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An adaptive control device includes an identifier and a feedforward controller. The identifier estimates an unknown coefficient in a discrete-time transfer function model of a controlled object to identify the discrete-time transfer function model. Estimation is performed based on a manipulated vari

An adaptive control device includes an identifier and a feedforward controller. The identifier estimates an unknown coefficient in a discrete-time transfer function model of a controlled object to identify the discrete-time transfer function model. Estimation is performed based on a manipulated variable supplied to the controlled object and a controlled variable of the controlled object to the given manipulated variable. When estimating each coefficient of the discrete-time transfer function model, the identifier estimates a single unknown coefficient in numerator in non-expanded form of the numerator.

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What is claimed is: 1. An image forming apparatus comprising: 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 ident

What is claimed is: 1. An image forming apparatus comprising: 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/{circumflex over (P)}(z) of an identification model {circumflex over (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, . . . , an: unknown coefficient, and h1, . . . , hn: known real number, the identifier, when estimating each coefficient b, a1, . . . , an 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. 2. The image forming apparatus according to claim 1, wherein the discrete-time transfer function model P(z) has no unstable zero point. 3. The image forming apparatus according to claim 2, wherein the discrete-time transfer function model P(z) is expressed by equation (i) having a numerator defined by b(z±1)n. 4. The image forming apparatus according to claim 2, wherein the discrete-time transfer function model P(z) is expressed by equation (i) having a numerator defined by b(z±1)mg(z) (where g(z) is an expression of degree n-m of z). 5. The image forming apparatus according to claim 1, wherein the discrete-time transfer function model P(z) is obtained by transforming into a discrete-time transfer function a continuous-time transfer function model P(s) (s: differential operator) of the controlled object introduced by applying physical law to the controlled object. 6. The image forming apparatus according to claim 5, wherein the continuous-time transfer function model P(s) is defined by expression of degree zero/n of s. 7. The image forming apparatus according to claim 6, wherein the discrete-time transfer function model P(z) is obtained by transforming the continuous-time transfer function model P(s) into a discrete-time system by bilinear transform, and the numerator of the discrete-time transfer function model P(z) is defined by b(z+1)n. 8. The image forming apparatus according to claim 1,wherein the identifier includes a coefficient update calculator that repeats calculation in accordance with adaptive update rule defined by equation (ii) to update an identification coefficient {circumflex over (θ)}(k) that is an estimate of each coefficient b, a1, . . . , an, {circumflex over (θ)}(k)={circumflex over (θ)}(k-1)-L·v(k){tilde over (e)}(k) (ii) where {circumflex over (θ)}(k)=[{circumflex over (b)}, ân, . . . , â1], v(k)=[u(k)+hnu(k-1)+hn-1u(k-2)+ . . . +h1u(k-n),-y(k-1), . . . ,-y(k-n)], {tilde over (e)}(k)-y(k)-ŷ(k), ŷ(k)={circumflex over (θ)}T(k-1)v(k), u(k): manipulated variable, y(k): controlled variable, k: calculation timing, and L: adaptive gain, an identification completion determiner that determines that identification is completed when {tilde over (e)}(k) in equation (ii) is equal to or below a predetermined update completion determination value. 9. The image forming apparatus according to claim 1 further comprising a feedback controller that compares the control target value with an actual controlled variable of the controlled object and generates a manipulated variable depending on error between the control target value and the actual controlled variable as a feedback manipulated variable such that the error is reduced, and a manipulated variable synthesizer that adds the feedback manipulated variable from the feedback controller to the feedforward manipulated variable from the feedforward controller to supply the sum as the manipulated variable to the controlled object. 10. The image forming apparatus set forth in claim 1 wherein the driving mechanism is a part of the conveyor device. 11. The image forming apparatus set forth in claim 1 wherein the driving mechanism is a part of the image forming device. 12. The image forming apparatus set forth in claim 1 wherein the image forming device ejects ink onto the recording medium to form an image on the recording medium.