Add uniform resistance when rotating by hand

developement
1

Hello,

I’m working on a motorized knob using a brushless DC motor and simpleFOC in closed loop position/angle mode. I’m just wondering if anyone has any suggestions on a potential way one might be able to use simpleFOC to add a slight resistance when rotating the knob to give it a “beefier” feel?

Thanks!

2

I have never done haptics, but I imagine you could apply torque with sign opposite to the sign of the velocity, so like a brake.
You would apply the torque only above a certain threshold velocity so that it’s not happening at 0 velocity, or even a torque proportional to the velocity so that it zeroes when not moving.

3

Please search for “haptics” in this forum. You might also consider joining our discord server (link is in header) and checking out the #haptics channel.

  • what you want is definately possible
  • it might be as simple as setting zero velocity as the target in velocity mode. This will cause the motor to oppose any motion
  • but there are many more ideas that people have discussed and implemented, and there is some code you could look at or use that might be helpful
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4

OK so I reinvented Proportional velocity control with 0 target :joy:

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5

Here’s a recent thread on the topic Explain like I'm 5: torque control

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6

you should check out some of the videos @schoch did a few years ago:
He did some really clever stuff with jogs and virtual detents

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7

Maybe the easiest would be to just short motor phases (passive brake) when resistance is needed.

8

My guess on what is best to try…

So you would at each “detent position” maybe at every 10 or so degrees, apply torque in the direction of movement for a couple milliseconds then reverse this and apply torque the other way for a few milliseconds.

In addition you might want to simulat friction. THis is a slight toque that is opposite the diretion of movement and proportionate to rotational velocity.

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