Simply built bicycle robot shows jumps and tricks
Mountain bikers elegantly ride through bumpy terrain on two wheels. That should be feasible for a robot too.
The UMV performs jumps, can ride on its rear wheel and in rough terrain.
(Image: RAI / Screenshot)
A research team from the Robotics and AI Institute (RAI) has developed a two-wheeled, bicycle-like robot platform called the Ultra Mobility Vehicle (UMV) that can jump over obstacles even at high speeds. It is also designed to perform tricks like riding on its rear wheel without losing balance. The agile robot is capable of moving in rough terrain.
The challenge with robots designed to move quickly over different types of terrain is keeping them balanced, as Ben Boser and Surya Sing, co-authors of the study „System Design of the Ultra Mobility Vehicle: A Driving, Balancing, and Jumping Bicycle Robot“, which appeared as a preprint on Arxiv, point out a challenge in developing mobile robots. Scientists could construct a robot with legs that can handle almost any terrain. However, such robots are complex, have high energy consumption, and mean higher development costs. Robots with wheels, on the other hand, move more efficiently and are simpler and cheaper to build. In developing their UMV, the researchers took inspiration from trial and mountain bikers who are able to overcome obstacles on two wheels, ride through difficult terrain at high speeds, and balance on one wheel.
The scientists considered how to mimic the movements of a cyclist as simply as possible. They decided to dynamically shift a mass on a two-wheeled vehicle to simulate a cyclist's body weight distribution. The movable structure should have as few degrees of freedom as possible to keep the joint mechanism simple and compact. At the same time, the robot should be able to achieve high speeds in difficult terrain and overcome obstacles larger than itself.
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The robot platform developed by the scientists at the RAI Institute consists of a bicycle-like frame equipped with two wheels arranged one behind the other. An electric motor drives the rear wheel, while the front wheel is used for steering. Between them, the researchers have placed a mass-based joint mechanism with five degrees of freedom. This essentially consists of a heavy head unit, which is movably connected to the bicycle frame via a neck and tie rods. The head houses the computing and control unit, as well as the batteries and actuators, thus forming the central robot mass. However, the construction is said to be relatively lightweight, easy to build, and has few sources of error due to its simple design, according to the scientists at the RAI Institute.
Weight Shifts
By changing the position of this mass, the robot's weight can be balanced on two wheels depending on the driving situation, and balance can be maintained. In addition, abrupt changes in the weight's position are possible, allowing the UMV to initiate jumps, for example.
The scientists trained the UMV using Reinforcement Learning (RL), initially in a simulation, and transferred the data to the real robot without further adjustments. As a result, the bicycle robot was not only able to perform trained movements but also developed new movement behaviors that the learning algorithm found independently.
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By using RL, the robot can continuously develop new movement strategies, for example, to best navigate around obstacles or overcome rough terrain. The UMV achieves this with astonishing agility. It can overcome obstacles with a height of one meter, about 130 percent of its own body height. In addition, the bicycle robot travels quite fast at 8 m/s (28.8 km/h).
(olb)
