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I would like to ask for some help.

My application is regulation of vertical speed of the camera, which is mounted on winding/unwinding reel. The camera follows the object (which moves vertically).

The load (weight) is constant, however due to the change in radius while winding, the torque changes. To maintain desired vertical (linear) speed constant, the rotational velocity decreases while the torque increases and other way around when unwinding.

The rotational speed of the motor would have to be calculated since its a function of the current radius and desired linear(verical speed). The feedback for closed loop control of the linear velocity comes from the camera image.

The required torques (only load, without considering losses, frictions,..) are: (for maximum desired linear vertical velocity of 2m/s)

0.165 Nm @ 2315 rpm

1.065 Nm @ 358 rpm

How do I choose the right motor size for this application? Would I need a gear? I'm searching for a BLDC motor. Do I need to select a motor with the rated torque/speed of maximum speed and torque of my application (2315 rpm, 1.065Nm) ? ... that would be a huge motor :(

Thank you for your help.

enter image description here

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  • $\begingroup$ change in radius while winding ... run the cable over a pulley that inludes a rotary encoder ... you could also move the cable past an optical mouse instead $\endgroup$
    – jsotola
    Feb 10 at 1:20

1 Answer 1

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I don't think the torques/speeds you specify are unreasonable for a BLDC motor. Here, for example, is the performance curve for a motor from Electrocraft:

enter image description here

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