Robust dynamic inversion control law design for civil aircraft take-off rotation

Abstract

The take-off phase of civil aircraft represents one of the stages with the highest risk and the most complex dynamic characteristics throughout the entire flight process. The pilot must manually input sidestick commands in an open-loop manner to control the aircraft’s pitch rate, which places the workload on the pilot. Improper operation by the pilot also poses serious safety risks during take-off. To address this issue, this paper designs a control law based on the nonlinear dynamic inversion (NDI) method, with the integration of the Robust Multi-Inversion (RMI) approach. Through desktop-based nonlinear simulations, the compensation effectiveness of the RMI-based robust term and the pitch rate tracking performance under take-off conditions with forward and aft centers of gravity are analysed under the same sidestick input conditions. The results indicate that the RMI method can compensate for the degradation of control accuracy induced by model mismatches in the dynamic inversion method. The control law designed based on the RMI method enables a consistent pitch rate under operating conditions with forward and aft centers of gravity. The proposed control law enables the aircraft to perform nose wheel rotation in accordance with the target pitch rate, even in cases involving horizontal stabilizer trim miss. In subsequent research, this approach can be further extended to investigate other take-off cases, thereby demonstrating considerable engineering application potential.