4 ms·

The LIDAR sensors should be able to handle most rain conditions, but it breaks down when you get into heavy rain. I'm not precisely sure where the line is draw

The LIDAR sensors should be able to handle most rain conditions, but it breaks down when you get into heavy rain. I'm not precisely sure where the line is drawn. Snow however is a different problem. I think even light snow is impossible for LIDAR to penetrate. Not to mention the issues that arise when tires slip on ice, snow is covering signage, etc, etc.

sigmar 13y ago
Do you have any sources for any of this information? Because they seem entirely made up and the "issues when tires slip on ice" have been mitigated with computerized ABS systems for the past 20 years
- Qworg 13y ago
  I've done a lot of work with perception systems and sensors. GP is right on the money with the problems. Rain is even difficult. Snow is the worst though - it is both wet and super reflective. Super reflective dazzles your laser/obscures cameras. Wet screws up your radar.
- chiph 13y ago
  Funny thing about ABS systems is that the pump actually forces the brake pads open. The designer's thinking is that a turning wheel is able to steer, while a vehicle with sliding wheels is directed pretty much by momentum alone. This results in longer stopping distances. So far as ice -- it's coefficient of friction in the real world is not a constant -- it varies based on local conditions. So you can't predict your ability to stop & steer on it - you can only react. Your best defense is to install ice-rated tires in early winter to increase your traction. Google will likely have to do some testing in Wisconsin to see how the software reacts to icy conditions, and is able to somehow automatically recognize ice/slush and adjust stopping/acceleration rates appropriately.
  - lutorm 13y ago
    Well, in principle ABS shouldn't necessarily result in longer stopping distance: sliding friction is lower than static friction, so if you can control the braking precisely enough, not locking the wheels should result in shorter stopping distance along with not losing control. I'm not saying current systems are that good, though.
    - sp332 13y ago
      "ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces for many drivers; however, on loose surfaces like gravel or snow-covered pavement, ABS can significantly increase braking distance, although still improving vehicle control." (with citations) http://en.wikipedia.org/wiki/Anti-lock_braking_system http://en.wikipedia.org/wiki/Anti-lock_braking_system
    - chiph 13y ago
      On dry surfaces, a professional driver is able to do Threshold Braking, which in non-ABS cars maximizes stopping power by taking braking just up to the limit before the tires start sliding. On cars with ABS, the intent is to minimize the rate at which the ABS pump activates in order to maximize stopping power (pulse ... pulse ... pulse vs. pulse.pulse.pulse) ABS has an advantage over regular systems in that the computer is able to control braking effort on a per-wheel basis. Something a human with only one pedal to push can't do. IIRC, the best ABS systems are able to cycle at about 10Hz. Something I vaguely recall reading about is that in a panic stop on ice, the heat from the sliding friction will melt a very small bit of ice under the contact patch, turning it into a hydroplaning situation. I need to see if I can find that reference again...
- fancyketchup 13y ago
  ABS allows you to take maximum advantage of the traction you do have, but it doesn't magically improve your traction. The problem the GP is referencing is that the driver (be it human or computer) operates the vehicle using some sort of model for the maximum available traction. (Some) Humans are able to notice when it is snowing, re-tune their model and drive at an appropriate speed. It doesn't seem impossible that some heuristic could be invented to do the same for a computer driver, but I don't think anyone has demonstrated that heuristic yet.
- aetherson 13y ago
  Well, I have some sources for that information: http://www.newyorker.com/reporting/2013/11/25/131125fa_fact_bilger?currentPage=all http://www.newyorker.com/reporting/2013/11/25/131125fa_fact_... It's a long article, but search for "rain." Here's the most important quote for our purposes: Left to its own devices, Thrun says, it could go only about fifty thousand miles on freeways without a major mistake. Google calls this the dog-food stage: not quite fit for human consumption. “The risk is too high,” Thrun says. “You would never accept it.” The car has trouble in the rain, for instance, when its lasers bounce off shiny surfaces. (The first drops call forth a small icon of a cloud onscreen and a voice warning that auto-drive will soon disengage.) It can’t tell wet concrete from dry or fresh asphalt from firm. It can’t hear a traffic cop’s whistle or follow hand signals.

sigmar 13y ago

Do you have any sources for any of this information? Because they seem entirely made up and the "issues when tires slip on ice" have been mitigated with computerized ABS systems for the past 20 years

Qworg 13y ago
I've done a lot of work with perception systems and sensors. GP is right on the money with the problems. Rain is even difficult. Snow is the worst though - it is both wet and super reflective. Super reflective dazzles your laser/obscures cameras. Wet screws up your radar.
chiph 13y ago
Funny thing about ABS systems is that the pump actually forces the brake pads open. The designer's thinking is that a turning wheel is able to steer, while a vehicle with sliding wheels is directed pretty much by momentum alone. This results in longer stopping distances. So far as ice -- it's coefficient of friction in the real world is not a constant -- it varies based on local conditions. So you can't predict your ability to stop & steer on it - you can only react. Your best defense is to install ice-rated tires in early winter to increase your traction. Google will likely have to do some testing in Wisconsin to see how the software reacts to icy conditions, and is able to somehow automatically recognize ice/slush and adjust stopping/acceleration rates appropriately.
- lutorm 13y ago
  Well, in principle ABS shouldn't necessarily result in longer stopping distance: sliding friction is lower than static friction, so if you can control the braking precisely enough, not locking the wheels should result in shorter stopping distance along with not losing control. I'm not saying current systems are that good, though.
  - sp332 13y ago
    "ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces for many drivers; however, on loose surfaces like gravel or snow-covered pavement, ABS can significantly increase braking distance, although still improving vehicle control." (with citations) http://en.wikipedia.org/wiki/Anti-lock_braking_system http://en.wikipedia.org/wiki/Anti-lock_braking_system
  - chiph 13y ago
    On dry surfaces, a professional driver is able to do Threshold Braking, which in non-ABS cars maximizes stopping power by taking braking just up to the limit before the tires start sliding. On cars with ABS, the intent is to minimize the rate at which the ABS pump activates in order to maximize stopping power (pulse ... pulse ... pulse vs. pulse.pulse.pulse) ABS has an advantage over regular systems in that the computer is able to control braking effort on a per-wheel basis. Something a human with only one pedal to push can't do. IIRC, the best ABS systems are able to cycle at about 10Hz. Something I vaguely recall reading about is that in a panic stop on ice, the heat from the sliding friction will melt a very small bit of ice under the contact patch, turning it into a hydroplaning situation. I need to see if I can find that reference again...
fancyketchup 13y ago
ABS allows you to take maximum advantage of the traction you do have, but it doesn't magically improve your traction. The problem the GP is referencing is that the driver (be it human or computer) operates the vehicle using some sort of model for the maximum available traction. (Some) Humans are able to notice when it is snowing, re-tune their model and drive at an appropriate speed. It doesn't seem impossible that some heuristic could be invented to do the same for a computer driver, but I don't think anyone has demonstrated that heuristic yet.
aetherson 13y ago
Well, I have some sources for that information: http://www.newyorker.com/reporting/2013/11/25/131125fa_fact_bilger?currentPage=all http://www.newyorker.com/reporting/2013/11/25/131125fa_fact_... It's a long article, but search for "rain." Here's the most important quote for our purposes: Left to its own devices, Thrun says, it could go only about fifty thousand miles on freeways without a major mistake. Google calls this the dog-food stage: not quite fit for human consumption. “The risk is too high,” Thrun says. “You would never accept it.” The car has trouble in the rain, for instance, when its lasers bounce off shiny surfaces. (The first drops call forth a small icon of a cloud onscreen and a voice warning that auto-drive will soon disengage.) It can’t tell wet concrete from dry or fresh asphalt from firm. It can’t hear a traffic cop’s whistle or follow hand signals.