A ballbot is a mobile robot that moves and balances on one wheel. It is dynamically stable and capable of a larger range of movement than other types of robots, because it can maneuver better in tighter spaces. It runs on the same principles as those of an inverted pendulum, It is thought that this robot could make great personal or service robots in the future. Currently, ballbot robots can only traverse smooth surfaces, but it is thought that models could be easily adapted to move on rough surfaces. There have been several ballbot characters developed for Hollywood films, giving this type of robot a varied future.

In the past, mobile robots were designed for stability while standing still and while moving, so they were equipped with a sturdy base and three or more wheels. This gives static stability, or the ability of expending no energy while the robot is stationary. In order to keep the robots from tipping, the bases were equipped with a heavy center of gravity and they could not move or stop quickly. In personal environments, like a business or homes, these types of robots are not able to navigate efficiently, unlike ballbots, which can move in cluttered areas and turn around while remaining stationary.

Because of the mobility limitations of stalky, wheeled robots, developers began focusing on taller robots that could have increased mobility and stability. The design of the ballbot features a narrow body with a spherical ball holding the body up, creating an underactuated system that gives the robot more freedom of movement. However, designing the systems to make the robots run smoothly can be difficult. The robot must first tilt forward while the ball moves backwards in order to move, and it must also lean into turns to move in varied directions. Although this looks elegant, the process can be difficult to achieve.

The designs of ballbots vary, but each robot has important design factors including height, maximum torque, and a center of gravity. All of these factors, and others, decide how efficiently each robot will move. The ball used to control the robot is the most important aspect of the entire machine, but it also takes the most damage. It is important to construct a ballbot with an efficient ball for movement, as well as actuators, sensors, and other equipment. Some ballbots have been equipped with special legs to help keep the robot stable in case of malfunction, like the CMU Ballbot’s three leg system. This robot can transition from a moving state to a static state using the legs. The CMU Ballbot is also the only ballbot to have arms, although these are not functional and are used only for testing purposes.

There are ballbots in many areas of the world, but the first was developed by Professor Ralph Hollis in 2005 in Pittsburgh, USA, but this robot was not patented until 2010. This robot is called the CMU Ballbot, because it was developed at Carnegie Mellon University, and is about as tall as a human is. Hollis and his team demonstrated that this robot is capable of great balance, by kicking and shoving it, as well as sturdy by running it into walls and furniture. The team also noted the smooth, autonomous movements of the CMU Ballbot, which at that time would be achieved by using programs and algorithms. In 2005, shortly after the CMU ballbot was announced, a team at University of Tokyo announced their design for a wheelchair ballbot that could be ridden by one person. This robot, known as B. B. Rider, balanced and moved on a basketball, but a demonstration was never made. A robot was being developed by László Havasi in Hungary that year as well, known as the ERROSphere. However, this model did not balance properly and no further information about it was reported.

After 2005, many other researchers began developing ballbots, including the BallIP that was developed by Prof. Masaaki Kumagai in 2008 in Japan, which was used to assess the transportation capabilities of ballbots. A team of students at ETH Zurich in Switzerland developed a robot called Rezero in 2010, which was used to enhance the smooth movements of ballbots. In Spain, Tomás Arribas created the first ballbot using LEGO Mindstorms NXT and created a simulation program with Microsoft Excel that would simulate the system of the robot. Using this robot, Arribas and his team published the article called A Monoball Robot Based on LEGO Mindstorms, which explained trajectory control and a mathematical model regarding the instability of non-linear control systems. Yorihisa Yamamoto of Japan was inspired by Arribas’ robot and created a ballbot using LEGO Mindstorms NXT.

Image Caption: This picture shows BallIP, a ball balancing robot developed by Prof. Masaaki Kumagai, Japan. Credit: Unagaraj/Wikipedia  (CC BY-SA 3.0)