(last updated 4/21/2007)
Leanerd is a unique, two-wheeled balancing robot that I started designing in June, 2006.
Balancing robots make very good projects for hobbyists and students because they are mechanically simple but pose interesting sensing and control problems. It is fascinating that unstable systems can be stabilized using electronic feedback control to produce useful and interesting machines. Inverted pendulum robots are also interesting since humans are inverted pendulums. When people walk, they instinctively keep their body balanced. Even though we do not consciously think about it, we are performing a complex task of determining our attitude (using our inner ear and our eyesight) and using our arms, legs and torso to stay balanced. Balancing robots also have some similarity to advanced aircraft designs. Aircraft like the F-117 Stealth Fighter, B-2 Bomber, and X-45 UCAV are all unstable platforms that are stabilized using electronic feedback control systems. There are quite a few balancing robots described on the web. Some of the best two-wheeled balancing robot websites I have seen are:
David Anderson's nBot (this site also contains a very good list of other projects)
The Swiss Federal Institute of Technology's Joe le Pendule
Ted Larson's Bender
In addition to being fun and interesting machines to build, inverted pendulum robots are an attractive configuration for robots that interact with people. This is due to the fact that an inverted pendulum robot can be a similar size to a person while being relatively safe. A fully stable robot that is as tall as a human would be quite heavy and require a large wheel base to be stable. If it were to malfunction, a robot this size would be capable of doing considerable damage to people and property. An inverted pendulum robot can be made as tall as a person without having a large, heavy base. Even if it malfunctions, an inverted pendulum robot has a very limited ability to harm people or property. If a balancing robot runs into something it will either fall down or recover it's balance by moving away from what it has collided with.
Balancing robots are an ideal configuration for robots that are lightweight, tall, maneuverable, and safe to operate around people. In order to build a robot that is tall and thin the robot needs to balance itself in two directions. There are a number of balancing robot configurations that solve this problem. The most obvious (and most complicated) way is to make a robot that walks like Honda's Asimo. Another solution is to build a robot that balances in two directions on a sphere like Ralph Hollis' Ballbot.
Most two-wheel balancing robots only balance themselves in one direction. This makes the design somewhat unstable in the sideways direction, which requires the robot to be relatively short and wide compared to a robot that balances in two directions. It seems to me that building a short and wide robot defeats the purpose of a balancing robot.
Leanerd is a compromise between rigid, two-wheeled robots and robots that balance in two directions. Leanerd balances in the forward/backward direction on two wheels just like the two-wheeled robots listed above. To improve stability in the sideways direction, Leanerd has a joint in between the two wheels that allows the main body of the robot to lean. This joint allows Leanerd to lean into sharp turns. The joint also allows Leanerd to travel over uneven terrain without tipping over. As one of Leanerd's wheels go over a bump, the base of the robot tilts but the main body remains vertical.
Leanerd leans into a turn.
Leanerd smoothly travels over uneven terrain.
Click on an item in the list for a detailed description of Leanerd's design.
Leanerd's hardware is complete, assembled, and tested. All of the mechanical systems seem to work well. I have checked that the sensors are read properly by the DSP and the control signals and communication components all work. Although I have written much of the software, I still need to select and tune many of the control law gains to make Leanerd stable.
Leanerd's head without the cover
Leanerd's brain!!
Leanerd's bottom without the cover.
Leanerd's fully assembled control box
Leanerd's completed chassis
Hello Leanerd!!!
A fully assembled Leanerd!!!
Troy and his new buddy...
Please email comments to troy@troys-toys.net (please use this link or type Leanerd Comments in the comment section of your email).
