Gain-scheduled inverse optimal satellite attitude control

Despite the theoretical advances in optimal control, satellite attitude control is still typically achieved with linear state feedback controllers, which are less efficient but easier to implement. A switched controller is proposed, based on inverse optimal control theory, which circumvents the complex task of numerically solving online the Hamilton-Jacobi-Bellman (HJB) partial differential equation of the global nonlinear optimal control problem. The inverse optimal controller is designed to minimize the torque consumption pointwise, while imposing the stabilization rate of a linear benchmark controller. The controller is then modified by gain scheduling to achieve a tradeoff enhancement compared with the benchmark controller, while maintaining torque saturation limits. The extent to which performance can be enhanced is shown to be dependent on the controller parameters. A controller tuning analysis shows how a design settling time limit can be achieved, within the problem's constraints on the maximum torque and the total integrated torque. The proposed optimization approach is globally stabilizing and presents low implementation complexity, which is highly desirable given the limited resources onboard satellites.