5 ms·

I see no mention of "advanced control techniques"? Sounds like there is just a limit on roll/pitch angles and a limit on distance applied. Saying "advanced cont

I see no mention of "advanced control techniques"? Sounds like there is just a limit on roll/pitch angles and a limit on distance applied. Saying "advanced control techniques [for multirotors]" sets an expectation for something along the lines of Tedrake's Underactuated Control approaches: http://underactuated.mit.edu/ http://underactuated.mit.edu/

idiotsecant 5y ago
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.
- njoubert 5y ago
  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.
  - arbirk 5y ago
    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
    - afrodc_ 5y ago
      How would you know which one is wrong in this scenario?
      - omeze 5y ago
        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#Chronometers https://en.m.wikipedia.org/wiki/Triple_modular_redundancy#Ch...
        kortex 5y ago
        Incidentally, I learned the hard way why you never run two instances of Consul (or any Raft powered stack), only 1 or 3. All sorts of wacky state can occur.
      - arbirk 5y ago
        You have the navigation system as a third ‘sensor’, but in this case the sensor with an abnormal spike could be disregarded
  - mrandish 5y ago
    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.
- jessriedel 5y ago
  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.
  - krisoft 5y ago
    > ... 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".
    - idiotsecant 5y ago
      In the motion control and process control industries deterministic systems or SISO systems like PID are typically considered in what someone would just call 'controls'. Advanced process control is an actual industry three-letter acronym term relating to 'meta-controls' where the controller is itself controlled by an outside system like the supply chain or a plant tuning system, etc. This is the point I was trying to make - i'm not making a judgement call on what is or is not sufficiently 'advanced' only pointing out that this term has a meaning that the parent post I was replying to might not have understood.
- baybal2 5y ago
  > 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. Not so advanced as very correctly pointed out by https://news.ycombinator.com/item?id=27554949 https://news.ycombinator.com/item?id=27554949 Motor-attitude control loop cannot, and should not be "fused" with navigation layer, whether INS, or optical flow sensor. The bog standard deterministic controls algorithm here is "bog standard superior." Computer vision/optical flow sensors have much lower precision than gyroscopes, and accelerometers, let alone aerospace grade ones.
  - caconym_ 5y ago
    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 benefit of the doubt. It's also worth considering that they are the only team that has ever flown such a vehicle on another planet, which imposes constraints that even other experts may not be familiar with; that they were working with a limited budget, and making heavy use of existing open-source code; and that, generally speaking, we weren't in the room. On the other hand, maybe they really are incompetents whose avionics system is "designed wrong", and who do need these things explained to them so that they can learn faster, as the commenter you linked so delightfully put it. In that view, I guess their groundbreaking achievement is probably more dumb luck than anything else--maybe JPL should do some firing and hiring so that things don't turn out worse next time! ^[1] https://spectrum.ieee.org/automaton/aerospace/robotic-exploration/nasa-designed-perseverance-helicopter-rover-fly-autonomously-mars https://spectrum.ieee.org/automaton/aerospace/robotic-explor...
    - deleted 5y ago
      [deleted]
    - stevenhuang 5y ago
- xtiansimon 5y ago
  > “You need not gatekeep here, this is a real term.” Not my monkey; not my circus. But… is critique of terms “gatekeeping”? I understand this term in the context of ownership (ie. gatekeepers for books are publishers/printers who own the means of production.) I greatly appreciate some level of debate of terms here on HN.
shadowgovt 5y ago
I wish they had gone into more detail. Unfortunately, my experience is that, yes, such limiters do count as "advanced." First time I got my hands on a working mounted arm, I was cautioned again and again the need to run any new program in low-speed mode first. Because the arm had no limiting logic and would cheerfully power-bomb its own base with all the force and torque its motors could muster if I told it to. Preventing that is still considered an "advanced technique."

idiotsecant 5y ago

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.

njoubert 5y ago
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.
- arbirk 5y ago
  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
  - afrodc_ 5y ago
    How would you know which one is wrong in this scenario?
    - omeze 5y ago
      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#Chronometers https://en.m.wikipedia.org/wiki/Triple_modular_redundancy#Ch...
      - kortex 5y ago
        Incidentally, I learned the hard way why you never run two instances of Consul (or any Raft powered stack), only 1 or 3. All sorts of wacky state can occur.
    - arbirk 5y ago
      You have the navigation system as a third ‘sensor’, but in this case the sensor with an abnormal spike could be disregarded
- mrandish 5y ago
  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.
jessriedel 5y ago
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.
- krisoft 5y ago
  > ... 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".
  - idiotsecant 5y ago
    In the motion control and process control industries deterministic systems or SISO systems like PID are typically considered in what someone would just call 'controls'. Advanced process control is an actual industry three-letter acronym term relating to 'meta-controls' where the controller is itself controlled by an outside system like the supply chain or a plant tuning system, etc. This is the point I was trying to make - i'm not making a judgement call on what is or is not sufficiently 'advanced' only pointing out that this term has a meaning that the parent post I was replying to might not have understood.
baybal2 5y ago
> 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. Not so advanced as very correctly pointed out by https://news.ycombinator.com/item?id=27554949 https://news.ycombinator.com/item?id=27554949 Motor-attitude control loop cannot, and should not be "fused" with navigation layer, whether INS, or optical flow sensor. The bog standard deterministic controls algorithm here is "bog standard superior." Computer vision/optical flow sensors have much lower precision than gyroscopes, and accelerometers, let alone aerospace grade ones.
- caconym_ 5y ago
  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 benefit of the doubt. It's also worth considering that they are the only team that has ever flown such a vehicle on another planet, which imposes constraints that even other experts may not be familiar with; that they were working with a limited budget, and making heavy use of existing open-source code; and that, generally speaking, we weren't in the room. On the other hand, maybe they really are incompetents whose avionics system is "designed wrong", and who do need these things explained to them so that they can learn faster, as the commenter you linked so delightfully put it. In that view, I guess their groundbreaking achievement is probably more dumb luck than anything else--maybe JPL should do some firing and hiring so that things don't turn out worse next time! ^[1] https://spectrum.ieee.org/automaton/aerospace/robotic-exploration/nasa-designed-perseverance-helicopter-rover-fly-autonomously-mars https://spectrum.ieee.org/automaton/aerospace/robotic-explor...
  - deleted 5y ago
    [deleted]
  - stevenhuang 5y ago
xtiansimon 5y ago
> “You need not gatekeep here, this is a real term.” Not my monkey; not my circus. But… is critique of terms “gatekeeping”? I understand this term in the context of ownership (ie. gatekeepers for books are publishers/printers who own the means of production.) I greatly appreciate some level of debate of terms here on HN.

shadowgovt 5y ago

I wish they had gone into more detail. Unfortunately, my experience is that, yes, such limiters do count as "advanced." First time I got my hands on a working mounted arm, I was cautioned again and again the need to run any new program in low-speed mode first. Because the arm had no limiting logic and would cheerfully power-bomb its own base with all the force and torque its motors could muster if I told it to. Preventing that is still considered an "advanced technique."