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I'm considering a potential product but I'm not sure about the core technology I'd need.

The fundamental idea is that there would be a cable (or something similar) that would be pulled. But as it was pulled with X force, the device (mechanically and/or electronically) would provide equal (but slightly less) resistance.

So if it's pulled with 10 pounds, it would respond with (for example) 9 pounds of resistance (so the net result would the cable moving at 1 pound pressure).

But it would also need to react in real-time (more or less instantly), as the pull force would be constantly changing.

Is there already some kind of device that does that I'm not an engineer, more on an entrepreneur, so I'm a bit out of my depth here. Thanks!

Alex Gold
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  • This appears confused: "cable moving at 1 pound pressure" means at the *acceleration* correpsonding to this force, correct? What other masses (aside from the cable) come into play? what is the ultimate goal? – mart Sep 03 '20 at 09:37
  • how long are the extensions? If short, a dashpot might work. – Eric S Apr 26 '22 at 14:49

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You can wind your cable around a flywheel connected to a shaft rotating a fan in a high viscosity grease. Like an automatic transmission.

Geared to correct proportion. This mechanism is basically a friction machine but doesn't create much wear and tear.

kamran
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  • Interesting concept, but I would think that would introduce inertia (aka, if it was pulled really hard it would then coast for some time)? – Alex Gold Apr 07 '20 at 18:20
  • If your convertor has stators in it, it won't. going back to the example of an automatic transmission, there is not much slip and slackness, or delayed response. – kamran Apr 07 '20 at 18:27
  • Ah, that makes sense. Thanks, I'll look into this more! – Alex Gold Apr 07 '20 at 20:16
  • minor nitpick: This device would not react to *force* but to *speed* – mart Sep 03 '20 at 09:25
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An electronic way is through a servomotor in torque control, where you can adjust the torque dynamically. If there is a sensor measuring the force applied to the cable, it can loop to the controller, adjusting and recalculating torque as needed.

Note that as commented, a continuous force will cause acceleration and with a motor you will possibly have to limit the speed in the control.

A permanent magnet servomotor can have an excellent dynamic response depending on the system, but you can also achieve a control like this with an asynchronous motor with encoder, or with a DC motor, what will define it is your application... like load limits, speed, response dynamics, cost...

Little explanation about Torque Control versus Speed Control

dwpessoa
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