LEAST-SQUARES SLIDING MODE CONTROL TRACKING OF SPACECRAFT LARGE-ANGLEMANEUVERS

A method for sliding mode control tracking of Euler parameter commands for large body angle maneuvers is presented. The closed-loop response s of the four attitude Euler parameters are specified as stable slidin g surfaces in the error-error rate Euler parameter phase planes. The m atrix coefficient of the typical discontinuous disturbance accommodati on portion of the sliding mode control law is chosen as the configurat ion dependent transformation between body-fixed coordinate angular vel ocities and the quaternion rates. This choice of control law parameter ization results in a globally asymptotically stable closed-loop respon se when the tracking performance matches the desired in a least square s sense. In addition, all inherent kinematic singularities are removed since the Euler parameters are directly tracked. Simulation results f or a typical satellite system are presented exemplifying theoretical d evelopment of robustness to mass property and initial condition uncert ainty.