Research On Compliant Control Method Of Manipulator In Assembly Operation

The increasing complexity of the assembly task program and the complexity of the operation environment of the automatic chemical plant lead to the problems of safety,cost and compliance in the process of the interaction between the end of the manipulator and the environment.In this paper,the UR5(Universal Robot 5)manipulator is taken as the research object and the manipulator is in the assembly task.The control method of compliant assembly is studiedThe object of this study is six degree of freedom manipulator,so that it can reach any position in the workspace and meet the basic needs of assembly tasks.In addition,the joints of mechanical arms are all sing le rotary structures,and it is easy to establish kinematic and dynamic models.The six dimensional force sensor is usually installed at the end of the manipulator to obtain the external contact force,which leads to the increase of the cost of the assembl y operation system.In order to reduce the cost,this paper indirectly estimates the external contact force between the end actuators and the environment by the state variables of the manipulator’s joint.Because the common assembly tasks need to meet the position control and security detection in different directions,the collision detection and compliance control are the key problems to be solved in the assembly task.It is also the focus of the research.Based on the above description,the paper is divid ed into three parts:In the first part,the positive kinematics and differential kinematics of the UR5 manipulator are solved.Then the kinetic energy,potential energy and dynamic equations of the UR5 manipulator are derived on the basis of the kinematic parameters.The second part analyses the generalized momentum and the joint disturbance moment of the manipulator,and uses the generalized momentum to design the virtual force observer and then according to the observation and estimation.The dynamic threshold parameters are estimated and the collision detection is finally completed.The third part introduces the traditional impedance control and the improved position internal loop impedance control,and derives the sliding mode impedance control adopted in this paper.Finally,the simulation results by VREP-MATLAB combined with UR5 and mechanical arm body test show that the content of this paper solves the following problems: one is the virtual force force estimation observer and dynamic threshold based collision detection,to solve the assembly task cost and safety issues;two is the avoidance of impedance control sliding mode control strategy based on effective to solve the compliant manipulator end effector contact task and environment control device.