Along with the Wheelbot, a research team at RWTH Aachen University and the Max Planck Institute for Intelligent Systems (MPI-IS) has developed a robot that, as a symmetrical reaction wheel unicycle, can stand itself on its wheel from any position. The minimalist robot is intended to serve as an experimental platform in research and teaching. It is easy to replicate due to simple construction and use of 3D printed parts.
The research team’s wheelboat is only 22 centimeters tall. When stationary, it has two wheels arranged vertically, offset by 90 degrees from each other. The robot rolls on a wheel. According to the paper published in IEEE Reaction and Automation Letters, the other wheel serves as a reaction wheel, which is controlled by electronics to ensure stable one-wheel balancing. “The Wheelboat: A Jumping Reaction Wheel Unicycle” Out.
Make it as simple as possible
“Previous unicycle robots were only designed to balance in their upright position, which severely limits the capabilities of these systems,” explains René Geist, lead researcher of the Wheelbot project and team member of Professor Sebastian Trimp at RWTH Aachen University. “To maximize the utility of a unicycle robot with responsive wheels, we decided that the wheelbot should be able to recover from fairly large perturbations, have an integrated power supply to prevent cables from limiting its maneuverability, and be able to right itself after a rollover.”
The structure of the robot should be as simple as possible. So the research team decided to use the reaction wheel technique. Unlike gyroscopes for stabilization, this technique is cheap and the balancing torques are low compared to the reaction torques of the reaction wheel.
As the video (from 2:19) shows, the robot uses reaction moments to stand up from any starting position. During this process, the small high-efficiency motor draws 16 A at 24 V. The researchers had to develop a suitable controller to control the motor as existing controllers were either too large or too weak. The research team 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” onto its wheels from any starting position. Additionally, WheelBot is “a sophisticated test bench for robotics research.” The WheelBot is therefore ideal as a teaching and experimental platform for introducing students to robotics.
The next version of Wheelbot should be even easier to build and use. The scientific 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 trying to make the wheelboat roll on a predetermined track. Then he should also be able to perform agile driving tricks.
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