Research On Spacecraft Attitude Control Methods With State Constraints

The space observation missions always expect spacecrafts to have the ability of large-angle attitude maneuvers with high precision and stability to improve the observation efficiency.However,some inappropriate attitudes of the spacecraft may cause communication interruption or damage to sensitive optical components.Thus,the problems,e.g.parameter uncertainty,external disturbance and actuator saturation,demand advanced control methods to realize the state constrained attitude maneuvering without any intrusion into the forbidden zones.This dissertation deeply studies the spacecraft attitude maneuver path planning and control method.The main contents are as follows:For the spacecraft with multiple attitude constraint zones(ACZs),path searching methods based on A~* algorithm and Gauss pseudo-spectral method are proposed.The modified Rodrigues parameters are used as the attitude parameter,and each ACZ is described in the three-dimensional discrete attitude space.The multi-path searching problem is transformed into a single-path one,and then the shortest maneuver path satisfying the attitude constraints is obtained by the A~* heuristic algorithm.Furthermore,considering the dynamic constraints,including actuator saturation and angular velocity constraints,the attitude optimal control methods with different optimization indexes are designed based on Gauss pseudo-spectral method.For the spacecraft with a single ACZ,an attitude controller based on Lyapunov method and potential function(PF) is proposed.The attractive PF and the repulsive PF(RPF) are designed based on the Euler rotation angles.To eliminate adverse effects of the RPF on the equilibrium point of the control system,the existence conditions of the RPF without empirical adjustment parameters are proposed.To satisfy the angular velocity amplitude constraint and improve the convergence speed near the equilibrium point,a nonlinear virtual angular velocity command is designed,and then a backstepping attitude controller is proposed.An auxiliary system driven by the difference between actuator's maximum torque and the command torque is introduced,which guarantees the stability of the spacecraft under the actuator saturation.A disturbance observer is presented to improve the robustness of the controller under external disturbance.A controller switching strategy for evading local minima of the PF is designed.For the spacecraft with multiple ACZs,an attitude controller based on Lyapunov method and strict convex PF is proposed.A strictly convex logarithmic boundary PF is designed,which has only one global minimum at the command attitude.Combining with the nonlinear virtual angular velocity command,a backstepping controller with actuator saturation is proposed.A new sliding surface that satisfies the constraints of ACZs and angular velocity amplitude is designed.Considering the actuator saturation and external disturbance,an adaptive sliding mode controller is proposed.By introducing adaptive parameters,the singular problem of controller is solved.An finite time extended state observer is designed to compensate the composite disturbance consisting of parameter uncertainty and external disturbance.For a spacecraft formation with multiple ACZs,a coordination reorientation controller is proposed,which is able to converge to reference attitude command.The virtual pilot spacecraft is introduced into the spacecraft formation.Assuming that the formation has a strong connective and balanced communication topology,a new formation convex PF is designed based on members' attitudes,and the PF obtains the minimum,if and only if formation attitude converges to the command attitude.A new sliding surface that satisfies the constraints of each member's ACZ and angular velocity amplitude is proposed,and a non-singular adaptive sliding mode coordination controller with actuator saturation is designed.If the reference attitude command is lost,the coordination controller can still guarantee the consensus of formation attitude.When the communication topology is complete and all members can obtain reference command,a coordination attitude tracking controller is proposed.The system equations are transformed into Euler-Lagrange form.The formation PF is designed based on the reference command,the relative attitude between members and individual ACZ.The switching strategy of intermediate variables is proposed based on the existence condition of the RPF.Then an adaptive coordination tracking controller under the actuator saturation is proposed.