81–90 of 101 posts
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How would you know which one is wrong in this scenario?
This reminds me of the adage “ Never go to sea with two chronometers; take one or three” [1] to avoid this exact conundrum [1] https://en.m.wikipedia.org/wiki/Triple_modular_redundancy#Ch...
Fusing video with IMU for navigation is called VIN (visual-inertial navigation) or VIO (visual-inertial odometry) and the field has made enormous progress over the last 10-15 years. It's the same technology that the iPhone uses for all its AR features. Dropped frames are one of the easiest things to handle. Yes, the visual feature tracking depends on frames of video but even cheap phone IMUs these days are good enoug…
It means that the people who know most about closed-loop vehicle control were not involved in the design of the copter. Such fragility is a really elementary design mistake any experienced engineer would not make. Certainly the vehicle that delivered the lander would not suffer from the same mistake. My interpretion is that the copter, as an inessential system component, was seen as an opportunity for junior people t…
Here's a research paper that might provide more information: "Vision-Based Navigation for the NASA Mars Helicopter" https://sci-hub.se/10.2514/6.2019-1411 > This paper provides an overview of the Mars Helicopter navigation system, architecture, sensors, vision processing and state estimation algorithms.
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Do any of these commenters have experience designing small "helicopter" "drone" avionics systems using off-the-shelf hardware, as in Ingenuity? For instance, you mention "aerospace grade" inertial sensors, yet Ingenuity apparently uses COTS components in that role^[1]. There are smart people on HN, but unless they have actual professional experience designing similar vehicles, I'm inclined to give the JPL folks the b…
Yes actually, any hobbyist who has done anything with drones and localization via optical flow positioning understands the problem. The commentator is correct. And saying something is done wrong is not the same as saying someone is incompetent. While I understand you're trying to point out hubris, you're swaying the other way and appealing to authority. See also: https://news.ycombinator.com/item?id=27555761
I'm appealing to the fact that they sent the thing to Mars and flew it. If you think "any hobbyist" could have trivially done a better job, which seems to be essentially what you're saying, there isn't much for me to say to you other than that I strongly disagree. And if I'm supposed to be the one who's appealing to authority here, I'm not sure what everybody else thinks they're doing.
I expect JPL tends toward having generalists working on projects like this, and I expect they do have things to learn. Nothing in my comment contradicts any of that. But the level of armchair quarterbacking in here is crazy and IMO largely unjustified.
It’s cool to see how they compensated for the IMU inaccuracy. I bought an IMU off of Amazon once and tried to use it to measure the position of a steering wheel. This worked for one rotation, but as it mentions, it’s incredibly hard to compensate for the error margin — as you integrate more measurements, the error builds up irreconcilably to the point where it’s a useless instrument. I am sure the one on the Mars hel…
I might be wrong, but I think the data from the accelerometers would be enough to know the position of the steering wheel without any accumulating error. Of course, the gyro data can be incorporated to improve the system.
Earlier quoted context omitted.
Yes actually, any hobbyist who has done anything with drones and localization via optical flow positioning understands the problem. The commentator is correct. And saying something is done wrong is not the same as saying someone is incompetent. While I understand you're trying to point out hubris, you're swaying the other way and appealing to authority. See also: https://news.ycombinator.com/item?id=27555761
> While I understand you're trying to point out hubris, you're swaying the other way and appealing to authority. I'm appealing to the fact that they sent the thing to Mars and flew it. If you think "any hobbyist" could have trivially done a better job, which seems to be essentially what you're saying, there isn't much for me to say to you other than that I strongly disagree. And if I'm supposed to be the one who's ap…
That is what's being discussed here, this is the failure mode in question. So yes, those experienced in optical flow and embedded control systems _would_ have handled this specific failure better.
But none of us are saying any hobbyist could have trivially sent it to Mars.
It should be obvious what we are specifically addressing: that this kind of error is not the sort that should happen in a properly thought out, bog standard real time system.
> JPL tends toward having generalists
And that's fine too, plus dumb mistakes always happen.
So it shouldn't be much surprise when the "armchair quarterback" responses show up, and rightly point out the issues. It would be more crazy not to be incredulous.
NASA systems appear to have the property that they are both perfectly designed when HN commenters do not understand the code and amateurishly designed when they have errors. This bathtub style curve for perception of NASA design by HN commenters makes me question if the perception correlates with reality.
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It might be related to the hostility of the environment. The chips aren't radiation proof, so it is expected to have some bit flops due to radiation.
Why on earth wouldn't they use rad-proofed chips on a planet closer to the sun, with virtually no atmosphere compared to earth?
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It means that the people who know most about closed-loop vehicle control were not involved in the design of the copter. Such fragility is a really elementary design mistake any experienced engineer would not make. Certainly the vehicle that delivered the lander would not suffer from the same mistake. My interpretion is that the copter, as an inessential system component, was seen as an opportunity for junior people t…
do you have ANY evidence to support this claim? or are you relying on a third party article's interpretation and then extrapolating that even further?
The exact nature of the design flaw is subject to further investigation.
I understand the IMU is not an ideal input and integration over time leads to positional errors. But gyros are much better and the orientation of the drone in flight is paramount. What I wonder is what ‚advanced‘ control law allowed the drone to become unstable wrt. orientation when there was noisy positional input.