Nonlinear Model Predictive Control for Trajectory Tracking and Obstacle Avoidance of Free-Floating Satellite Manipulator

This paper investigates trajectory tracking with obstacle avoidance of a Free-Floating Satellite Manipulator (FFSM) under the communication failure problem. The end effector of the manipulator is desired to follow the reference path of a virtual leader while avoiding dynamic obstacles in real-time. The main idea behind this work is the use of a nonlinear model predictive controller (NMPC) with a robust optimization approach to achieve the path following and real-time collision avoidance with predefined objectives subject to the input, output and obstacle constraints. While on-line quadratic programming is adopted to achieve the real-time constrained optimal control decisions over a receding horizon. However, from the practice, it emerges that the coordinates of the virtual leader may fail very often to reach the end effector of the FFSM because of communication failure problems that are caused by many practical reasons. Therefore, a polynomial fitting algorithm is implemented in the NMPC controller based on Cramer’s rule to predict the reference trajectory, which enhances the stability and robustness of the system and makes the manipulator capable to overcome efficiently the communication failure problems. The main novelty of this work is to cope with the above circumstances simultaneously in practice based on the NMPC approach, which is also found suitable to fulfill the physical limits of the system in real-time applications. At the end, the performance of the proposed approach is validated with a Matlab example, and the simulations results show the superiority and advantage of this work compared to the previous works in terms of efficiency and robustness.