Continuum, or “snake-arm,” robots are normally designed with a number of actuators in a tube-like body, allowing them to appear to curve continuously like a snake. Having multiple actuators in the “trunk,” however, limits how small they can be, and makes them somewhat complicated, especially if you add in sensing capabilities.
Researchers Yunosuke Satom, Ayato Kanada, and Tomoaki Mashimo have come up with an alternative which “snakes” around using a twin-coil design. The device is ingeniously simple, and instead of a traditional linear actuator design, two coil springs are each housed in a stator assembly that vibrate using ultrasonic piezoelectric actuators to induce peristaltic motion. Each spring is slightly larger in diameter than the stator’s through-hole, enabling the stator to move each spring forwards and backwards. When combined, these two linked springs can move together, or “look” left and right with differential motion.
For feedback, voltage is applied to each spring and sensed through the stator itself, which changes linearly depending on extension. This allows for measurement without additional components, and the two spring measurements together can be used to work out how the end is turning in space. The simplicity of the design is truly ingenious, and it could be ideal for soft robotics applications.
As you can see in the short video below, the device uses an Arduino Uno-based control setup for its experiments. More details on the project can be found in the researchers' paper.