Study On Dynamic Simulation And Control Problems Of Mechanism With Bearing Clearance

With the rapid development of technology,the demands for the stability and reliability of mechanical system are getting higher and higher,but the clearance may lower the stability and kinematic precision of the mechanism.To lower the influence of clearance on the mechanism,the mechanism is usually lubricated or controlled.However,there are few studies on the control issue of lubricating mechanism,meanwhile,the dynamic characteristics of lubricating joint clearance are relatively complicated,and its system modeling,value calculation,and dynamic simulation are very difficult.Aiming at this problem,this paper proposes a new thought to simply and effectively understand the dynamic characteristics of the rotary articulated mechanism with lubricating clearance,takes the slider-crank mechanism as an example to discuss the influence of clearance and lubrication on the dynamic characteristics of multi-body mechanism,and further make error analysis of the lubricating mechanism and motion compensation control.The main contents of this paper are as follows:(1)This paper introduces the research status of clearance-containing mechanisms at home and abroad.Further description of the joint clearance includes vector model and mathematical model of clearance,contact force model and friction model and fluid dynamic model at clearance.In this paper,taking the slider-crank mechanism with clearance as an example,using "two state" model to introduce the vector model and mathematical model of the joint clearance,to establish kinematics and dynamics equations of mechanism.Using Simulink design the dynamic simulation model of the slider-crank mechanism with clearance.Its dynamic characteristics are obtained and compared with the ideal mechanism.The results show that: the existence of clearance makes the slider acceleration,link angular acceleration,clearance force and crank torque appear to fluctuate violently,and there is a large deviation from the ideal characteristics,but the clearance has lower influence on the slider displacement and velocity.(2)Lubrication is introduced on the basis of joint clearance,and a new idea is proposed on how to easily and efficiently solve the dynamic characteristics of rotating rotary hinge mechanism with lubrication clearance.Taking the crank-slider mechanism as an example,the kinematics equations,dynamics equations and Simulink simulation models of the mechanism are established according to the idea in this paper.The simulation results show that the dynamic performance of the mechanism is significantly improved when considering lubrication,and the dynamic curve is more smooth and close to the ideal situation,the stability and reliability of the organization have been significantly improved.At the same time,it also illustrates the correctness and feasibility of the idea.The effects of clearance sizes,fluid viscosity and crank rolling velocity on the dynamic performance of the mechanism are further discussed.The results showed that: the larger of clearance,the more frequent the components and the more violent the vibration.With the increase of the viscosity coefficient,the dynamic performance of clearance force,link angular acceleration and the slider acceleration are obviously improved.As the crank rolling velocity increases,the curve becomes smoother and closer to the ideal model.(3)In order to further meet the requirements of higher motion accuracy,the motion compensation control of the mechanism is carried out by the incomplete differential PID controller on the basis of considering the lubrication and clearance.The simulation results show that the displacement error and velocity error of the mechanism are greatly reduced after the control,which greatly improves the motion accuracy and stability of the mechanism.