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DRV201: Need help in finding appropriate voice coil actuator driver

Nishant Kathpal
Prodigy 50 points
Part Number: DRV201
Other Parts Discussed in Thread: DRV8844, DRV8412

Hello all,

Please forgive me if I asked a similar question. I have searched up to my maximum patience but could not find out the appropriate driver for my voice coil actuator (linear actuator having a stroke length of 10mm).

I am having a voice coil actuator having an impedance of 8 ohms and need a driver which should have a maximum current capacity of 2A and current should be controlled by one of the methods, either PWM or SPI/I2C. I am able to find some of the drivers on TI website but their current capacity is either limited to 100mA or those are for voice coil inside the camera. 

Please help me as it's been around a month working on the same problem of controlling the position with the help of voice coil actuator.

  • 0
    TI__Guru** 114905 points

    Hi Nishant,

    It may be possible to use one of the motor drivers to perform this function assuming the PWM regulation frequency is sufficient.

    Please look at the DRV8881E and DRV8881P as possible options.

    If neither work for you, please let us know why and we may be able to recommend a different device.

  • 0 in reply to Rick Duncan
    Prodigy 50 points

    Hello Rick,

    Thanks for your reply. However, We have considered these drivers before. What happened? If we try to control the voice coil actuator with PWM, as you may be knowing PWM is having a lot of harmonics, so it starts vibrating. We don't need to vibrate the actuator. We need to control the position of the actuator.

    Please let me know if you need more information and help me in finding the specific driver. 

    Thank you.

  • 0 in reply to Nishant Kathpal
    TI__Guru** 114905 points

    Hi Nishant,

    All of the motor driver devices operate using PWM. Some can operate at higher PWM frequencies, like the DRV8844 (200kHz) and DRV8412 (500kHz)

    Both of these devices may work, but external circuitry would be required to close the loop.

    Also how did you PWM the DRV8881E or DRV8881P?

    You can use the AVREF and BVREF, and set ATE (DRV8881E only) to allow the device to control the current. The PWM inputs will only set the current direction.

  • 0 in reply to Rick Duncan
    Prodigy 50 points

    Hello Rick, Thanks again for your reply.

    I used PWM at AVREF of DRV8881E to control the output current which actually produces PWM at the output. 

    Do you have any other way to control the output current without using PWM at AVREF?

  • 0 in reply to Nishant Kathpal
    Prodigy 50 points

    Hello Rick,

    I also want to share one observation, that if I use frequency above 20KHz, voice coil actuator doesn't produce vibrations. I think the inductance of the voice coil will rectify all the harmonics. Now, if that is correct then I am now able to control the position of the actuator.

    But I am having one more problem here, After moving the actuator to a specific position, I actually want to produce vibrations at a specific frequency of around 100-150 Hz sinusoidally. So, Do you have any idea on how to mix these two signals (PWM + Sine) and feed into voice coil?

    Thank you for helping me.

  • 0 in reply to Nishant Kathpal
    TI__Guru** 114905 points

    Hi Nishant,

    If you have a DAC output, it should be easier to control the AVREF input.

    Without a DAC, you should still be able to mix the signals by adjusting the PWM duty cycle. You may need to change the frequency of the PWM timer to provide better control. 

  • 0 in reply to Rick Duncan
    Prodigy 50 points

    Hi Rick,

    Thank you very much for your support. I am really glad.

     

    Conclusion: (For newbies like me)


    We can use AVREF pin of DRV driver for controlling the voice coil actuator using PWM. While if we want to mix the signals, we can use DRV driver by controlling AVREF pin with DAC.

    Regards,

    Nishant Kathpal

  • 0 in reply to Nishant Kathpal
    TI__Guru** 114905 points

    Hi Nishant,

    You are welcome.

    In addition, using setting ATE high with minimum Toff (10us) should provide the highest PWM frequency. Using this is the suggested starting point to maximize PWM frequency and minimize current ripple.