Dynamic Analysis And Optimization Of Flexible Manipulator Considering Joint Clearance

With the development of modern robot technology in the direction of low quality,high precision and fast speed,the flexible arm system with the advantages of high power-to-weight ratio,low energy consumption and high flexibility has been widely used.The existence of arm flexibility will produce elastic deformation and affect the running accuracy of the system.At the same time,the clearance in the system joint will also affect the dynamic characteristics of the mechanism,and the coupling effect between arm flexibility and joint clearance will further affect the dynamic characteristics and working performance of the system.Therefore,in order to study the influence mechanism under the coupling effect of arm flexibility and joint clearance,this thesis studies the dynamic characteristics of flexible manipulator considering joint clearance,which provides a theoretical basis for the stability and reliability research and structural design of flexible manipulator system.The specific research contents of this thesis are as follows :(1)Firstly,the joint clearance simplification method is described,and the axial clearance and radial clearance of the motion pair in the space state are characterized to obtain the joint clearance model.Secondly,the characterization methods of different joint normal collision force and tangential friction model are compared and studied,and the L-N normal collision force model and the velocity-related tangential friction model are determined as the characterization methods of joint contact collision force in this thesis.(2)The arm flexibility is described by the assumed mode method,and the dynamic model of the dual flexible manipulator is derived according to the Lagrange method.In order to introduce the clearance joint into the flexible manipulator system,the step function is used to introduce the contact collision force model of the clearance joint into the dynamic equation of the double flexible manipulator,and the dynamic model of the joint clearance and the flexible coupling manipulator is obtained,which lays a foundation for studying the influence of flexible clearance and other factors on the dynamic characteristics of the system.(3)Based on the dynamic model established in the third chapter,firstly,the comparison of ideal joint and clearance joint,the dynamic characteristics of rigid arm and flexible arm based on clearance joint are studied.Secondly,the influence of joint clearance size,arm flexibility,driving speed,system load size and friction coefficient on the dynamic characteristics of the system is studied in detail.The results show that different parameters have different effects on the contact collision force and axis trajectory of the joint and the displacement,velocity and acceleration of the end of the manipulator.(4)Finally,taking the flexible manipulator with multiple joint clearances as the research object,the multi-objective particle swarm optimization algorithm is used to optimize the joint clearance size,and the joint clearance design is completed,which provides a reference for the joint clearance design of the manipulator.