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Comment by Mithaldu | Hacker News Reader

How do you feel about his claim that this would be good for energy efficiency?

Or the claim that this would allow for easier human-safety by having the torque, if lowered, not be dependent on logic, but on the actual mechanics, making it possible to stop the entire system if a failure in the torque-change motor is detected?

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How do you feel about his claim that this would be good for energy efficiency?

It's unproven. If you have to haul more mass around, that's worse for energy efficiency.

easier human-safety by having the torque (limited)

There are mechanical 'fuses' for torque limiting.[1] Having a transmission that can downshift into a very high torque mode is probably worse for safety. If torque is directly proportional to motor current, there are lots of standard safety devices for limiting motor current.

[1] https://www.mayr.com/en/products/torque-limiters

Interesting, thanks for expanding. If you don't mind another question:

> a transmission that can downshift into a very high torque mode

I'm missing something here i guess, how is this different from a motor that can deliver full torque just because the logic chip is driving it at full power? Is it because the motor wouldn't be able to reach such high torque in the first place? (Which might be a point in favor of the transmission.)

Actually the gear shifting would also be done by logic, so nothing gained by that.

Not quite. In order to lower the torque on a stepper motor you need to have the logic controlling the motor control the torque for every single step the motor takes and that can switch from low to high between two steps. You can ward against this either with continuously checking logic or the torque limiters Animats mentioned: https://www.mayr.com/en/products/torque-limiters

If the inception drive is set to low torque a second motor needs to actively set it to a higher torque, which you can guard against by cutting power to the second one while in low torque mode, and having mechanical interlocks that cut power entirely if the shape of the drive changes to a high torque configuration while it's supposed to be low torque. Neither of these require continuous logic.

How cannot you have a continous checking logic in the driver logic of a gearless drive?

Let me help: you can, and I have taken part in developing one.

Link to patent?

Lol?

Electric servos for steering wheels use safety critical code, with lot of safety checks, and use direct drive. No need for silly patent for common sense out of the United States.

What's the difference between continous checking logic and safety critical code with lot of safety checks?

I'm not a mech engineer, i do code. I'm asking to learn and if you can prove me wrong by teaching something, yay.

Those safety checks need to be run continously, actually, or the software will not get the certifications necessary to be released on the roads. There are passive means: practices and coding guidelines, static checks, but also active measures: defensive coding, redundancy, continously active safety check logics.

So my original point was: it doesn't matter if you use direct drive or a transmission, as both will be controlled by software, and ultimately the safety of that software will determine whether the System is safe overall. The same design principles and safeguards will need to be implemented in both cases to provide the needed integrity.

But I doubt there are any patents on this. I guess it would be illogical to demand vendors to use patents by someone. But there are lots safety regulations on the topic.

Fair enough, and it makes sense. Thanks for explaining. :)

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