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Method to control a process variable

  • US 10,407,328 B2
  • Filed: 12/14/2015
  • Issued: 09/10/2019
  • Est. Priority Date: 12/15/2014
  • Status: Active Grant
First Claim
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1. A method to control a process variable representing an air volume to be fed into a liquid volume inside a container including a fluid intake and a fluid discharge in a process for treating the liquid, said process being conducted in the container and said method being performed using an air-mass flow controller and comprising the steps:

  • measuring values of a first measurand representing a load of one or more substances to be degraded in the process and found in a settable volume unit of the liquid in the fluid intake;

    sequentially determining values of a reference variable to be supplied to the air-mass flow controller based on the values of the first measurand, said reference variable representing a nominal value of the air volume to be fed into the liquid volume;

    sequentially determining values of a regulating variable using both values for the reference variable and sequentially determined values of the process variable, said regulating variable being a variable for an aerator that serves to supply air into the liquid volume in the container and said variable influencing the air volume fed into the liquid volume using the aerator; and

    determining a current value for the reference variable by;

    sequentially saving values of the first measurand, or values derived therefrom, in a first FIFO memory having a number K of memory locations for saving one value respectively, namely a memory featuring a number K of logically consecutive memory locations (j=i) in such a way that the oldest value saved in the first FIFO memory is saved in a first memory location (j=1) and the value saved last in the first FIFO memory is saved in a final memory location (j=k);

    using only the n oldest values saved in the first FIFO memory to determine the current value for the reference variable, with n being a number of values that is smaller than the number K of the values saved in the memory locations of the first FIFO memory and greater than or equal to 1; and

    adjusting the aerator using the air-mass flow controller using the values of the regulating variable;

    wherein the values of the first measurand or air requirement values derived from at least one value of the first measurand using a proportionality factor are saved sequentially in the first FIFO memory, and each air requirement value represents an air volume to be fed into the liquid to degrade the substance load represented by the at least one value of the first measurand.

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