How to select values in QEP Speed Calculator block in Altair Embed ?

Swapnil Bongale_21857
Swapnil Bongale_21857 Altair Community Member
edited January 2021 in Community Q&A

Hi there...I am using Teknic M2310P-LN-04K motor...in this motor incremental encoder is provided with 4000 counts/revolution and "QEP speed calculator" block is provided. In this block one has to provide three parameters...

1. Base Electrical frequency(Hz)=100

2.Control sampling rate(Hz)=15000

3. low pass cut off(Hz)=200

I need to know about 1 & 3....So Can you please describe on which factors it is selected...is there any formula for that ?

 

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Answers

  • Mayank_21559
    Mayank_21559 New Altair Community Member
    edited January 2021

    Hi Swapnil,

    The following formula is used for Speed Calculation using linear encoders:

    RPM = (Frequency * 60/Line count)

    The QEP speed calculator block generates a per unit electrical shaft speed(fse)

    fse = (nm *p)/60 Hz

    which when multiplied by full scale scale speed gives actual shaft speed.

    Here, the Base electrical frequency should be 6000 * 4 /60 = 400, if motor is rated as 6000rpm for maximum speed with 4 pole pair

    Low pass cutoff frequency is used to place a pole for speed estimation and is mostly empirically chosen(200, 400)

     

    However, here I am attaching another file for Speed Estimation which you can use in your diagram and you can see within the compound block the implementations using band pass filters (LPHPF) and Speedpole (2000Hz). 

  • Swapnil Bongale_21857
    Swapnil Bongale_21857 Altair Community Member
    edited January 2021
    Mayank_21559 said:

    Hi Swapnil,

    The following formula is used for Speed Calculation using linear encoders:

    RPM = (Frequency * 60/Line count)

    The QEP speed calculator block generates a per unit electrical shaft speed(fse)

    fse = (nm *p)/60 Hz

    which when multiplied by full scale scale speed gives actual shaft speed.

    Here, the Base electrical frequency should be 6000 * 4 /60 = 400, if motor is rated as 6000rpm for maximum speed with 4 pole pair

    Low pass cutoff frequency is used to place a pole for speed estimation and is mostly empirically chosen(200, 400)

     

    However, here I am attaching another file for Speed Estimation which you can use in your diagram and you can see within the compound block the implementations using band pass filters (LPHPF) and Speedpole (2000Hz). 

    Dear Mayank,

    Thanks for the help...It was helpful...

    Can you please signify what is speed pole and why 2000 Hz value you have used here ? 

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