Enhanced disturbance rejection control based test rocket control system design and validation

Test rocket has been an attractive platform for scientific and educational experiments during the last several years. Aiming at providing a potential engineering application of disturbance rejection control to aircraft control system design following traditional frequency-domain methods, this paper presents an enhanced disturbance rejection control of two degrees of freedom based on H_∞ synthesis and equivalent-input-disturbance (EID) for 3-axis attitude controller design of a small solid test rocket. The establishment of an EID system regards the mismatched disturbance as a 'total disturbance' in the input channel for compensation. The H_∞ synthesis based on classical frequency-domain analysis is applied to the design of a disturbance filter and of a composite feedback controller. In terms of the controller design, the system including the filter is considered as a whole to guarantee the stability of the overall system without separate design. Furthermore, the proposed method is successfully applied to the 3-axis attitude controller design of the test rocket by modeling the nonlinear dynamics as linear EID formulations of attitudes. The simulation and validation including Monte-Carlo bias simulation and comparison with active disturbance rejection control (ADRC) based design, Hardware-in-the-Loop (HIL) simulation and flight test are conducted specifically. The results verify the effectiveness of the proposed method with excellent performance and practical prospects.