A monowheel is a sort of auto that rides on a single wheel. It’s possible you’ll suppose that sounds lots like a unicycle or a Onewheel-style electrical skateboard, however the distinguishing characteristic of a monowheel is its large diameter. A conventional monowheel automobile carries its rider inside the center, the place the hub could be. Within the case of smaller robots, the motor and all the digital parts sit inside the circle of the rim. However like a unicycle, it’s arduous to maintain a monowheel upright whereas shifting slowly or standing nonetheless. To skirt that challenge, James Bruton constructed a mechanically steady monowheel robotic.
Calling this a “monowheel” is a little bit of a cheat, as a result of it technically has two wheels — they’re simply very shut collectively. The usage of two wheels comes with benefits. First, it lets the robotic stability in place with out tipping to both facet. Second, it makes steering easy. Like a tank, this robotic has differential drive: spin one wheel sooner than the opposite and it’ll flip. It might probably even rotate in place if the wheels spin in reverse instructions.
However the large innovation right here is the kind of wheels that Bruton selected. Every of these is a pedrail wheel, which is an odd contraption with a complete bunch of sliding legs in a radial association with pivoting ft. It rotates like a wheel, however retains not less than a couple of ft involved with the bottom at any given time. Not solely does that assist it traverse sure obstacles, like steps, however it additionally means the pedrail wheel can stay stationary with out rolling forwards or backwards.
Bruton 3D-printed virtually all the mechanical elements for this robotic, together with the legs and ft. The one elements that weren’t 3D-printed have been the fasteners and bearings. Due to the distinctive drive system, this robotic’s electronics are fairly easy — no IMU (inertial measurement unit), gyroscope, or accelerometer crucial. There are two DC motors that spin the wheels and a Teensy 3.2 growth board controls these. It receives instructions from Bruton’s common distant by way of OrangeRX DSM transceivers.
Testing proved that this idea works pretty effectively. The robotic strikes round simply and might stay nonetheless with none type of lively balancing. It might probably additionally climb over small obstacles, although the top-heavy nature of the design makes it considerably unstable if uneven terrain causes it to tip to both facet. Spacing the wheels additional aside would clear up that challenge, however then it will be even tougher to categorise this robotic as a monowheel.