3 ms·

I used to do GNC: it’s interesting that the slower sensor (the camera) affected the orientation that much (instead of just pos).

• jcims 5y ago
  It sounds like the alignment error persisted for the remainder of the flight. Depending on the direction of the slip, the visual system would either record motion that wasn’t yet sensed by the IMU or it would record no motion when there was some recorded by the IMU. In both cases the control loops would likely try to correct for the discrepancy. The large control inputs sound a bit like ’integral windup’ in a PID loop where persistent error between desired and observed states are essentially summed over time resulting in larger control input (in the case of a drone this would be helpful for overcoming wind). Unless they box that in with limits you could easily get to a point where it starts flying like there’s a chimp on the yoke and either crash or saturate the navigation system and have it fall back/fail entirely.
  • isatty 5y ago
    The control systems behavior is less interesting to me (yes it could be windup or many other reasons for oscillation) than why the (u?)kf behaved this way. The single frame could have caused a time slip for the rest of the flight but usually there’s something that syncs timestamps before the filter acts on it. I hope we can get a technical postmortem.
    • jcims 5y ago
      Me too, would be interesting (possibly by virtue of being boring). Hopefully one of these days we'll have a vehicle on Mars taking PRs on github.
• wongarsu 5y ago
  An small error in position would lead to a larger error in speed estimate. To correct speed, you have to pitch the helicopter. But the speed keeps being wrong, leading to oscillation.