Optimized Torque Allocation Strategy And Fault Tolerant Controlfor Multiple Reaction Wheels System

With the rapid development of aerospace technology, high-precision attitude pointing and quick maneuvering and the issue of reliability of spacecraft have got more and more attention. Carrying multiple reaction wheels with the spacecraft is a viable solution to these questions, this dissertation aiming at carrying multiple reaction wheels with the spacecraft would course energy consumption increased, managing complex angular momentum, issues of uncertainty of the configuration matrix and reaction wheels failed, proposed a series of optimized torque allocation strategy.First derived a kind of a new energy optimal torque allocation strategy for multiple reaction wheels system. The strategy based on instantaneous energy consumption. This dissertation didn’t take into account the energy storage of reaction wheel when it slows down, the proposed allocation strategy is modified based on the traditional torque minimum strategy that is pseudo-inverse method.The traditional torque allocation strategy is limited and the effective solution of which is unique, it cannot take the advantages of multiple reaction wheels system. To solve this problem, this dissertation gives maximum angular momentum envelope of an arbitrary configuration of n reaction wheels, and on this basis, angular momentum based optimal torque allocation strategy is given. In the practical application, however, is likely to appear in a particular maneuvering tasks performed during the last maneuvering tasks. In this way, the initial value of the angular momentum of each reaction wheel is not the same, as if the pursuit of maximum output capacity of angular momentum, is likely to generate the angular momentum of the reaction wheel to saturation. Therefore, proposed the concept of angular momentum margin, angular momentum margin indicator is designed based on angular momentum margin, and margin based optimal allocation strategy is proposed, achieved a reasonable allocation of the angular momentum of the multiple reaction wheels system.In the practical application of the spacecraft, the configuration matrix of reaction wheels cannot be obtained accurately, because reaction wheel misalignment cannot be zero. With the increase in number of reaction wheels installed, the impact of uncertainties of configuration matrix would be expanded. To solve this problem, this dissertation designed a kind of optimized closed loop torque allocation strategy, and with a saturated proportional-derivative controller, to suppress disturbances caused by uncertainties of configuration matrix. Finally, actuator faults are not considered directly in the closed loop torque allocation strategy, derived a kind of second order sliding mode observation to observe the fault torque of reaction wheels system. Through the analysis of the failure mode, it can quickly and accurately determine the fault of the reaction wheel, and according to the second order sliding mode observation, designed a fault-tolerant control law, achieved on fault-tolerant control of multiple reaction wheels system.