Control of Mutual Dragging Test for Motorized Spindle Based on Improved Direct Torque Control

Motorized spindle is widely used as the core functional part of CNC machine tools. In order to detect failures and correct in time before the products are released, shorten the reliability test cycle and reduce test cost, the development of reliability test system for motorized spindle has become one of the key technologies. The control method of spindle is crucial for the reliability test system and the commonly method is direct torque control. But the traditional direct torque control will cause large torque pulsation due to the application of the hysteresis controller. Aiming at this problem, this paper takes the motorized spindle mutual dragging test system as the control object and uses sliding mode variable structure control to improve the direct torque control. According to the principles of direct torque control and sliding mode variable structure control, the control equation of the improved method is established based on the switching functions of torque and flux. The control method is simulated under specific conditions in Matlab/Simulink. The simulation results show that compared with the traditional direct torque control method, the improved method can make the spindle reach the predetermined working state faster, make fluctuations of the flux linkage and torque smaller and make the control more accurate. The improved method is verified effective to control the motorized spindle.