Composite DOBC and Adaptive TSM controller for Relative Position and Attitude Coupling Spacecraft

This paper studies the control problem of approaching and docking autonomous system including an on-orbit servicing spacecraft with flexible appendages and an out-of-control target considering the coupled relative position and attitude dynamics. Choosing relative position and relative attitude quaternion as the system state and considering relative position and attitude coupled which is produced by propulsion installation, relative position and attitude coupled dynamics model of servicing spacecraft with respect to the out-of-control target is established. While considering the flexible appendages of servicing spacecraft such as robotic arm and solar panel etc., vibration from flexible appendages is modeled as a derivative-bounded disturbance to the position and attitude control system of rigid body. Aiming at attenuating the modeled disturbance, a disturbance-observer-based control (DOBC) is formulated for feeding forward compensation of elastic vibration. Then we designed a composite controller with a hierarchical architecture by combining DOBC and TSM control, where DOBC is used for rejecting the vibration effect from the flexible appendages. Numerical simulations are performed to demonstrate that by using the composite hierarchical control law, disturbances can be effectively attenuated and the TSM control law is robust with perfect tracking performance.