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

control.com

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

#21

Post by the8472 »

anvandare wrote: post #6
anticristi wrote: post #3

Time to set up a GPS constellation on Mars? Somehow forgot that this navigation aid -- that we take for granted on Earth -- is missing on this other planet.

Pretty sure SpaceX's first deliveries to Mars (orbit) will include just that. I think they could probably use Starlink satellites without much modification (most important one I can think of would be more panels to cope with the reduced solar irradiance)? The GPS constellation has 32 satellites. A GPS satellite weighs ~2000kg. Starship should get 100-150 tons to Mars - the math checks out! (Disclosure: I got all my r…

> satellites without much modification (most important one I can think of would be more panels to cope with the reduced solar irradiance)?

atomic clocks

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

#22

Post by ealloc »

The article says the problem was a dropped frame from the camera, but that just further piques my curiosity:

Presumably they use some kind of Kalman Filter, but those are easy to program to account for missing frames, or frames at non-discrete timepoints, perhaps even for screwy camera images if the programmer had a reasonable prior for the likelihood of it happening. Kalman Filters by design account for measurement error.

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

#24

Post by bonzini »

idiotsecant wrote: post #10
anticristi wrote: post #3

Time to set up a GPS constellation on Mars? Somehow forgot that this navigation aid -- that we take for granted on Earth -- is missing on this other planet.

Yes, but wouldn't help with this particular problem. This was a roll/pitch issue, not fundamentally a position issue.

It stemmed from incorrect estimation of the position and thus of the velocity, which the helicopter attempted to correct.

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

#25

Post by bombcar »

TheAdamAndChe wrote: post #11
anvandare wrote: post #6

Earlier quoted context omitted.

Pretty sure SpaceX's first deliveries to Mars (orbit) will include just that. I think they could probably use Starlink satellites without much modification (most important one I can think of would be more panels to cope with the reduced solar irradiance)? The GPS constellation has 32 satellites. A GPS satellite weighs ~2000kg. Starship should get 100-150 tons to Mars - the math checks out! (Disclosure: I got all my r…

It's funny/amazing to me how we lived without GPS for thousands of years, but it's become so integral to our society that it's one of the first things we're setting up there before visiting.

GPS is also “easy” to setup if you’re already coming in from space.

I wonder what the “useful minimum” for satellites would be if you wanted, say, relatively accurate positioning once every orbit or each day.

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

#26

Post by krisoft »

jessriedel wrote: post #18
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.

I don't think this is gate keeping. Regardless of the terminology used within the field, the intended audience of this pop article will interpret "advanced" to mean actually unusual or at the cutting edge. Relying on the public's misinterpretation of jargon ought to be criticized.

> ... intended audience of this pop article ...

Are we reading the same page? I see datasheets linked in the navbar, an article about an EtherCan box, and white papers about encoders. If any site is then certainly this one has a very specialist audience in mind.

Besides i believe what constitutes "advanced" gets wider rather than narrower when you move towards a less specialised audience. To the generic population even two stacked PID loops would qualify as "advanced" while practitioners would call that "conservative" or "old-fashioned".

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

#27

Post by quesera »

TheAdamAndChe wrote: post #11
anvandare wrote: post #6

Earlier quoted context omitted.

Pretty sure SpaceX's first deliveries to Mars (orbit) will include just that. I think they could probably use Starlink satellites without much modification (most important one I can think of would be more panels to cope with the reduced solar irradiance)? The GPS constellation has 32 satellites. A GPS satellite weighs ~2000kg. Starship should get 100-150 tons to Mars - the math checks out! (Disclosure: I got all my r…

It's funny/amazing to me how we lived without GPS for thousands of years, but it's become so integral to our society that it's one of the first things we're setting up there before visiting.

I get the humor, but if you think about it:

Almost all of the technologies that we would need for survival and productivity on Mars are recently-invented.

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

#28

Post by mfsch »

JoeAltmaier wrote: post #13
anticristi wrote: post #3

Time to set up a GPS constellation on Mars? Somehow forgot that this navigation aid -- that we take for granted on Earth -- is missing on this other planet.

GPS doesn't have to be satellites. It can simply be beacons on the ground. Often used terrestrially to get a few more decimal points on a fix.

Not sure what techniques exactly you’re referring to, but the commonly used techniques for GPS enhancement (e.g. RTK [1]) are not simple distance measurements between GPS receivers and base stations but rather both stations measuring the satellite signal and using the difference of the signal in both locations to improve position estimates.

I imagine it’s possible to set up a ground-based network, but you would need a high density to cover large surfaces (you want to see at least four stations from every position). I also imagine that it would be difficult to get accurate vertical positions if the stations are all in the same horizontal plane.

[1]: https://en.wikipedia.org/wiki/Real-time_kinematic_positionin...

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

#29

Post by ncmncm »

The control system is clearly designed wrong. Navigation input should not be able to affect the closed-loop control system directly. It should affect only the calibration, incrementally. If that had been done, there would have been no flight instability, just disagreement between the IMU and navigation about how far they had flown.

There are certainly people involved in the project who could have explained this to them. I hope they are learning fast.

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

#30

Post by baybal2 »

ncmncm wrote: post #29

The control system is clearly designed wrong. Navigation input should not be able to affect the closed-loop control system directly. It should affect only the calibration, incrementally. If that had been done, there would have been no flight instability, just disagreement between the IMU and navigation about how far they had flown. There are certainly people involved in the project who could have explained this to th…

> There are certainly people involved in the project who could have explained this to them. I hope they are learning fast.

This is how nearly all modern high-end quadcopter drones fly - navigation using optical flow camera sensors short circuited directly into attitude/motor control loops.

I guess there is not a small chance they entrusted helicopter autonomous operations programming to people with quadcopter background.

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