The particularly cool thing of this video though is that they could mount the new sensor within the motor itself, making it all a lot more compact.
[1] https://en.wikipedia.org/wiki/Inertial_measurement_unit
It's by far the best value for money for an introductory 32bit ARM/Risk embedded device right now.
A reputable vendor: https://www.lcsc.com/product-detail/Microcontrollers-MCU-MPU...
The IMXRT1064 can be had at $7: https://www.lcsc.com/product-detail/Microcontrollers-MCU-MPU...
That's cool and all but what are the tradeoffs?
An ESC can cheat by reading out the back EMF but this only works once the motor has started spinning, such as in a drone, but in a robot arm that is supposed to hold its position.
I sort of struggle to see how getting good positioning accuracy from a high backlash system under zero load can have a useful application.
Maybe just lack of imagination on my part.
There is this trend that says make and buy bad hardware, the software will solve it. I haven't noticed that paying off. Tesla using webcams for self driving is an example. Boeing designing their planes and then using faulty attitude sensors is another.
I would be way more impressed if the robot did something useful. My suspicion is that its real world application capabilities are rather limited.
Which with how floppy that rig is, is pretty impressive.
Notably though, those gauges do need to be ‘preloaded’ (compressed into their ‘positive’ range) to be able to measure negative direction shifts, and while it looks like that was done, I can’t be 100% sure without analyzing it far more than I want to do right now.
Also, those gauges provide a degree of preload (not much, but some), which might be taking a bunch of slop out of the system and giving overly rosy accuracy numbers.
Often there is a second needle indicating which of these situations you're in, but I assume it's not considered necessary because if you're 1mm off, the situation is (in the contexts in which these devices are used) very obvious.
It's not control theory, but mechanics and steppers.
Also depends on how much travel you need. It is easier to get 50 micron accuracy over a total length of 100 micron compared to a total length of 1 meter.
It's used to cut precise wood pieces or carve wood or metal etc.
https://en.wikipedia.org/wiki/Pantograph
You use the "big" part to drive the "small" one, which gives it great precision.
This uses DC motors. If you use modern 3-phase servomotors, you know more of what the motor is doing.
Said that, I'm impressed how precise this rather flimsy looking robot actually is.
It would be sick if they use a pure vision ML approach to train a heuristic understanding of its own muscles, instead of these fixed rotary encoders which do not account for material deflection, sensor dislodgement, etc. sort of like meta quest player tracking in the SLAM loop.
Kudos!
To do this they needed bigger engines on the same frame, which in turn needed to be mounted further forward affecting flight characteristics and requiring retraining. Retraining would be a sales killer so they hacked on some software systems to attempt to make the plane fly like an older 737.
Then they can just use an iPad training course for pilots to upgrade. The augmentation had to avoid the pilot knowing about (I think) the plane getting stuck in a stall at a too high AoA (this is where my memory might be off...) so the MCAS software uses AoA sensors to nose down based on the detected AoA.
The AoA sensors were never designed to be used for a direct life and death critical use case and sometimes they got stuck or failed. MCAS only used one as an input. If MCAS incorrectly asseses a nose down is required and the pilot follows their 737 training they are having their last day. That plane is going down.
Bascially people were murdered by Boeing so at every stage of this wretched plan they can make more money.
I think you are right but Boeing was more of perhaps the worst possible asshole design, and deserves it's own league.
Boeing’s argument is that an MCAS trim runaway is able to be addressed by the (memory item) Trim Runaway checklist and the crew of ET302 correctly used the STAB TRIM CUTOUT on that checklist during their attempt to save the flight. They then undid that action, in order to manually command nose-up trim (also reasonable under the circumstances, though contrary to the checklist), then stopped commanding nose-up trim while leaving the trim runaway checklist item reverted, allowing MCAS to continue the trim runaway that they’d previously correctly stopped by following basic 737 training. Then the flight was lost.
Boeing did wrong here, but their argument was that if a 737 pilot correctly executed the emergency checklist that is drilled into them during initial type training and in recurrent training, they’d be able to overcome that emergency. That falls into at least the probably technically correct category to me.
(The yoke displacement method to disconnect the autopilot was not part of the emergency checklist for stab trim runaway.)
One example of real work: https://www.youtube.com/watch?v=GCHXNcpq3OA
There's a reason the larger and faster printers often use the CoreXY design instead.
And as we know the FAA also was clueless, as they approved Boeing's "safety analysis".
>>> Extensive interviews with people involved with the program, and a review of proprietary documents, show how Boeing originally designed MCAS as a simple solution with a narrow scope, then altered it late in the plane’s development to expand its power and purpose. Still, a safety-analysis led by Boeing concluded there would be little risk in the event of an MCAS failure — in part because of an FAA-approved assumption that pilots would respond to an unexpected activation in a mere three seconds.
And, just to drive whatever point home, on top of all this the FAA completely dropped the ball, because it did not notice that they allowed Boeing to break their own base conditions which in effect invalidated the safety analysis.
>>> As Boeing and the FAA advanced the 737 MAX toward production, they limited the scrutiny and testing of the MCAS design. Then they agreed not to inform pilots about MCAS in manuals, even though Boeing’s safety analysis expected pilots to be the primary backstop in the event the system went haywire.
It's understandable that Boeing wanted to avoid simulator training, but apparently this regulatory discontinuity (ie. either same or different, no in-between, as far as I understand) forced them to concentrate so much on avoiding the need for new type certification that they ended up completely believing their own crazy tale about the two models' sameness, which led to hiding information from pilots.
https://www.seattletimes.com/seattle-news/times-watchdog/the...
https://www.sciencedirect.com/science/article/abs/pii/S10575...
Whereas maybe before on older planes you get in a stall and you nose down to reduce AoA. You don't need a sensor to know this look at altitude etc.
So now you need perfect ten nines of reliability AoA sensors. Their use case has gone from a data point to mission critical, but the sensor is the same.
Chances are, if your AoA is anywhere near the critical AoA, a competent pilot is likely aware of it. The sensors are just another safety factor on top of that to help ensure situational awareness.
Bean counters bathing in blood, all the way down.
https://electroimpact.com/Company/PatentFiles/US8989898B2.pd...
Robot arms have existed long before 2015. And a lot of them use some combination of encoders. The term "secondary feedback" by itself without clarification doesn't really mean anything specific, and in terms used by the patent I would call this more of adding primary/primary feedback system. The part that the patent seems to repeat is having secondary position sensor attached to the mechanical joint of robot (I assume as opposed to encoders already builtin into the servo drive), although patentability of even that seems somewhat questionable in 2015. I am not that good at reading patents, so maybe I am missing the actually relevant/novel part of that patent.
In the video both encoders are builtin the servo, instead of attached to the arm itself, even more the extra angle sensor introduced by author is attached directly to motor before the gearbox and it's slop which is complete opposite of what the patent tries to claim. The angle servo attached to output shaft after gearbox is what all hobby servos have.
If you go through the actual claims of patent most of them are not applicable to the video. 1) "system for large-scale assembly operations, ... secondary feedback mounted to joint ...". Not suitable for large scale asembly operations, no feedback attach to joint, both feedback systems are built in the hacked servos and can't measure any slop within the joint itself or servo to joint connection. 2) angular accuracy of 0.05 arcminutes - very unlikely 4) system of claim 1 wherein the manufacturing assembly is an aerospace assembly - no aerospace assembly making here, 5) 6rotary axis and 1 linear axis - no linear axis, 6) secondary feedback system is optical encoder -> questionable whether the optical angle sensor attached before gearbox matches the definition of "secondary encoder" as described by rest of the patent, also optical encoders is typically used for describing relative postion/angle sensor based on bunch of slits and counting pulses instead of analog amplitude measurement which gives absolute position. Typically I wouldn't bother with minute differences in classification of how the angle sensor is implemented, but since patent explicitly lists very specific sensor technologies I guess it matters. Otherwise they could just claim that there is an angle sensor/encoder. 7) secondary feedback system is inductive encoder - no inductive encoders here, 8) magnetic encoder - no magnetic encoders, 9) secondary feedback system is resolver - no resolver here (as in analog angle sensor based on ac coupling change depending on angle between two parts to directly generate the sin/cos of angle), 10) "system for acurate large scale-manufacturing assembly operations, ... >3 axis robot arm, with end tool, secondary feedback mounted on rotary joint" - this just more or less restates claim 1 only this time mentioning >=3 instead of >= 6 axis for some reason and mentions an end tool. Is ballpoint pen an end tool for large-scale manufacturing operations? Also the secondary feedback thing discussed before.
No resource is infinite and money is an important constraint in any engineering project. Engineering is all about making compromises. Good engineering is making the right compromises: especially when life and death decisions are being made.
Casually blaming "bean counters" is a distracting fantasy available to anyone that doesn't have to make real-world decisions. Understanding the causes of how Boeing systematically screwed up requires a bit more maturity than you appear to show. "Bean-counters" particularly comes across as childish name-calling to me, and clichés don't help either.
The fact that the MAX has been cleared to fly again shows that the design decisions were not utterly flawed.
Bean counters bathing in blood, all the way down.
The forward mounting of the engine nacelles could have been countered with a small adjustment of the sweep or the surface area of the horizontal stabiliser, instead of the faulty flight control software solution, keeping the aircraft an aerodynamically safe aircraft as had been earlier generations. But that would have been a de-facto admission that the fundamental aerodynamic characteristics of the aircraft as certified were changed by the forward mounted nacelles.
They chose to monkeypatch the flight control system instead of making a minor change that would have produced the inherently safe aerodynamic characteristics that the aircraft was certified with.
They did this to avoid the delay and cost that would have resulted if they had been required to prove the aircraft design was still airworthy. There’s a reason that new designs must be certified to be used in passenger transport. They tried to work around the fact that the 737 max is a substantially new aircraft by monkeypatching the FCS to compensate for a potentially dangerous aerodynamic flaw that was introduced by the new location of the engines.
They chose to produce a more profitable but potentially dangerous aircraft instead of letting the engineers do their job and make the aircraft stable with the new engines. Regulators were also complicit in the regulatory evasion. Hundreds died as a direct result of this malfeasance.
Bean counters bathing in blood, all the way down.
> instead of letting the engineers do their job
This is your central point - that you imply engineers are infalliable and therefore it most be someone else's fault.
A problem due to systematic effects. As you point out the mistakes have obvious fixes if you have perfect 20/20 hindsight.
Clearly, it doesn't look like Boeing was hurting for money whatsoever. Bean counters allocate money to billion dollar fines but they won't allocate it to safety and good engineering.
There aren't any deep or hidden truths behind the crashes. Turn off the MCAS and you don't get autopiloted into a crash, but telling pilots to turn off the MCAS would defeat its purpose, which is to save money on recertification and pilot training precisely by keeping it a secret.
You are correct in saying that the accountants are a critical part of the company and the engineering, it’s the MBAs in leadership that I’m referring to derisively.