Speed Tracking Control Of Direct Drive Permanent Magnet Synchronous Motor

With the development of AC servo technology, power electronics and control theory, direct drivePMSM servo system is becoming the mainstream of the high-end servo system. Direct drive systemremoved deceleration transmission mechanism between the drive motor and the load, increased indriving accuracy and drive shaft, so that the servo system has high positioning accuracy and fastfrequency response performance; However direct drive motor directly exposed to large changes in theload torque and the moment of inertia, so the servo system demanded high challenge on anti-interference and adaptation.In this paper, treat a direct-drive PMSM as the control object, design and build a direct-driveservo experimental platform, according to the special requirements of the nonlinear characteristics ofPMSM and direct drive occasions, choose nonlinear control-backstepping control to implementspeed tracking of the servo system. Also design a linear controller-PI controller based on classicalcontrol theory for the servo system simulation and experiment to compare the overall performance ofthe nonlinear control and linear control. The simulation results show that backstepping control canachieve accurate, rapid speed tracking and has a smaller overshoot, load torque or moment of inertiachanges have limited impact on the speed tracking, overall performance is superior to the PI control.On experimental platform, the load torque and the moment of inertia is unknown, so add loadtorque and moment of inertia identification mechanism to backstepping control, that is backsteppingadaptive control. The simulation results show that, under backstepping adaptive control, the loadtorque and the moment of inertia can be estimated accurately. Experimental results show that thebackstepping adaptive control can estimate the load torque accurately, realize speed trackingaccurately and quickly with a small overshoot, and the load torque or moment of inertia change has alimited impact on the speed tracking, so the performance of speed tracking is superior to PI control.Adaptive Backstepping controller doesn’t estimate electrical parameters and doesn’t have integralregulator, resulting in the steady-state error of current tracking; in addition, the change of load torqueimpacts the estimation of moment of inertia, but did not have a significant impact on the speedtracking performance.