Attitude Control Of Spacecraft Subject To Actuator Characteristics

The key to spacecraft in-orbit mission is how to ensure the stability and accuracy of spacecraft attitude control system, controller must be well-designed to meet the stability and performance of the control system. Spacecraft in orbit inevitably suffers from a variety of limits, such as input saturation, input nonlinearity, actuator uncertainty and attitude angular velocity limits, due to the physical constraints of actuators and gyros, which seriously affect the stability and accuracy of spacecraft attitude control. So the study on spacecraft attitude control considering such constraints is of great significance. The main content of this paper includes the following aspects:Firstly, convert constraints the spacecraft facing to mathematical abstraction and reasonable assumptions, and then base on that establish a rigid spacecraft mathematical model considering a variety of constraints, which is the basis for the synthesis of the controllers.A nonlinear sliding mode controller that consider actuator input saturation constraint explicitly is designed, which can guarantee asymptotical stability of closed-loop system under the condition of input saturation. On this basis, further expand the input saturation into variable input saturation problem and an adaptive sliding mode controller is designed. The proposed controller explicitly satisfies variable input saturation and guarantee that closed-loop system is asymptotically stable. In addition, an adaptive controller taking actuator variable saturation and actuator uncertainties into account simultaneously is designed, which guarantees the stability of the system and offsets actuator uncertainties.Based on the above basis, input non-linear attitude control is further studied. Adaptive controllers that take actuator variable saturation or actuator input nonlinearity and the angular velocity limit into account simultaneously are proposed. The angular velocity of the spacecraft attitude control system satisfies certain constraints and input nonlinearity is offset. The proposed controllers maintain the stability of the system considering input variable saturation.Finally, numerical simulation verification are conducted to verify the validity and superiority of the proposed controllers. And the proposed controllers are not affected by system parameters change and strongly robust the bounded external disturbance and system uncertainties.