Control method including feedforward signal

A method to control a process wherein at least one parameter of the process is influenced by a disturbance variable and by a manipulated variable which control method comprises:

• a. automatically measuring said disturbance variable,
• b. automatically generating a disturbance signal ds as a function of time corresponding to said disturbance variable as measured,
• c. converting said disturbance signal ds in a computer into a feedforward signal cs which is related to the disturbance signal ds by the control equation ##EQU15## wherein K.sub.1 is the steady state gain of the process parameter caused by the unit change of the disturbance variable, K.sub.2 is the steady state gain of process parameter caused by the unit change of the control variable, D.sub.d is the dead time of the disturbance dynamics, D.sub.c is the dead time of the control dynamics, L is the Laplace transform operator, T.sub.1 and T.sub.2 are defined by the following relation with T.sub.c and T.sub.d :
• ##EQU16## wherein T.sub.c is the time constant of the control dynamics and T.sub.d is the time constant of the disturbance dynamics,
• with the further provision that either T.sub.c = t.sub.d or D.sub.d = d.sub.c ;
• d. automatically converting said feedforward signal cs into a corresponding control signal, and
• e. utilizing said control signal to adjust said manipulated variable.