Omniwheel robot build uses a bit of everything


Machinist, electronics engineer, programmer, and factory worker are all skills you can wield if you take on a project like building this omniwheel robot (translated).

The omniwheels work in this tripod orientation because they include rollers which turn perpendicular to the wheel’s axis. This avoids the differential issue cause by fixed-position wheels. When the three motors are driven correctly, as shown in the video below, this design makes for the most maneuverable of wheeled robots.

An aluminum plate serves as the chassis. [Malte] milled the plate, cutting out slots for the motor with threaded holes to receive the mounting screws. A few stand-offs hold the hunk of protoboard which makes up the electronic side of the build. The large DIP chip is an ATmega168. It drives the motors via the trio of red stepper motor driver boards which he picked up on eBay.

So far the vehicle is tethered, using a knock-off of a SixAxis style controller. But as we said before, driving the motors correctly is the hard part and he’s definitely solved that problem.

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Tribot robotics platform

For a number of children born of geek parents, the WowWee Tribot is sure to make an appearance underneath a Christmas tree this year. By New Year’s, though, this toy will surely make its way to the back of a closet to sit unused until spring cleaning. It’s a shame to let such an interesting robotics platform go to waste, so [haltux] sent in a nice guide to unlocking the motor controller of this talking robot.

The ‘legs’ of the WowWee Tribot have three omnidirectional wheels mounted 120 degrees apart. We’ve seen this drive system before, so getting a pre-built platform out of the toy box is pretty interesting.

[haltux] found three H-bridges inside the Tribot and connected the direction and enable pins for each motor directly to an Arduino. The build was a success, and the new robot platform scurried along the floor. There are also rotary encoders on the Tribot, but these run at 12 Volts. [haltux] said he’ll cover these in a future post, and we’re waiting to see it.

Omniwheel robot

Like all of us, [Jonathan Guberman] has a list of projects and builds that ‘will get done when I have time.’ His Kiwi drive robot is no exception. It’s intended to be one piece of a much larger project, but he decided to document it anyway (we think in the hope of getting is rear in gear).

The robot uses a holonomic drive to get around. A holonomic drive uses three fixed wheels placed 120 degrees apart. The wheels can be independently controlled and with some vector addition the robot can move in any direction and rotate 360º inside its own wheelbase. Of course the wheels will have to be able to roll in two dimensions, so an omniwheel is used. Everything is controlled with a Wiimote nunchuck, and the movement is very smooth.

[Jonathan] has had a few projects featured on Hack A Day before, like his Mechanical Pac-Man and his adorable Portal turret plushie. [Jonathan] really demonstrates his artistry and skill in his project, so we’re really wondering what his ‘larger project’ actually is. Take a guess in the comments section, that might get [Jonathan]’s rear in gear.

Check out the video of the omnidirectional robot after the break.

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Tennis ball fetcher


Reader [Julian von Mendel] and his team built this tennis ball fetching robot for a competition (translated). The first version used distance sensors to locate the tennis balls for pick-up, but they changed to a camera based approach. The robot has three omniwheels and is designed to calculate the shortest path to the ball despite orientation since it can rotate while traveling. The wheels are monitored using rotation sensors from PS/2 mice. The control is provided by 3 Atmel microcontrollers that communicate via SPI. The multiprocessor design is fairly generic and could be reused for a different style of robot. While their robot performed fairly well, there were some shortcomings. The limited storage space meant frequent trips to drop off balls. The tilting bucket kept them from picking up tennis balls that were against the wall. Also, the bot had to be disassembled for battery swaps. The project is very well documented and they’ve released all of their control code. You can see the robot retrieving a ball after the break. Continue reading “Tennis ball fetcher”