Practical use of robotic manipulators made from soft materials requires generating and executing complex motions. We present the first approach for generating trajectories of a thermally-actuated soft robotic manipulator. Based on simplified approximations of the soft arm and its antagonistic shape-memory alloy actuator coils, we justify a dynamics model of a discretized rigid manipulator with joint torques proportional to wire temperature. Then, we propose a method to calibrate this model from experimental data and demonstrate that the simulation aligns well with a hardware test. Finally, we use a direct collocation optimization with the robot's nonlinear dynamics to generate feasible state-input trajectories from a desired reference. Three experiments validate our approach for a single-segment robot in hardware: first using a hand-derived reference trajectory, then with two teach-and-repeat tests. The results show promise for both open-loop motion generation as well as for future applications with feedback.
@article{arxiv.2110.09474,
title = {Trajectory Optimization for Thermally-Actuated Soft Planar Robot Limbs},
author = {Anthony Wertz and Andrew P. Sabelhaus and Carmel Majidi},
journal= {arXiv preprint arXiv:2110.09474},
year = {2022}
}
Comments
8 pages, 6 figures, accepted at RoboSoft conference