Research On Loading And Control Method Of Friction Torque For Servo Test System

The servo loading test system(namely,load simulator)is mainly used to simulate the physical environment of the key mechanism of the aircraft(steering gear).It is widely used in the aerospace field.It mainly simulates various load indicators of the steering gear,such as hinge torque,friction torque,installation stiffness,etc.Among them,the friction torque is a key indicator of the load simulator.In the actual test,the nonlinearity of friction will lead to the fluctuation of loading torque.At the same time,its loading accuracy is affected by the coupling characteristics of friction and multi-factors.Therefore,research on the loading and control method of friction torque according to the characteristics of working conditions has become one of the research hotspots of servo loading test system.The thesis relies on a scientific research project of an aerospace institute and takes the hydraulic friction loading system as the research object.In order to improve the loading accuracy of the friction torque,a pressure closed-loop friction torque loading control method based on the friction model is proposed in this paper.Then this method is analyzed and verified.First,the characteristics and application environment of each loading method is analyzed by investigating the friction loading methods in many engineering fields.And then determine the best loading method for this servo loading test system.The thesis also studies the friction loading characteristics and qualitatively analyzes the relationship between friction loading and testing factors(materials,pressure,speed,etc.).Secondly,the Loading control method of pressure closed-loop friction torque based on friction model is proposed,in order to solve the problem of constant loading of the friction torque of the servo loading experimental system.The effect of the torque sensor link on the system loading accuracy is analyzed,and the friction torque loading method and principle is described.And the selection of each link of the hydraulic friction loading system is determined.Thirdly,the Stribeck model is selected to describe the friction torque loading characteristics and is modified according to the operating conditions of the system;Based on the revised friction model,the Genetic Algorithm(GA)and Particle Swarm Algorithm(PSO)are used to conduct a comparative study of friction parameter identification,and Particle Swarm Algorithm is confirmed to have a better identification effect according to simulation.Then,mathematical modeling is carried out for each link of the friction torque loading system,and the design and algorithm derivation of PID,fuzzy PID and backstepping adaptive controller are carried out based on the mathematical model.And the friction torque constant value loading simulation is performed in Matlab / Simulink.Comparative study of the analysis of the control effects of different controllers is carried out.Finally,the servo loading experiment system is designed according to the loading index of the actual project,and the physical processing of the mechanical and hydraulic parts is basically completed,and the measurement and control system is built.After comparative analysis,the Stribeck model can satisfy the description of the friction characteristics of the friction torque loading.The backstepping adaptive control strategy can achieve the accurate loading of the positive friction pressure.The proposed pressure closed-loop friction loading method based on the friction model can effectively improve the spindle stiffness and promote dynamic loading performance,achieving fast and accurate friction torque loading.