A Rapid Retargetable Goals Driven Approach to Autonomous Spacecraft Plan Repair with Concurrent Actions

Plan repair is more preferred over replanning when the agent suffers from plan failures. Most of the existing work on autonomous plan repair regards the action as an instantaneous point, preventing it from being directly applied to the field of spacecraft operation, where is full of concurrent actions with varying duration. In this paper, a reactive rapid autonomous plan repair algorithm based on retargetable goals, Retargetable Goals Plan Repair Method (ReGPR), is proposed. In ReGPR, both the mechanism for transforming a plan into a state queue and the method of determining the optimal states, i.e. retargetable goals, based on evaluation are presented. For transformation, ReGPR discretizes the concurrent actions into two state nodes distributed at their beginnings and ends, which encapsulates much information such as logic, value, duration and start time. Then, the plan repair problem is transformed into the puzzle of state transition by mapping them into the same timeline, which forms the retargetable goals. To determine the optimal goal for repairing, an evaluation expression including goal reachability, search time estimation and makespan is designed. With the help of this expression, ReGPR gets rid of searching for the recovery plan by the try-error method and finds the solution quickly. Several experiments with either logic failures or energy shortage or both were done to demonstrate the effectiveness and efficiency of ReGPR by compared with the corresponding results of the replanning method.