Research On Flywheel Control System

This thesis is on the study of flywheel control used in satellite attitude control system. Flywheel is used as torque executive component in attitude control system. Ideal flywheel torque output is identical with torque instruction. Unfortunately, there are some undesirable factors in flywheel applied in engineering, which limit satellite attitude control system accuracy. In this thesis, this problem is solved with control theory in an engineering way.Firstly, the state of art, the structure and principle of flywheel are introduced. The problems in flywheel engineering are pointed out, and the way to improve flywheel performance is put forward.A deeply analysis of noise and disturbance in flywheel control system gives a sound foundation of flywheel control system study. Analysis reveals there are two factors playing key role in depressing flywheel performance, nonlinear friction torque disturbance and parameters varying with flywheel velocity changing in large range.The friction torque in flywheel is nonlinear in the vicinity of zero velocity which disturbs flywheel output. A velocity feedback control scheme is adopted to eliminate this disturbance. To avoid jitter in flywheel working state change, the control system is constructed with pulse width modulation and linear adjusting. Flywheels are used as velocity mode or torque mode in satellite engineering. It is proven in this thesis that the performance of flywheel in these two modes could be improved by suppressing unavoidable disturbance with velocity feedback, this theory is a new type of flywheel control system foundation. Using integral of output as feedback in flywheel system, including disturbance in feedback loop to suppress disturbance effect, is an important constructive work.Flywheel operates in a wide range of velocity, which induces parameters to vary greatly, to keep feedback system stable and performance in large velocity range is a challenge. In this thesis, a Gain Scheduling Controller is designed to cope with parameters varying, and the designed system has desirable dynamic performance. The controller is used in velocity mode or torque mode flywheel, as a result the effect of friction torque is greatly suppressed especially in low velocity band, and the dynamic performance and static accuracy of flywheel torque/velocity output are met in full velocity range. An application of designed flywheel system in a satellite is given in the thesis; comparative analysis shows the performance of attitude control system with velocity feedback flywheel is distinctly improved.The study result was used in"FY-3"satellite and"SZ-7"companion satellite lunched lastly, remote data showed the designed flywheel contributed a lot in satellites attitude performance, this proved the thesis work is valuable in engineering point of view.