TY - THES ID - 147264353 TI - Unbalance control for an active-passive magnetic bearing in a spacecraft reaction wheel AU - Deckers, Niel AU - Gryllias, Konstantinos AU - Vandepitte, Dirk AU - Baekeland, Mante AU - Lanting, Jelle AU - KU Leuven. Faculteit Ingenieurswetenschappen. Opleiding Master of Mechanical Engineering (Leuven) PY - 2024 PB - Leuven KU Leuven. Faculteit Ingenieurswetenschappen DB - UniCat UR - https://www.unicat.be/uniCat?func=search&query=sysid:147264353 AB - This work investigated the suppression of vibrations due to the rotor unbalance of a passive magnetically suspended flywheel in a space satellite. For this purpose eight electromagnetic actuators were virtually added to the passive system, subsequently creating an active-passive magnetic bearing. Two types of vibration suppression were investigated. The first type is the rejection of the synchronous bearing reaction force, which aims at minimising the transmitted forces from the flywheel to the surrounding, in this case, the satellite. The rotor regime where this is the case corresponds to making the flywheel rotate around its principal axis of inertia. To achieve this, a control loop was developed, targeting to compensate the forces in the permanent magnetic bearing, thereby creating a free-floating condition of the rotor. Regarding stability, a sensitivity analysis on the estimated stiffness of the permanent magnetic bearing was required and a stable range for the accuracy of this estimate was determined. In this stable range, the control scheme proved to be able to reduce the transmitted forces, with increasing performance for increasing accuracy of the stiffness estimate. A secondary type of vibration suppression aimed at minimising the displacements of the flywheel, thus making it rotate exactly around its geometric axis. This requires much higher forces, as the unbalance force, caused by the rotor unbalance, needs to be compensated here. A control law that enables control of the rotor’s parallel and conical mode separately, called decoupled control, was designed for this concrete system and improved with an iterative learning control scheme. This control scheme was able to reduce the rotor displacements to zero with a zero steady-state error, albeit with a very low convergence rate for high rotor speeds, up to 10000 RPM. An actual electromagnetic actuator was designed and manufactured to validate the two control schemes against reality. A test campaign was set up to perform static and dynamic tests, which led to the finding that the amplitudes of the sinusoidal forces that are required, do not reach the expected values, based on calculations. Probable reasons for this are magnetic hysteresis and electromagnetic inductance. This implied the need for an extra frequency- and amplitude-dependent compensation factor in the control schemes, which could be obtained from further actuator characterisation, including extensive test campaigns. Taking into account this need, two valuable vibration suppression algorithms were developed. ER -