Hobby Humanoid Robot KHR3HV Rides Bike At 10k/h

An anonymous reader points out a fun robot project from Japan, writing: "The robot pedals with its feet at variable speed. The steering is done by the robot hands as with a normal bike, and remote controlled by a human. Stability is achieved by relying on the inertial centrifugal effect of the front wheel and on a gyro aided by a PID controller that takes over steering when driving in a straight line. Seems like when the robot steers his arms he also bends the waist leaning a bit into the turn. Braking is achieved by taking the feet off the pedals and pointing them down to the ground using the metal feet as friction breaks."

Stability is NOT achieved that way.

[Jane Q. Public]

A number of very thorough studies have been done. Neither "inertia" or "centrifugal effect" from either front wheel or rear contribute anything significant to the stability of a bicycle. [wired.com] The fact is that even today, we do not fully understand the phenomenon. The only thing we are sure of is that it does not work the way most people think it does.

Re:Stability is NOT achieved that way.

[subreality]

Actually, no, it's still not the gyroscopic effect keeping you upright. The caster and trail (parameters of a bike's front suspension geometry) result in the bike having a self-balancing effect: as you lean to the right, it wants to steer right, and the centrifugal force of the turn pushes you left, keeping you from falling over. This works fine with zero-mass wheels that do not have any gyro effect.

At low speeds this effect is not enough for stability: with no active control it wants to turn constantly, and follows a squiggly, unsettled path. At mid-speeds it will want to turn, but they will be stable turns. At high speeds the bike becomes over-stable: if you let go mid-turn, the bike will automatically straighten itself out and return to a stable straight line. This is contrary to what you'd expect from the gyro effect, which would be to hold the bike leaning into the turn.

The gyro effect does exist, but its really not that strong compared to your weight and all the other forces involved.