Normal-matrix-based nonlinear H∞ attitude tracking for spacecraft

Purpose - The purpose of this paper is to develop a novel nonlinear H infinity control approach for the nonlinear multivariable attitude tracking of rigid spacecraft. Design/methodology/approach - Based on the transformation of the attitude tracking problem into quaternion error stabilization, the feedback control law is developed by using the normal matrix control theory with the inverse-additive perturbation description of systems uncertainties, and the Hamilton-Jacobi-Isaacs (HJI) partial differential inequality is employed for providing the nonlinear Ho. control criteria for the proposed control law. The onboard recursive least squares (RLS) estimation algorithm of inertia tensor is used for the further improving of the normal matrix property of the control system. The RLS algorithm is simple enough for the spacecraft borne computer. Computer simulation is performed to demonstrate the effectiveness of the control law proposed. Findings - By the normal matrix control theory, the nonlinear H infinity control law for attitude tracking is developed without solving the HJI inequality and with the inflight estimation of inertia, the proposed control law is adaptive and robust to the variation of mass properties, and its normality is further improved. Research limitations/implications - The paper is limited in rigid spacecraft with slowly changing mass property. The flexible influences are not considered. Practical implications The paper provides an alternative to the spacecraft researchers/engineers for developing the robust attitude control law with a simple structure and self-tuning ability. Originality/value - The paper is the first to provide a robust control based on the normal matrix approach, the HJI inequality, and the estimation of inertia.