A 3-year journey to construct a response wheel

How do unstable issues keep upright? True passive balancing could be very tough and isn’t dynamic, so it doesn’t assist when there may be motion. Energetic 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 identical precept behind “self-balancing robots” that make the most of response wheels. However the management scheme essential to get that proper could be very tough 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 may be. It stands on a single foot designed to be unstable in a single horizontal axis, however secure 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’t stand upright with out tipping to 1 facet or the opposite. A response wheel with bolts for weights is chargeable for stopping that tipping.

That is imagined to work by spinning so as to “push” in opposition to nothing (because of 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 difficult. Every variable must be on the precise worth — relative to the others — for PID to work as supposed. 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.