反革命

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По умолчанию я пишу под замок, но даю доступ всем, с кем общаюсь на этой платформе. Это публичный повтор старого поста, привожу его в качестве примера.

After 139 miles I have finally built a reasonable mental model of how an EUC stays upright.

Start with a simpler problem of quiet standing. To balance while standing still, humans use a combination of two stabilization strategies:

1. Center of pressure strategy (COPS), where one controls toe-heel and left-right pressure difference, shifting center of pressure relative to center of mass projection, and
2. Center of mass strategy (COMS), where one changes body position, and therefore mass distribution, causing the center of mass projection to shift relative to center of pressure.

To better understand the difference between the two, consider standing on a tightrope or a narrow balancing beam. In such case, balancing in sagittal plane (front to back) is no different from regular quiet standing and is mostly done with COPS. The basis of support (BoS), i.e. the convex hull that encloses all points of contact between the feet and the supporting surface, is large enough to always contain projection of center of mass. But balancing in coronal plane (side to side) can only be done with COMS, as BoS is too narrow. That's why a balancing rod helps, as its weight and rotational moment of inertia makes it easier to shift the center of mass.

Now back to the EUC case.

• Balancing in sagittal plane can again be done mostly with COPS, reverting to COMS only for rapid acceleration and emergency braking. EUC maintains its balance in sagittral plane, providing solid BoS.
• But COPS does not work for balancing in coronal plane, as in that plane EUC is unstable, and without a balancing rod COMS would be quite hard. But an EUC that is moving forward gives the rider another control — instead of moving center of pressure within BoS, it allows to move the entire BoS laterally by steering the wheel (changing its yaw).

Steering is achieved by a combination of two methods:

• Steer with the feet in relation to yaw (vertical) axis, while rotating the upper body in the opposite direction. To increase upper body rotational moment of inertia during the turn, hold the arms further away from the body and bend the knees more. To decrease upper body rotational moment as you return to neutral position after the turn, hold the arms closer to the body and stand more straight.
• At higher speeds when gyroscopic precession is no longer negligible, one can use that for more precise steering by tilting the wheel (relative to the roll axis) in the direction of the turn. For example, to turn right, lower the right pedal, the wheel will react with 90° delay and turn right.