Omnidirectional bike rolls on a ball
The Briton James Bruton has constructed a vehicle that rolls on a ball. It works, but has its quirks.
James Bruton on the Omni-Directional One-Ball Bike
(Image: James Bruton / Screenshot)
A little over a year ago, British tinkerer James Bruton surprised with an electrically powered bike that has two large balls instead of two wheels. With his new creation, he goes a step further: This bike rides on just one ball. In a YouTube video, Burton shows that his construction basically works.
The Omni-Directional One-Ball Bike consists of a ball about 60 centimeters in size, on which a frame balances. This contains the drive as well as the seat for the rider, including the control unit. The drive consists of three omnidirectional wheels arranged vertically, forming an equilateral triangle. Each of them is fitted with a 2 kilowatt ODrive-S1 electric motor.
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The power is supplied by six 6S lithium polymer batteries, providing a system voltage of 50 volts. The system is controlled by a Teensy 4.1 microcontroller from ODrive, which is coupled with a BNO086 inertial sensor from Sparkfun and a PID controller: The sensor measures the inclination, and the PID controller controls the motors to keep the bike upright.
The wheels turn at different speeds
The direction of travel is regulated by the wheels turning at different speeds: The bike moves forward when the two wheels, which are at a 60-degree angle to the direction of travel, rotate at half the speed of the wheel that is aligned with the direction of travel. A change in direction is achieved by accelerating and braking the wheels.
However, steering is not that easy: The Two-Ball Bike could be steered by the balls rotating in opposite directions. For the new bike, he finally found an emergency solution: He built a wing from a wooden stick and a foam board, which he extends to the side in the direction he wants to turn. Air resistance then turns the bike in that direction.
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The omnidirectional wheels also caused difficulties: Commercially available ones overheated too quickly and were not suitable for this purpose. Bruton therefore designed his own, with an aluminum core. Each of them has two rows of passive rollers, 18 per row. Bruton made the rollers from thermoplastic polyurethane (TPU) using a 3D printer.
Another problem: The friction between the wheels and the plastic ball generated static electricity, which made the constructor's hair stand on end. But it also interfered with the electronics and led to malfunctions. Bruton was able to solve the problem with a sprayed-on metal coating.
(wpl)
