Research On Friction Pair And Control Method Of A New Electro-Hydraulic Load Simulator

Electro-hydraulic load simulator(EHLS)is a semi-paysical equipment,which can repeat the torque load of steering gears.It has the advantages of saving cost and shortening product development cycle compared with traditional physical experiments,as well as a wide range of applications in the field of aerospace.Therefore,developing the high performance of EHLS has a very important profound impact on the development of our country aerospace industry.The performance of the EHLS depends on the ability of reproduce the load signal.While,the existence of redundant force has limited the traditional EHLS loading accuracy.In recent years,using the hardware structure and control strategies to reduce the redundant force can not fundamentally eliminate this interference.In this paper,the new electro-hydraulic load simulator(NEHLS)is based on the theory of friction load.It separates the test steering gear from the loader system,which can totally eliminate redundant force in theory.After synthesizing numerous related literature and reference materials home and abroad,it is clear that the purpose of this study is aimed at analyzing the factors that affect the performance of the loading system,solving the problem and improving the load performance of the simulator.Firstly,this paper elaborated the load theory of the NEHLS,calculated friction torque using different shapes of friction plates,proposed the uniform friction torque formula,verified the rationality of the formula and analyzed the influence of friction coefficients and size factors on the moment;Meanwhile,a mathematical of the loading system is established,which provides the theoretical basis for the thermal-mechanical coupled simulation analysis and the design of the controller.The NEHLS is based on the theory of friction load,to solve the problem of the friction coefficient instability caused by friction plate surface temperature rise during the friction loading process,a thermal-mechanical coupled simulation and experimental research was carried out.Through the different initial conditions simulation research,the causes of different temperature changes was analyzed.In order to record the changes of material temperature and friction coefficient,a friction plate experiment was carried out by pairing cast iron,steel and composites with each other.According to the mathematical model of the loading system,this paper analyzed the basic performance of the system and did a research on the influence of nonlinear factors and uncertain parameters on the system.The design of the back-step controller was used to improve the loading performance of the NEHLS.What is more,combining the back-step controller with adaptive controller,designing a back-step adaptive controller and improving the system time varying parameters can also weaken the influences of uncertainty factors in a deeper degree;Through the xPC Target real-time simulation of experimental systems,the extra torque which is caused by the mechanical mechanism and movement of the steering gear was tested when the input signal is zero;At last,a dynamic and static loading experiment was tested based on the different controller.