Research On Force Compliance Control For Multi-robot Collaborative Grinding

Compared with single robot,multi-robot cooperation system has more flexible operation ability,larger load and working space,and it can realize more complex operation tasks,so it has broad application prospects.In this paper,aiming at the industrial task of multi-robot collaborative grinding,the researches of grinding process trajectory planning,force compliance control and multi-robot coordinated control are mainly carried out.The simulation model and experimental platform is built to verify the control algorithm and test the grinding experiment.In order to solve the problem of tool path planning for grinding process,an tool path generation method based on STL model is proposed.The tool path with approximate equal spacing in three-dimensional Cartesian space is obtained by adaptively adjusting the distance between cutting planes.The Bezier curve is used to fit the boundary curve formed by two vertices of triangular mesh.The intersection point between the section plane and the boundary curve is quickly obtained by using the bisection idea.It not only improves the fitting accuracy,but also improves the calculation efficiency.Aiming at the problem of force tracking in uncertain contact environment,the limitation of traditional impedance control for force tracking on complex curved surface is analyzed,and a dynamic adaptive impedance control method based on integral compensation is proposed.An adaptive law based on integral compensator is designed to compensate the uncertainty of environmental position and eliminate the force tracking error caused by the error of environmental information estimation.The problem of force tracking overshoot is solved by using an exponential decay function to adjust the adaptive update rate dynamically.A force signal filtering method based on Kalman filter is used to eliminate the high frequency noise in grinding force control,and the gravity compensation method of robot end tool is introduced to obtain accurate contact force.Aiming at the closed-chain constraints in the tight coordination operation of dual-arm,the decomposition strategy of position,velocity and acceleration is introduced.The dynamics of operation target is analyzed,and the operation force of end-effectors is decomposed into the internal force and external force of the system through the force constraint relationship.Then,the dual arm coordinated compliance control method is studied.Aiming at the task of dual-arm holding an object interacting with the external environment,a dual loop impedance control strategy is introduced to realize the internal and external force tracking of the dual-arm cooperative system.Finally,a multi-robot cooperative grinding system experimental platform is built by UR5 manipulators and a series of grinding experiments are completed.The experimental results show that the force compliance control method proposed in this paper has a good performance of force control in multi-robot cooperative grinding operation.