4 ms·

This lab has several other videos with quad rotor robots like this (e.g. http://www.youtube.com/watch?v=MvRTALJp8DM http://www.youtube.com/watch?v=MvRTALJp8DM),

This lab has several other videos with quad rotor robots like this (e.g. http://www.youtube.com/watch?v=MvRTALJp8DM http://www.youtube.com/watch?v=MvRTALJp8DM), but don't worry about them escaping and starting a robot domination: they rely on infrared motion capture systems in that room for extremely precise location sensing. Once GPS gets sub-meter accuracy, then we should start worrying.

sliverstorm 16y ago
GPS + Accelerometer is already pretty darn accurate, I'm not really sure why they use the IR room. Perhaps simply easier to set up, and easier to co-ordinate the bots?
- eftpotrm 16y ago
  These things don't look very powerful, to put it mildly. GPS means outdoors which means wind which is a bit harder for a small, light hovering robot to handle. Indoor lets them demonstrate the principle with a useful simplifying assumption of no wind.
  - burgerbrain 16y ago
    Did you watch the same videos I did? They have these things lifting sizeable pieces of 2x4's (https://www.youtube.com/watch?v=YBsJwapanWI https://www.youtube.com/watch?v=YBsJwapanWI) and they pull of some pretty absurd manoeuvring (https://www.youtube.com/watch?v=MvRTALJp8DM https://www.youtube.com/watch?v=MvRTALJp8DM) and recovery (https://www.youtube.com/watch?v=geqip_0Vjec https://www.youtube.com/watch?v=geqip_0Vjec). Navigational issues resolved, I have a hard time seeing these things having trouble with a modest wind.
    - eftpotrm 16y ago
      Yes, I did see the same videos. And I still think no wind is a useful simplifying assumption for them, particularly on power grounds. A constant wind I agree looks like it would be within their capabilities, though their route planning software would need to take account of it and approach the target from upwind by default - not impossible but another thing to account for. The real issue for me is gusting. They are definitely small and light enough that power-to-weight issues, particularly when carrying a load with a higher surface area to the wind than the craft itself, means that it will get knocked off course by gusts. That obviously needs allowing for when navigating to and from the construction site, but particularly when dropping off a load - if the release comes at the same point as the gust, the part simply won't end up where they wanted. Do I think all of these problems are unsolvable? No, but it makes a useful simplifying assumption for their version 1 that they don't have to deal with any of them because they're flying indoors.
- thalur 16y ago
  Depending on which waveband you use, different vision tasks become a lot easier. It looks to me like all the sensing is done by the room, not the quadrotors, hence why its all room-mounted.
jakevoytko 16y ago
Solutions based on expensive IMUs [0], SLAM [1], or visual odometry are more realistic than GPS. As a rule, never use GPS for fine-grained control. Even ignoring accuracy, GPS fails when you lack line-of-sight to GPS satellites, which is extremely dangerous on a quadrotor - how do you safely land a flying chainsaw with no feedback? When finely controlling a platform, you need accurate relative position. The global position is usually unimportant when the platform's position on Earth doesn't matter. Sensors designed for computer vision applications are surprisingly light and small! Board-level cameras can fit in the palm of your hand, and reasonable IMUs are not much bigger than a matchbox. The biggest obstacles today are tradeoffs between performance/weight and performance/battery life. The platform needs algorithms with acceptable results, requiring almost no supporting hardware, and that are robust to the thousands of things that go wrong when trying to sense (noise, errors, resolution, occlusions, etc). Algorithms that fit all of these requirements are very uncommon. In fact, I would not be surprised if there was an Iron Triangle in there somewhere. [0] Inertial Measurement Units: Devices that estimate acceleration (or some other measure of movement). [1] Simultaneous Localization and Mapping. Using stereo vision, lidar, radio ranging, etc. to estimate your position, plus how the environment looks.
adamsmith 16y ago
You can also use acoustic ranging, since sound travels at about 1 foot per millisecond. We did this with ultrasound at MIT -- http://nms.csail.mit.edu/papers/index.php?detail=9 http://nms.csail.mit.edu/papers/index.php?detail=9 You can get about 1cm of ranging error (median), and say 10cm of positioning error.
asdkl234890 16y ago
Once GPS gets sub-meter accuracy, then we should start worrying. Or once the kinect shrinks to size of a short stack of quarters.

sliverstorm 16y ago

GPS + Accelerometer is already pretty darn accurate, I'm not really sure why they use the IR room. Perhaps simply easier to set up, and easier to co-ordinate the bots?

eftpotrm 16y ago
These things don't look very powerful, to put it mildly. GPS means outdoors which means wind which is a bit harder for a small, light hovering robot to handle. Indoor lets them demonstrate the principle with a useful simplifying assumption of no wind.
- burgerbrain 16y ago
  Did you watch the same videos I did? They have these things lifting sizeable pieces of 2x4's (https://www.youtube.com/watch?v=YBsJwapanWI https://www.youtube.com/watch?v=YBsJwapanWI) and they pull of some pretty absurd manoeuvring (https://www.youtube.com/watch?v=MvRTALJp8DM https://www.youtube.com/watch?v=MvRTALJp8DM) and recovery (https://www.youtube.com/watch?v=geqip_0Vjec https://www.youtube.com/watch?v=geqip_0Vjec). Navigational issues resolved, I have a hard time seeing these things having trouble with a modest wind.
  - eftpotrm 16y ago
    Yes, I did see the same videos. And I still think no wind is a useful simplifying assumption for them, particularly on power grounds. A constant wind I agree looks like it would be within their capabilities, though their route planning software would need to take account of it and approach the target from upwind by default - not impossible but another thing to account for. The real issue for me is gusting. They are definitely small and light enough that power-to-weight issues, particularly when carrying a load with a higher surface area to the wind than the craft itself, means that it will get knocked off course by gusts. That obviously needs allowing for when navigating to and from the construction site, but particularly when dropping off a load - if the release comes at the same point as the gust, the part simply won't end up where they wanted. Do I think all of these problems are unsolvable? No, but it makes a useful simplifying assumption for their version 1 that they don't have to deal with any of them because they're flying indoors.
thalur 16y ago
Depending on which waveband you use, different vision tasks become a lot easier. It looks to me like all the sensing is done by the room, not the quadrotors, hence why its all room-mounted.

jakevoytko 16y ago

Solutions based on expensive IMUs [0], SLAM [1], or visual odometry are more realistic than GPS. As a rule, never use GPS for fine-grained control. Even ignoring accuracy, GPS fails when you lack line-of-sight to GPS satellites, which is extremely dangerous on a quadrotor - how do you safely land a flying chainsaw with no feedback? When finely controlling a platform, you need accurate relative position. The global position is usually unimportant when the platform's position on Earth doesn't matter. Sensors designed for computer vision applications are surprisingly light and small! Board-level cameras can fit in the palm of your hand, and reasonable IMUs are not much bigger than a matchbox. The biggest obstacles today are tradeoffs between performance/weight and performance/battery life. The platform needs algorithms with acceptable results, requiring almost no supporting hardware, and that are robust to the thousands of things that go wrong when trying to sense (noise, errors, resolution, occlusions, etc). Algorithms that fit all of these requirements are very uncommon. In fact, I would not be surprised if there was an Iron Triangle in there somewhere. [0] Inertial Measurement Units: Devices that estimate acceleration (or some other measure of movement). [1] Simultaneous Localization and Mapping. Using stereo vision, lidar, radio ranging, etc. to estimate your position, plus how the environment looks.

adamsmith 16y ago

You can also use acoustic ranging, since sound travels at about 1 foot per millisecond. We did this with ultrasound at MIT -- http://nms.csail.mit.edu/papers/index.php?detail=9 http://nms.csail.mit.edu/papers/index.php?detail=9 You can get about 1cm of ranging error (median), and say 10cm of positioning error.

asdkl234890 16y ago

Once GPS gets sub-meter accuracy, then we should start worrying. Or once the kinect shrinks to size of a short stack of quarters.