Shape-centric Modeling for Soft Robot Inchworm Locomotion

Soft robot modeling tends to prioritize soft robot dynamics in order to recover how they might behave. Soft robot design tends to focus on how to use compliant elements with actuation to effect certain canonical movement profiles. For soft robot locomotors, these profiles should lead to locomotion. Naturally, there is a gap between the emphasis of computational modeling and the needs of locomotion design. This paper proposes to consider modeling and computation efforts directed more toward understanding soft robot-world interactions with locomotion in mind. With a SMA-actuated inchworm as the soft robot to model and control, the framework is a combination of shape identification and geometric modeling that culminates in control equations of motion. When applied to the task of gait-based locomotion, the equations operate in a low dimensional shape-based gait space. Simulated and experimentally applied gaits for an inchworm model showed qualitatively similar outcomes, while the measured net displacement per gait cycle coincided within 9%. This result advances the idea that a shape-centric approach to soft robot modeling for control and locomotion may provide predictive locomotive models.