Study On Hydraulic Transmission And Control System Of Torsional Vibration/fatigue Testing Machine

Torsional vibration / fatigue testing machine is used to conduct static and dynamic tests and torsion fatigue tests on the flexible shaft parts (such as flexible coupling). It is important testing equipment for researching the performance of flexible shaft parts, and it is widely used in shipbuilding, automobile industries, aerospace departments and other related laboratory of universities and research institutes. It plays an important role on the research of new materials, improvements of process, improvements of product quality, reduction of costs, reinforcement of product safety and reliability.The research is based on a 30kN·m torsional vibration / fatigue testing machine R&D project. The intension of study is to design the power source of torsional vibration / fatigue testing machine, namely design hydraulic servo system, which provide the axial feed force for tension and compression tests and torsion tests. Hydraulic servo system is an important part of testing machine, also a key factor in determining test performance and accuracy. When hydraulic servo system is designed, the static design specifications shall be satisfied, besides, better dynamic performance is also necessary. In addition, when testing machine is used to conduct static and dynamic performance test and torsional vibration fatigue test on flexibility shaft parts, for the difference of specimens, testing conditions and system conditions, some system parameters will change in a certain range. Therefore, based on the static design of the system, it is necessary to analyze the effects of system parameters on the control system, which provides a theoretical basis for the design of control program.The research object of paper is hydraulic servo system of testing machine. Firstly, according to the system technical requirements, hydraulic system circuit is designed. Hydraulic power mechanism has been optimized so that the output characteristics of the hydraulic power matches load characteristics to the best. The main parameters of components are calculated and parts type is selected. Secondly, the mathematical model of angle and torque control system is built. With the MATLAB/Simulink, dynamic simulation of the two control systems is performed. Effects of the main variable parameters on the control system and system bandwidth are analyzed, and the torque control system is corrected. Finally, with the AMESim, the physical model of testing machine control system is established and some nonlinear factors are added. Then dynamic simulation of control systems is performed. Effects of the main variable parameters on the control system and system bandwidth are analyzed, and the torque control system is corrected. Meanwhile, by comparing two simulation results the control system mathematical model is verified. Simulation results show that servo amplifier gain is the main factor affecting system performance in the control system. And servo amplifier gain and load torsional stiffness are the most important factor affecting system performance in the torque control system; When the parameters change, the trend of system amplitude diagram in AMESim simulation is same with the MATLAB simulation results, which shows that control system mathematical model could better express the characteristics of the system. On the condition of same parameters, the system bandwidth in AMESim is less than when the system bandwidth in MATLAB simulation; Angle control system can meet the system bandwidth requirements. Torque control system stability is poor, and the bandwidth can not meet the technical requirements. After correction, the torque control system can meet the system bandwidth requirements; design of hydraulic servo system can achieve the system's static targets and meet the system bandwidth requirements.