PID automatic / manual disturbance-free switching simulation experiment - Database & Sql Blog Articles

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When the BOOL input parameter MAN_ON of the S7-300 PID control function block FB41 is 1 state, the controller is in manual mode and the 0 state is in automatic mode. In the manual mode, the output value of the PID controller is replaced by the manual input value MAN.
The output value of the PID consists of proportional, integral, derivative component () and disturbance amount DISV, ie
PID output value = LMN_P + LMN_I + LMN_D + DISV
In manual mode, the integral component in the controller output is automatically set to LMN–LMN_P–DISV and the derivative component is automatically set to zero. The PID output at this time is
PID output value = LMN_P + (LMN - LMN_P - DISV) + 0 + DISV = LMN
This can ensure manual to automatic bumpless switching, that is, the output value LMN of the PID controller before and after switching will not be abrupt.