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Mars helicopter employs advanced control techniques to survive in-flight anomaly

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Re: Mars helicopter employs advanced control techniques to survive in-flight anomaly

#51

Post by afrodc_ »

arbirk wrote: post #37
njoubert wrote: post #15

Earlier quoted context omitted.

The article title is still misleading. The sensor fusion was the root cause of the malfunction, it was not the advanced control technique that was deployed to survive the anomaly.

Agree. It's interesting that they don't treat the optical and gyroscopic systems as two separate sensors with the possibility to disregard one if it disagrees too much. A quick restart of the visual system would have been the most optimal solution #2020-hindsight

How would you know which one is wrong in this scenario?

Re: Mars helicopter employs advanced control techniques to survive in-flight anomaly

#52

Post by rsp1984 »

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 enough to dead-reckon for a second or two, especially when embedded into a sensor fusion framework, so the prediction errors resulting from a single lost frame should be very minimal and not enough to throw off the tracking.

That's why I find it hard to believe that the VIN in use by the Mars Helicopter (part of a multi billion dollar program) wouldn't be able to deal with a dropped frame. It just doesn't add up. I suspect that the situation is much more complex than what the article suggests and that more things went wrong than just a dropped camera frame.

Re: Mars helicopter employs advanced control techniques to survive in-flight anomaly

#53

Post by fermuch »

HALtheWise wrote: post #49

I can't think of a polite way to say this, but as someone who professionally develops drone software, both of the software failures experienced by Ingenuity have been embarrassingly amateur at a technical level. The first failure, which delayed the initial spin test, was described as a "watchdog timeout", which for anyone not familiar with embedded development basically means the code crashed. We all write code that…

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.

Re: Mars helicopter employs advanced control techniques to survive in-flight anomaly

#54

Post by mrandish »

njoubert wrote: post #15
idiotsecant wrote: post #8

Earlier quoted context omitted.

Sensor fusion is part of the control system. Sensor fusion that incorporates visual information is outside of the typical classical controls sphere and is likely considered part of an advanced controls segment of the devices firmware as opposed to the bog standard deterministic controls algorithm. You need not gatekeep here, this is a real term.

The article title is still misleading. The sensor fusion was the root cause of the malfunction, it was not the advanced control technique that was deployed to survive the anomaly.

My understanding from reading an earlier explanation from JPL was that it appeared the issue wasn't so much from the missing frame itself but rather the software not being tolerant of the frame count being off.

IIRC, it seemed more like a missing test case or scenario in the software validation suite might have been the ultimate root cause.

Re: Mars helicopter employs advanced control techniques to survive in-flight anomaly

#55

Post by ncmncm »

rsp1984 wrote: post #52

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 to get some end-to-end experience. I hope they are learning the right things.

Re: Mars helicopter employs advanced control techniques to survive in-flight anomaly

#56

Post by ehsankia »

ncmncm wrote: post #55
rsp1984 wrote: post #52

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…

The article makes it sound like after the missed frame, every subsequent frame had the wrong timestamp and was processed wrong, so it sounds like more of a bug. If the subsequent timestamps had the right timestamps, and the calculation was based on delta timestamps, then it would basically basically interpolate over the missing frame and then recover. The fact that every subsequent frame was assumed to be 33ms in the past was the issue here.

Re: Mars helicopter employs advanced control techniques to survive in-flight anomaly

#57

Post by ghaff »

usepgp wrote: post #43
ghaff wrote: post #36

Earlier quoted context omitted.

>(I think I'm supposed to bang rocks together to make fire, right?) Won't work very well unless you have flint specifically :-) Even if you know the techniques, starting fire without any manufactured tools or manufactured tools to make the devices is really really hard.

Its possible to just spin a dry stick against another dry stick with your hands. takes < 5 minutes to get a fire going.

As someone who did this sort of things in Boy Scouts, this is not super-simple just using natural materials. Maybe you're superman but starting fires with just natural materials was actually very difficult for our ancestors for a very long time. And is difficult today.

Re: Mars helicopter employs advanced control techniques to survive in-flight anomaly

#59

Post by mrandish »

HALtheWise wrote: post #49

I can't think of a polite way to say this, but as someone who professionally develops drone software, both of the software failures experienced by Ingenuity have been embarrassingly amateur at a technical level. The first failure, which delayed the initial spin test, was described as a "watchdog timeout", which for anyone not familiar with embedded development basically means the code crashed. We all write code that…

Thanks for your interesting post. I wouldn't be surprised if you are correct, at least based on my experiences with pseudo-governmental software development. I've noticed that, as a percentage, there seem to be fewer folks who've developed the grizzled paranoia that comes from repeatedly shipping commercial software under unreasonable constraints.

As an amateur RC pilot familiar with some of the excellent RC flight control systems, it would have been a huge missed opportunity if JPL didn't invite some experienced engineers from the commercial and consumer drone community to provide input (QA folks too!). It's hard to imagine they wouldn't have gotten ample volunteers to spend a few days helping out.

I understand JPL is already designing a larger and more capable iteration. It would be cool if experienced drone flight control devs such as yourself dropped the team a note.

Re: Mars helicopter employs advanced control techniques to survive in-flight anomaly

#60

Post by x86_64Ubuntu »

fermuch wrote: post #53
HALtheWise wrote: post #49

I can't think of a polite way to say this, but as someone who professionally develops drone software, both of the software failures experienced by Ingenuity have been embarrassingly amateur at a technical level. The first failure, which delayed the initial spin test, was described as a "watchdog timeout", which for anyone not familiar with embedded development basically means the code crashed. We all write code that…

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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