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Thread: Going around the resonance issue

  1. #1
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    Going around the resonance issue

    Hi guys, how's everyone doing? This is my first post here.

    I'm having problem driving my motor at certain velocity under load. Below are my specs:

    Stepper motor 1.8deg (i do not have the complete details, sorry)
    Power settings 24V 1.5A
    KT-5191 bipolar stepper motor chopper driver (using L297 & L298), running at half-step
    http://www.oceancontrols.com.au/moto...opManualV3.pdf
    Desired final velocity 16rps

    I'm running at half-step, the final freq to generate my desired velocity is 6400Hz (16rps*360deg/0.9deg=6400). Since i can't have my motor start at 6400Hz i'm ramping my motor speed by incrementing my freq up to 6400Hz (under load). However, i have problems achieving this value without my motor stalling. I need to met certain accel specs thus i can't ramp too slowly.

    Initially i tweaked with my ramping profile (through trial and error), thinking the motor may not have sufficient torque to overcome the load => unsuccessful

    Recently i've discovered such a thing as the resonance issue with stepper motors. Based on what i have read i've concluded there are 2 ways around this:
    1) Create a damping circuit between my stepper driver and my motor
    2) Avoid the resonant bands altogether
    2) Use micro-stepping driver

    What are your comments on the 3 methods above?

    Secondly,
    With (1), i'm currently googling literature on this but no success yet. Can someone help me by pointing me to the right direction?

    With (2), how do i first find this resonant band? I understand i can find the lower range by slowly ramping my freq up to a value until my motor stalls, but how do i find the upper range?

    With (3), involves extra costs. No 100% sure it'll solve the problem, it's my Plan B if (1) and (2) fails.

    Any comments?


  2. #2
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    Check out this thread My take on a stepper damper


  3. #3
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    Microstepping driver helps, but doesn't eliminate it. A driver with midband adjustment will help even further. Simplest solution is a stepper damper. The other issue is your desire for 16rps. Steppers naturally loose power as their rpms increase. Take a look at an example here: http://pminmo.com/PMinMOwiki/index.p...chanical_Power

    It's based on a commercial Vexta motor and their own data.
    Phil, Still too many interests, too many projects, and not enough time!!!!!!!!
    Vist my websites - http://pminmo.com & http://millpcbs.com


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