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Are there electric motors, which apply force not in rotational motion, but in longitudinal motion?

They should have electromagnetic design and no gears and worms.

Such motors would be great for linear actuators. They could transfer both force and feedback.

What is the name of such devices?

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There are solenoids, which are electromagnetic linear actuators, and there are linear voltage differential transformers LVDTs, which are electromagnetic linear position sensors.

I don't think you could use one for positioning and sensing because solenoids operate primarily on DC while LVDTs operate on AC. Additionally, solenoid positioning is generally poor and they do not output a position but rather a force, like pneumatics or hydraulics.

Hydraulics can utilize the fact that their working fluid is essentially incompressible for position control - i.e., proportional control until position is reached then just shut inlet and outlet valves, but "compressible" actuators such as pneumatics and solenoids have a SIGNIFICANTLY more difficult time achieving performance even remotely on par with hydraulics.

Controllers for pneumatic positioning exist, as I'm sure they do for solenoids as well, but solenoids are primarily used for on/off switching. Anything more advanced and you're looking at an expensive position controller. LVDTs are also expensive.

Any particular reason a regular geared linear actuator is insufficient?

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  • $\begingroup$ Solenoid is too primitive. I was imagining something like multiple electromagnets, mounted linearly, similarly as it done in advanced normal (circular) motors. I wish single device to provide both force and feedback. I need not position feedback, just force (momentum flow). May be normal linear actuators also can this, I am a newbie. $\endgroup$ – Dims May 31 '15 at 8:44
  • $\begingroup$ P.S. Just found that there are just "linear motors": en.wikipedia.org/wiki/Linear_motor $\endgroup$ – Dims May 31 '15 at 8:46
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    $\begingroup$ Yes, those exist, but nearly every application for those devices is transportation, from monorails to baggage handling conveyor lines (as discussed in the Wikipedia article). You ask for an electric piston, which implies for me that you would like a short range solution. Granted you can still set up a linear motor for a short distance, this is how a coilgun works, but also notice that a coilgun is just a stack of solenoids that are precision timed. $\endgroup$ – Chuck May 31 '15 at 16:29
  • $\begingroup$ Also as mentioned, you are unlikely to find a solution that does actuation and feedback. Given your statement above that you are not interested in position, I can only assume that means you are looking for force feedback, which I can pretty much guarantee you will not find in one package. We could be of more use if you could elaborate on your application. $\endgroup$ – Chuck May 31 '15 at 16:30

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