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The primary benefit of multiple sensor fusion from a safety standpoint isn't an absolute decrease in errors. It's the ability to detect sensor disagreements at

by ethbr1 1y ago

The primary benefit of multiple sensor fusion from a safety standpoint isn't an absolute decrease in errors. It's the ability to detect sensor disagreements at all. With single modality sensors, you have no way of truly detecting failures in that modality, other than hacks like time-series normalizing (aka expected scenarios). If multiple sensor modalities disagree, even without sensor fusion, you can at least assume something might be awry and drop into a maximum safety operation mode. But we'd think that the budget config of the Boeing 737 MAX would have taught us that tying safety critical systems to single sources of truth is a bad idea... (in that case, critical modality / single physical sensor)

leoc 1y ago
> If multiple sensor modalities disagree, even without sensor fusion, you can at least assume something might be awry and drop into a maximum safety operation mode. Also, this is probably when Waymo calls up a human assistant in a developing-country callcentre.
- ethbr1 1y ago
  Saw that happen a week ago, actually. Non-sensor problem, but a Waymo made a slow right turn too wide, approached the left turning lane of cars, then safed itself by stopping, then remote assistance came online and extricated it.
AnIrishDuck 1y ago
> With single modality sensors, you have no way of truly detecting failures in that modality, other than hacks like time-series normalizing (aka expected scenarios). "A man with a watch always knows what time it is. If he gains another, he is never sure" Most safety critical systems actually need at least three redundant sensors. Two is kinda useless: if they disagree, which is right? EDIT: > If multiple sensor modalities disagree, even without sensor fusion, you can at least assume something might be awry and drop into a maximum safety operation mode. This is not always possible. You're on a two lane road. Your vision system tells you there's a pedestrian in your lane. Your LIDAR says the pedestrian is actually in the other lane. There's enough time for a lane change, but not to stop. What do you do?
- esafak 1y ago
  > Two is kinda useless: if they disagree, which is right? They don't work by merely taking a straw poll. They effectively build the joint probability distribution, which improves accuracy with any number of sensors, including two. > You're on a two lane road. Your vision system tells you there's a pedestrian in your lane. Your LIDAR says the pedestrian is actually in the other lane. There's enough time for a lane change, but not to stop. Any realistic system would see them long before your eyes do. If you are so worried, override the AI in the moment.
  - qingcharles 1y ago
    We're trying to build vehicles that are totally autonomous, though. How do you grab the wheel of the new Waymos without steering wheels? Especially if you're in the back seat staring at Candy Crush.
    - esafak 1y ago
      Waymos are safer, and drive more defensively than humans. There is no way a Waymo is going to drive aggressively enough to get itself into the trolley problem.
  - AnIrishDuck 1y ago
    > They don't work by merely taking a straw poll. They effectively build the joint probability distribution, which improves accuracy with any number of sensors, including two. Lots of safety critical systems actually do operate by "voting". The space shuttle control computers are one famous example [1], but there are plenty of others in aerospace. I have personally worked on a few such systems. It's the simplest thing that can obviously work. Simplicity is a virtue when safety is involved. You can of course do sensor fusion and other more complicated things, but the core problem I outlined remains. > If you are so worried, override the AI in the moment. This is sneakily inserting a third set of sensors (your own). It can be a valid solution to the problem, but Waymo famously does not have a steering wheel you can just hop behind. This might seem like an edge case, but edge cases matter when failure might kill somebody. 1. https://space.stackexchange.com/questions/9827/if-the-space-shuttle-computers-all-output-contradictory-commands-how-is-it-chos https://space.stackexchange.com/questions/9827/if-the-space-...

by ethbr1 1y ago

leoc 1y ago

> If multiple sensor modalities disagree, even without sensor fusion, you can at least assume something might be awry and drop into a maximum safety operation mode. Also, this is probably when Waymo calls up a human assistant in a developing-country callcentre.

ethbr1 1y ago
Saw that happen a week ago, actually. Non-sensor problem, but a Waymo made a slow right turn too wide, approached the left turning lane of cars, then safed itself by stopping, then remote assistance came online and extricated it.

AnIrishDuck 1y ago

> With single modality sensors, you have no way of truly detecting failures in that modality, other than hacks like time-series normalizing (aka expected scenarios). "A man with a watch always knows what time it is. If he gains another, he is never sure" Most safety critical systems actually need at least three redundant sensors. Two is kinda useless: if they disagree, which is right? EDIT: > If multiple sensor modalities disagree, even without sensor fusion, you can at least assume something might be awry and drop into a maximum safety operation mode. This is not always possible. You're on a two lane road. Your vision system tells you there's a pedestrian in your lane. Your LIDAR says the pedestrian is actually in the other lane. There's enough time for a lane change, but not to stop. What do you do?

esafak 1y ago
> Two is kinda useless: if they disagree, which is right? They don't work by merely taking a straw poll. They effectively build the joint probability distribution, which improves accuracy with any number of sensors, including two. > You're on a two lane road. Your vision system tells you there's a pedestrian in your lane. Your LIDAR says the pedestrian is actually in the other lane. There's enough time for a lane change, but not to stop. Any realistic system would see them long before your eyes do. If you are so worried, override the AI in the moment.
- qingcharles 1y ago
  We're trying to build vehicles that are totally autonomous, though. How do you grab the wheel of the new Waymos without steering wheels? Especially if you're in the back seat staring at Candy Crush.
  - esafak 1y ago
    Waymos are safer, and drive more defensively than humans. There is no way a Waymo is going to drive aggressively enough to get itself into the trolley problem.
- AnIrishDuck 1y ago
  > They don't work by merely taking a straw poll. They effectively build the joint probability distribution, which improves accuracy with any number of sensors, including two. Lots of safety critical systems actually do operate by "voting". The space shuttle control computers are one famous example [1], but there are plenty of others in aerospace. I have personally worked on a few such systems. It's the simplest thing that can obviously work. Simplicity is a virtue when safety is involved. You can of course do sensor fusion and other more complicated things, but the core problem I outlined remains. > If you are so worried, override the AI in the moment. This is sneakily inserting a third set of sensors (your own). It can be a valid solution to the problem, but Waymo famously does not have a steering wheel you can just hop behind. This might seem like an edge case, but edge cases matter when failure might kill somebody. 1. https://space.stackexchange.com/questions/9827/if-the-space-shuttle-computers-all-output-contradictory-commands-how-is-it-chos https://space.stackexchange.com/questions/9827/if-the-space-...