The Research Of Electro-hydraulic Proportional Fatigue Loading Test Rig Based On S7-300

Fatigue test is an effective way to analyze the components' fatigue strength, which can ensure the reliability of the parts, it is widely used in automotive, aerospace, marine, construction and other fields. Through test rig to simulate different types and different parameters loading force(such as sine, triangle, ladder, step and other force waveform) can we verify parts' fatigue strength under different working conditions, help us to adjust the devices' working parameters, to ensure the safety of equipment and staff.The electro-hydraulic proportional fatigue loading test rig is the experimental device which independently designed for specific load, need to the comprehensive application of electric control, hydraulic systems, mechanical design, and other related technologies. In consideration of the control of asymmetric hydraulic cylinder's output force by PLC and proportional valve is the research difficulty, to realize the accurate control of output force of test rig, the electro-hydraulic proportional fatigue loading test rig's hydraulic system have been designed and simulation analyzed to determine the optimum hydraulic system-—the proportional direction valve closed loop control system which can meet the functional requirements, then preliminary exploration of the control strategy that valve controlled asymmetrical hydraulic cylinder based on S7-300 has been carried out, to complete system control programming and control interface configuration also put forward static compensation control strategy based on PID control in order to realize the symmetry control of asymmetric hydraulic cylinder. Considering this test rig's output force has the characteristics of high peak, alternating fast, in order to ensure the strength and stability of loading test mechanical system's parts, the detail calculation and finite element analysis of the mechanical system's key parts has been done at the same time.The quality of test rig's electrical control system determines the security and reliability of whole system, after finished the work above, the test rig's electrical control system be designed in detail, then build the test rig's prototype and test analysis the static load and dynamic load test performance of test rig, including the static loading test, the sinusoidal periodic loading test, the sinusoidal with offset cycle load test and step loading test.The test results show that the test rig can simulate the actual working conditions of components, also it can simulate the force curve of other working conditions, conform to the expectations functional requirements, with good reliability and practicality.