Process control methods and apparatus

A method for controlling a processor by providing a deviation between a setpoint variable and a process variable to a controller to calculate a controlled manipulated variable and then providing said controlled/manipulated variable to said process, said method comprising the steps of:

• determining conditions for said process variable to settle within a finite length of time from a final value theorem;
• determining a transfer function of said controller from said conditions;
• and
• using said transfer function to calculate value or change of said controlled/manipulated variable within which to control said process;
• wherein said process has a dead time, a settling time, and a control period;
• and wherein an integer m is defined as a ratio of said dead time and said control period, and an integer k is defined as a value obtained by subtracting said integer m from a ratio of said setting time and said control period, whereby a latest value or change of a controlled/manipulated variable Wn outputted by said contoller is calculated according to the following:
• W n = 1 K ⁢ ( 1 - α k ) ⁡ [ E n - α ⁢ ⁢ E n - 1 - α k ⁢ { E n - k - α ⁢ ⁢ E n - ( k + 1 ) } ] + α ⁢ ⁢ W n - 1 - α ⁢ ⁢ W n - 2 + 1 - α 1 - α k ⁢ { W n - ( m + 1 ) - α k ⁢ W n - ( m + k + 1 ) }
• where En, En−1, En−k and En−(k+1) are the values of said deviation in the current control period, in the previous control period, in the period k control periods earlier, and in the period k+1 control periods earlier, respectively, Wn−1, Wn−2, Wn−(m+1) and Wn−(m+k+1) are the values of said controlled/manipulated variable in the previous control period, in the period two control periods earlier, in the period m+1 control periods earlier, and in the period m+k+1 control periods earlier, respectively, and α and K are constants.