Core Concepts
Rollbot is the first spherical robot capable of controllably maneuvering on a 2D plane with a single actuator by exploiting non-holonomic rolling constraints.
Abstract
The paper presents Rollbot, a spherical robot driven by a single actuator that can achieve controlled 2D motion on the ground. The key highlights are:
Theoretical analysis: The authors derive the general equations of motion for a spherical robot driven by internal point masses. They then apply this model to Rollbot and analyze its quasi-static state and stability under perturbations.
Hardware design: The authors carefully design Rollbot's hardware to closely match the theoretical model, including positioning the center of mass, selecting the pendulum mass, and introducing damping.
Control strategy: The authors develop a control algorithm that controls the center of curvature of Rollbot's trajectory by modulating the driving speed of the single actuator. This allows Rollbot to perform stable circular motion and move between waypoints.
Experimental validation: The authors conduct various experiments to verify the accuracy of their theoretical analysis and demonstrate Rollbot's capabilities, including open-loop motion, stable circular motion, and waypoint navigation.
The authors conclude that Rollbot is a promising testbed for underactuated robotics and can inspire the design of other minimalist robot systems.
Stats
Rollbot has an outer diameter of 24 cm and weighs 1.2 kg.
The revolving radius of Rollbot can vary from 0.12 m to 1.28 m by changing the driving speed from 0 to 3π rad/s.
Rollbot can recover from perturbations with a characteristic time of about 7 seconds.
Quotes
"Rollbot can move on 2D plane by exploiting the non-holonomic rolling constraint."
"Rollbot is the first spherical robot capable of controllably maneuvering on 2D plane with a single actuator."
"Rollbot rolls on the ground in circular pattern and controls its motion by changing the curvature of the trajectory through accelerating and decelerating its single motor and attached mass."