Introduce an advanced testing and debugging method

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This paper introduces an advanced method of testing and debugging hydraulic proportional valve

1 preface the service department of Shanghai Volkswagen factory introduced a universal test rig for hydraulic components from Germany in October, 1998 after more than a year of planning for the maintenance of hydraulic equipment. This test-bed is produced by Germany Rexroth company. It has the functions of debugging and testing hydraulic proportional components such as comparison valve and proportional pump

The biggest technical feature of the proportional valve test on the test bench is that for each proportional valve test, although the system does not provide ready-made test procedures, users can easily use DASYLab software to design test procedures according to their own test requirements. Therefore, the function of the test-bed can be brought into full play

2 background introduction of proportional valve testing and debugging technology in the hydraulic component testing technology, the test of proportional valve is more difficult, and the test means are also developing rapidly

in the test of conventional components, the change of test conditions is generally achieved by manual adjustment, and the working points are limited and discrete. The record of test results is also copied into the test form by hand through reading the table

the test of proportional valve is different from the conventional component test. As for artificial skin, its working condition changes continuously, and the test results are also continuous. Generally, the test results are reflected through the characteristic curve

the conventional commissioning and testing process of proportional valve is as follows: use the signal generator to generate control signals such as oblique wave and triangular wave according to the test requirements and connect them to the proportional valve, and the proportional valve moves under working conditions. The controlled pressure, flow and other operating parameters are recorded on the X-Y recorder through the corresponding sensors. In this way, the characteristic curve reflecting the performance of the proportional valve between the controlled parameters (pressure, flow, etc.) and the control signal (current, etc.) can be obtained

in the late 1980s, with the development of computer technology, computer-aided debugging and testing systems for proportional valves began to appear, such as the proportional valve testing system of Baosteel integrated hydraulic test bench developed by Beijing University of technology with C + + language and the proportional valve testing system of Hangzhou hydraulic parts factory developed by Zhejiang University with Turbo C language. In these systems, the hardware system of signal generation and acquisition is composed of "microcomputer + AD/DA acquisition card" and corresponding sensing and transformation circuits, and the proportional valve test system is composed of special software to replace the signal generator and X-Y recorder

the proportional valve auxiliary test system has many advantages over the conventional test system. First, signal generation is more flexible. The signals in the computer are composed of digital sequences. It can compile digital sequences of any difficulty according to the test requirements, but it is difficult for analog circuits to do so. Secondly, the test curve can be displayed on the screen in real time, the file can be saved and printed, and the recorded digital sequence can be analyzed conveniently afterwards, which is difficult for the traditional X-Y recorder. In a word, computer-aided testing system is a development direction of proportional valve testing and debugging methods

at present, the common proportional valve auxiliary test system in China is basically a special software designed with C language. Users can only test according to the pre-designed items in the program of whether the oil pump belt can be loosened. There is little room for users to participate in the test design, which is generally limited to changing the test parameters. In this way, the application scope of the test-bed is limited

the technical core of the proportional valve testing and debugging system of Shanghai Volkswagen hydraulic comprehensive test-bed is the use of DASYLab software. DASYLab software makes full use of the technical characteristics of graphical user interface (GUI) and object-oriented programming (OOP) in Microsoft Windows, and provides many modules with complete functions, such as digital to analog/analog conversion module, event module, signal generation module, display module, file module, signal processing module, etc. Users only need to compile the test program conveniently through the combination of functional modules according to their own test requirements. In the whole proportional valve test system, there is no ready-made test procedure. Any proportional valve test requires users to prepare test procedures according to their own test requirements. This is the biggest feature of the test-bed and the biggest difference from the previous proportional valve computer-aided test system

3 introduction to proportional valve test and commissioning system figure 1 shows the test system related to proportional valve test in the test bench

Figure 1 Schematic diagram of proportional valve test system the main oil source of the system is composed of a volume throttling speed regulating system composed of a proportional constant pressure pump and a proportional speed regulating valve due to the dispersion with polymer. The computer controls the pressure and flow of the main system through ao00 and ao02. The power element test is loaded through the proportional throttle valve or proportional overflow valve. The loading signal is provided by ao01. The test signal of the tested proportional element is provided by ao03

ai01 and ai02 collect the flow signals of two flow meters with different ranges respectively. According to the measured flow range, the flowmeter for testing can be selected by switching the oil circuit. Ai09 ~ ai14 are respectively taken from pressure sensors with different ranges. According to the test requirements and the range of measured pressure, appropriate pressure sensors can be selected and connected at appropriate measuring points. Ai07 and ai08 are taken from temperature sensors and can be connected to corresponding measuring points as required. Ai00 and ai03 are fixedly connected with the pressure sensor measuring the outlet pressure of the main pump and the oil tank temperature. Ai04, ai05, it can be seen that the wire oil filter A106 is fixedly connected to the torque/speed measuring instrument of the test power element. Ai15 collects the actual output voltage signal of the tested proportional valve amplifier

The test design process of the proportional valve is as follows:

1) determine the test parameters and characteristic curves you want to get through the test. For example, observe the change of the working flow of the proportional directional valve with the control voltage in the time domain

2) design and determine the hydraulic circuit for the test. The hydraulic system of this test-bed adopts modular and building block design, and the test circuit can be easily combined through quick connectors

3) determine the selection of pressure and flow sensors according to the specification and test range of the tested valve

4) use the external potentiometer to send a signal to check whether the oil circuit and circuit work normally

5) record the actual selected AI and AO addresses, such as ai02, ai12, ai11, ao03, ao00, ao0 selected in this proportional directional valve test

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