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DRV10983EVM: Kt value in case of max motor speed

Hirotaka Matsumoto
Guru 27585 points
Part Number: DRV10983EVM
Other Parts Discussed in Thread: DRV10983

Hi all

Would you mind if we ask DRV10983EVM?

In case of low speed : Operation is OK.
In case of max motor speed(450rpm) : Operation is indefinite.

-> At first, should we set KT setting?
    And, should we check speed command buffer?

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Mastermind 19720 points

    Hi Hirotaka-san,

    I would suggest you follow the DRV10983 Tuning guide when first starting up the motor:http://www.ti.com/lit/ug/slou395d/slou395d.pdf

    Can you elaborate more on:

    "In case of low speed : Operation is OK.
    In case of max motor speed(450rpm) : Operation is indefinite."

    Regards,

    Michael W.

  • 0 in reply to Michael.Walker
    Guru 27585 points

    Michael san

    Thank you for your help.

    We would like to sent you the customer setting.
    It may contain customer's information, so is it possible to send by private message on E2E?
    We sent "friend request" to you, could you accept it?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Mastermind 19720 points

    Hi Matsumoto-san,

    I have accepted your friend request. You can send me the file there.

    Regards,

    Michael

  • 0 in reply to Michael.Walker
    TI__Mastermind 19720 points

    Hi Matsumoto-san,

    I received your files, and will not share any of them here for confidentiality, but I would like to work through the problem here publicly in case some one has the same issue and this might help them solve it. 

    Can you capture a picture of the "Display" tab of the GUI with the motor running and also a picture of what faults the device is hitting when the motor stops spinning and send it to me. You can send it to me via the private message if you would like. I want to make sure that the device is reading the correct Kt from the motor.

    Regards,

    Michael

  • 0 in reply to Michael.Walker
    Guru 27585 points

    Michael san

    Thank you so much for your reply.
    No, we are checking the fault condtion in case of start and speed changing.
    We will feedback you later.

    And then, when the file doesn't contain customer's confidential things(wave form), we would like to discuss at E2E forum.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Michael.Walker
    Guru 27585 points

    Michael san

    Thank you for your cooperation always.

    capture a picture of the "Display"
    ->We will attach the file. The fault is abnormal speed.
    20191007_DRV10983_EVM setting.pdf

    And then, we will send the wave form using private message on E2E.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Michael.Walker
    Guru 27585 points

    Hi Michael san

    We have some additional questions.

    <Question1>
    It seems that customer's Lood time setting 1.12ms is too big.
    Default is 150us, if this setting is not fitable, might it occur current limit fault or abnormal speed faiulre?
    And then, what situation is Lead Time used for? To increase efficiency only??

    <Question2>
    In Adj mode, there are two modes, one is full cycle and another is half cycle.
    There is the description "Use the full cycle adjustment for low current (<1 A) applications because it offers more tolerance for current measurement offset errors." on the datasheet.
    Which doers this current mean peak or average?


    Kind regards,

    Hirotaka Matusmoto

  • 0 in reply to Michael.Walker
    Guru 27585 points

    Michael san

    Thank you for your cooperation always.

    We solved the the customer's problem.
    We evaluated the customer's motor with DRV10983EVM.
    As the result, customer's lead time setting was too big(1.12ms).
    After changing lead time from 1.12ms to 150us , the device normally operated at any setting.

    We attach the wave form with lead time =1.12ms which has abnormal failure.
    20191011_DRV10983EVM.pdf

    <Additional Question1>
    It seems that big lead time effects for closed loop.
    According to big lead time, might it cause of abnormal speed?

    <Additional Question2>
    We heard that the devices Phases will become high-z when a fault occurs on E2E forum.
    Is it possible to use brake function(all low side FET's=ON) in case of fault occurring?
    Because of high-z, it occurs fast decay, VCC is more than absolute maximum rating(please refer to attachment file).

    <Additional Question3>
    If the motor has torque load with Lead time=1.12ms or 2.08ms, it doesn't occur abnormal failure.
    Does it mean BEMF decreases in case of torque load?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Mastermind 19720 points

    Hi Matsumoto-san,

    That is great that you got your issue solved!

    <Additional Question1>

    Yes large lead times can cause the device to think that the speed of the motor is abnormal.

    <Additional Question2>

    If there is a fault, the phases go High-Z and cannot be changed until the device tried to restart. you can bypass this by powering down VCC and then repowering VCC quickly.

    <Additional Question3>

    BEMF does not change with change in torque, it only changes with change in speed. But usually if you increase the torgue load on the motor the speed of the motor will decrease causing the BEMF to decrease.

    Regards,

    Michael W.

  • 0 in reply to Michael.Walker
    Guru 27585 points

    Michael san

    Thank you so much for your reply!

    Yes large lead times can cause the device to think that the speed of the motor is abnormal.
    ->Could you let us know why large lead times can cause the device to think that the speed of the motor is abnormal?
       Abnormal speed is the situation which BEMF is more than the output voltage.
       Because of large lead times, it migh be big BEMF?  


    <Additional question1>
    On the GUI Display, there is the motor speed description.
    This "motor speed" is calculated the way on the datasheet P37, right?
    As the background of this, the customer told us that there is the some difference between Display's motor speed and actual motor speed.

    <Additional question2>
    Do you have any idea to prevent abnormal speed failure with large lead time?
    Especially, during changing from open loop to closed loop, is it possible to prevent abnormal speed failure?
    2480.20191011_DRV10983EVM.pdf
    As the background of this, if it is possible,  the customer would like to use large lead time for good efficiency and good motor's characteristic.
    Of course, we don't have any idea for it,,,,

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Michael.Walker
    Guru 27585 points

    Michael san

    We assume that your days are so busy, however could you let us know the reply for last our update?
    If you reply for, all of things which the customer needs will be clear.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Mastermind 19720 points

    Hi Matsumoto-san,

    Let me renumber your questions so that it is easier for me to answer.

    Yes large lead times can cause the device to think that the speed of the motor is abnormal.
    ->Could you let us know why large lead times can cause the device to think that the speed of the motor is abnormal?
    Abnormal speed is the situation which BEMF is more than the output voltage.
    <Additional question 4>Because of large lead times, it migh be big BEMF?

    if you look in the datasheet under section 8.4.7.2. It explains that the abnormal speed is caused when "If motor BEMF is much higher than output amplitude for a certain period of time, tLCK_ETR, it means the estimated speed is wrong, and the motor has gotten out of phase." With large lead times the applied voltage can be so far out of phase with the BEMF that the BEMF is larger than the applied voltage. 


    <Additional question 5>
    On the GUI Display, there is the motor speed description.
    This "motor speed" is calculated the way on the datasheet P37, right?
    As the background of this, the customer told us that there is the some difference between Display's motor speed and actual motor speed.

    This is a know issue. Please refer to this thread:https://e2e.ti.com/support/motor-drivers/f/38/p/747894/2768583#2768583

    <Additional question 6>
    Do you have any idea to prevent abnormal speed failure with large lead time?
    Especially, during changing from open loop to closed loop, is it possible to prevent abnormal speed failure?
    As the background of this, if it is possible, the customer would like to use large lead time for good efficiency and good motor's characteristic.
    Of course, we don't have any idea for it,,,,

    I do not think your Lead times should be 1.12ms.How did you come up with that number? Why do you think your lead time should be that long?

    Regards,

    Michael 

  • 0 in reply to Michael.Walker
    Guru 27585 points

    Michael san

    Thank you so much for your reply!

    I do not think your Lead times should be 1.12ms.How did you come up with that number? Why do you think your lead time should be that long?
    ->The customert would like to use two types motor 2W and 5W with the same characteristic.
        So, in order to matchthe same characteristic, they need large lead time.(We heard it from customer.)
        OK, we will persuade the customer to use small lead time to prevent abnormal speed.

    Kind regards,

    Hirotaka Matsumoto