Application Of Fixed-order H_∞ Controllers In Antenna Servo System

The increasingly complex application scenarios of the antenna system put forward higher and higher performance requirements for the antenna servo system.However,the mechanical structure of the antenna system generally has flexible resonance characteristics,which limits the improvement of the antenna servo performance.Since the H_∞ controller can effectively suppress the flexible resonance,its application in the antenna servo system is gradually paid more attention.However,the problem of low numerical reliability caused by the high order of the H_∞ controller make it seldom used successfully in the antenna servo system.In order to design the H_∞ controller that can be applied to the antenna servo system with high reliability requirements,the research of the fixed-order H_∞ controller is of great significance.This paper focus on the application of the fixed-order H_∞ controller on the 0.8-meter-diameter airborne antenna provided by the 54th Research Institute of China Electronics Technology Group Corporation.Firstly,based on the identified velocity loop model of the azimuth axis of the airborne antenna,the full-order H_∞ controller is designed.However,the full-order H_∞ controller has the problem of low numerical reliability and is difficult to apply to the antenna servo system.Then,the common non-H_∞-performance-preserving and H_∞-performance-preserving fixed-order H_∞ controller design methods are analyzed through simulation.Due to the conservativeness of the common H_∞-performance-preserving methods,their performance is very limited;the non-H_∞-performance-preserving methods do not take the closed-loop H_∞ norm as the design index,so it cannot guarantee the H_∞ performance of the controllers,but due to its good performance,its design ideas are of reference significance.After that,based on the design ideas of non-H_∞-performance-preserving methods,this paper proposes two new fixed-order H_∞ controller design methods,based on two H_∞-performance-preserving weighted controller reduction conditions and bounded real lemma.These two new methods use the LMI optimization method to obtain the fixed-order H_∞controller,which has less design conservativeness.Numerical simulation verifies the effectiveness of the two methods.Finally,based on the new discretized algorithm,the H_∞robust controller of the airborne antenna azimuth axis velocity loop is designed.The experimental results show that the H_∞ robust controller of the new algorithm is better than the full-order H_∞ robust controller in the actual antenna servo system.