How can I compare the performance of stepper motors and DC motors?

by Mikael Lindqvist   Last Updated October 10, 2019 06:25 AM

I'm designing a cost sensitive robot and I'm trying to decide weather to use stepper motors or DC motors. Reading up on the basic difference between DC motors and stepper motors it is clear that DC motors are cheaper than stepper motors. However, for my application DC motors will be a bit more complicated to work with. It is possible to attach a rotary encoder to a DC motor, and implement PID control in software, and be able to control it kind of like a stepper motor. But this adds an extra layer of complexity to the design. So the question is if this extra complication is worth it for me, so I would like to do a calculation in order to compare specific stepper motors and DC motors in terms of price per performance. Put another way, how much more expensive are stepper motors compared to DC motors, are they 50% more expensive or twice as expensive or what?

So, how can I compare these performances? The information in datasheets specifies different things. A data sheet for a DC motor usually specifies a torque and a RPM. A stepper motor has a few different values for its torque (detent torque and holding torque), but no specification for the RPM since this is controlled in software. So it is a bit like comparing apples and pears. However, the following is one way I have thought about comparing them, and I want to check if this is resonable.

According to this answer: https://www.quora.com/What-is-the-maximum-speed-of-a-stepper-motor the maximum speed at which a stepper motor should be ran is 1200 RPM. So my idea is to use the value 1200 and multiply it with the holding torque of the stepper motor, and call this value the power of the stepper motor (yes?). For the DC motor I simply multiply the RPM and the torque specified. Then I compare the two power values for the stepper motor and DC motor. If they are the same, they can be said to be equally "performant" and it is then resonable to compare their prices.

Is this a good way of doing the comparision or am I missing something?



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