Hydraulic Loading In The Static Test Lab Implementation Of Intelligent Digital Control

Static strength tests of structures are necessary to appraise the static strength of products. The tests can not only check the theoretical calculation results of strength and hardness of structures, but also verify the reasonableness of structures. The test load can be put on samples by the way of mechanical, electric or hydraulic equipment. The hydraulic equipment has been widely used in practice because of the stability and low noise features. Based on the hydromechanics principle, the hydraulic equipment can push compressive oil into actuators by the pressure and direction control circuits. The piston of actuator translates distributed pressure into centralized force of piston rod. In formerly static strength tests, no attention was paid to the process of test load. According to their experiences, experimenters adjusted pressure in actuator only by hand to control the test load value and the load value was read from instruments. This kind of load can not be content with the increasing request of process of test load, when the test is needed to simulate actual working condition of the products. Now, process of test load can be controlled with computer automatically. With the digital control, volume of compressive oil provided by hydraulic power unit in actuator can be regulated to modulate the test load value. In conformity with the idea, we developed two systems-force and displacement control system in this paper. Though in appearance the two systems are alike, the kinds of transducers that feed back information of load to computer are different. And their stability and dynamic features are discrepant. This is the reason why we designed two kinds of control method. In this paper, we set up the transfer function of whole system and components and introduce two control methods. The main contents of the paper are as following:1- The basic background of this program is introduced. And a wide survey about related theory of automatic control and modern test techniques are presented in this paper.2. Main components of system-actuator, servo valve and transducer , and mathematicalmode) of system are analyzed in detail.3. The stability and dynamic features of two systems are analyzed.4. PID arithmetic by which the loading process of displacement system is controlled is successfully adopted in two control systems.5. Self-adaptive identification and control of pole placement used in force system is deeply studied.6. Software is programmed using modularized program language-VISIDAQ.7. The static strength test system with digital control is established. The test results by the system show that the system is satisfactory.