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A 3-year journey to construct a response wheel
Arduino Group — April 2nd, 2024
How do unstable issues keep upright? True passive balancing could be very troublesome and isn’t dynamic, so it doesn’t assist when there may be motion. Lively balancing is all about inertia and that is how a tightrope walker can traverse a chasm by making small changes with an extended pole. This is similar precept behind “self-balancing robots” that make the most of response wheels. However the management scheme essential to get that proper could be very troublesome to good, as demonstrated by Nikodem Bartnik’s venture that was three years within the making.
Bodily, that is about so simple as a self-balancing robotic will be. It stands on a single foot designed to be unstable in a single horizontal axis, however steady within the different. It’s lengthy, front-to-back, so the robotic can’t tip ahead or backward. However the backside of the foot has a curve to it, so it may possibly’t stand upright with out tipping to at least one facet or the opposite. A response wheel with bolts for weights is liable for stopping that tipping.
That is purported to work by spinning with the intention to “push” towards nothing (due to inertia), which generates torque to cease the tip. However Bartnik found that it was a large problem to tune that spin.
An Arduino Nano board controls a small brushless DC motor that spins the response wheel. A gyroscope sensor lets the Arduino monitor tilt and energy comes from a interest LiPo battery. The Arduino makes use of PID (proportional-integral-derivative) algorithms to strive an apply simply sufficient spin to counteract tipping, however not a lot that it overcorrects.
That’s the place Bartnik bumped into hassle, as a result of PID tuning is tough. Every variable needs to be on the actual worth — relative to the others — for PID to work as meant. After numerous hours of struggling, Bartnik added a Bluetooth module to the Arduino to alter these values wirelessly with out flashing new code each time. That sped up the method dramatically, permitting Bartnik to discover a set of values that works fairly properly to maintain the robotic upright.
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