Wheelbot: self-supporting, one-wheeled robot

With Wheelbot, a research team from RWTH Aachen University and the Max Plank Institute for Intelligent Systems (MPI-IS) has developed a robot that, like a symmetrical reaction wheel unicycle, can autonomously stand on its wheel from anywhere. position. The minimalist robot is intended to serve as a testing platform in research and teaching. It is easy to replicate due to its simple construction and use of 3D printed parts.

The research team’s Wheelbot is just 22cm tall. When standing still, it has two vertically arranged wheels, which are offset from each other by 90 degrees. The robot rolls on a wheel. According to the article published in IEEE Reaction and Automation Letters, the other wheel serves as the reaction wheel, which is electronically controlled to ensure a stable balance of one wheel. “The Wheelbot: A Jump Reaction Wheel Unicycle” outside.

Build as simple as possible

“Previous unicycle robots are designed to balance only in their vertical balance position, which severely limits the capabilities of these systems,” explains René Geist, Principal Investigator of the Wheelbot project and a member of Professor Sebastian Trimpe’s team at RWTH University. Aachen. “To maximize the utility of a reaction wheeled unicycle robot, we decided that the Wheelbot had to be able to recover from fairly large disturbances, that it had to have an integrated power supply to prevent cables from limiting its maneuverability, and that it also had to be able to to right itself after rolling over.

The structure of the robot should be as simple as possible. Therefore, the research team decided to use the reaction wheel technique. Unlike gyros for stabilization, this technique is cheaper and the balance torques are lower compared to the reaction torques of the reaction wheel.

self-righting

The robot then uses the reaction moments to stand up from any starting position, as the video (from 2:19) shows. During the process, the small, high-performance motor draws 16 A at 24 V. The researchers had to develop a suitable controller to control the motor because existing controllers were either too large or too weak. The research team also developed a “state estimator,” an algorithm that can estimate the robot’s roll and pitch angles. Four IMUs (Inertial Measurement Units) and wheel encoders provide the necessary data.

According to the research team, Wheelbot is the first unicycle robot that can efficiently “jump” on its wheels from any starting position. Furthermore, Wheelbot is “a sophisticated testbed for robot research.” Therefore, Wheelbot is suitable as a teaching and experimentation platform to introduce students to robotics.

The next version of the Wheelbot should be even easier to build and use. The science team wants to make the robot more accessible. The Wheelbot V3 will be slightly smaller, have a more powerful microcontroller, “and be easier to use in terms of firmware design,” Geist promises. The team is also working on making the Wheelbot roll on a predefined track. Then you should also be able to perform agile driving maneuvers.

(ob)