UWE Bristol Engineering showcase 2015

Olly McBride
BEng (Hons) Robotics
Project Supervisor
Dr Alexander Lenz
BallBot – An Investigation Into A Ball Balancing Robot
Introduction
A mobile robot capable of balancing on
a ball only has a single contact point
between the ball and the ground. This,
coupled with the requirement of a
‘falling motion’ in order to move, allows
for a very unique form of locomotion.
This locomotion is rarely seen in
robotics, as it is mechanically complex
due to its lack of static stability,
meaning that the robot has to actively
balance itself by changing its centre of
gravity (COG) by imparting a force on
the ball.
This investigation discusses the design
processes, problems and solutions in
the production of BallBot, a robot that
is able to balance on top of a ball. This
investigation also discusses the design
decisions behind the production of two
of the most advanced ball-balancing
robots, CMU Ballbot (Left) and Rezero
(Right).
Overview
A ball-balancing robot is comprised of a balance
sensor, a controller and a ball actuation section.
The controller is the brains of the robot and
interfaces with the balance sensor to read the
current angle of the robot. The controller then
performs various control algorithms to calculate
the force required to be applied through each of
the motors to stay balanced.
Design
BallBot is comprised of two main structural
components, the main body and the ball
actuation section. The main body is designed as a
laser cut acrylic platform, allowing for the
mounting of the electronics, batteries and the
ball actuation section. The the ball actuation
section consists of the motors, wheels and the
ball. The 3D printed motor mounts connect the 3
geared DC motors to the main body of BallBot.
The motors actuate the ball by applying force
through a set of omnidirectional wheels in order
to remain balanced. The wheels allow for force to
be applied in the rolling direction, but allow for
free motion in the lateral direction.
Electronics
The electronics of BallBot are designed to be
modular and consist of a balance sensor, motor
drivers, a bluetooth module and a
microcontroller. The sensor includes a 3 axis
gyroscope and a 3 axis accelerometer to sense
the balance angle and falling motion of the robot.
The microcontroller is used to implement various
balance control architectures, which allows for
the calculation of the force required to be
applied by each motor in order to stay balanced.
The bluetooth module allows for wireless
interaction with the user and allows for control of
the robot.
Software
The embedded software element of this project
involved the implementation of various balance
and position control architectures, as well as
control of communication with the balance
sensor, motor drivers and bluetooth module.
Project summary
A ball-balancing robot allows for a unique
form of motion rarely seen in robotics. This
motion is suited to working within human
orientated environments, such as offices and
households.
This project involved the investigation into
the various elements and design processes in
order to construct BallBot, a ball-balancing
robot. This required working within multiple
disciplines, from electronic and mechanical
design, to the design and implementation of
embedded software.
Project Objectives
The aim of this investigation was to produce
BallBot, a robot capable of balancing on a
ball, thus allowing further investigation into
this unique form of locomotion.
Project Conclusion
This project involved the design and
construction of a complete robot system,
from the overall conceptual design to the
embedded control architectures used for
balancing.
Figure 1 – CMU Ballbot (Left) and Rezero (Right)
Figure 2 – 3D model of BallBot (Left and Middle) in AutoCAD, and the final result of BallBot balancing on a ball (Left)