Single Actuator Undulation Soft-bodied Robots Using A Precompressed Variable Thickness Flexible Beam

TL;DR

This paper introduces a novel soft robot design that uses a single actuator and a precompressed flexible beam to generate undulation locomotion, simplifying control and reducing weight compared to multi-actuator systems.

Contribution

The paper presents a new tendon-driven flexible beam mechanism with precompression that enables undulation with only one actuator, enhancing simplicity and efficiency.

Findings

Precompression induces a controllable traveling wave along the beam.

Tendon pre-tension correlates with the motor winding/unwinding behavior.

The proposed design successfully demonstrates undulation locomotion.

Abstract

Soft robots - due to their intrinsic flexibility of the body - can adaptively navigate unstructured environments. One of the most popular locomotion gaits that has been implemented in soft robots is undulation. The undulation motion in soft robots resembles the locomotion gait of stringy creatures such as snakes, eels, and C. Elegans. Typically, the implementation of undulation locomotion on a soft robot requires many actuators to control each segment of the stringy body. The added weight of multiple actuators limits the navigating performance of soft-bodied robots. In this paper, we propose a simple tendon-driven flexible beam with only one actuator (a DC motor) that can generate a mechanical traveling wave along the beam to support the undulation locomotion of soft robots. The beam will be precompressed along its axis by shortening the length of the two tendons to form an S-shape, thus pretensioning the tendons. The motor will wind and unwind the tendons to deform the flexible beam and generate traveling waves along the body of the robot. We experiment with different pre-tension to characterize the relationship between tendon pre-tension forces and the DC-motor winding/unwinding. Our proposal enables a simple implementation of undulation motion to support the locomotion of soft-bodied robots.