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Can anyone advise me on why in a Proportional only control, we need to add a Bias term?
The equation for "P" only control is
Controller Output = Error*Gain + Bias
Hence when the measured variable (PV) equals to the setpoint (SP), the error is zero, hence the equation above becomes;
Controller Output = 0*Gain + Bias = Bias
I do understand that this offset (Bias) is an inherent problem with "P" only control when error is zero. The controller output will keep adjusting the control valve and the PV will never be equal to the SP! (Assuming a level control loop in a water tank)
Why is it that we need this Bias since it introduces this offset problem? Can't we just do away with it?
Help in any form is appreciated.
If you have any other info, please email me at [email protected]
Thanks.
The equation for "P" only control is
Controller Output = Error*Gain + Bias
Hence when the measured variable (PV) equals to the setpoint (SP), the error is zero, hence the equation above becomes;
Controller Output = 0*Gain + Bias = Bias
I do understand that this offset (Bias) is an inherent problem with "P" only control when error is zero. The controller output will keep adjusting the control valve and the PV will never be equal to the SP! (Assuming a level control loop in a water tank)
Why is it that we need this Bias since it introduces this offset problem? Can't we just do away with it?
Help in any form is appreciated.
If you have any other info, please email me at [email protected]
Thanks.