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

TL;DR

This paper introduces OptiWB, an optimal whole-body trajectory planner for mobile manipulators in planetary exploration, leveraging dynamic programming and kinematic redundancy to generate energy-efficient, collision-free, and visibility-optimized paths.

Contribution

The paper presents a novel integrated planning approach that optimizes the entire robot body movement simultaneously, improving over traditional separate base and arm planning methods.

Findings

Successfully integrated with ESA's mission planning software

Demonstrated improved collision avoidance and visibility

Validated on a simulated planetary rover platform

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 and energy consumption are all important factors to consider to be able to generate feasible and optimal plans. When mobile manipulators (terrestrial, aerial) are employed, the base and the arm movements are often separately planned, ultimately resulting in sub-optimal solutions. We propose an Optimal Whole Body Planner (OptiWB) based on Discrete Dynamic Programming (DDP) 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 ROS (Robot Operating System), interfaces 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-DOFs robotic arm mounted on a four wheels non-holonomic platform.