The LISA DFACS: Preliminary Model Predictive Control Design for the Test Mass Release Phase

This paper presents a preliminary control design for the test mass release phase of the LISA space mission. LISA will feature a triangular constellation of three spacecraft dedicated to the detection of gravitational waves. Each spacecraft carries two cubic free-falling test masses needed for the scientific experiment, which are initially locked by a clamp mechanism. When the plungers are retracted, the free-floating test masses are captured electrostatically by means of an electrostatic suspension system. However, the low actuation authority and the critical initial conditions, make the attitude and translation control of the test mass a difficult task. Model Predictive Control (MPC) appears to be a suitable technique for this application because of its ability to deal with the state constraints and the input saturations. In the present paper, the TM release context is briefly analysed, then the preliminary MPC design and simulation results are shown.