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CCS/TMS320F28379S: DC motor control with PWM

PaulLee
Intellectual 480 points
Part Number: TMS320F28379S


Tool/software: Code Composer Studio

Hi,

My code controls the maxon DC motor by PWM with H-Bridge.

The DC motor's Nominal voltage is 12Vdc and nominal speed is 5990 rpm.

But my custom motor controller module can not get max speed of this motor.

When I control this motor by Maxon motor controll, EPOS2, this motor can operate with max speed.

But, my custom board can not.

My custom board use 12Vdc power and max peak voltage of PWM is 12Vdc.

To get max speed, I drive the PWM signal to H-bridge with almost high, duty is 99.9%. average is almost 12Vdc

I have check what the EPOS2 does, I got the the information that the EPOS2 drives the motor with 24Vdc peak with 50% duty(average 12Vdc) for max speed.

I assume that my problem is from this difference.

Am I right?

The 24Vdc peak with 50% duty is better than 12Vdc with 100% duty for motor power to get max speed?

BR

Paul

 

  • 0
    TI__Guru** 116290 points
    1. Did your customer and you use the same control algorithm and motor with the same load? Just on different two boards? What's a speed difference between these two boards? You might increase the input voltage of your customer's board, to look at what happens, and if the motor needs field weakening control for high speed.
    2. A little better, especially under heavy load since the conduction loss will be lower if the input voltage is high.
  • 0 in reply to Yanming Luo
    Intellectual 480 points

    1. The custom board means the board I made, not customer's board.
    2. I did test with same load and same motor. Just control boards are different. One try by my board, another try by Maxon motor controller, EPOS2.
    3. Load is a lot heavy.
    4. As far as I know, for DC motor's speed can be controlled by voltage level. I have check the power on DC motor power cable of DC motor for two motor controller and find that voltage levels and shapes are different for two board. EPOS2 supply the motor power with 50% duty 24Vdc but I use 100% duty 12Vdc for motor power.
    So, I asked you that this voltage shape comes difference speed or not. Which one is best choice for speed?
    If 50% duty 24Vdc is good solution, I have to redesign my board.

    BR
    Paul

  • 0 in reply to PaulLee
    TI__Guru** 116290 points
    Per you replied, you are testing the motor with two different controllers, one is the h/w and control algorithm designed by you, another one is designed by Maxon. It seems like the input voltage is not enough for your motor, you may try to increase the input voltage.

    High voltage is much better than low voltage one, especially the Rdson of the power module is higher.