Adaptive Second Order Sliding Mode Control For Direct Drive NC Rotary Table

In the thesis, taking Liaoning Province National Nature Science Foundation “Study onDirect Drive Numerical Control (NC) Rotary Table High Stiffness Precision ControlStrategy”(No.201133029) as background, according to the characteristic of the direct driveNC rotary table system and the requirements of strong robustness and high precision, theadaptive control and second-order sliding mode control with the use of the uncertaintiespresent in the system studied. The main contents are as follows:For the characteristics of the ring permanent magnet torque motor used in direct drivenumerical control (NC) rotary table suffering from the effect of load disturbances andparameters variations, and based on the ring permanent magnet torque motor mathematicalmodel is established, in the thesis, using two control strategies designed controller to solvethe problem of uncertainty in the servo system.The first method: the twisting algorithm of the second-order sliding mode controller isdesigned. And the introduction of the adaptive control is the control gain of the twistingcontrol law with dynamic adjustment. This method retains the advantages of the traditionalsliding mode control invariance, not only attenuates chattering of the traditional slidingmode control, and to overcome dependence of control gain required to determine theboundaries of the uncertainty. Simulation results show that the designed strategy enablesservo system to have strong position location performance, and to have very strongrobustness against uncertainties of the system, simultaneously attenuates chatteringeffectively.The second method: the second sliding mode controller is designed by exponentialreaching law. Exponential reaching law can ensure that system track reaches a smallertrack speed sliding surface, and maintain a good dynamic quality. Then aiming at the faultsthat the sliding mode control system is difficult to determine the bounds of uncertainty,variable parameters and external interference of the system are be identified by adaptivelaw. To dynamic adjust the control gain of control law. Simulation results show that the designed controller enables system to have strong position location performance,robustness, and eliminates chattering.