SRL-Gym: A Morphology and Controller Co-Optimization Framework for Supernumerary Robotic Limbs in Load-Bearing Locomotion

Abstract

Supernumerary Robotic Limbs (SRLs) can assist human motions by providing extra degrees of freedom (DoFs) and body support. The extra DoFs lead to larger design space in structure and control policies, which is complex and time-consuming with the traditional manual design process. In this pilot study, we proposed a novel morphology-controller co-optimization framework to automatically generate and optimize the SRL structure based on the locomotion task input. There are two layers, with the inner layer optimizing the controller to achieve human-robot synchronization, and the outer layer optimizing the morphology parameters for performance enhancement. We validated the proposed framework through simulations using SRLs in a load-bearing locomotion task. The results demonstrate that the controller optimization can automatically generate realistic gait patterns and stable human-robot synchronization, while the SRLs significantly improve the user's load-bearing capability. Additionally, the co-optimization process reduces both the manufacturing cost of the SRL and the torque on the joints. This approach shows potential for exhaustive exploration of the design space and acceleration of the design process. Future works will be done in a more realistic SRL generative design model and achieve Sim2Real for practical uses.