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How can this 6 axis robot have a static accuracy of 0.05 mm? (2021) [video]

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Re: How can this 6 axis robot have a static accuracy of 0.05 mm? (2021) [video]

#71

Earlier quoted context omitted.

You have oversimplified the Boeing one: their goal was to create an efficient plane to compete with Airbus without needing the expense and delays of a new type certification. 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…

> 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. 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 ord…

Arguably the problem is that Boeing absolutely and utterly failed to do what they set out to do. After all, if the MCAS failures would present like the usual 737 runaway stabilizer, then the certified pilots would have been able to handle it as such. Since the "runaway MCAS" was a completely new phenomenon (one factor being the absolutely idiotic "on for a few seconds and then off for some" cycle).

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...

Re: How can this 6 axis robot have a static accuracy of 0.05 mm? (2021) [video]

#72
post #20

If anyone wants to build this sort of thing the new Raspberry Pie Pico 2 is both orders of magnitude more capable than the chip used here and also around half the price. It's by far the best value for money for an introductory 32bit ARM/Risk embedded device right now.

It’s relatively old at this point, but I’m still getting excellent performance from the Teensy 4.1. It’s a little more expensive, around $30, but runs Cortex M7 @ 600MHz and includes a generous compliment of I/O and protocols.

Re: How can this 6 axis robot have a static accuracy of 0.05 mm? (2021) [video]

#74
post #71

Earlier quoted context omitted.

> 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. 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 ord…

Arguably the problem is that Boeing absolutely and utterly failed to do what they set out to do. After all, if the MCAS failures would present like the usual 737 runaway stabilizer, then the certified pilots would have been able to handle it as such. Since the "runaway MCAS" was a completely new phenomenon (one factor being the absolutely idiotic "on for a few seconds and then off for some" cycle). And as we know the…

I think it may have been a contractual term where Boeing could avoid a $1M reduction in purchase price per aircraft (times 280 aircraft) if simulator training could be avoided for the launch customer, Southwest Airlines.

https://www.sciencedirect.com/science/article/abs/pii/S10575...

Re: How can this 6 axis robot have a static accuracy of 0.05 mm? (2021) [video]

#75
post #44

There are larger industrial robots that use secondary encoders to improve "out of the box" accuracy for more demanding tasks. The secondary joint feedback is paired with a kinematic model of the robot structure/mechanics to accurately predict where the robot tool point actually is. https://electroimpact.com/Products/Robots/AchievingAccuracy

Of what use are the primary encoders then?

BLDC motors require electronic commutation. The motor controller must read the current angle of the motor so that it knows which phases U V W to enable via six MOSFETs.

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.

Re: How can this 6 axis robot have a static accuracy of 0.05 mm? (2021) [video]

#76
post #20

If anyone wants to build this sort of thing the new Raspberry Pie Pico 2 is both orders of magnitude more capable than the chip used here and also around half the price. It's by far the best value for money for an introductory 32bit ARM/Risk embedded device right now.

It’s relatively old at this point, but I’m still getting excellent performance from the Teensy 4.1. It’s a little more expensive, around $30, but runs Cortex M7 @ 600MHz and includes a generous compliment of I/O and protocols.

I think it's still king of the hill. I've bought dozens.

Re: How can this 6 axis robot have a static accuracy of 0.05 mm? (2021) [video]

#78
post #38
post #33

Earlier quoted context omitted.

Or, in the case of the 737Max, to trigger a chain of events that proved lethal to hundreds to people. That’s the secondary use of the AOA sensor in combination with the FC software that they implemented. It would have been relatively easy to integrate the AOA input with other sensors to eliminate this problem, but it would have invited a deeper look at the hazards of their design decisions. Bean counters bathing in b…

> Bean counters bathing in blood, all the way down. 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. U…

Except anyone who has read up on this topic knows that Boeing got fined for several billion dollars by the FAA and that the FAA has increased the training requirements and that Boeing has lost 20 billion dollars from aircraft groundings and cancelled orders.

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.

Re: How can this 6 axis robot have a static accuracy of 0.05 mm? (2021) [video]

#79
post #49
post #38

Earlier quoted context omitted.

> Bean counters bathing in blood, all the way down. 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. U…

The design decisions were acceptable, if they had admitted the fact that the new design necessitated significant new training for the pilots, who were now flying a version of the 737 that could lose positive stability in some corners of its flight envelope….a fact they buried to reduce scrutiny (or facilitate deniability) from regulators and to make it an easier sell to airlines. Bean counters bathing in blood, all t…

The accountants are part of the engineering on large engineering projects.

> 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.

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