Rollbot: A Spherical Robot Driven by a Single Actuator
Jingxian Wang, Michael Rubenstein
AI summary
Problem
Spherical robots traditionally require multiple actuators or degrees of freedom to maneuver in 2D space, limiting their simplicity, cost, and reliability in harsh environments.
Approach
The robot uses a single motor to rotate an internal pendulum mass, and controls its 2D trajectory by accelerating and decelerating the motor to dynamically change the rolling circle's radius based on derived quasi-stable dynamics.
Key results
- First real-world demonstration of precise 2D planar locomotion in a spherical robot using a single actuator
- Derivation of quasi-stable state dynamics and perturbation analysis showing stable recovery within ~7 seconds
- Experimental validation of controllable circular motion and waypoint tracking via motor speed modulation
- Proof-of-concept hardware design with optimized mass distribution and damping for rapid transient recovery
Why it matters
Provides a lightweight, fail-safe locomotion strategy for spherical robots in hostile environments like space exploration and enables simpler, more robust swarm robotics designs.
Abstract
Spherical robots typically require at least two actuators to achieve controlled 2D planar motion. Here we present Rollbot, the first spherical robot capable of controllably maneuvering on a 2D plane with a single actuator, challenging this assumption. Rollbot rolls on the ground in a circular pattern and controls its motion by changing the trajectory’s curvature by accelerating and decelerating its single motor and the attached mass according to our derived quasi-stable state dynamics and control laws. We present the theoretical analysis, design, and control of Rollbot, and demonstrate its ability to move in a controllable circular pattern and follow waypoints, validating the efficacy of the proposed theoretical framework.