Orbit-Attitude Coupled Guidance and Control for Constrained Trajectory Generation and Tracking During Final Approach to Non-Cooperative Spacecraft

The paper proposes an original guidance and control architecture applicable to close-range rendezvous and final approach to a non-cooperative space target. The coupled rotational and translational guidance solution is obtained by solving a minimum propellant consumption problem (considering constraints on collision avoidance, target visibility in the sensor field of view, and actuators’ limitation) applying a sequential convex programming (SCP) method. The SCP approach converts the original non-linear problem into a series of linear ones, thanks to a linearization of the translational and rotational dynamics models and formulating the collision avoidance and sensor field of view constraints into affine inequalities. Trajectory tracking is entrusted to a roto-translational H-infinity controller designed following a mixed-sensitivity loop shaping approach, including reference trajectory, actuation disturbances and relative navigation errors as exogenous inputs. The proposed architecture is tested in a realistic numerical environment, in which orbital and rotational dynamics are reproduced accounting for environmental disturbances, i.e., atmospheric drag, solar radiation pressure and non-sphericity of the Earth. The simulator considers chaser absolute navigation errors and integrates a state-of-the-art LIDAR-based relative navigation filter. Additionally, it includes actuators’ models (for cold gas thrusters and reaction wheels) and a dispatching function for the distribution of the commanded control actions. A statistical analysis of achieved performance is done considering 100 runs of the proposed architecture in a final approach scenario to a non-cooperative target, accounting for initial control and navigation errors and environmental uncertainties. Results demonstrate robustness of the guidance optimization algorithm against the accounted uncertainties and capability of the H∞ controller to follow the reference trajectory with a high tracking accuracy throughout the simulation and a promptly respond in correcting the estimated relative errors.