Date of Award

8-2019

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Committee Member

Phanindra Tallapragada, Committee Chair

Committee Member

Yue Wang

Committee Member

Suyi Li

Abstract

Vibration driven robots utilize periodic forced vibration of an internal mass to achieve directed locomotion. Bristle bots are a class of vibration driven robots which are characterized by the presence of bristles or cilia on their surface and contain an internal mass that is driven to oscillate at a high frequency. Besides well-known applications in investigating swarming behaviour, such robots have potential applications in rescue operations in the rubble, inspections of pipes and other inaccessible confined areas and in medical devices where conventional means of locomotion is ineffective. Bristle bot or its commercially available variants such as hexbugs are popular toy robots. Despite the apparent simplicity of these robots, their dynamic behaviour is very complex. Vibration robots have attracted surprisingly few analytical models all which can only explain some regimes of locomotion. In this work, a wide range of motion dynamics of a bristlebot is explored using a mathematical model which accounts for the slip-stick motion of the bristles with the substrate. Analytical conditions for the system to exhibit a particular type of motion are formulated and the system of equations defining the motion are solved numerically using these conditions. The numerical simulations show transitions in the kinds of locomotion of a bristlebot as a function of the forcing frequency and amplitude. These different kinds of locomotion include stick-slip and pure slip motions along with the important phenomenon of the reversal of the direction of motion of the robot. In certain ranges of frequencies, the robot can lose contact with the ground and `jump'. These different regimes of locomotion are a result of the nonlinear vibrations of the robot and the friction between the robot's bristles and the ground. The results of this work can potentially lead to more versatile vibration robots with predictable and controllable dynamics.

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