The Study Of Reactive Flywheel Control Scheme And Variable Structure Control For Its Rare Earth Permanent Magnet Motor

The reactive flywhell is a good choice to satisfy high accuracy and high stability request of the satellite attitude control system. Because rare earth permanent magnet (REPM) motor has simple structure, small bulk, light weight, credible performance, little ullage and high efficiency, it has been applied in the reactive flywheel more and more. The thesis studies the work principle of the reactive flywheel, and designs the control scheme of the reactive flywheel, and studies the variable structure control of the REPM motor used in the reactive flywheel. The works of this thesis mainly include following several aspects:1. According to the function and principle of the reactive flywheel in the satellite attitude control system, this thesis analyzes the requirement of reactive flywheel controlling the high stability satellite, and puts forward to the key control index of the reactive flywheel. Two kinds of control schemes are studied and compared, the speed control method (or call the speed feedback control method) and the moment control method (or call the electric current feedback control method). The comparision result shows that the speed control method is fitable to engineering problem better.2. The concept and the work principles of sinusoidal current driven REPM motor and trapezoidal current driven REPM motor are studied. The mathematic models of sinusoidal current driven REPM motor and trapezoidal current driven REPM motor are built up, and the advantages of the two kinds of REPM motors are analyzed resceptively. The research result shows that it can reduce the unsteady degree of the satellite attitude, that the reactive flywheel uses sinusoidal current driven REPM motor at low speed and uses trapezoidal current driven REPM motor at high speed.3. The concept, characteristic and basic method of variable structure control with sliding mode (VSS) are studied. VSS can adapt the interferential moment, and it has many advantages, such as quick speed of respond, not sensitive to the exterior disturb etc.4. This thesis adopts the different mathematic model and the control strategy in one system, and utilizes the advantage of sinusoidal current driven REPM motor and trapezoidal current driven REPM motor respectively, and realizes the high accuracy and steady control of REPM motor through Sinusoidal/Trapezoidal VSS control. The moment pulsation problem of thereactive flywheel when low speed or pass zero rotate speed is resolved.The result of this thesis can provide the actual method to control the reactive flywheel better for the high accuracy satellite attitude control system. The key technique of the reactive flywheel applied in the high accuracy satellite attitude control system is mastered. "Zero momentum control" at three mutually perpendicular axes of satellite is realized on the real meaning. The part result of this thesis has been successfully applied to attitude control system of some satellite.