Anti-disturbance inverse optimal attitude control design for flexible spacecraft with input saturation

In this paper, we propose a new control strategy for flexible spacecraft attitude maneuvers in the presence of an uncertainty inertia matrix, actuator constraints and external disturbances. The Vibration of flexible appendages, inertia matrix uncertainty and external disturbances (coming from space environmental, sensors and actuators error, etc.) are considered as the total disturbance to be estimated on-line by extended state observer. An inverse optimal control law is designed based on the Sontag-type formula and the control Lyapunov function. A radial basis function neural network based saturation compensator is embedded into the controller to reduce the effect of the control input saturation on the system. It shows that extended controller guarantees stabilization, input constraint satisfaction and achieves exact asymptotic disturbance rejection and H-infinity optimality without solving the associated Hamilton-Jacobi-Isaacs partial differential equation directly. The performance of the proposed control approaches are illustrated through numerical simulations.