Control apparatus having a limit cycle auto-tuning function

A control apparatus comprising:

• manipulated variable output means for outputting first and second manipulated variables having a constant amplitude to an object to be controlled, the first manipulated variable being output to the object in normal operation and the second manipulated variable being output to the object in executing limit cycle auto-tuning;
• arithmetic means for calculating a limit cycle auto-tuning control parameter for adjusting a control parameter to the object on the basis of a control response corresponding to the first and second manipulated variables from said manipulated variable output means;
• first lower limit setting means for setting in advance a first lower limit value representing a lower limit value of the first manipulated variable;
• first upper limit setting means for setting in advance a first upper limit value representing an upper limit value of the first manipulated variable;
• second lower limit setting means for setting in advance a second lower limit value representing a lower limit value of the second manipulated variable;
• second upper limit setting means for setting in advance a second upper limit value representing an upper limit value of the second manipulated variable;
• and
• controlling means for performing feedback control calculation based on the control parameter for a deviation between a set point and a controlled variable to calculate the first manipulated variable, and outputting the calculated first manipulated variable to the object,
• wherein in executing limit cycle auto-tuning, said arithmetic means outputs to the object the second manipulated variable having the second lower limit value as the lower limit value and the second upper limit value as the upper limit value, calculates the control parameter of said controlling means on the basis of a control response corresponding to the manipulated variable output, and sets the calculated control parameter in said controlling means, further comprising manipulated variable control means for outputting to said arithmetic means the first lower limit value as the lower limit value of the second manipulated variable when the second lower limit value is smaller than the first lower limit value in executing limit cycle auto-tuning.

A control apparatus comprising:

• manipulated variable output means for outputting first and second manipulated variables having a constant amplitude to an object to be controlled, the first manipulated variable being output to the object in normal operation and the second manipulated variable being output to the object in executing limit cycle auto-tuning;
• arithmetic means for calculating a limit cycle auto-tuning control parameter for adjusting a control parameter to the object on the basis of a control response corresponding to the first and second manipulated variables from said manipulated variable output means;
• first lower limit setting means for setting in advance a first lower limit value representing a lower limit value of the first manipulated variable;
• first upper limit setting means for setting in advance a first upper limit value representing an upper limit value of the first manipulated variable;
• second lower limit setting means for setting in advance a second lower limit value representing a lower limit value of the second manipulated variable;
• second upper limit setting means for setting in advance a second upper limit value representing an upper limit value of the second manipulated variable;
• and
• controlling means for performing feedback control calculation based on the control parameter for a deviation between a set point and a controlled variable to calculate the first manipulated variable, and outputting the calculated first manipulated variable to the object,
• wherein in executing limit cycle auto-tuning, said arithmetic means outputs to the object the second manipulated variable having the second lower limit value as the lower limit value and the second upper limit value as the upper limit value, calculates the control parameter of said controlling means on the basis of a control response corresponding to the manipulated variable output, and sets the calculated control parameter in said controlling means, further comprising automatic stop operation means for automatically stopping execution of limit cycle auto-tuning when the second lower limit value is smaller than the first lower limit value in executing limit cycle auto-tuning.

A control apparatus comprising:

• manipulated variable output means for outputting first and second manipulated variables having a constant amplitude to an object to be controlled, the first manipulated variable being output to the object in normal operation and the second manipulated variable being output to the object in executing limit cycle auto-tuning;
• arithmetic means for calculating a limit cycle auto-tuning control parameter for adjusting a control parameter to the object on the basis of a control response corresponding to the first and second manipulated variables from said manipulated variable output means;
• first lower limit setting means for setting in advance a first lower limit value representing a lower limit value of the first manipulated variable;
• first upper limit setting means for setting in advance a first upper limit value representing an upper limit value of the first manipulated variable;
• second lower limit setting means for setting in advance a second lower limit value representing a lower limit value of the second manipulated variable;
• second upper limit setting means for setting in advance a second upper limit value representing an upper limit value of the second manipulated variable;
• and
• controlling means for performing feedback control calculation based on the control parameter for a deviation between a set point and a controlled variable to calculate the first manipulated variable, and outputting the calculated first manipulated variable to the object,
• wherein in executing limit cycle auto-tuning, said arithmetic means outputs to the object the second manipulated variable having the second lower limit value as the lower limit value and the second upper limit value as the upper limit value, calculates the control parameter of said controlling means on the basis of a control response corresponding to the manipulated variable output, and sets the calculated control parameter in said controlling means,
• wherein when the first lower limit value is not larger than the second lower limit value and the first upper limit value is not smaller than the second upper limit value, letting Pb be a proportional band, Ti be an integral time, and Td be a derivative time, said arithmetic means calculates control parameters:
• Pb=250—Er2−Er1_/(OH—AT−OL—AT)
• Ti=6(Th1+Th2)
• Td=1.2(Th1+Th2).