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DRV10983-Q1: How to adjust the driving torque

user5831319
Intellectual 260 points
Part Number: DRV10983-Q1
Other Parts Discussed in Thread: DRV10983

hello .I have two DRV10983-Q1 EVM boards here, which drive a three-phase brushless DC motor with one pair of poles through an external 24V DC power supply. Control via PC software

when i try to use the evm board to drive the motor,i found some questions :

1 When testing with a separate motor (without hysteresis load), when the speed setting is not very high, the motor shaft can be pinched with a little force, and the motor stops and tries to restart.
2 After the motor drives the hysteresis load, as the hysteresis load increases, the motor speed obtained by the same speed command becomes lower and lower.
3 Earlier, I built a circuit with the DRV10983 chip according to the official typical application myself. I found that after the motor was pinched (not stopped) for a period of time, the motor entered an abnormal state: the motor maintained a very low and low speed. Don't speed up or stop.

The above questions, I want to know, are these problems caused by my parameter settings incorrect? Or any other reason? Is there a solution?
Attached Figure 3 is the motor speed that I read through the client software under different loads. Please check.
The attached figure 4-6 is my parameter setting, please refer to it.

thank you.

pictures.zip

  • 0
    Intellectual 260 points

    There is also a problem, after clicking "eeWrite" in the software interface, an error will be reported, and except that the set parameters have not changed after power off, the default selection after the restart is to control the speed through analog input? Is this normal?

  • 0 in reply to user5831319
    TI__Mastermind 24415 points

    Hi,

    Thanks for posting your question in MD forum.

    1. When testing with a separate motor (without hysteresis load), when the speed setting is not very high, the motor shaft can be pinched with a little force, and the motor stops and tries to restart.

    Do you see "Abnormal BEMF" fault being triggered? The reason why you see this behavior is because in closed loop, the device will sense the motor BEMF to determine when to commutate the motor. When you apply external force in the motor, the speed drops and device senses wrong BEMF and triggers Abnormal BEMF fault. The speed drops because the device does not have a speed loop to regulate the speed.   

    2. After the motor drives the hysteresis load, as the hysteresis load increases, the motor speed obtained by the same speed command becomes lower and lower.

    The device will take in the speed command via Analog, PWM or I2C signal and convert this signal into a percentage and then apply that percentage of Vm to the motor. When the load increases, motor demands more current and draws more current which the device may not be able to provide because of the limited motor voltage that's decided by the sped command. If you want to keep the speed stable, you can implement an external PI speed loop using FG or Hall sensor and use the speed command to increase or decrease the speed applied to keep it at a more stable speed.

    3. Earlier, I built a circuit with the DRV10983 chip according to the official typical application myself. I found that after the motor was pinched (not stopped) for a period of time, the motor entered an abnormal state: the motor maintained a very low and low speed. Don't speed up or stop.

    Do you see any fault being triggered at this abnormal state? Again, this could be the same issue I mentioned in Qn 1. 

    4. There is also a problem, after clicking "eeWrite" in the software interface, an error will be reported, and except that the set parameters have not changed after power off, the default selection after the restart is to control the speed through analog input? Is this normal?

    I'm not sure if you followed all the steps mentioned in the Datasheet to write data to EEPROM. Please check the datasheet Chapter 8.3.6 and let me know if you still have issues.

    Regards,

    Vishnu

  • 0 in reply to Vishnu Balaraj
    Intellectual 260 points

    Hi,

    Thanks for your reply.
    1 When this problem occurs, there is indeed a prompt of bemf abnormality.
    2 I understand what you mean. If I use this chip for applications where the external load is variable, an external speed control loop is required to implement it, right?
    3 I will take a closer look at the datasheet for a while. If the EEPROM write error still occurs, I will consult you again.
    We are here today on the weekend, I will test it next Monday

  • 0 in reply to Vishnu Balaraj
    Intellectual 260 points

    Hi,

    I tested the evm board again.Just as you said,an "abnormal bemf" error was triggered when i pinched the motor.

    about the 4th point above,i tested the board via PC "DRV109xx GUI",when i clicked the "eeWrite "button,an error box popped up，

    when i clicked “retry” button,this box disappeared.This problem ooccurs very time i write the eeprom.

    Another question,is this device default to speed control in analog mode after power on,and do i need to switch ithe speed control mode to iic  manually？

    thanks

  • 0 in reply to user5831319
    TI__Mastermind 24415 points

    Hi,

    Yes, an external Speed loop is required to keep the speed stable with load variations. 

    Qn: I tested the board via PC "DRV109xx GUI",when i clicked the "eeWrite "button,an error box popped up, when i clicked “retry” button,this box disappeared.This problem occurs very time i write the EEPROM.

    This is normal, when the user clicks the button, the GUI reads the EEPROM write enable bit (0x35[2]) and if it is 0, the window will flag it and write the bit for you. Clicking retry will check if the bit is enabled (and since it is) the EEPROM write process will begin. If the write was not successful or the bit wasn't set, then the error message would appear again. In your case, when you clicked "Retry" button, the box disappeared so your EEPROM write is successful. 

    Qn: Is this device default to speed control in analog mode after power on,and do i need to switch the speed control mode to I2C manually？

    Yes, by default the EVM board will read the analog speed input. Bit 15 in SpeedCtrl Register (address = 0x30) should be set to 1 to write the speed command directly through I2C. This can also be done by clicking the "I2C Speed control override" in display tab in GUI.

    Regards,

    Vishnu

  • 0 in reply to Vishnu Balaraj
    Intellectual 260 points

    I know.Thank you very much.