Pid Bias

HELLO ALL

DOES ANYONE KNOW HOW TO USE BIAS WHEN TUNING PID?

REGARDS

GOKALP

Yes!

The bias should be used to make a good estimate of what the drive should be. This estimate does not need to be perfect just close. The closer the better.

If you are controlling a oven or dryer you may find from experience that the output needs to be roughly 100 units for every meter per minute of the line speed. If the line speed is 10 meters per minute the bias should be set to 1000 units. In other words, from experience you should be able to calculate a formula that is a close estimate of the required output. This greatly reduces the amount of work the PID must do and greatly reduces tracking error.

Also see feedforward.

For a temperature PID control of simple pack machine,

How you should you adjust the BIAS term. Normally if you change setpoint and do not reset the bias term, bias causes overshoot for the new setpoint.

For PID control of temp. systems I read different approaches. To change the setpoint over time instead of changing setpoint instantly, to create a band to use PID around setpoint or to deactivate the integral term for the PID output over some level.

Thanks