a conveyor device that conveys a recording medium along a predetermined conveyor path;

an image forming device that forms an image on the recording medium conveyed by the conveyor device; and

an adaptive control device including

an identifier that estimates an unknown coefficient in a discrete-time transfer function model P(z) (z: delay operator) of a controlled object, base on a manipulated variable supplied to the controlled object and a controlled variable of the controlled object to the manipulated variable, to identify the discrete-time transfer function model P(z),

a feedforward controller that is expressed by a discrete-time transfer function model using an inverse model 1/P(z) of an identification model P(z) which is resulted from identification by the identifier and that generates a feedforward manipulated variable as at least a part of the manipulated variable to an input control target value, wherein the controlled object is configured such that the discrete-time transfer function model P(z) of the controlled object is expressed by equation (i),

where b, a₁, . . . , a_n: unknown coefficient, and

h₁, . . . , h_n: known real number,

the identifier, when estimating each coefficient b, a₁, . . . , a_n of the discrete-time transfer function model P(z) of equation (i), estimates a single unknown coefficient b of numerator in non-expanded form of the numerator.

wherein the adaptive control device controls, as the controlled object, a motor and a driving mechanism driven by the motor of the image forming apparatus.