Finite-Time Attitude Control of a Nano-Satellite in the Presence of Actuator Failure

It is an interesting and challenging problem to control a satellite with only two orthogonal reaction wheels. In this regard, a nonlinear Euler angle feedback regulator is developed in this paper to yield a three-axis attitude stabilization of an under-actuated nano-satellite with two body-fixed control torques. The developments are based on the nonlinear model of spacecraft equipped with three reaction wheels, which one wheel has failed totally and two wheels are functioning. The control law has been driven under zero total angular momentum condition assumptions and based on linearized kinematics equations. In fact, the controller has to use the coupling between principal axes to control the un-actuated axis. Thus we had to develop a nonlinear feedback control to perform this. The proposed controller yields local stability near the nadir-pointing attitude. The nano-satellite is expected to return to Nader-pointing attitude after failure mode. The results of the numerical simulations illustrate the controller’s ability to recover nadir pointing by controlling two functioning reaction’s angular rate.

Keywords:

Nano-satellite , Under-actuated , Nonlinear control , Actuator failure , Attitude control