A constrained optimal PID-like controller design for spacecraft attitude stabilization

In this paper, an optimal PID-like controller is proposed for a spacecraft attitude stabilization problem subject to continuous inequality constraints on the spacecraft angular velocity and control, as well as terminal constraints on the spacecraft attitude and angular velocity. The closed-loop stability is established using the Lyapunov stability theory. The constraint transcription method and a local smoothing technique are used to construct a smooth approximate function for each of the continuous inequality constraints on the angular velocity and control. Then, by using the concept of the penalty function, these approximate smooth functions are appended to the quadratic performance criterion forming an augmented cost function. Consequently, the constrained optimal control problem under the PID-like controller is approximated by a sequence of optimal parameter selection problems subject to only terminal constraints on the spacecraft attitudes. A reliable computational algorithm is derived for the tuning of the optimal PID-like control parameters. Finally, numerical simulations are carried out to illustrate the effectiveness of the methodology proposed. & 2011 Elsevier Ltd. All rights reserved.