Fault Tolerant Attitude Control Incorporating Control Allocation For Spacecraft

Spacecraft attitude control technology, which requires high precision, high stability, and autonomous, plays an important role in spacecraft on-orbit servicing mission. However, a lot of limits, such as nonlinearity of spacecraft attitude tracking system, external disturbance, actuator saturation and output velocity constraints, and inevitable actuator partial loss of effectiveness fault which is caused by severe space environment, may lead to degradation of spacecraft attitude control performance even on-orbit mission failed. Against this background, this paper is going to develop a series research of spacecraft attitude tracking fault tolerant control incorporating online control allocation, and mainly includes the following respects.Based on overview of spacecraft attitude control system research status, the significance of this research is proposed, then this paper establish es the mathematic description of spacecraft attitude tracking model and control objectives under various limits, which lay the foundation of controller design.In order to estimate actuator partial loss of effectiveness fault accurately, this paper introduces a first-order regression filter, and designs a fault observer based on this information. An active fault tol erant controller is proposed, and the asymptotic stability of closed loop system fault estimation error and attitude tracking errors is given.As for spacecraft attitude tracking system with redundant actuators, this paper improves the traditional pseudo-inverse control allocation by using the inverse matrix of actuator partial loss effectiveness estimation matrix as weigh matrix. Taken further actuator saturation and output velocity constrains into consideration, this paper proposes an open loop dynamic co ntrol allocation based on vector quadratic optimal planning.The deviation of actuator installation matrix may result in error between actual moments generated by open loop control allocation with expected moments provided by the virtual controller. This p aper proposes a closed loop control allocation, and provides a sufficient condition of stability.Incorporation online closed loop control allocation, an active fault tolerant controller based on fault observer is proposed, and lots of numerical comparati ve simulation results are conducted to verify the superio rity of the algorithms.