Evaluation and Characterization of Tendon Routing Methods for Soft, Flexible Foam Robots

Tendon-actuated flexible foam robots have proven manipulation and locomotion capabilities while remaining soft and human-safe. However, the compliant nature of foam makes tendon integration a challenging design and fabrication problem. This can be seen by the variety of approaches used by researchers to date. Existing foam robots externally route tendons using textile skins or shallowly embedded eyelets. To expand upon this, we present a method for internally routing tendons through a novel casting process. We fabricated simple foam "finger" actuators using each of the fabrication strategies in order to compare these tendon routing methods. We then measured the actuation requirements, trajectories, and repeatability of each method. Using this data, we evaluate and characterize each tendon routing strategy in order to inform future tendon-actuated foam robot designs. Ultimately, tendon placement strategies determine the achievable poses and actuation force required. In addition to these physical properties, we present other design aspects for consideration such as repairability, reconfigurability, fabrication difficulty, and overall design complexity. By presenting these qualities we hope to provide future foam robot designers guidelines to consider when choosing a tendon routing method.