Coupled control of relative position and attitude based on θ-D technique for on-orbit operations

For the problems of relative dynamics and control in the on-orbit operations such as module replacement, fuel charge and so on, coupled dynamics model of relative orbit and attitude was established to describe the relative motion of two spacecrafts in close range. Orbit perturbation and attitude disturbed torque was used to illustrate the impact of the coupled terms on the model. With the consideration of the nonlinear and time-varying of dynamic model based on the state dependent coefficient form, θ-D suboptimal control algorithm was adopted to design the controller of the coupled model of the relative translation and rotation. For the mission of space refuel during the final approach of an uncontrolled rotating satellite, the θ-D method is validated to be capable to realize the synchronization control of the relative orbit and attitude through the numerical simulation, which simplifies the calculation of controller and achieves a comparatively high precision.