| Electric drive manipulators are widely used in handling,welding,sheet metal bending,medical and other fields.It is driven by the joint servo system to realize the operation of the manipulator.However,due to the existence of flexible links at the joints,there is vibration in the system,which seriously affects the position control accuracy.In this thesis,the mechanical vibration problem caused by the flexibility of the manipulator joint is studied.The variation law of load torque when the flexible joint manipulator moves vertically and horizontally was analyzed,and a mathematical model of the servo system of the flexible joint manipulator considering variable stiffness coefficient and large reduction ratio was established.Through the system control block diagram and transfer function,the frequency domain analysis was used.Method and electromechanical equivalent circuit method were used to analyze the causes of system vibration.The influence degree of parameters such as stiffness coefficient and moment of inertia on the system vibration was analyzed.Aiming at the problem of system vibration caused by the existence of flexible links,a vibration suppression strategy based on dynamic torque feedback was proposed.Based on the frequency domain method,the parameter tuning rules of the speed loop controller with the flexible link servo system were given.The position loop controller adopts the compound control strategy of proportional speed feedforward,and based on the engineering method,the parameter tuning rules of the position loop controller were given.On the basis of the original three-loop control,the real-time shaft torque was obtained through the designed shaft torque dimension reduction observer.The difference between the electromagnetic torque and the shaft torque constitutes the dynamic torque,and the dynamic torque was fed back to the speed loop through the feedback coefficient output,and introduce a dynamic torque controller to form a dynamic torque closed-loop to realize four-loop control.The transfer function from electromagnetic torque to motor speed after introducing dynamic torque feedback control was deduced,and the vibration suppression mechanism was analyzed.Through simulation analysis and verification,vibration suppression effect is obvious,disturbance rejection ability is strong,position control error is small,meet the requirements of the system operation.In order to solve the problem that the speed fluctuation of the manipulator is still large due to the real-time load torque change in the process of vertical movement,the rotational speed ring variable gain PI control method was adopted based on the dynamic torque feedback control strategy introduced previously.Based on the rotational speed ring axial torque disturbance model,the relationship between the rotational speed ring torque and the parameters of the rotational speed ring PI controller was obtained based on the frequency domain method.The rotational speed ring variable gain PI controller was designed and the adjustment strategy of PI parameters was given.The simulation model and simulation results show that the speed fluctuation is small,the disturbance rejection ability is strong,and the position control error is small,which can meet the requirements of the system operation. |
