4 ms·

Auto racing is an example of this being the optimal strategy, not just a simple or cheap implementation. Disregarding cases where you have to feather the thrott

by guscost 11y ago

Auto racing is an example of this being the optimal strategy, not just a simple or cheap implementation. Disregarding cases where you have to feather the throttle or brakes to maintain traction, the best racing line is always (I think) where you mash the throttle on a straightaway until the absolute last possible instant, then immediately mash the brakes to slow down just enough to squeak through the turn. It takes some getting used to.

thatcat 11y ago
Braking is also used to control weight distribution before cornering, shifting weight to the front wheels to allow for a sharper turn. Optimization occurs when the centrifugal force's direction is counter balanced by the friction of the tires, which varies with acceleration and braking. Optimal lines depend on the shape of the turn, but max braking always occurring right before the apex and shifts to high acc after. Really though, its max brake/acc without slipping not just 1/0. Traction control/abs simplify the situation at the racer input level, allowing optimal strategy to approach 1/0 by functioning as a micro instance of the bang bang strategy. The abs/tcs is 1/0 due to optimization, not simplicity, since a variable input would not allow the wheels to return to a rolling state anymore quickly.
- guscost 11y ago
  Great point about shifting weight to the front wheels. Real life racing theory is definitely much more complicated than my amateur understanding, especially when you're talking about high-performance cars and trained drivers.
nocarrier 11y ago
This isn't really correct. There's four things you have to be aware of when going through a corner--throttle, brake, orientation, and traction. Oftentimes the fastest route through a corner doesn't match the bang-bang approach you describe. A good example is a series of chicanes where the bang-bang approach would actually make you slower. To put it another way, traction factors a lot more heavily into the best route around a corner and therefore demands fewer instances of full-on/full-off throttle and braking that you describe.
ArkyBeagle 11y ago
Kinda. But you have an input with (presumably) finer control than is usually available with an actual bang bang. Throttle control in racing is what I'd consider a "pun" on bang bang. While it's shaped the same, the rationale doesn't quite line up with a real life bang bang. In racing, it is "cheap" in the sense of a sort of cost function based on response time.

by guscost 11y ago

thatcat 11y ago

Braking is also used to control weight distribution before cornering, shifting weight to the front wheels to allow for a sharper turn. Optimization occurs when the centrifugal force's direction is counter balanced by the friction of the tires, which varies with acceleration and braking. Optimal lines depend on the shape of the turn, but max braking always occurring right before the apex and shifts to high acc after. Really though, its max brake/acc without slipping not just 1/0. Traction control/abs simplify the situation at the racer input level, allowing optimal strategy to approach 1/0 by functioning as a micro instance of the bang bang strategy. The abs/tcs is 1/0 due to optimization, not simplicity, since a variable input would not allow the wheels to return to a rolling state anymore quickly.

guscost 11y ago
Great point about shifting weight to the front wheels. Real life racing theory is definitely much more complicated than my amateur understanding, especially when you're talking about high-performance cars and trained drivers.

nocarrier 11y ago

This isn't really correct. There's four things you have to be aware of when going through a corner--throttle, brake, orientation, and traction. Oftentimes the fastest route through a corner doesn't match the bang-bang approach you describe. A good example is a series of chicanes where the bang-bang approach would actually make you slower. To put it another way, traction factors a lot more heavily into the best route around a corner and therefore demands fewer instances of full-on/full-off throttle and braking that you describe.

ArkyBeagle 11y ago

Kinda. But you have an input with (presumably) finer control than is usually available with an actual bang bang. Throttle control in racing is what I'd consider a "pun" on bang bang. While it's shaped the same, the rationale doesn't quite line up with a real life bang bang. In racing, it is "cheap" in the sense of a sort of cost function based on response time.