Fractional-Order Sliding Mode Control for Maglev Rotary Table Based on Disturbance Compensation
In view of the high-precision motion control problem of the maglev rotary table with nonlinearity,coupling,and uncertainty,a fractional-order sliding mode control method based on a nonlinear disturbance observer was proposed to improve the tracking accuracy.Firstly,based on the electromagnetic force model of the system and the dynamic decoupling method,the dynamical model of the six-degree-of-freedom maglev rotary table system was constructed.Secondly,a nonlinear disturbance observer was designed to estimate the lumped disturbance including system error,coupling term between six degrees of freedom,and external interference.It was proved that the estimation error was bounded and could be made arbitrarily small.Then,a fractional-order sliding surface was proposed in the discrete domain,where the fractional power function was used instead of the traditional symbolic function to suppress jitter,and the fractional calculus was introduced to reduce the tracking error.Finally,a fractional-order sliding mode control strategy with finite time convergence was designed,and the stability of the closed-loop system was proved by Lyapunov stability theory.The experimental results reveal that compared to the integer-order sliding mode control method,the proposed method reduces the root mean square of tracking error for triangular waves by 12.8％,16.8％,and 23.7％for the two horizontal degrees of freedom and the rotational degree about the vertical axis,respectively,while the maximum tracking errors are reduced by 9.26％,13.00％,and 33.20％respectively.When tracking a circular trajectory,the mean square values of tracking errors for two horizontal degrees of freedom are decreased by 6.39％and 12.40％,and the maximum tracking errors are reduced by 9.90％and 12.10％,respectively.
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维普
