PWM output control CDC shock absorber

[David]

#17120

Function to be achieved: PWM output controls CDC shock absorbers to achieve different damping force adjustments (essentially achieving different control currents)
The controller we use is the FlexBench controller. The rated input voltage of CDC shock absorbers is 12V, and different damping forces of the shock absorbers can be achieved by adjusting the input current. How to achieve different sizes of current input for shock absorbers, we use low edge drive to adjust the duty cycle. Control the CDC shock absorber by connecting one end of the CDC shock absorber to+12V and the other end of the shock absorber to C-44 (FTM1-CH5) of the controller. The problem now is that the duty cycle has a non-linear relationship with the output current. When the duty cycle reaches 0.87 and the current reaches around 1.5 amperes, the current will rapidly decrease to a very small level. May I ask if this phenomenon is normal.
Is there a problem with the Simulink control model, wiring, or other issues?
The attachment includes wiring photos and screenshots of the Simulink control model.

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[David]

#17122

The attached image below is a supplementary data table showing the relationship between the measured current and the duty cycle.

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[Rhyse Maryniuk]

#17128

Hi David,

Thank you for the detailed posting. Based on the data you provided I believe you are triggering the current protection mechanism on the FlexBench, which has a continuous current maximum of 1.1A and trip current of 1.95A.

My recommendation would be to try and distribute the current among two low side drives simultaneously (using the same FTM) if you can. The next safest approach would be to use an external, higher current output driver.

Please let me know if you have any followup questions,

Rhyse

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