MIMO active vibration control of magnetically suspended flywheels for satellite IPAC service



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Theory and simulation results have demonstrated that four, variable speed flywheels could potentially provide the energy storage and attitude control functions of existing batteries and control moment gyros (CMGs) on a satellite. Past modeling and control algorithms were based on the assumption of rigidity in the flywheel?s bearings and the satellite structure. This dissertation provides simulation results and theory which eliminates this assumption utilizing control algorithms for active vibration control (AVC), flywheel shaft levitation and integrated power transfer and attitude control (IPAC) that are effective even with low stiffness active magnetic bearings (AMB), and flexible satellite appendages. The flywheel AVC and levitation tasks are provided by a multi input multi output (MIMO) control law that enhances stability by reducing the dependence of the forward and backward gyroscopic poles with changes in flywheel speed. The control law is shown to be effective even for (1) Large polar to transverse inertia ratios which increases the stored energy density while causing the poles to become more speed dependent and, (2) Low bandwidth controllers shaped to suppress high frequency noise. These two main tasks could be successfully achieved by MIMO (Gyroscopic) control algorithm, which is unique approach. The vibration control mass (VCM) is designed to reduce the vibrations of flexible appendages of the satellite. During IPAC maneuver, the oscillation of flywheel spin speeds, torque motions and satellite appendages are significantly reduced compared without VCM. Several different properties are demonstrated to obtain optimal VCM. Notch, band-pass and low-pass filters are implemented in the AMB system to reduce and cancel high frequency, dynamic bearing forces and motor torques due to flywheel mass imbalance. The transmitted forces and torques to satellite are considerably decreased in the present of both notch and band-pass filter stages. Successful IPAC simulation results are presented with a 12 [%] of initial attitude error, large polar to transverse inertia ratio (IP / IT), structural flexibility and unbalance mass disturbance. Two variable speed control moment gyros (VSCMGs) are utilized to demonstrate simultaneous attitude control and power transfer instead of using four standard pyramid configurations. Launching weights including payload and costs can be significantly reduced.