General > General Technical Chat
Determining rotational accuracy of a drive unit.
Doctorandus_P:
Stepper motors don't have "25000 steps/rev".
Stepper motors usually have 200 steps/rev, but 400 steps/rev also exist, and it can be as low as 24 steps/rev.
With microstepping you can increase resolution a bit, maybe by a factor or two or four, but if you try to go further, then you get into the magnetic elasticity too far and position is too much load dependent.
Siwastaja:
Yes I don't believe the OP has a "25000 steps/rev" motor, it would be very special.
Larger and larger error towards one end sounds like you have just some slightly wrong number somewhere. For example, if you expect your reduction gear is 1:20 but in reality it is 1:21, you would have linearly increasing error ending up at 5%.
Recheck all numbers.
Regarding microstepping, the point is not to magically generate ridiculously high positional accuracy, the point is to drive the motor with sinusoidal waveform instead of square wave and minimize stutter / vibration. The more microsteps, the better it approximates sinusoidal drive. You can't have too much really, use as much as you can implement.
Regarding missed steps, you'll notice if that happens from the jerk and sound it makes. If it is sitting on your lab table and operating smoothly without you noticing any weird, you are not missing steps.
Backlash compensation can be implemented by always stopping the motion in one certain direction. If you need to go to the opposite direction, go half a degree over the destination then come back half a degree.
Steppers are OK for many applications if you know and accept the limitations.
mikerj:
--- Quote from: Siwastaja on May 21, 2021, 03:09:27 pm ---Yes I don't believe the OP has a "25000 steps/rev" motor, it would be very special.
--- End quote ---
I wonder if the 25,000 steps/rev is after the 20:1 reduction, that seems more feasible when combined with microstepping.
Puffie40:
--- Quote from: Doctorandus_P on May 21, 2021, 03:47:34 am ---Stepper motors don't have "25000 steps/rev".
Stepper motors usually have 200 steps/rev, but 400 steps/rev also exist, and it can be as low as 24 steps/rev.
With microstepping you can increase resolution a bit, maybe by a factor or two or four, but if you try to go further, then you get into the magnetic elasticity too far and position is too much load dependent.
--- End quote ---
That is rather curious. It took me a bit to determine the stepper motor model, but I found it here: https://www.moonsindustries.com/series/stm23r-series-integrated-stepper-motors-a01020402
It has an integrated driver and claims to have a microstepping resolution of up to 25,000 steps.
Benta:
Note that resolution is not the same as accuracy (which the data sheet does not specify).
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version