Formation flying control for satellites: anti-windup based approach

Control theory has significantly evolved in the field of the nonlinear control. However, the methods used in the aerospace industry lie usually on linear techniques applied to linearized models. The increasing requirements in terms of operational reliability and performance ask for the development of new control techniques more complex in order to meet the new demands. Therefore the industry is moving to the modern control theory looking for new nonlinear approaches. In particular, actuators saturation represents a nonlinear phenomenon common in almost all physical applications. This can then lead to performance degradation, limit cycle appearance, non-desired equilibrium conditions and even system instability. The objective of this chapter is to adapt and develop the anti-windup compensator design to the control with high precision for the angular and the linear axes of a satellite. In the aerospace application field, this situation meets with the drag-free or the formation flying missions. These missions use high precision thrusters as actuators whose capacity appears to be critically low. Moreover thrusters have a particular modeling. Allocation functions adapted to the anti-windup design are then explored. In addition considering the current state of the art of the anti-windup design, there is a strong necessity of using symmetrizing techniques for the saturation. The main objective of this work consists in applying the developed tools on an aerospace study case. As an example, a complete methodology is proposed to control a formation flying mission controlling both attitude and relative position.