Evolutionary development of an optimized manipulator arm morphology for manipulation and rover locomotion

The planetary exploration rover Sherpa is equipped with a manipulator arm used for handling payload items as well as for improving its locomotive abilities. Due to the high weight of Sherpa of approx. 200kg and the maximum weight of a payload item of 5 kg, both applications need high torques. In addition, a dextrous operating space is needed which has to allow ground contact and the placement of payload items on pre-defined positions on the rover itself. In this paper we describe an optimization method which evolves a manipulator arm morphology that requires minimal torques to accomplish these to some extent conflictive applications. Covariance Matrix Adaptation Evolution Strategy in parallel processing is used to optimize the link lengths of the manipulator arm. A real-time simulation is used to model the rover, all constraints, and to evaluate each morphology by analyzing the required torques for accomplishing pre-defined tasks. The paper presents the simulation results and the final manipulator arm morphology.