Proprioceptive Inchworm Robots for Space Applications

Inchworm robots are an emerging tool for construction and maintenance tasks in extraterrestrial environments. We are interested in developing a new class of inchworm robots that can sense and regulate the forces they exert through proprioception, allowing for safer robot-structure interactions and for more dexterous manipulation. Designing such robots presents significant challenges, especially in gravity environments where motor units must exert large torques to support the robot's own weight. This paper introduces a framework for the simulation, design, and control of proprioceptive inchworm robots that use large diameter, low gear ratio brushless motor actuators and impedance-based control strategies. We develop a symbolic physics model to determine torque requirements at the main drive joints, accounting for robot geometry, mass distri-bution, payload characteristics, and gravity. An impedance control strategy is implemented alongside a trajectory generation pipeline to enable smooth, continuous motion based on high-level user inputs as keypoints. Utilizing simulations, we select suitable commercial off-the-shelf actuators and design the Modular Scaling Omnidirectional Lattice Locomoting Explorer (mSOLL-E), an improved inchworm robot for the NASA AR-MADAS project that is lower in cost, higher in performance, and more modular than its predecessor. Physical experiments validate our simulation results and control methods, demonstrating mSOLL-E's ability to execute autonomous stepping trajectories and gravity compensation modes effectively. Our work provides a pathway toward autonomous construction and maintenance of extraterrestrial structures by fleets of proprioceptive inchworm robots.