In a system for controlling a plant (engine) 10 having an input u, there
are provided with applying device (vibration signal) 100 for applying a
component p that changes at a predetermined cycle to the plant, parameter
calculating device (Washout Filter) 102 for calculating a parameter h
based on an output y of the plant, integrating device (finite interval
integrator) 104 for integrating a value j obtained by multiplying the
calculated parameter h by the applied component p in an interval of
integral multiple of a cycle of the component p, and input calculating
devices (infinite interval integrator 106a, multiplier 106b, adder 106c)
for calculating the input u based on the integrated value g obtained by
the integration. Owing to this configuration, it becomes possible to
provide a system that can optimize the output y, while preventing the
resonance of the control system while, thereby enabling to control the
output of the plant to the extremum point.