• controllo nonlineare
• controllo ottimo
• filtro di Kalman
• stabilità primo ordine

In this thesis, a control strategy that maximizes exploitation of the available electrostatic
actuation authority is studied, and its application to the case of the LISA Pathfinder
Accelerometer Mode is carried out.
The successful catching of test masses after release from their launch lock is crucial to the
operation of spaceborne inertial sensors. Due to potentially high release velocities, high
electrostatic forces need to be applied while avoiding saturation of the sensor electronics.
Work on the LISA Pathfinder mission showed that this particular phase is still critical
and, for possible future missions, improvements of the existing design are desirable.
Three main components can be identified as involved in this particular phase: the available
hardware, the force to voltage conversion law, and the test mass control law.
The present work contributes to the research of a control strategy that best exploits the
available hardware, with the goal of increasing robustness of the catching process.
In order to do so, the limits of linear control are explored, by designing and comparing
several different concepts. The idea of maximum actuation exploitation is then developed,
and a nonlinear bang-bang velocity breaking controller is designed. An extension
of the existing actuation algorithm is developed, that realizes the maximum possible
force generation out of the current electronics and geometric configuration. In ideal
testing environment, the new concept shows ability to exploit the system electrostatic
actuation up to 96.5% of its theoretical limit. The velocity breaking controller is finally combined with a linear controller and a Kalman filter, to define a complete control
strategy. Controller testing is then carried out using the nonlinear LISA Pathfinder
performance simulator. Comparison with the existing design shows an improvement in
maximum tolerable release velocity by a factor of approximately 2.5.