Analysis Of Dynamic Characteristics Of Manipulators Considering Multiple Clearances And Flexible Arms

With the extensive use of space manipulators in the aerospace field,the efficiency and safety of space station construction,operation and maintenance have been greatly improved.With the increasing complexity of space missions,the development of high-performance robotic arms becomes increasingly important.Space manipulators generally consist of a plurality of lightweight slender rods.Therefore,the flexibility of the arm can cause vibration when the robot arm is moved in a large range,which poses a great challenge to the control accuracy of manipulator system.In addition,impact collisions at the joint clearance of the arm can also cause vibration.The robotic arm generally contains multiple flexible arms and joint gaps.The coupling between elastic deformation of flexible arm and elastic deformation of flexible arm,the coupling between gap and gap,and the coupling between the gap and elastic deformation of flexible arm have great impact on the dynamic characteristics of the system.Therefore,this paper analyzes the dynamic characteristics of the multi-gap and multi-flexible arm manipulator system to provide theoretical guidance for the stable control and operation of the manipulator arm.Firstly,based on the theory of flexible multi-body system dynamics,the dynamic model of flexible manipulator system is established through modal synthesis method.In order to introduce the influence of joint clearance,a step function is introduced to embed the established gap mathematical model and vector model,which promotes the dynamics model of flexible manipulator system with clearance.The formation of system dynamics model for flexible manipulator with clearances is fully prepared for analyzing the dynamic characteristics of multi gap and multi flexible manipulator system.Because of the existence of clearance,collision between shaft and bearing will be caused.In order to reasonably describe the collision characteristics at the gap,the Coulomb friction model and the nonlinear spring damping model are respectively used to describe the normal and tangential friction forces generated by the clearance collision.Secondly,based on theoretical support and the established models,the paper makes the planar two-degree-of-freedom space manipulator the object of study.The influence ofdifferent elastic moduli and the number of different flexible arms on the dynamic characteristics of the space mechanical system were respectively analyzed,as well as influence of different clearance sizes and number of gaps on the system dynamics of the manipulator.Finally,the influence of the coupling between a single gap and a single flexible boom on the dynamic characteristics of the manipulator system and the effect of the number of different gaps on the dynamic characteristics of the manipulator system are analyzed,which provides some help for improving the operation stability of space manipulator.