Interference Cancellation And Control Based On Back Recursive Observer

Sinusoidal disturbance is a common phenomenon in real control systems,which affects the control accuracy of the system and even leads to the instability of the system.A method used to eliminate and supress disturbances based on output feedback has been proposed,utilizing an auxiliary filter to construct virtual interference,and the relationship between the interference frequency,virtual interference and actual input interference has been obtained by the reverse recursive method.The disturbance observer and feedback controller parameters have been adjusted under the disturbance observer control structure.As a result through the analysis of the stability of the compound closed loop system,the control performance of the disturbed system has been guaranteed.The innovative research of this thesis is listed as follows.(1)Considering a series of stable systems with known sinusoidal disturbances described as a modeled external system in the input channel,the inverse recursive disturbance observer structure has been designed.And also the interference characteristics have been directly derived from the output feedback.Meanwhile,the relationship between the interference frequency,the virtual disturbance and the actual input interference have been analyzed to avoid the solution of the linear matrix inequalities.The interference estimation has been gained through backstepping and then compensated in the feed forward channel,and the feasibility of the control strategy has been verified by simulation.(2)A class of compound control problems of unstable systems with multiple interferences have been discussed.Multiple interferences,including sinusoidal harmonic and unmodeled dynamics,are described as a modeled external system and an uncertain bounded function respectively.Aiming at the critical unstable poles in the controlled plant,the pre stabilizing controller has been added to the internal model controller to ensure the internal stability of the system.According to the separation principle,the disturbance observer structure has been used to realize the estimation and compensation of sinusoidal disturbances.The correctness and effectiveness of the control structure havebeen verified by simulation as well.(3)The estimation and cancellation of the sinusoidal disturbance of the unknown frequency have been introduced into the control structure on the basis of the disturbance observer,with the applicability of the inverse recursive interference observer being further extended.Via the structure of the nonlinear observer,the unknown constants related to the disturbance frequency have been estimated and the relationship between the unknown constant and the disturbance deduced theoretically,by which the effect of sinusoidal disturbances with unknown frequency on the system has been eliminated.Accordingly the influence of the unknown frequency of the sinusoidal disturbance on the system has been offset.Ultimately the system can be guaranteed to be asymptotically stable by combining a stabilization controller.