Coordinated Control Of Multi-joint Robot Drive System

Robot’s joint driven system is a complex and strong coupling nonlinear system.Permanent Magnet Synchronous Motor(PMSM)is choosen to be the driven motor of the robot’s joint driven system because it has the characteristics of simple structure,high accuracy and high operational reliability.So the performance of the robot’s joint driven system is defined by the performance of the PMSM.This paper divides robot’s driven system into two process of dynamic and steady state.Signal controller and energy controller are designed.Choosing coordination control strategy to design coordination controller of robot’s joint driven system.Firstly,the purpose and significance of this research are introduced.Also the current research state of the robot and PMSM at home and abroad are simply introduced.Derived the equation of kinematics,inverse kinematics,dynamics of the robot and the mathematical model of PMSM.Secondly,aiming at the poor performance of the robot’s joint driven system,sliding mode control is employed to be the controller for dynamic process of the system.Therefore Port-controlled Hamiltonian(PCH)control is proposed to control the steady state process of the system.Next,coordination control strategy is proposed to ensure two methods play a major role in different time.So,coordination control can overcome their own shortcomings when they play a major role alone.The simulation results show that coordination control has the advantages of both methods and overcome the shortcomings both of them.Thirdly,in order to solve the problem how to combine the robot dynamics with the control of driven motor,coordination control of proportional differential(PD)gravity compensation and PCH is proposed.In addition using current transformation and designing backstepping controller of current loop to combine robot dynamics with the control of PMSM.The simulation results show that not only can coordination control reach the reference position fastly but also has a better steady state performance and has little influences by parameters.Forthly,aiming at the problem that the load torque is unknown in reality robot’s joint driven system,coordination control of PD gravity compensation and PCH is designed.Then the load torque observer is designed based on the error of the position.The simulation results show that the observer can observe the load torque accurately and the system fluctuates less when load torque disturbance occurs.To summarize,for the purpose of solving the poor performance of robot’s joint driven system,how to combine the robot dynamics with the control of PMSM and the system which load torque is unknown.This paper proposed the coordination control of sliding mode and PCH to improve the performance of the system.Next coordination control of PD gravity compensation and PCH is presented to combine robot dynamics with the control of PMSM though current transformation.Finaly the load torque observer is designed to solve the situation that the load torque is unknown.Coordination control system has the ability of resisting torque disturbance.