Electronics > Electronics

Effect of PWM on Motor Torque

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jwatte:
 If pwm is tuned right, the motor will be at equilibrium and thus hold the load exactly. A small increase in pwm duty cycle from there will result in a slow acceleration of the motor. If your two options are 'can't hold the load' and 'moves too fast' then you don't have enough resolution in your pwm.
Because the load will be varying, the only way to make this happen is to use an encoder and read the speed and tune a control loop based on this.
Finally, you say 'the servo' - are you thinking of a particular servo? There are many servos available with various speed, control, and power options, typically in the industrial automation and motion control industries.

oscyes:
Thanks for your replies, Now I understand a lot and this url helped me a lot too:

http://arduino.cc/forum/index.php?topic=87473.0

The conclusion I have done is:
When you vary pwm duty cycle is going to behave similar to vary the source voltage, when u reduce ur duty cycle then the average voltage in the motor decreases as well, and decreasing too the current passing trought it and afecting the torque the motor can raise.

I have decided to control my pwm duty cycle as much as the motor speed decreases with load for maintain velocity trough a pid control as jwatte  and Billy says.

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