The Research On Stiffness Modeling And Optimization Of Multiple Coordinated Robots System

With the rapid development of robot technology,the robot work coorperatively with multi arms will become an important development direaction in the future.Robot stiffness is an important parameter of the robot,which indirectly affects the accuracy and operational performance of robot system.In this paper,the static stiffness and optimization of multi-arm coorperative system are deeply studied.First of all,this paper established the kinematic model for multi-arm coorperative system with the application of D-H method,constructed the motion Jacobian matrix and force Jacobian matrix in this sytem with the method of differential transformation and established the pose constraint equation of multi-arm's coordinated motion according to the form of their coordination task.Then,based on enhaced Monte Carlo method,this paper analysed the coorpative workspace of multi-arm system which lay a solid foundation for the follow-up research on system stiffness.This paper proposed the the concept of system static stiffness for multi-arm coorperative system,and developed the theoretical model.First,considering the influence of joint flexibility and arm flexibility,a comprehensive stiffness model of robot arm unit is established.Second,utilizing the concept of virtual inertia and mass stick,the multi closed loop deformation chains is decoupled,and the general stiffness model is established for multi-arm cooperative system.Third,based on proposed stiffness model,the static deformation simulation in ADAMS is carried out to verify the correctness of proposed stiffness model of multi-arm system.Finally,we anlysed the influence of loading position variation on system stiffness performance.Based on the proposed model,we analysed the stiffness performance of multi-arm robot system.Acoording to the type of applications,three kinds of stiffness performance indexes are proposed in this paper,including system stiffness ellipsoid,load distribution ellipsoid and task-oriented Stiffness ellipsoid coincidence.Taking the third stiffness index as the optimization object,we optimize the stiffness performance of the multi-arm machining system composed of three 6R industrial robots with Genetic algorithm.Based on UR5 and UR3 robot,the experimental platform of the dual arm cooperative system is established.By using the static deformation measurement method,we determined the joint stiffness of each manipulator.Then,a multi-arm cooperative system stiffness verification experiment is designed to prove that the static stiffness model for multi-arm cooperative system is effective.Finally,the model of clamping pose optimization for dual-arm robot system is established,and we proved the validation of the optimization scheme according to the experiment resulst.