High inertia ratio for stepper motor
High inertia ratio for stepper motor
(OP)
Hi
I wonder if the inertia ratio for stepper motor is very high, what is the impact? Will there by mis-step?
I wonder if the inertia ratio for stepper motor is very high, what is the impact? Will there by mis-step?





RE: High inertia ratio for stepper motor
TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
www.bluetechnik.com
RE: High inertia ratio for stepper motor
I would say that more often than not I violate that matching criteria for steppers, ostly, and especially for speed.
So I say it is application specific. Name the application and I think you can get a tailored solution.
RE: High inertia ratio for stepper motor
I am actually sizing a stepper motor for my optical filter wheel indexing. Previously, I have size a suitable motor with a gear ratio. It is working fine until we encounter a problem due to backlash. In order to resolve the backlash issue, I suggest using a larger motor without gearbox. However, my load inertia is > 50 times the rotor inertia. It seems to be overloaded according to the vendor
RE: High inertia ratio for stepper motor
If you're feeling mathematical today, search on "phase plane analysis" applied to stepping motors.
If you've got the budget/time, you might just go to controlled current drivers for the coils, or microstepping.
Mike Halloran
Pembroke Pines, FL, USA
RE: High inertia ratio for stepper motor
Am I right to say that problems results from large inertia ratio of stepper motor can be overcome by using microstepping?
RE: High inertia ratio for stepper motor
the speed of indexing
amount of allowed overshoot and settling time
load inertia
A geared system is usually satisfactory, despite the backlash, since it gets smaller as the gear ratio is increased.
I would be interested in the problem as you see it with backlash in your case; a 50:1 inertia ratio is too large and will result in excessive transients.
RE: High inertia ratio for stepper motor
Thanks for all the information. Let me try to explain my design:
1) I am using a 9: 1 gear ratio stepper motor with a backlash of 2deg max
2) I have a timing pulley system with a 2: 1 ratio. Meaning to say I would see a max backlash of 1 deg max at my wheel.
3) If I design the whole system as per the current design, I will not have problem with the load inertia. However, if I remove the gear box at the stepper motor, then I believe the inertia ratio is too high
4) The problem with the backlash is that when the system decelerates, there might be problem with the backlash due to vibration.
RE: High inertia ratio for stepper motor
Where is it measured?
What are you trying to do?
Steppers may not be the best way to go.
RE: High inertia ratio for stepper motor
The backlash specs is provided by the motor vendor. The gearbox comes attached to the motor. I wonder whether there are seperate gearbox available in the market for stepper motor. Maybe I can source for a better gearbox.
RE: High inertia ratio for stepper motor
Sorry, a bit late to this!
Is it possible to move the motor to one side, throw out the troublesome gearbox and drive it from the stepper with a 9:1 ratio timing belt. I assume that your optical filter wheel is a fair diameter, so you could incorporate it into the larger pulley and use a couple of plain idler wheels to get a good "wrap" and tension the belt around the small motor pulley at a minimal centre distance. This would give you a simple, virtually zero-backlash drive.
RE: High inertia ratio for stepper motor
The big wheel doesn't need to be fully toothed. You can make it smooth, at the minor diameter of an equivalent pulley, with a couple of regular teeth inserted 180 degrees apart.
Mike Halloran
Pembroke Pines, FL, USA