Multi-saturation anti-windup structure for satellite control

Future space missions demand high precision control in both angular and linear axes. Therefore propulsion systems providing effort in both axes with a high precision are needed. Microthrusters can satisfy these requirements. These actuators are usually subject to present an allocation problem. Moreover, because of this demand on high precision, the maximal propulsion capacity appears to be critically low, leading to a possible saturation of the actuators. A multi-saturation based model for a highly non-linear allocation function is presented. An anti-windup strategy dealing with the actuator saturation is proposed. Simulations consider a two satellites flight formation scenario. They show the improvement on performance and stability tolerance to off-nominal initial conditions. Simulations are based on a nominal model provided by Thales Alenia Space (TAS).