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MCF8316AEVM: Speed Feedback falls behind Reference Speed

Chris Esser
Prodigy 30 points
Part Number: MCF8316AEVM

Tool/software:

When using the MCF8316AEVM (with the MCF8316C installed), I cannot get my motor to spin at full speed after going through the MPET routine. When controlling the speed of the motor in the 'Quick Spin' dialog, the motor will correctly follow the commanded speed up to about 75%. The screen shot below shows correct tracking at 50% speed

After about 75% speed, the 'Reference Speed' continues up to 1500Hz but the 'Speed Feedback' stops around 1100Hz. The screenshot below shows this difference

I have verified with a different set of drive electronic that this motor is capable of spinning at this higher speed and there are no mechanical limitations preventing it from spinning that fast. I also verified with an optical tachometer that the motor is spinning with an electrical frequency of 1100Hz (66,000 RPM) and not the desired speed of 1500Hz (90,000 RPM). 

Can you provide some help on how to troubleshoot this lack of performance?

-Chris

  • 0
    TI__Mastermind 24720 points

    Hi Chris,

    Can you Enable the saturation flags to check if the ILIMIT threshold is being reached? 

    Could you also provide:

    1. the current register configuration being used?
    2. A capture of the voltage at VM, the phase current of the motor, and the signal at the FG pin the the motor is at max speed?
    3. The motors datasheet or at least the motors rated max phase current?

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 30 points

    Hi Joshua,

    0) I enabled those flags and saw that 'SPEED_LOOP_SATURATION' flag tripped around 1100HZ when accelerating to full speed. The feedback speed remained constant after that while the reference speed continued to increase to 1500Hz.

    1) I have attached the file.

    Fullscreen C035A_Registers.txt Download 
    {
"signature":"oneui-register-data",
"data":[
[
{
"idx":0,
"id":"ISD_CONFIG",
"value":"0x6C230C3C",
"addr":"0x00000080"
},
{
"idx":1,
"id":"REV_DRIVE_CONFIG",
"value":"0xA8200000",
"addr":"0x00000082"
},
{
"idx":2,
"id":"MOTOR_STARTUP1",
"value":"0x6568C700",
"addr":"0x00000084"
},
{
"idx":3,
"id":"MOTOR_STARTUP2",
"value":"0x9A82200D",
"addr":"0x00000086"
},
{
"idx":4,
"id":"CLOSED_LOOP1",
"value":"0x0E3191BD",
"addr":"0x00000088"
},
{
"idx":5,
"id":"CLOSED_LOOP2",
"value":"0x99E53903",
"addr":"0x0000008A"
},
{
"idx":6,
"id":"CLOSED_LOOP3",
"value":"0x0C800002",
"addr":"0x0000008C"
},
{
"idx":7,
"id":"CLOSED_LOOP4",
"value":"0x288A2328",
"addr":"0x0000008E"
},
{
"idx":8,
"id":"REF_PROFILES1",
"value":"0x00000000",
"addr":"0x00000094"
},
{
"idx":9,
"id":"REF_PROFILES2",
"value":"0x00000000",
"addr":"0x00000096"
},
{
"idx":10,
"id":"REF_PROFILES3",
"value":"0x00000000",
"addr":"0x00000098"
},
{
"idx":11,
"id":"REF_PROFILES4",
"value":"0x00000000",
"addr":"0x0000009A"
},
{
"idx":12,
"id":"REF_PROFILES5",
"value":"0x00000000",
"addr":"0x0000009C"
},
{
"idx":13,
"id":"REF_PROFILES6",
"value":"0x00000000",
"addr":"0x0000009E"
}
],
[
{
"idx":0,
"id":"FAULT_CONFIG1",
"value":"0xBEEA4327",
"addr":"0x00000090"
},
{
"idx":1,
"id":"FAULT_CONFIG2",
"value":"0xFF0220B8",
"addr":"0x00000092"
}
],
[
{
"idx":0,
"id":"INT_ALGO_1",
"value":"0xA43141BD",
"addr":"0x000000A0"
},
{
"idx":1,
"id":"INT_ALGO_2",
"value":"0x000001A3",
"addr":"0x000000A2"
}
],
[
{
"idx":0,
"id":"PIN_CONFIG",
"value":"0x08000000",
"addr":"0x000000A4"
},
{
"idx":1,
"id":"DEVICE_CONFIG1",
"value":"0x00101465",
"addr":"0x000000A6"
},
{
"idx":2,
"id":"DEVICE_CONFIG2",
"value":"0xC0003107",
"addr":"0x000000A8"
},
{
"idx":3,
"id":"PERI_CONFIG1",
"value":"0x81E81F00",
"addr":"0x000000AA"
},
{
"idx":4,
"id":"GD_CONFIG1",
"value":"0x00000000",
"addr":"0x000000AC"
},
{
"idx":5,
"id":"GD_CONFIG2",
"value":"0x00000000",
"addr":"0x000000AE"
}
],
[
{
"idx":0,
"id":"GATE_DRIVER_FAULT_STATUS",
"value":"0x00000000",
"addr":"0x000000E0"
},
{
"idx":1,
"id":"CONTROLLER_FAULT_STATUS",
"value":"0x00000000",
"addr":"0x000000E2"
}
],
[
{
"idx":0,
"id":"ALGO_STATUS",
"value":"0x00000004",
"addr":"0x000000E4"
},
{
"idx":1,
"id":"MTR_PARAMS",
"value":"0x00000000",
"addr":"0x000000E6"
},
{
"idx":2,
"id":"ALGO_STATUS_MPET",
"value":"0x0A000000",
"addr":"0x000000E8"
}
],
[
{
"idx":0,
"id":"ALGO_CTRL1",
"value":"0x20000000",
"addr":"0x000000EA"
}
],
[
{
"idx":0,
"id":"ALGO_DEBUG1",
"value":"0x80000000",
"addr":"0x000000EC"
},
{
"idx":1,
"id":"ALGO_DEBUG2",
"value":"0x00000000",
"addr":"0x000000EE"
},
{
"idx":2,
"id":"CURRENT_PI",
"value":"0x012D012E",
"addr":"0x000000F0"
},
{
"idx":3,
"id":"SPEED_PI",
"value":"0x022A012A",
"addr":"0x000000F2"
},
{
"idx":4,
"id":"DAC_1",
"value":"0x00000000",
"addr":"0x000000F4"
},
{
"idx":5,
"id":"DAC_2",
"value":"0x00000000",
"addr":"0x000000F6"
}
],
[
{
"idx":0,
"id":"ALGORITHM_STATE",
"value":"0x00000000",
"addr":"0x00000190"
},
{
"idx":1,
"id":"FG_SPEED_FDBK",
"value":"0x7FFFFFFF",
"addr":"0x00000196"
},
{
"idx":2,
"id":"BUS_CURRENT",
"value":"0x00000000",
"addr":"0x00000410"
},
{
"idx":3,
"id":"PHASE_CURRENT_A",
"value":"0x00000000",
"addr":"0x00000440"
},
{
"idx":4,
"id":"PHASE_CURRENT_B",
"value":"0x00000000",
"addr":"0x00000442"
},
{
"idx":5,
"id":"PHASE_CURRENT_C",
"value":"0x00000000",
"addr":"0x00000444"
},
{
"idx":6,
"id":"CSA_GAIN_FEEDBACK",
"value":"0x00010003",
"addr":"0x00000468"
},
{
"idx":7,
"id":"VOLTAGE_GAIN_FEEDBACK",
"value":"0x00000002",
"addr":"0x00000472"
},
{
"idx":8,
"id":"VM_VOLTAGE",
"value":"0x0197E000",
"addr":"0x00000476"
},
{
"idx":9,
"id":"PHASE_VOLTAGE_VA",
"value":"0x0001F2D4",
"addr":"0x0000047A"
},
{
"idx":10,
"id":"PHASE_VOLTAGE_VB",
"value":"0x0001F2D4",
"addr":"0x0000047C"
},
{
"idx":11,
"id":"PHASE_VOLTAGE_VC",
"value":"0x0001F2D4",
"addr":"0x0000047E"
},
{
"idx":12,
"id":"SIN_COMMUTATION_ANGLE",
"value":"0x00000000",
"addr":"0x000004B6"
},
{
"idx":13,
"id":"COS_COMMUTATION_ANGLE",
"value":"0x00000000",
"addr":"0x000004B8"
},
{
"idx":14,
"id":"IALPHA",
"value":"0x00000000",
"addr":"0x000004D2"
},
{
"idx":15,
"id":"IBETA",
"value":"0x00000000",
"addr":"0x000004D4"
},
{
"idx":16,
"id":"VALPHA",
"value":"0x00000000",
"addr":"0x000004D6"
},
{
"idx":17,
"id":"VBETA",
"value":"0x00000000",
"addr":"0x000004D8"
},
{
"idx":18,
"id":"ID",
"value":"0x00000000",
"addr":"0x000004E2"
},
{
"idx":19,
"id":"IQ",
"value":"0x00000000",
"addr":"0x000004E4"
},
{
"idx":20,
"id":"VD",
"value":"0x00000000",
"addr":"0x000004E6"
},
{
"idx":21,
"id":"VQ",
"value":"0x00000000",
"addr":"0x000004E8"
},
{
"idx":22,
"id":"IQ_REF_ROTOR_ALIGN",
"value":"0x00000000",
"addr":"0x00000524"
},
{
"idx":23,
"id":"SPEED_REF_OPEN_LOOP",
"value":"0x00000000",
"addr":"0x0000053C"
},
{
"idx":24,
"id":"IQ_REF_OPEN_LOOP",
"value":"0x00000000",
"addr":"0x0000054C"
},
{
"idx":25,
"id":"SPEED_REF_CLOSED_LOOP",
"value":"0x00000000",
"addr":"0x000005D4"
},
{
"idx":26,
"id":"ID_REF_CLOSED_LOOP",
"value":"0x00000000",
"addr":"0x00000606"
},
{
"idx":27,
"id":"IQ_REF_CLOSED_LOOP",
"value":"0x00000000",
"addr":"0x00000608"
},
{
"idx":28,
"id":"ISD_STATE",
"value":"0x00000000",
"addr":"0x00000682"
},
{
"idx":29,
"id":"ISD_SPEED",
"value":"0x00000000",
"addr":"0x0000068C"
},
{
"idx":30,
"id":"IPD_STATE",
"value":"0x00000000",
"addr":"0x000006C0"
},
{
"idx":31,
"id":"IPD_ANGLE",
"value":"0x00000000",
"addr":"0x00000704"
},
{
"idx":32,
"id":"ED",
"value":"0x00000000",
"addr":"0x0000074A"
},
{
"idx":33,
"id":"EQ",
"value":"0x00000000",
"addr":"0x0000074C"
},
{
"idx":34,
"id":"SPEED_FDBK",
"value":"0x00000000",
"addr":"0x0000075A"
},
{
"idx":35,
"id":"THETA_EST",
"value":"0x00000000",
"addr":"0x0000075E"
}
]
]
}

    2) Below is a trace capture of the items you requested. A speed of 1500Hz was commanded but it only ever reached about 1100Hz. I noted that the FGOUT turned into that square wave once the Open Loop/Closed loop transition happened. During this capture, the benchtop power supply was reading 11.99V @ 2.23A. 

    3) Unfortunately I don't have a datasheet for the motor. Its a turbofan ordered from AliExpress and they have limited information about it. Below is a link to what I'm using. I have manually measured Rph = 0.11 ohm, Lph = 0.0078 mH, and Ke = 4.00 mV/Hz based on What are motor parameters, why are they needed, and how do I measure them?

    Also, the motor comes with built in drive electronics. My goal with using the MCF8316 is to reduce the audible noise from the motors, so I am working to remove their electronics and replace them with the MCF8316. I was able to capture a phase current trace of the motor when using the drive electronics that come with it. The trace looks more cleaner than I was expecting. Based on this trace, Would you expect to have a reduction in audible noise when switching to the MCF8316?

    Link to the motor: DC9-12V/7-24V Brushless Turbo Fan Motor 100000RPM

  • 0 in reply to Chris Esser
    TI__Mastermind 24720 points

    Hi Chris,

    Please allow me some time to look into this speed limitation issue. I will aim to provide a response next week.

    For your noise related question:

    1. There is a lot of ripple in the phase current when driving with the MCF8316C which will lead to more generated noise. Can you try increasing the PWM switching frequency of the motor to see if the ripple lowers? Keep in mind that with higher switching frequencies the power losses of the half-bridge MOSFETS will increase.
    2. The OEM phase current is fairly smooth but there is still come ripple that could be ironed out. I cannot guarantee that the MCF8316C can generate less noise but with some tuning the MCF8316C could have better noise performance.

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    TI__Mastermind 24720 points

    Hi Chris,

    Can you check the value of Voltage Magnitude when the motor is running at max speed?

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 30 points

    Voltage Magnitude reached about 88%. This is the fastest I've seen the motor spin. Usually it stops around 1100Hz, but it got up to 1384Hz today. I don't know why it went faster today, as I haven't changed anything about the setup. 

    Also, the 'SPEED_LOOP_SATURATION' fault still appeared. 

  • 0 in reply to Chris Esser
    TI__Mastermind 24720 points

    Hi Chris,

    Can you read all registers when the motor is able to achieve the higher speed? I would like to check if any register values have changed, maybe due to EEPROM settings for example.

    Regards,

    Joshua