Dynamic all-electric feedback servo valve automatic detection system

Abstract: Taking the MK dynamic servo all-electric feedback servo valve manufactured by Japan KYB Industrial Co., Ltd. as an example, the characteristics of moving full electric feedback servo valve are introduced. The testing method of moving full electric feedback servo valve is described in detail. And the principle of automatic detection system, and gives the use of the automatic detection system for the MK valve test results. 1 Introduction Traditional electro-hydraulic servo valve is the most typical and most commonly used dual-nozzle baffle spool valve force feedback servo valve, which uses the torque motor as the electro-mechanical conversion device, dual nozzle flapper valve for hydraulic amplification components, the force Feedback lever and spring tube form mechanical feedback. Although the torque motor has the advantages of high natural frequency and compact structure, in order to limit the non-linearity, the output displacement of the torque motor armature is generally small and the manufacturing precision is high. The mechanical feedback formed by the force feedback lever and the spring tube makes the torque motor anti- Poor pollution, high prices. Moving coil type motor does not change the length of the air gap when moving in the air gap. It has the characteristics of large displacement. The direct drive of the slide valve by the force motor can increase the anti-pollution ability of the valve. Early dynamic motor servo valve, because in order to take full advantage of the linear motor force, spool stroke large, the spring is generally less rigid, and the moving coil and the pilot valve connected together, moving parts of mass, resulting in Low frequency motor, the response speed is slow. With the development of electronic technology and sensor technology, it is no longer difficult to increase the output force of a force motor by increasing the drive current of a moving coil type force motor. It is not only feasible but also economical to utilize the advanced displacement detection technology to realize the high-accuracy detection of the position of a valve core , So in recent years, hundreds of Hertz and above high-frequency high-flow servo valve almost all use dynamic coil motor structure. In this paper, the Japanese KYB Industrial Co., Ltd. MK servo valve for example, the analysis of moving coil servo valve characteristics and testing problems. 2 MK valve and amplifier features MK electro-hydraulic servo valve is a full electric feedback, two-drive, two-position electro-hydraulic servo valve. It has high frequency response, high precision, good anti-pollution, stable performance and so on. Compared with force feedback, the use of electrical feedback not only simplifies the structure of the servo valve, but also provides a technical basis for changing the valve characteristics using electrical parameters. Figure 1 for the dynamic all-electric feedback MK valve and its amplifier composed of electrical schematic. Servo valve from the pilot valve, the main valve and pressure reducing valve and other components. Pilot level are mainly: dynamic motor, slide valve and the eddy current displacement sensor and other components, the electrical part is completely dry, dynamic movement directly to promote the movement of the spool, spool displacement by the embedded eddy current displacement sensor detection feedback The input to the amplifier forms an electrical closed loop. This direct action plus electrical feedback, making its structure is particularly simple, greatly improving the reliability. The main valve driven by the pilot, the main spool and embedded differential transformer displacement sensor core connected to the displacement of the main spool by the differential transformer displacement sensor feedback to the amplifier input to form a second-level feedback. Pressure reducing valve is located between the main valve and the pilot valve to ensure that the pilot valve can be a stable supply pressure. The servo amplifier consists of power amplifier, main valve loop, addition circuit, DC power supply and detection circuit. Its current drive capability is ± 3.5 A @ ± 48V. Sensor, amplifier placed close to the servo valve, in charge of the pilot valve, the main valve spool displacement signal processing and amplification, and the displacement signal is converted to 4 ~ 20 mA of electrical signals. This current transmission, greatly improving the anti-interference ability of the system. 1. Pilot valve 2. Pressure reducing valve 3. Main valve Figure 1 Dynamic all-electric feedback MK valve and its amplifier composed of electrical schematic Figure 1 can be seen that this all-electric feedback, two drive, dual position Closed-loop electro-hydraulic servo valve itself is a machine, electricity, liquid complex sophisticated control system, its performance parameters, quality indicators of the test is not only an important measure of its performance advantages and disadvantages, but also to adjust the electrical parameters to ensure its normal , Efficient, stable operation and intensive maintenance necessary means. 3 automatic detection system components principle From the above analysis we can see: dynamic all-electric feedback MK valve performance testing is actually the whole electric feedback electro-hydraulic servo system performance testing. In order to ensure that the detection system impedance effect does not affect the performance of MK valve and adjust its parameters, the detection system in addition to complete the pilot valve, the main valve flow characteristics, pressure leak characteristics, spool displacement characteristics and frequency characteristics of detection, To take isolation and effective anti-jamming technology to ensure that the valve performance is not affected. Figure 2 for the automatic detection system block diagram. System software in the WINDOWS environment, with a good man-machine interface and operability. The system hardware mainly consists of monitoring computer, excitation signal generating unit, sensor and its transmission unit, signal acquisition and processing unit, test result output unit, test device and servo valve under test. Figure 2 automatic detection system block diagram (1) monitoring computer monitoring computer using industrial control machine, is the main control system of the test system. Through the friendly man-machine interface, it is responsible for receiving user's instructions, monitoring and managing the working status of intelligent instruments such as programmable signal generator, BCDGPIB data conversion unit, 1253 gain phase analyzer, PM3384 four-channel digital-analog combined oscilloscope, And is responsible for controlling the DS P interface board to be measured by the analog acquisition, analysis and processing. At the same time, the monitoring computer through the big screen display and printer test status and results of the display, print output. Through the IEEE488 bus, the monitoring computer and program-controlled signal generator, BCDGPIB data conversion unit, 1253 gain phase analyzer, PM3384 four-channel digital - analog oscilloscopes and other intelligent digital communication to complete these intelligent instruments working mode and range of working conditions Settings, access to test data and more. (2) Excitation signal generation unit The excitation signal generation unit includes two parts, one is a programmable signal generator and the other is an excitation signal output part of a 1253 gain phase analyzer. Programmable signal generator can generate sine wave, triangle wave, pseudo-random signal, step signal, 1253 gain phase analyzer excitation signal output is a sine wave. The monitoring computer operates the excitation signal generation unit through the IEEE488 bus to set parameters such as the type and amplitude of the signal and generate various excitation signals required for the test project. (3) Sensor and its transmission unit The sensor and its transmission unit are important components of the servo valve detection system. The physical parameters that characterize the performance or state of the tested servo valve, such as pressure, flow, temperature and other parameters, need to be converted by the corresponding sensors into electrical signals and then processed by the transmitter or secondary instrument, displayed and sent to the signal Acquisition and processing unit for analysis and processing. Pressure detection using the British DRUCK's PDCR-961 pressure sensor and DPI-280 digital pressure indicator, measuring range of 0 ~ 35 MPa, accuracy of ± 0.1%; flow measurement using the German VSE GmbH VSE1, VSE 2, VC0 .2 and VSE0.04 four types of gear flow sensor, the second instrument using MFI digital flow indicator, the performance parameters of the flow sensor in Table 1; temperature measurement using semiconductor thermal sensors, transmission and digital instrumentation to develop, test Temperature range: -50 ~ 150 ℃, accuracy of 0.5 ℃. Pressure, flow figures show that the instrument can also display analog output (4 ~ 20 mA / 0 ~ 10 V) and BCD digital. Table 1 Flow Sensor Performance and Application Model VSE2 VSE1 VC0.2 VSE0. 04 Linearity 0.3 0.3 1 0.3 Measurement Range (L / min) 1.5 ~ 125 0.8 ~ 16 0.2 ~ 16 0.04 ~ 4 Applications Flow characteristics Flow characteristics Leakage characteristics of leakage characteristics (4) signal acquisition and processing unit signal acquisition and processing unit mainly by the signal conditioner, DSP interface board, BCDGPIB data conversion unit, 1 253 gain phase analyzer, PM3384 four-channel digital-analog combo oscilloscope and monitoring Computer and other components, responsible for the signal from the sensor isolation, amplification, filtering, acquisition, processing and other functions. In addition to complete the signal from the sensor or secondary instrument analog signal amplification, blocking, filtering and other functions, it also provides isolation of analog signals, effectively eliminating the sensor network to the test system. Servo amplifier input and output and the pilot valve spool displacement, the main valve spool displacement signal and the test system is isolated by the regulator connected to avoid the test system on the servo valve and servo amplifier to ensure that the servo valve and servo amplifier The normal work and the independence of parameter adjustment. While collecting the analog signal from the signal conditioner in the DSP interface board, the monitoring computer collects the BCD digital quantity from the secondary instrument through the BCDGPIB data conversion unit, so that the on-line calibration and zeroing of the analogue can be conveniently realized. The static characteristic curve of the servo valve is plotted with the digitally calibrated analogue to ensure the data accuracy of the static characteristic of the servo valve and the resolution and integrity of the static characteristic curve of the servo valve. Frequency characteristics of the phase analyzer can be completed by the 1253 gain, the results sent to the monitoring computer through the IEEE488 bus for secondary processing by the monitoring computer to display, print and other output. Step characteristics collected by the PM3384 four-channel - analog combo oscilloscope, and then through the monitoring computer analysis and processing display, printing and so on. (5) Test result output unit XY recorder, large screen display, printer, and PM3384 four-channel - analog oscilloscope and other test results constitute the test system output unit. 4 Test Circuits and Experiments (1) Static Characteristic Test Circuits and Experimental Electro-Hydraulic Servo Valves The static characteristic tests mainly include the contents of unloaded control flow characteristics, pressure gain characteristics and internal leakage characteristics. From these three characteristic curves, Electro-hydraulic servo valve flow gain, linearity, hysteresis, symmetry, polarity, pressure gain, zero bias and internal leakage and other characteristic parameters. Figure 3 for the electro-hydraulic servo valve static characteristics test loop. In order to ensure that the valve core moves, the test system is not disturbed, and the pressure closed loop of the test loop is formed by a proportional amplifier, a proportional valve, a servo valve P, a T port pressure sensor and a PI regulator to meet the requirements of the flow characteristics test. Valve pressure drop to maintain a constant demand. In the no-load control flow characteristic test, the stop valves 1, 3, 5, 6 and 7 are opened and the stop valve 8 is closed. Pressure gain characteristics and internal leakage characteristics of the test, open the stop valve 1, 3, 8, closing the stop valve 5,6,7. The test signal of the static characteristic test loop adopts the 25 mHz triangular wave frequency. Under the condition of the oil supply temperature of 44.2 ℃, the pilot loop gain of 3.0, the main valve loop gain of 3.0, the speed damping gain of 6.0 and the valve pressure drop of 6.6 MPa, On a MK valve no-load flow control curve, the main spool displacement characteristics of the test results shown in Figure 4. Figure 4 No-load control of a MK valve flow characteristics of the main spool displacement characteristics of the test signal frequency of 20 mHz triangular wave at the supply temperature of 40.2 ℃, the pilot loop gain of 3.0, the main valve loop gain of 3.0, the speed damping gain of 6.0 , The supply pressure of 21.2 MPa conditions, the pressure gain of a MK valve characteristic curve, the internal leakage characteristics of the test results shown in Figure 5. Figure 5 a MK pressure gain characteristics of the internal leakage curve (2) dynamic characteristics of the test loop and the experiment Figure 6 is the electro-hydraulic servo valve frequency characteristics of the test circuit, the test, close the stop valve 6, 7, open the other stop valve . Figure 6 frequency characteristics of the test circuit diagram in the system pressure of 11.7 MPa, the supply temperature of 40.9 ℃, the pilot loop gain of 3.0, the main valve loop gain of 3.0, the speed damping gain of 6.0, the input amplitude of 0.35 V conditions, the use of frequency The response of a MK valve obtained by the frequency characteristics shown in Figure 7. Figure 7 a MK valve frequency curve 5 Conclusion Dynamic all-electric feedback servo valve automatic detection system has the following characteristics: (1) the use of digital automatic online calibration of analog technology to ensure that the electro-hydraulic servo valve static characteristics of the test accuracy (2) In order to ensure that the no-load flow control test valve constant pressure conditions, the use of proportional valve constitutes a closed loop pressure; (3) The system uses isolation and other anti-jamming measures to ensure the accuracy of the test system and all-electric feedback Servo valve normal work; (4) multiple intelligent instruments through the IEE488 bus and monitoring machine communication, data transmission and reliable, fast; (5) software in the WINDOWS environment design, with a friendly man-machine interface. Through the practice of Baosteel Group in Shanghai nearly a year proved that the system is stable, easy to operate, the experimental data is accurate and reliable.