Optimal Whole Body Trajectory Planning for Mobile Manipulators in Planetary Exploration and Construction

Abstract

Space robotics poses unique challenges arising from the limitation of energy and computational resources, and the complexity of the environment and employed platforms. At the control center, offline motion planning is fundamental in the computation of optimized trajectories accounting for the system’s constraints. Smooth movements, collision and forbidden areas avoidance, target visibility (TV), and energy consumption are all important factors to consider to be able to generate feasible and optimal plans. When mobile manipulators (terrestrial and aerial) are employed, the base and the arm movements are often separately planned, ultimately resulting in suboptimal solutions. We propose an optimal whole body planner based on discrete dynamic programming and optimal interpolation. Kinematic redundancy is exploited for collision and forbidden areas avoidance, and to improve target illumination and visibility from onboard cameras. The planner, implemented in the Robot Operating System (ROS), interfaces the 3D Rover Operations Control Software (3DROCS), a mission planner used in several programs of the European Space Agency (ESA) to support planetary exploration surface missions and part of the ExoMars Rover’s planning software. The proposed approach is exercised on a simplified version of the Analog-1 Interact rover by ESA, a 7-degrees of freedom robotic arm mounted on a four wheels nonholonomic platform.