Sliding-mode control system for the three-axis attitude control of rigid-body spacecraft with unknown dynamics parameters

Sliding-mode control is shown to be an advantageous new approach to the three-axis attitude control of rigid-body spacecraft in which accurate pre-launch estimation of the dynamics parameters is unnecessary. The control-system accuracy is shown to depend almost entirely on the attitude-measurement system, control-actuator misalignments and scale-factor errors being permitted. If the control actuators are operated in hot redundance, actuator failures are permitted while guaranteeing uninterrupted service from the control system. Extreme stiffness is also presented to disturbance torques. Continuous control actuators are assumed. Control smoothing integrators, introduced to facilitate continuous control action with negligible limit cycling, are treated as part of the controlled plant by including the three angular acceleration components in the state feedback. Closed-loop response independent of the dynamics parameters for a demanded attitude may be designed via pole assignment. The new ideal multivariate c...