Autonomous Mission Planning And Execution For Two Collaborative Mars Rovers

One of the most important lessons learnt from more than ten years of robotic exploration in Mars is the high value of autonomy in terms of operations and science return. So far, only a few full-scale experiments to foster autonomy for planetary exploration have been conducted in Europe. One of the most relevant is the recently completed FASTER FP7 framework project, with one of the main scientific contributions being the application of autonomous planning and execution under uncertainty for two collaborative rovers in a Mars scenario where it is not possible to have humans in the loop. This paper presents the results of implementing the QuijoteExpress (abbreviated QE) mission planner and SanchoExpress executive to tackle these problems. QuijoteExpress is a novel platform-independent planner which strengths are performance, plan robustness and expressiveness. QuijoteExpress was able to produce robust collaborative plans for both rovers with only minor tuning under undeterministic and unstructured scenarios. SanchoExpress is a ROS-based, platform-independent timeline executive that can command multiple subsystems in parallel. SanchoExpress (abbreviated SE) can encode platform-dependent knowledge including repair methods for some errors which allow the executive to fix the plan in certain fault scenarios without the need of the replanner, therefore contributing to a more robust execution of the plan. The combined system was found to operate successfully and reliably during the FASTER field trials, enhancing the systems autonomy and enabling complex behaviour to be executed in a robust and fault tolerant manner