Research On The Sliding Mode Variable Structure Method To Improve The Reaching Law

The difference between sliding mode variable structure control and other control lies in the discontinuity of its control,the control system performs small amplitude and high frequency up and down switching motion under the expected trajectory,it is this characteristic that makes the system show good robustness,but this robustness is only reflected in the sliding mode,and this switching motion will cause the motion trajectory of the system to shake back and forth around the switching surface,resulting in chattering problems.The presence of chattering can affect the accuracy of the control and increase the energy consumption of the system,even if the parts of the system will be damaged.In order to improve the chattering problem in sliding mode variable structure control,a method is proposed of the improve fast reaching law,the method consists of two parts,a power function term and an exponential function term,and theoretically analyzes the proposed approach law,the designed reaching law has a faster convergence speed whether it is away from the sliding mode and the near sliding mode,and the reaching law can converge to the sliding mode for a limited time.By demonstrating that the reaching law has a second-order sliding model characteristic,the speed at which the system approaches the sliding mode is zero,which czan effectively reduce the chattering of the system.When there is external interference in the system,it can converge to a neighborhood of the equilibrium state.And the Buck converter is taken as the controlled obj ect,and its control performance is simulated and analyzed,the fastness and effectiveness of the reaching law are verified.Based on the above the improved fast approach law,combined with the control idea of global fast terminal sliding mode,a global fast terminal sliding mode controller based on the improved fast reaching law is designed,the controller not only has the idea that the global fast terminal sliding mode converges to the equilibrium zero point in a finite time,but also has the strategy of the improve fast reaching law to reach the sliding mode for a limited time,the controller was applied to the actual control system for simulation,and its effectiveness was analyzed.Combined with the theoretical knowledge of fractional calculus,a fractional order reaching law is designed,and the traditional integer-order sliding surface is reconstructed into a fractional sliding surface.The controller of the Buck converter is designed by using the fractional sliding surface,compared with its integer-order controller,simulation results demonstrate the effectiveness of the controller.