Design of new reaching law of sliding mode controller for permanent magnet synchronous motor
In order to solve the problem that the jitter caused by the function discontinuity in the tradition-al exponential reaching law and the approaching speed and jitter suppression of the traditional exponential reaching law cannot meet the requirements of the high-performance control system at the same time,a new sliding mode reaching law based on system state variables was proposed and applied to the speed and current controller of permanent magnet synchronous motor. By introducing the power terms of the system state variable and the hyperbolic sine of the state variable,the system state variable tends to the sliding-mode surface at two rates:isokinetic and exponential. The speed at which the system reaches the sliding-mode surface can be accelerated by this method. And when the system approaches the sliding-mode sur-face,the exponential term approaches zero,and the isokinetic term begins to play a key role in suppress-ing the jitter of the system. At the same time,the hyperbolic tangent switch function was used instead of the symbolic function to eliminate the jitter problem caused by the discontinuity of the function. This method can not only improve the speed of the system reaching the sliding-mode surface,but also effec-tively suppress the inherent jitter and improve the dynamic performance of the system. Simulation and ex-perimental results show that compared with the traditional exponential approach law,the new approach law can effectively reduce the speed overshoot of the permanent magnet synchronous motor when starting,improve the response speed of the system,and suppress the jitter of the system.
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