Tetrabot: Resonance based locomotion for harsh enviroments

We describe a robotic architecture that combines the benefits of existing enclosed robots with passive dynamics. This combination results in a mobile robot with no moving parts exposed to the environment, making it ideal for tasks where wheeled or legged robots fail. Instead of suppressing resonance, the new robot morphology relies on the dynamics of resonance for locomotion. Actuators mounted on a central sphere excite a natural mode of vibration by pulling on strings through which the sphere is mounted to a tetrahedral frame. A simple open loop controller is sufficient to cause directed motion by hopping and sliding in a prototype. Rolling as a further gait is investigated theoretically. Fully enclosed resonant dynamic robots could lead to a new type of robot locomotion powered from a vibration source only. This is useful in the microscale where traditional actuators are not available, and at the macroscale where the robot's high ruggedness is favorable.