracy ±0.2% FS sensor Power Supply Voltage90 ~250VAC Weight 1.65kg
From the above-mentioned controller technical indicators and practical application experience, it can be found that:
(1) Single-channel measurement and control: that is, only one vacuum gauge signal and one control valve can be collected. Although there are multiple analog and digital input and output channels, only one closed-loop control can be performed. This single channel controller will not be able to cover the wide range that requires two vacuum gauges to cover.
(2) No PID self-regulating function: Sometimes the optimal PID parameters cannot be obtained in the end, which seriously affects the control effect.
(3) Poor control accuracy: The control accuracy is ±5% of the full scale of sensor, which basically shows that acquisition and control circuit in the controller uses 12-bit A/D and D/A converters, which is the key to determining the control accuracy.

3. KaoLu’s electronic air flow control valve replaces INFICON and PFA control valves
The control valve of KaoLu's Electronic Air Flow Control Valve is a typical electronic air flow control valve driven by stepper motor. The performance indicator is very superior. The only disadvantage is that the opening of needle valve is small, thus it causes a small flow. Moreover, the price is too expensive.
In order to reach the replacement of gas flow control valve and improve the low cost high performance, KaoLu also used stepper motor in needle valve technology for localization, and developed a series of electronic air flow control valve with different flow rates.

As shown in Figure 3, fully realized it has been replaced, and the price is only one-third of foreign products. The detailed technical indicators are shown in Figure 4. Please visit https://www.genndih.com/proportional-flow-control-valve.htm

(Figure3 KaoLu’s FC electronic air flow control valve)

Model FC-20 FC-120 FC-300 FC-1000 Valve type Needle Valve Spool Drift Diameter 0.9mm 2.25mm 2.75mm 4.10mm Actuator Bipolar stepper motor control Response time 0.8sec(Open to close) Standard size G1/8” G3/8” Fluid Inert gas and liquid Contact Materials Stainless Steel Pressure Range -1 ~ 7bar -1 ~ 5bar Maximum Flow 50L/min @7bar 240L/min @7bar 290L/min @7bar 600L/min @7bar Linearity ±2% ±0.1 ~ 1% ±0.2 ~ 5% ±11% Repeatability
(Full scale) ±0.1% Flow Resolution (Step length) 0.1L/min 0.1 ~ 0.2L/min 0.2 ~ 0.75L/min 1L/min Shift Resolution (Step length) 12.7um 25.4um Operating Temperature Range 0 ~ 84ºc Seal Standard FKM or other choices of seals Control Signal DC: 0 ~ 10V (or 4 ~ 20mA) Power Supply DC: 24V (12W)

(Figure4 Technical indicators of KaoLu’s FC electronic air flow control valve)

3. Localized high-precision dual-channel PID controller replaces INFICON and PFA controllers
In order to use the measurement accuracy of vacuum gauges fully (such as capacitive film pressure gauges), at least 16-bit analog-to-digital and digital-to-analog converters are required for data acquisition and control of controller. In recent years, KaoLu have developed the FC series of high-precision 24-bit general-purpose PID controllers, as shown in Figure 5. This series of PID controllers is far more powerful than foreign products, but the price is only one-eighth of foreign products. Its main performance indicators are as follows:
(1) Precision: 24-bit A/D, 16-bit D/A.
(2) Multi-channel: independent 1-channel or 2-channel. 2 channels can realize the simultaneous measurement and control of temperature and pressure.
(3) A variety of output parameters: 47 kinds of input signals (thermocouple, thermal resistance, DC voltage) can reach simultaneous test, display and control of different parameters.
(4) Multi-function: forward, reverse, forward and reverse two-way control.
(5) PID control: The improved PID algorithm supports PV differential and differential advance control. There are 20 groups of PIDs.
(6) Dual sensor switching: Each channel can support dual sensor switching of high and low temperature and high and low vacuum. Two channels can form a control combination with a total of four sensors connected.
(7) Program control: You can create and store up to 20 condensation programs by yourself, and you only need to select and call to start condensation (program control mode).

In the vacuum degree control, downstream control mode is more suitable for vacuum degree close to atmospheric pressure, but upstream air intake control mode is required for vacuum degree control of less than 10mbar. Therefore, in order to satisfy the full control degree of vacuum, the dual sensor and two-way control mode as shown in Figure 6 can be used.
In the control mode shown in Figure 6, it is necessary to use the forward and reverse control and dual sensor automatic switching functions of the above FC-20 series dual-channel controller, that is, during different air pressure control processes; the controller automatically switches the corresponding range. Vacuum gauge, and select the corresponding electronic air flow control valve for control.

Question 14

Atmosphere Pressure Control in Vacuum Laser Powder Bed Fusion

Accepted Answer

Atmosphere Pressure Control in Vacuum Laser Powder Bed Fusion

Low pressure SLM fusion process
Features: The molten pool is more stable and reduces porosity. Low-pressure atmosphere requirements: Fast and accurate air pressure control is reached within the process window of 5kPa~101kPa.

Pressure Control
Control method: two-way control method, adjusting upstream air intake electronic air flow control valve and downstream electric ball valve at the same time. It can also adjust the air intake flow and vacuum pump exhaust rate. For further information on electronic air flow control valve, please visit https://www.genndih.com/proportional-flow-control-valve.htm

Sensor: vacuum pressure sensor, the measurement range is 5kPa~101kPa, and the accuracy is ±0.2%.
Controller: two-way PID controller, two-way control function

Question 15

Glass handling in glass manufacturing site

Accepted Answer

Our customer is glass substrate factory manufacturing company. The design is to adjust the stroke of cylinder through an electronic pressure regulator. There is a rubber roller on the cylinder axis. The roller will be used to clamp the glass, so two sets of such designs are required. Due to the different sizes of glass, the clamping force will be controlled according to the thickness of glass, and the force will be controlled between the glass that will not be damaged and can be horizontal and fixed. Through the electronic pressure regulator control, this condition can be effectively achieved.

Question 16

Comparison of proportional pressure regulators

Accepted Answer

The proportional pressure regulator is a type of valve used to control the pneumatic pressure in the pneumatic system or through the pressure input signal. Proportional pressure regulators mainly include relief valve, pressure reducing valve and sequence valve. This article would introduce what are the similarities and differences between these three valves, how they are used in the system, how the controlled pressure changes, and so on.
(1) The relief valve is divided into a direct-acting relief valve and a pilot-operated relief valve.
The pilot valve of the pilot-operated relief valve is a small-flow direct-acting relief valve. The pressure reducing valve is also divided into a direct-acting pressure reducing valve and a pilot-operated pressure-reducing valve. The pilot valve of the pilot-operated pressure-reducing valve is not a direct-acting pressure reducing valve, but a direct-acting relief valve with a small flow. The sequence valve also has a direct-acting sequence valve and a pilot-operated sequence valve. The pilot valve of the pilot-operated sequence valve is not a direct-acting sequence valve, but also a small-flow direct-acting relief valve. That is to say, the pilot valve of the pressure control valve is a direct-acting relief valve with a small flow.
(2) Comparison of pressure reducing valve and relief valve
The pressure reducing valve is controlled by the outlet pressure to ensure that the outlet pressure is a fixed value. The relief valve is controlled by the inlet pressure to ensure that the inlet pressure is a fixed value. Both are valves that control the air pressure in the pneumatic system.
The valve port of the pressure reducing valve is normally open. The valve port of the relief valve is normally closed. The pressure reducing valve has a separate exhaust port. The leaking oil in the spring chamber of the relief valve is drained to the outlet through the flow passage in the valve body. The pressure reducing valve has the same remote control port as the overflow valve.
(3) The pressure of each valve under different working conditions
Suppose: the pressure generated by the load F is pF, the pressure set by the relief valve is pY, and the set pressure of pressure reducing valve is pJ, and pJWhen pFWhen pF≥pJ, p=pJ, the relief valve works, the inlet pressure of the relief valve and the pump outlet pressure are pY.

The sequence valve is divided into internal control and external control. The external control sequence valve is a valve controlled by a pressure signal. It is an on-off valve. The internal control sequence valve has different uses and functions. They are introduced separately below.

Internal control and external leakage, used as sequence valve
Suppose: the pressure generated by the load F is pF, the pressure set by the relief valve is pY, and the set pressure of the sequence valve is pS.
When pYpressure of the relief valve.
When pY≥pS
When pS≥pF, p=pF

When pSWhen pF
When pF≥pY, p=pY

Internal control and internal leakage have the same symbol as the relief valve, and also have the same function. External control internal leakage and external control external leakage sequence valve, their control pressure has nothing to do with the pressure before and after the valve. When the control pressure is greater than the pressure set by the external control sequence valve, the pressure before and after the valve is equal. When the control pressure is less than the pressure set by the external control sequence valve, the primary and secondary pressures are determined according to their own loads.

For further information about KaoLu proportional pressure regulator or proportional pressure reducing valve, please visit https://www.genndih.com/proportional-pressure-regulator.htm

Question 17

Application of solenoid valve in automatic transmission

Accepted Answer

Application of solenoid valve in automatic transmission
When it comes to automatic transmission, its driving convenience, power and comfort are more and more approved by consumers. The working principle and components of automatic transmission have also attracted more attention. The application of solenoid valve in automatic transmissions will be introduced in this article.

Hydraulics and solenoid valves in automatic transmissions
No matter it is a DCT, AT or CVT automatic transmission, the mainstream technical solutions are indispensable to the hydraulic system. The hydraulic system accepts the signal from controller, outputs oil pressure or flow, and acts on the actuator. The functions of hydraulic system mainly include: controlling the clutch, synchronizer or band pulley to reach the change of transmission ratio, controlling the state of torque converter clutch, and controlling the cooling and lubrication of the system. The performance of hydraulic system directly affects the smoothness of shifting and fuel economy of the entire vehicle, and is an important part of automatic transmission.

In the hydraulic system, the solenoid valve, which as an actuator, reaches the transformation from electrical signals to hydraulic signals, and controls the pressure and flow in the hydraulic system. It is a key component in the hydraulic system.

Classification and application of solenoid valve
The solenoid valve is divided into pilot control and direct drive control in the hydraulic system. The control pressure and flow of the pilot solenoid valve are relatively low, and the actuator cannot be directly driven, only the pilot control pressure is provided. The direct-drive solenoid valve has a larger electromagnetic force than the pilot valve, and control pressure and flow can directly drive the actuator. The hydraulic system using the direct-drive solenoid valve reduces the number of mechanical valves and simplifies the structure of system. Another solenoid valve product is the proportional electromagnet. Compared with other solenoid valves, the proportional electromagnet only has the electromagnetic part, which provides electromagnetic force. The hydraulic part is integrated on the hydraulic valve body. It is designed by customers according to the needs of the specific system. It has higher flexibility, but at the same time increases the integration difficulty of the hydraulic system.

Pilot control method: → Standard solenoid valve + mechanical valve
Advantage: Strong robustness
Disadvantage: 1. Many valves 2. Complex structure of system

Direct drive electromagnet control method: → Direct drive electromagnet + mechanical valve
Advantage: High flexibility
Disadvantage: Difficult integration

Direct drive electromagnet control method: → Solenoid valve drive actuator directly
Advantage: 1. Simple structure of system 2. High precision
Disadvantage: High cost

The introduction of proportional pressure regulator
Bleed type valve:
As shown in the figure below, the valve core is affected by hydraulic pressure, spring force and electromagnetic force. The balance state determines the valve core position, thereby determining the area of drain port. The pressure of control chamber at the left end depends on the input pressure, the input orifice and the area of the drain port determined by the variable adjustment surface. Therefore, the bleed valve achieves the effect of controlling the pressure by controlling the electromagnetic force. Since the Bleed valve regulates the pressure through overflow, the leakage of this valve is relatively large, and the control pressure is more sensitive to the fluctuation of input pressure.

Spool type pressure valve:
As shown in the figure below, ignoring the influence of hydraulic power, the spool of
pressure valve is affected by the spring force, electromagnetic force and hydraulic
feedback force. Under the stable condition, the spool is in a balanced condition. The
electromagnetic force is positively related to the control current of solenoid valve.
Since the characteristics of the spring are fixed, in equilibrium, the electromagnetic
force determines the output pressure. Therefore, the solenoid valve converts the
current signal into a pressure signal.

Question 18

Types, symbols, working principles and applications of  proportional pressure regulator

Accepted Answer

The pneumatic valve can adjust, control and guide the pressure in pneumatic system by changing the position of spool, which can also reach the flow control, direction control and pressure control of air.
In addition, the pneumatic valve control methods are: manual, electronic control, and proportional control.
Today we will talk about the electronic air pressure regulator. The electronic air pressure regulator includes a relief valve, a pressure reducing valve and a control valve. The electronic air pressure regulator has the function of pressure regulation and constant pressure in system. It uses the principle that control pressure is balanced with the spring. Its working state is directly affected by the control pressure, and its state is changing.

(1) Pressure reducing valve
It’s also known as pressure regulating valve, fixed value device (precision pressure reducing valve), etc., it has the function of pressure reduction and pressure regulation.
In general, the working pressure of pump is selected according to the pressure of actuator that requires the highest pressure among the actuators in the system. In this way, since the working pressure of other actuators is lower than the supply pressure of the pump, it can be used in each actuator. A pressure reducing valve is connected in series, and each actuator can obtain a suitable working pressure by adjusting the pressure reducing valve.

(2) Relief valve
It’s also known as safety valve, pressure limiting cut-off valve, etc., it has the function of pressure limiting safety protection. The relief valve reliefs the corresponding pressure through the valve port, adjusts the working pressure of system or limits its maximum working pressure, and prevents the system from overloading the working pressure. The main requirements for the relief valve are good static and dynamic characteristics. Static characteristics refer to good pressure-flow characteristics. Dynamic characteristics refer to stable operation, small pressure overshoot and fast overflow response after sudden external disturbance.

(3) Sequence valve, balance valve
A sequence valve is a pressure valve that uses different or the same pressure as a control signal to automatically connect or cut off a certain oil circuit, and control the actuator to act in a certain order.

For further information about electronic air pressure regulator, please visits:
https://www.genndih.com/proportional-pressure-regulator.htm

Question 19

What are the advantages and disadvantages of hydraulic  transmission technology?

Accepted Answer

1. Advantages
①The unit power is light in weight. Statistics show that the weight per unit power of hydraulic pump and hydraulic motor is only 1/10 of generator and motor, and the hydraulic pump and hydraulic motor can be as small as 0. 03N/W. As for size, the former is about 12%-13% of the latter. In terms of output force, it is easy to obtain extremely high pressure hydraulic oil with a pump, and after this oil is sent to the hydraulic cylinder, a large force can be generated. Therefore, hydraulic technology has the outstanding characteristics of light weight, small size and large output, which is conducive to miniaturization and miniaturization of mechanical equipment and its control system, and high-power operation.

② The layout is flexible and convenient. The arrangement of hydraulic components is not restricted by strict spatial position, and it is easy to reach the connection of various parts in system through pipelines according to the needs of machine. The layout and installation have great flexibility, and can form complex systems that are difficult to form by other methods.

③ The speed range is large. Through the control valve, the hydraulic transmission can reach a large range of infinitely-variable-speed regulation of hydraulic actuator during operation, and the speed regulation range can reach 2000e.

④ It works stable and fast. The oil is elastic and can absorb impact force, so the hydraulic transmission transmits the movement evenly and smoothly. It is easy to reach quick start, braking and frequent reversing. The commutation frequency of reciprocating rotary motion can reach 500 times /min, and the commutation frequency of reciprocating linear motion can reach 1000 times/min.

⑤ Easy to operate and control and reach overload protection. The hydraulic system is easy to operate and control, and it is easy to reach automatic control, long-distance remote control and overload protection. It can be self-lubricated during operation, which is beneficial to heat dissipation and prolong service life.

⑥ Easy to automate and integrate electromechanical and hydraulic. Hydraulic technology is easy to integrate with electrical and electronic control technology to form an electromechanical-hydraulic integrated composite system to reach automatic working cycle.

⑦ It is easy to reach linear motion. Using hydraulic transmission to achieve linear motion is simpler than mechanical transmission.

⑧ The hydraulic system is easy to design, manufacture, use and maintain. Hydraulic components belong to the basic parts of the machinery industry, and have achieved standardization, serialization and generalization. Therefore, it is convenient for the design, manufacture, use and maintenance of hydraulic systems, and is conducive to shortening the design and manufacturing cycle of machinery and equipment and reducing manufacturing costs.

2. Disadvantages
① The fixed ratio hydraulic transmission can’t be guaranteed. Due to the influence of factors such as compressibility and leakage of liquid, the hydraulic technology can’t strictly guarantee the fixed ratio transmission.
② The transmission efficiency is low. During the hydraulic transmission process, two conversions are required, and there is often a lot of energy loss, so the transmission efficiency is low.
③ The working stability is easily affected by temperature. The performance of hydraulic system is sensitive to temperature, and it is not suitable to work at too high or too low temperature. When using petroleum-based hydraulic oil as the transmission medium, it is necessary to notice fire prevention problem.
④ The cost is high. The manufacturing precision of hydraulic components is required to be high to prevent and reduce leakage, so the cost is high.
⑤ Difficulty in fault diagnosis. Hydraulic components and systems are prone to system failures due to hydraulic oil contamination and other reasons, and failures are difficult to diagnose.

For further information about selections pneumatic pressure regulator, please visit
https://www.genndih.com/proportional-pressure-regulator.htm

Question 20

Common errors of proportional valves and cause root analysis

Accepted Answer

What are the common errors of proportional valves? What is the reason of these errors? How to avoid them?

1. Proportional electromagnet error
① Due to the aging of wiring socket (base) of plug assembly, poor contact, and de-soldering of electromagnet lead, the proportional electromagnet cannot work (cannot pass current). At this time, the meter can be used for testing. If the resistance is found to be infinite, the lead wire can be re-soldered, the socket can be repaired and the socket can be inserted firmly.

② The errors of coil components include coil aging, coil burnout, internal disconnection of the coil, and excessive temperature rise of the coil. If the temperature of coil is too high, the output force of proportional electromagnet will be insufficient, and the rest will make the proportional electromagnet unable to work.

If the temperature of coil rises too high, you can check whether the passing current is too large, whether the insulation of enameled wire of coil is poor, whether the valve core is stuck due to dirt to find out the reasons and eliminate them one by one. For disconnection, burnout, the coil must be replaced.

③ The error of armature assembly is mainly due to the wear of the friction pair formed by the armature and the magnetic guide sleeve during use, which leads to an increase in the force hysteresis of the valve. There is also a misalignment between the push rod guide and the armature, which will also cause an increase in the force hysteresis, which must be ruled out.

④ The welding part of the magnetic guide sleeve is broken due to the weak welding or the pulse pressure of the proportional valve during use, so that the proportional electromagnet loses its function.

⑤ The magnetic guide sleeve is deformed under the impact pressure, and the friction pair formed by the magnetic guide sleeve and the armature is worn during use, resulting in an increase in the force hysteresis of the proportional valve.

⑥ The proportional amplifier is shut down, causing the proportional electromagnet not working. At this time, various components of amplifier circuit should be checked to eliminate the error of proportional amplifier circuit.

⑦ The connection between proportional amplifier and the electromagnet is broken or the connection of amplifier terminal is disconnected, so that the proportional electromagnet does not work. At this time, the broken wire should be replaced and reconnected firmly.

2. Error analysis and elimination of proportional pressure regulator
Since the proportional pressure regulator is just based on the ordinary pressurevalve, the pressure regulating handle is replaced by a proportional electromagnet. Therefore, the various errors caused by ordinary pressure valves will also cause error and troubleshooting methods of ordinary pressure valves, which are also completely applicable to the corresponding proportional pressure valves (such as the relief valve corresponding to proportional relief valve), and can be handled with reference.
Beside this there is:

① When the voltage regulation fails, you can first check the current value with electric meter to determine whether there is a problem with the control circuit of electromagnet, proportional electromagnet, or valve part, which can be treated symptomatically.

②Although the current flowing through proportional electromagnet is the rated value, but the pressure cannot go up at all, or the required pressure cannot be obtained, between proportional pilot pressure regulating valve (relief valve) and the main relief valve. The pilot-operated manual pressure-regulating valve of common pilot-operated relief valve is still retained, which acts as a safety valve here. When the regulating pressure of valve is too low, although the passing current of proportional electromagnet is the rated value, the pressure cannot rise. If the set pressure of valve is too low, the pilot flow will flow back to the tank from valve, so that the pressure cannot rise. At this time, the set pressure of valve should be adjusted to be about 1MPa higher than the maximum working pressure of valve.

③ The current flowing through proportional electromagnet has been too large, but the pressure still cannot go up, or the required pressure cannot be obtained. At this time, the coil resistance of proportional electromagnet can be checked. If it is far less than the specified value, then the coil of electromagnet is internally open circuited. If the solenoid coil resistance is normal, then the connection line connected to proportional amplifier is short-circuited. At this time, the proportional electromagnet should be replaced, the wiring should be connected, or the coil should be rewound
and installed.

④ When the pressure is changed stepwise, the pressure fluctuation of small amplitude is continuous, and the reason for the instability of the set pressure is mainly due to the adhesion of dirt between the iron core of the proportional electromagnet and the guide part (guide sleeve), which hinders the movement of the iron core. In addition, the sliding part of the main spool is stuck with dirt, which hinders the movement of the main spool. Due to the influence of these contaminants, the hysteresis is increased. In the range of hysteresis, the pressure is unstable and the pressure fluctuates continuously. Another reason is the wear of the iron core and the magnetic guide sleeve, the gap increases, and the adjusted pressure (through a certain current value) is unstable.

⑤ The pressure response is delayed and the pressure changes slowly because the air in the proportional electromagnet is not cleaned. It is blocked by dirt, and the movement of proportional electromagnet core and the main valve core is unnecessarily hindered. In addition, air enters the system, which usually occurs when the equipment starts to run after being installed or after an occasion of long-term shutdown.

The solution is to loosen the bleed screw before the proportional pressure regulator starts to use, and let out clean air until the oil flows out. In the case of dirt blocking the damping hole, the proportional solenoid and the main valve should be disassembled for cleaning, and at the highest position of the system oil circuit where the air is easy to concentrate, it is best to set the air release valve to release air or loosen the pipe joint to release air.

⑤ The pressure response is delayed and the pressure changes slowly because the
air in the proportional electromagnet is not cleaned. It is blocked by dirt, and the
movement of proportional electromagnet core and the main valve core is
unnecessarily hindered. In addition, air enters the system, which usually occurs
when the equipment starts to run after being installed or after an occasion of long-
term shutdown.

⑤ The pressure response is delayed and the pressure changes slowly because the
air in the proportional electromagnet is not cleaned. It is blocked by dirt, and the
movement of proportional electromagnet core and the main valve core is
unnecessarily hindered. In addition, air enters the system, which usually occurs
when the equipment starts to run after being installed or after an occasion of long-
term shutdown.

⑤ The pressure response is delayed and the pressure changes slowly because the
air in the proportional electromagnet is not cleaned. It is blocked by dirt, and the
movement of proportional electromagnet core and the main valve core is
unnecessarily hindered. In addition, air enters the system, which usually occurs
when the equipment starts to run after being installed or after an occasion of long-
term shutdown.

⑥Two faults of electro-hydraulic proportional relief valve
a. When the rated current (50mA) is input to the coil, the inlet pressure cannot reach the rated working pressure (21MPa), but is 2-6MPa lower than the rated pressure. The reason is: after long-term use, due to the loosening of the fastening screws of the magnetic gap adjustment gasket, the magnetic gap increases, and the magnetic resistance of the magnetic gap (air gap) in the magnetic circuit is very large.

F=k(iN/Rm)2S

where k-constant;
i——the coil input current;
N - the number of turns of the coil;
Rm - magnetoresistance;
S - the cross-sectional area of the magnetic circuit.

It can be seen that as long as the magnetic gap is slightly increased, the reluctance Rm increases significantly, and the electromagnetic force F decreases in a square relationship. The hydraulic clearance increases, the pressure upstream of the nozzle decreases, so the pressure in the upper chamber of the main spool decreases. The force added by reduced pressure and weak spring in the upper chamber of the main valve decreases, so that the opening pressure of the main spool decreases, that is, the inlet pressure decreased, and the maximum pressure (21MPa) could not be reached.

Solution: Appropriately increase or decrease the thickness of the magnetic gap adjustment gasket, tighten the fastening screws of the magnetic gap adjustment gasket, and reduce the magnetic gap, which can increase the inlet pressure. The initial setting of the magnetic gap should be 0.89 ~ 0.94mm.
b. When the input current of the coil is zero, the initial pressure of the valve is too high (4-7MPa). Normally, the initial pressure should be about 1MPa. The minimum set pressure mainly depends on the initial gap 8 of the nozzle baffle. The normal gap is 0.1 to 0.13 mm. If it is too small, the initial pressure will be too high.

3. Error analysis and elimination of proportional flow valve
①The flow cannot be adjusted, and the throttling adjustment function is invalid. In addition to the error analysis and troubleshooting method of speed control valve, there are the following two points: a. Proportional electromagnet failed to energize.
The reasons are: aging of the proportional electromagnet socket and poor contact; unsoldering of the electromagnet lead; wire breakage inside the coil, you can refer to the above "(1) Proportional electromagnet error" method for troubleshooting.

b. Proportional amplifier error. Same as ①, ⑤, ⑥ in the above (2).
②The adjusted flow is unstable. The flow adjustment of the proportional flow valve is reached by changing the current flowing into its proportional electromagnet. When the input current value remains unchanged, the adjusted flow rate should remain unchanged. But in fact, the adjusted flow rate (when the same signal value is input) often changes in the working process, which is caused by the increase of the force hysteresis. Hysteresis means that when the same signal (current) value is input, the maximum change value of the output flow (or pressure) is caused when the same current signal value is passed due to different input directions (forward and reverse directions).

The factors affecting the force hysteresis are mainly caused by the existence of radial unbalanced force and mechanical friction. Then measures such as reducing the radial unbalanced force and reducing the friction factor can reduce the influence of mechanical friction on the hysteresis. The hysteresis is reduced, and the natural change of the adjusted flow is small. The following measures can be taken specifically:
a. Minimize the wear of the armature and the magnetic guide sleeve.
b. The push rod guide rod and the armature should be same.
c. Pay attention to the cleaning of the oil to prevent the dirt from entering the gap between the armature and the magnetic guide sleeve and jam the armature, so that the armature can move evenly in proportion to the input current value without sudden jumping. Once the sudden jump phenomenon occurs, the output flow of the proportional flow valve will also follow the sudden jump and make the adjusted flow unstable.
d. After the magnetizing sleeve armature is worn, noticing repair, so that the gap between the two is kept within an appropriate range. These measures are quite beneficial and effective to maintain the stability of the flow rate adjusted by the proportional flow valve.

In addition, the hysteresis of proportional valve driven by the general proportional electromagnet is 3% to 7%, the hysteresis of proportional valve driven by the torque motor is 1.5% to 3%, and the proportional valve driven by the servo motor is about 1.5%. The proportional flow valve driven by the servo motor has a relatively small change in flow.

For further information about electro-pneumatic pressure regulator, please visit https://www.genndih.com/proportional-pressure-regulator.htm

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