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Originally Posted by andy
In summary, any nonlinearity you see in the duty cycle is caused by the input signal, in this case, the robot controller.
Good luck everyone!
-Andy
*disclaimer I am not an expert, and something above is probably wrong, I also have thick skin, have at it  |
I disagree completly. I'll try and explain my theory a little better. The output of the speed controller, connected to a resistive load, gives us a nice square wave. With a square wave voltage/current are directly proportional to the duty cycle. Now if you throw an inductor in there, you no longer have a square wave, you have a funny sawtooth shaped wave and the output voltage/current are no longer linearly proportional to the duty cycle. They become related to the rise and fall times of the inductor and the length of the switching period. This non-linearity will become more pronounced at lower PWM frequiencies as the voltage/current have more time to rise and fall between the on and off switches. I'm sure you're right in that the duty cycle varies linearly, but I can definetly see how the voltage/current dont have to respond linearly.