Line-of-sight nonlinear model predictive control for autonomous rendezvous in elliptical orbit

The paper investigates the trajectory planning and control of autonomous spacecraft rendezvous in the orbital plane with line-of-sight dynamics. The control problem, based on nonlinear model predictive control, is formulated in terms of line-of-sight range and azimuth angle. The state feedback with measurement uncertainties is introduced to form a closed-loop optimal control problem by integration of receding horizon strategy. Furthermore, the control input increment instead of total control input is considered in the cost function to generate a smooth transient response. The formulated nonlinear optimal control problem is then transformed into convex quadratic programming problems over the predictive horizon, leading to a computationally efficient algorithm implementable for spacecraft. The numerical results show that the newly proposed line-of-sight nonlinear model predictive control scheme is able to effectively generate optimized approach trajectories with satisfactory control accuracy and the proposed method is insensitive to the measurement uncertainties.