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TMS320F28035: C2000 QEP Strobe Position Latch QPOSSLAT issue

Eric Ma
Intellectual 2630 points
Part Number: TMS320F28035
Other Parts Discussed in Thread: CONTROLSUITE

Hi C2000 champion

Customer used F2837xD QEP strobe position latch function to get the motor position, but found the QPOSSLAT will change in low speed, but constant in high speed.

I used the High voltage kit, F28035, and ESTUN motor,  can re-produce this issue. Detail as below:

1) source code: C:\ti\controlSUITE\development_kits\HVMotorCtrl+PfcKit_v2.1\HVPM_Enhanced_Sensorless_2803x

2) QEP initial:

qep1.LineEncoder = 2500;
qep1.MechScaler = _IQ30(0.25/qep1.LineEncoder);
qep1.PolePairs = POLES/2;
qep1.CalibratedAngle = 0;
QEP_INIT_MACRO(1,qep1)
EQep1Regs.QEPCTL.bit.PCRM=01; // Position counter reset on the maximum position 15000
EQep1Regs.QEPCTL.bit.SEL = 01; 

3) test cases:

When motor run in anti-clockwise, set speedref = IQ(0.1) (300 rpm), the QPOSSLAT  will vary in 9999, 10000, 10001;  But QPOSSLAT keep constant 10000 in high speed > 1000 rpm.

When motor run in clockwise, QPOSSLAT  keep constant in low speed and high speed.

Please help to analysis this issue that why QPOSSLAT will vary in low speed at anti-clockwise direction.

Eric 

  • 0
    TI__Intellectual 2630 points
    Hi C2000 champion
    Can you help to look at this case?

    Eric
  • 0 in reply to Eric Ma
    TI__Mastermind 24095 points

    Hi Eric,

    from what i understand - it seems like the relative edge position of the A or B inputs w.r.t. to the strobe input which is causing the difference in the behavior.
    Do you have a plot of the QEP input signals (A, B, S and I) captured?
    What is the edge relation between the Strobe input and the A and B inputs?
    One thing you can try is to delay inputs A and B w.r.t. Strobe or vice versa and check the behavior. 
    You can simply increase the GPIO Qual settings for the purpose of this test.
    Possible reason for this behavior is that if the edges of A and B occur at different times w.r.t. strobe input when the speed is high vs. low - that may result in different values being latched.

    -Bharathi.