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Encoder position count reading is not proper but speed is measured correctly

rathinavel j
Intellectual 645 points

Other Parts Discussed in Thread: TMS570LS1227, DRV8301

Hi,

I am using Encoder output from my DSpace and reading in my DRV8301LS12  kit with TMS570LS1227 control card.

My Line count is 1000 and pole pair is 8. 

When I give constant speed of 1000RPM, I am getting bellow reading in mechanical position count and in electrical angle.  The readings looks , there is something wrong. Could you please help?. Also when I change the log scale from 1 to 5. The electrical angle looks good, but the frequency of waveform is wrong ( Still my motor speed RPM is showing exactly 1000 RPM inside the CCS debug environment.)

I have attached both the waveform.

logscale1

Logscale5

My sampling frequency is 8KHz. and clock frequency is 80MHz. Encoder QUPRD=800000

Thanks & Regards,

Rathinavel

  • 0
    Intellectual 645 points

    When I am doing my experiment repeatedly, I am able to get correct graph when the logscalar i s5 in the standard TI FOC software. ie) for 1000RPM, my mechanical cycle will exactly end with 96 sample. ( 96*5* (1/8e3)=60ms=1000rpm).

    But When I make to logscalar 1, its always something wrong, this is only due to some log problem or actual values itself varying randomly?

  • 0 in reply to rathinavel j
    TI__Guru 59540 points

    Hello Rathinavel,

    I have forwarded your post to one of our DRV8301 experts. They should be back to you shortly.

  • 0 in reply to Chuck Davenport
    Intellectual 645 points

    Hi, 

    Thanks you for your support, the problem is solved. It is due to the same issue, that is mentioned in this thread

    http://e2e.ti.com/support/development_tools/code_composer_studio/f/81/t/345907.aspx.

    Also We should maintain display size and acquisation size of the Graph should be same as buffer size  to avoid confusion in reading data.

    Regards,

    Rathinavel