Modeling And Compensation Of Friction Torque Of Joint Rolling Bearing In Low Gravity Simulator

With the development of manned space engineering and the emergence of deep space exploration missions,the current low-gravity environment simulation method cannot satisfy a large number of ground-based space mission verification and astronaut training.Considering that the current neutral pool simulation weightlessness,suspension method simulation weightlessness,and free fall method simulation weightlessness have the disadvantages of high manufacturing and maintenance costs or limited simulation time and simulation freedom.A passive model based on conservation of potential energy is proposed.Low-gravity environment simulation system.The system has the advantages of low manufacturing and maintenance costs,unlimited simulation time,high safety,and can simulate 0～1g arbitrary low-gravity environments.The development of this equipment is of great strategic significance to the development of aerospace engineering.The low-gravity simulation device described in the article is designed based on the principle of mutual transformation between the elastic potential energy of the spring system and the gravity potential energy of the mechanism and the weightless object and maintains the total potential energy conservation.The technical difficulty lies in how to ensure the lossless transmission of potential energy,that is,how to eliminate it.In the process of potential energy transfer,the low-gravity simulation device joint rolling bearing friction force loss of potential energy.In order to solve the above problems,a low-gravity simulation device joint rolling bearing friction torque modeling and compensation scheme is proposed.In order to quantitatively analyze the influence of joint bearing friction on the dynamic characteristics of the low-gravity simulation system,the principle of the lowgravity simulation system is first derived based on the conservation of potential energy,and the mapping relationship between the spring system stiffness and the system dynamic parameters is derived;combined with the second type of Lagrange The equation method derives the dynamic equations of the low gravity simulation system,and simulates and analyzes the friction of the joint bearing.In order to establish the friction torque model of the bearing,a set of bearing friction torque measurement device was designed,and the bearing friction torque value under different positive pressure was obtained through experimental measurement,and the function model between the bearing friction torque and the positive pressure was obtained by fitting;Aiming at the problem of inaccurate measurement caused by the coupling of force sensors in the process of bearing friction torque measurement,the error identification method of forward and reverse rotation to eliminate friction and the error identification method of BP neural network are proposed.Because the friction torque compensation system of the joint bearing of the low gravity simulation device needs to meet the torque following and position following,a set of torque compensation scheme based on the motor-force sensor combined control system is designed,and the PID control algorithm of the motor controller is designed,and the compensation scheme and control algorithm are verified experimentally on the pendulum device.Secondly,the above-mentioned friction compensation scheme and compensation algorithm are applied to the secondgeneration low-gravity simulation device.The structure of the joint bearing friction torque compensation device is designed according to the structural characteristics of the low-gravity simulation device,and the motor is controlled according to the structural characteristics of the compensation device.The device has been redesigned;in response to the problem that the positive pressure of the joint bearing cannot be obtained through the sensor in the physical experiment of the low-gravity simulation device,it is proposed to obtain the bearing force of the low-gravity simulation device under different joint configurations through simulation before the compensation experiment.A scheme of bearing force offline data set is established;finally,the effectiveness of the above-mentioned bearing friction compensation scheme and compensation algorithm in the friction torque compensation of the joint bearing of the low gravity simulation device is verified by simulation.