Mixture control apparatus and mixture control method

A mixture control apparatus for mixing two fluids having different process variables to obtain a third fluid having a desired process variable, comprising:

• flow rate detecting means for detecting the flow rate of the third fluid;
• gain correction quantity calculating means for detecting process variables of the first and second fluids, receiving an output signal from said flow rate detecting means, and for calculating a gain correction quantity in accordance with the difference between the process variables of the first and second fluids and with the flow rate of the third fluid;
• set point variable input means for receiving a set point variable which is externally supplied for the process variable of the third fluid;
• feed forward control signal generating means for receiving an output signal from said gain correction quantity calculating means and the set point variable of the process variable of the third fluid which is generated from said set point variable input means, detecting the process variable of the first fluid, and for generating a feed forward control signal in accordance with the gain correction quantity, the set point variable of the process variable of the third fluid and the process variable of the first fluid;
• feedback control signal generating means for detecting the process variable of the third fluid, receiving the set point variable of the process varible of the third fluid and the output signal from said gain correction quantity calculating means, and generating a feedback control signal in accordance ith the process variable of the third fluid, the set point variable of the process variable of the third fluid and the output signal from said gain correction quantity calculating means;
• and
• flow controlling means for controlling mixing quantities of the first and second fluids in accordance with the feed forward control signal and the feedback control signal.