Optimization of tracking control and ESO vibration suppression for free-floating flexible space robot with bounded torque

Considering bounded torque and the existence of parameter uncertainties, the trajectory tracking control of joint and the active suppression of flexible vibration for a free-floating flexible space robot (FFFSR) are discussed. Based on singular perturbation method, the FFFSR system is decomposed into a slow subsystem tracking joint trajectory and a fast subsystem describing flexible vibration. Then a combination controller including a slow and a fast control component is proposed. For the slow subsystem, an optimized control method is proposed based on State-Dependent Riccati Equation (SDRE), making it possible to optimize the performance index function constituted by the output torque and the tracking error to ensure tracking accuracy while reducing their energy consumption as much as possible. For the fast subsystem, an extended state observer is adopted to estimate the coordinate derivatives of flexible modal and uncertain disturbance that are difficult to measure, and then LQR is used to suppress the flexible vibration. The numerical simulation results show that the combination controller can suppress the flexible vibration effectively while tracking the desired joint trajectory stably with bounded torque.