Research And Simulation Of Fractional Order Anti-disturbance Control Method For Large Antenna

The influence of disturbance on the control system exists everywhere.The tracking accuracy of large aperture reflector antenna is particularly affected by wind disturbance.With the increase of antenna size,the proportional-integral-differential(PID)control applied in the existing antenna system has been difficult to meet the requirements.Due to the complexity of antenna model and the randomness and time-variation of wind disturbance,the robust control algorithm designed by accurate model is difficult to applied in practice.Active disturbance rejection control(ADRC)and PID control combined with disturbance observer have become more promising anti-disturbance methods because they do not rely on accurate model and are easy to upgrade from the existing PID algorithm.With the development of fractional order theory,fractional order control shows its advantages in improving the dynamic performance and robustness of the system,which makes the research on fractional order anti disturbance control methods has theoretical and practical significance.Aiming at the typical large aperture reflector antenna,this thesis studies the fractional anti-disturbance control method in order to improve the performance of the antenna system under wind disturbance.First,the application of fractional order proportional-integral(FOPI)controller in antenna is studied.A FOPI controller for 35 m antenna is designed using the dominant pole method.The simulation results show that the FOPI controller can realize the stability of the antenna position loop system,and its fractional order integral operator has a significant effect on reducing the overshoot and setting time of the system.It is concluded that 0.8-order FOPI is superior to integer order PI in overshoot,setting time and error integral criterion.Second,for the antenna system with known model information,a disturbance observer is designed to resist wind disturbance,and a genetic algorithm based on parameter stability region is proposed to optimize FOPI parameters.The integer order disturbance observer and fractional order disturbance observer are designed for 35 m antenna.The stability region of fractional order proportional-integral-differential(FOPID)is calculated,and the parameters of FOPI are designed by taking the stability region as the optimization constraint of genetic algorithm.The simulation results show that both the disturbance observer and the fractional order disturbance observer can effectively suppress the wind disturbance of the antenna system.The dynamic performance of FOPI optimized by genetic algorithm based on parameters stability region is no overshoot.The combination of optimal FOPI and disturbance observer has good comprehensive performance.Then,considering the disturbed system with unknown model information,a fractional order active disturbance rejection control(FOADRC)is proposed,and its stability and frequency domain characteristics are studied.Fractional integration is introduced into the extended state observer to improve its disturbance estimation ability,and proportional-differential(PD)is combined to compensate the disturbance.The convergence of the fractional order extended state observer(FOESO)is proved using Lyapunov method,and the parameter selection conditions satisfying the bounded input bounde output(BIBO)stability of the system are given through the equivalent transfer function.The internal relationship between FOADRC and fractional order proportionalintegral-differential(FOPID)is given,moreover the suppression ability of FOESO and FOADRC to external disturbance and their anti-noise characteristics are systematically analyzed.Finally,the FOADRC is applied to the antenna system,and the calculation method of FOADRC stability region and the differential evolution algorithm combined parameter stability region are proposed to optimize FOADRC parameters.The FOADRC stability region of 35 m antenna is calculated by D-partition method.Taking the stability region boundary as the optimization constraint of differential evolution algorithm,the parameters of FOADRC are designed.The simulation results show that the FOADRC designed by the transition process and parameter stability region combined with differential evolution algorithm can achieve the comprehensive performance of small overshoot,fast setting time and small error integral criterion.It has strong robustness to the perturbation of model parameters and the increase of wind disturbance.