JPH10200700A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow an image reader to read an image with high image quality by improving the precision of position control of a scanning optical system. SOLUTION: This image reader has a scanning optical system, that emits a light onto an original for main scanning and moves the scanning optical system in the sub-scanning direction by a motor for sub-scanning, so as to read an image of the original. Then a position output (x) which is a rotation angle of the motor is detected, and a deviation, in an object position due to fluctuation in parameters of the scanning optical system and external disturbance or the like which are caused when the motor drives the scanning optical system is taken into the design as a robust controller Kr. Robust control is applied to the motor based on the detected position output (x), so as to allow the scanning optical system to trace the object position and a feedforward FF is used to provide a torque required for the rising of the motor to the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus, and more particularly, to an image reading apparatus capable of accurately controlling the position of a photoelectric conversion unit having a scanning optical system.

[0002]

2. Description of the Related Art In an image reading apparatus such as a scanner or a copier, when reading an image of an original, the original placed on a contact glass is moved by moving a photoelectric conversion unit equipped with a scanning optical system. The configuration of reading an image is often adopted. Therefore, in the image reading apparatus having such a configuration, it is important to accurately control the position of the photoelectric conversion unit in reading an image from a document with high accuracy.

[0003] As an example of the prior art of such a device,
Japanese Patent Publication No. 6-83339 discloses an "image reading apparatus".
In this image reading apparatus, an original on a platen glass is scanned and exposed by an exposure light source of an optical system, and a light image of the obtained original is guided into an imaging unit by a plurality of mirrors of the optical system. A stepping motor is used as a drive motor for driving the moving part of the optical system, and the value obtained by multiplying the natural frequency of the mirror and the basic drive frequency of the stepper motor by an integer or the natural frequency of the mirror and the basic drive of the stepper motor are used. It is configured so that a value obtained by dividing the frequency by an integer is different. That is, in this image reading device, mirror resonance is prevented by preventing the basic driving frequency of the stepping motor from becoming an integral number n or 1 / n times the natural frequency of the mirror.

As another example of the prior art, Japanese Patent Publication No.
No. 14,194, “Image forming apparatus”. This image forming apparatus optically scans a document a plurality of times by scanning a document a plurality of times by using a pulse control motor to reciprocate a plurality of times, reads image data of a plurality of colors, and forms an image of one page. In the multi-color image forming apparatus, the driving of the motor of the scanning optical system at the time of the return drive other than the last drive is performed when the number of pulses of the motor at the time of the return drive is a predetermined number N, that is, the scanning optical system for reading a document. Is stopped when the number of pulses of the motor of the scanning optical system at the time of reciprocation is reached. That is, in this image forming apparatus, in the return drive other than the final scan, the open control is performed without referring to the output of the home position sensor.

[0005]

However, in the above-mentioned Japanese Patent Publication No. 6-83339 "Image reading apparatus", the basic driving frequency of the stepping motor does not become an integer n times or 1 / n times the natural frequency of the mirror. In order to prevent mirror resonance in this manner, when the image reading apparatus has a magnification mode in which image data is scaled at a predetermined magnification, there are a plurality of image reading speeds, and the stepping motor has In some cases, the basic drive frequency becomes an integral number n times or 1 / n times the natural frequency of the mirror, resulting in a problem that the quality of the read image is deteriorated.

Also, in the above-mentioned Japanese Patent Publication No. 7-14194, "image forming apparatus", a motor for driving a scanning optical system is controlled by open control, so that when a disturbance such as frictional force occurs, a color image is generated. There is a problem that color misregistration occurs.

The present invention has been made in view of the above, and has as its object to improve the accuracy of position control of a photoelectric conversion unit equipped with a scanning optical system and to enable reading of high-quality images. .

[0008]

According to a first aspect of the present invention, there is provided an image reading apparatus, comprising: a scanning optical system for irradiating a document with light to perform a main scanning; In an image reading apparatus that moves in a scanning direction to perform sub-scanning and reads an image of the original, a detection unit that detects a rotation angle of the motor, and the scanning optical generated when the scanning optical system is moved by the motor. A robust controller incorporating a target position shift due to system parameter fluctuations and disturbances in its design is configured, and based on a detection result of the detection unit, the motor is robustly controlled, thereby moving the scanning optical system to a target position. Control means for causing the motor to follow, wherein the control means supplies the motor with a torque required when the motor starts up as a feedforward amount. It is.

According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the control means performs second order differentiation of a function that gives a target position trajectory of position following control for the motor. The second derivative value is multiplied by the equivalent moment of inertia of the motor and the image reading device, and divided by the torque constant of the motor to obtain the feedforward amount, and the obtained feedforward amount is given to the motor. Things.

According to a third aspect of the present invention, in the image reading apparatus of the second aspect, the control means further provides a feedforward amount for correcting a friction torque to the motor.

According to a fourth aspect of the present invention, in the image reading apparatus according to the second or third aspect, the control means reads the original as a function that gives the target position trajectory when the motor starts up. Zero acceleration before position
And a fourth-order or higher function that makes the speed constant is used.

According to a fifth aspect of the present invention, there is provided the image reading apparatus according to any one of the second to fourth aspects,
When the function for giving the target position trajectory is such that the approach distance q1, the target document scan speed Ref_speed, and the time delta1 spent for the approach have the following relationship,

(Equation 2) When the Ref_speed is multiplied by N (N is a positive real number), the delta1 is multiplied by N and the q1
Is multiplied by N ² .

According to a sixth aspect of the present invention, in the image reading apparatus according to any one of the second to fifth aspects, the control means includes a function value for giving the normalized target position locus. Storage means for storing in advance a second derivative value of a function for providing the target position trajectory, and a function value for providing the predetermined target position trajectory from the storage means in response to a change in the target position trajectory; A second-order differential value of a function that gives a position trajectory is selected, and the motor is robustly controlled.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an image reading apparatus according to the present invention will be described with reference to the drawings in the order of [Embodiment 1], [Embodiment 2], [Embodiment 3]. This will be described in detail.

[First Embodiment] FIG. 1 is a configuration diagram showing a configuration of an image reading apparatus according to a first embodiment. The image reading apparatus 1 shown in FIG. 1 includes a contact glass 3 as a document table above a main body case 2, and a fluorescent lamp 4 as a light source 4, a first mirror 5, a second mirror 6 below the contact glass 3. CCD (Ch) as a lens 7 and a photoelectric conversion element
A photoelectric conversion unit 9 (corresponding to the scanning optical system according to claim 1) equipped with an "arranged coupled device" 8 is provided.

An original 10 is set on the contact glass 3 with the original surface facing the contact glass 3, and a fluorescent lamp mounted on the photoelectric conversion unit 9 is placed on the original 10 set on the contact glass 3. 4 irradiates light. The reflected light from the document 10 is reflected in the order of the first mirror 5 and the second mirror 6 along the optical axis 11 shown by the arrow line in FIG. The CCD 8 photoelectrically converts the incident light and outputs the original 10
Read the image. The CCD 8 for optically scanning the original 10 a plurality of times and reading image data of a plurality of colors.
Has a configuration of three lines of R, G and B.

Although not shown, the photoelectric conversion unit 9 is guided by a guide plate or the like so as to be movable in the sub-scanning direction (the left-right direction indicated by a double arrow in FIG. 1).
It is locked by a wire 12 stretched in the sub-scanning direction. The wire 12 is engaged with a pair of pulleys 13 and 14 disposed at both ends in the sub-scanning direction in the main body case 2.
The pulley 13 is driven to rotate by a motor (for example, a DC servomotor) 16 via a power transmission mechanism 15 such as a gear. An encoder 17 (corresponding to a detecting means according to claim 1) is mounted coaxially with the rotation axis of the motor 16, and the encoder 17 detects the rotation angle of the motor 16.

In the above configuration, when the motor 16 rotates, the rotation of the motor 16 is transmitted to the pulley 13 via the power transmission mechanism 15, and the pulley 13 rotates, so that the wire 12 connects the pulley 13 and the pulley 14 to each other. Rotate between. When the wire 12 rotates, the photoelectric conversion unit 9 connected to the wire 12 moves in the sub-scanning direction along with the movement of the wire 12, and the photoelectric conversion unit 9 moves the original from the fluorescent lamp 4 to the original on the contact glass 3. The main scanning and sub-scanning are performed to read the image of the original 10 while irradiating the CCD 10 with light and introducing the reflected light to the CCD 8 along the optical axis 11.

FIG. 2 is a block diagram of the image reading apparatus according to the first embodiment. The image reading device 1 includes a microcomputer 21 (corresponding to a control unit according to claim 1),
The state command unit 21 (corresponding to the control means according to claim 1), the interface 23 (the drive circuit 24, the motor 16, the encoder 1 corresponding to the control means according to claim 1)
7 and an interface 25 (corresponding to the control means of claim 1).

The microcomputer 21 includes a microprocessor 26 and a ROM (Read Only Memory).
y) 27 (corresponding to the storage means according to claim 6) and RAM (Random Access Memory)
28 (corresponding to the storage means of claim 6) and the like. In FIG. 2, reference numeral 29 denotes a bus.
, The microcomputer 21, the state command unit 22,
The interface 23 and the interface 25 are mutually connected.

The microprocessor 26 controls each part of the image reading apparatus 1 based on the program in the ROM 27 while using the RAM 28 as a work area, in particular,
The drive control of the motor 16 is performed.

The state command section 22 outputs a state command signal for commanding the state of the motor 16 (target position and target speed), that is, a position command signal, a speed command signal, and the like. A drive control signal for controlling the drive of the motor 16 is output to the interface 23 based on the command signal.

The interface 23 is a driving interface device. As will be described later, a driving control signal, which is a digital value of an operation result of the microcomputer 21, is transmitted to a power semiconductor constituting the driving circuit 24, for example, a pulse for operating a transistor. The signal is converted into a drive control signal and output to the drive circuit 24.

The drive circuit 24 controls the voltage and current applied to the motor 16 based on the pulse drive control signal input via the interface 23. As a result,
The motor 16 is driven to rotate at a desired speed.

As described above, for example, a DC servo motor is used as the motor 16, and this motor 16 is driven under the control of the drive circuit 24, and the position and speed controlled by the drive circuit 24, ie, the microcomputer 21 Rotate at a controlled position and speed.

The encoder 17 detects the rotation angle of the motor 16 and outputs the detection result to the state detection interface 25.

The interface 25 includes the encoder 17
And a counter for counting the output pulses of the encoder 17. The output of the interface 25 is connected to an interrupt terminal of the microprocessor 26 and includes a timer and a register for counting a reference clock. Is detected.

In FIG. 2, an example using a discrete type microcomputer has been described.
The present invention is not limited to this, and it goes without saying that the same function can be obtained by using a microcomputer in which the state command unit 22, the interface 23, and the interface 25 are integrated into one chip.

The microcomputer 21 forms a robust control system as shown in FIG. 3 together with the state command unit 22 based on a program in the ROM 27, and controls the position of the motor 16 and, consequently, the position of the photoelectric conversion unit 9. Performs robust control. Robust control is control that is hardly influenced by disturbance and can quickly follow a target.

FIG. 3 is a block diagram for explaining position control of the photoelectric conversion unit in the image reading apparatus according to the first embodiment. The operation of the image reading apparatus according to the first embodiment will be described with reference to FIG. In FIG. 3, R
ef_posi indicates a target position function that gives a target position trajectory, Kr indicates a gain of a robust controller, Kt indicates a motor torque constant (DC motor torque constant), and J indicates a motor shaft converted equivalent moment of inertia. , S indicates a Laplace operator, x indicates a position output, and FF indicates feedforward.

The microcomputer 21 feeds back the position output x (rotation angle) of the motor 16 detected by the encoder 17 via the interface 25, and outputs a target position function Ref_posi as a state command signal output from the state command section 22 and a target position function Ref_posi. The deviation e is obtained by comparison.

Then, the microcomputer 21 multiplies the obtained deviation e by the gain Kt of the robust controller to obtain a current value as a pulse-like drive control signal to be given to the drive circuit 24.

A current value for giving a necessary torque to the motor 16 at the time of start-up is added to the obtained current value by the feedforward FF, and this current value is given to the drive circuit 24 via the interface 23.

The drive circuit 24 includes the microcomputer 2
The motor 16 is driven in accordance with the current value given from step (1). The motor 16 rotates under the control of the drive circuit 24 to move the photoelectric conversion unit 9 in the sub-scanning direction, and the photoelectric conversion unit 9 reads an image of the document 10 according to the movement.

The encoder 17 detects a position output x (rotation angle) of the motor 16, and outputs the detected position output x via the interface 25 to the microcomputer 21.
Will be fed back.

In FIG. 3, a position output x (rotation angle of the motor 16) is obtained by multiplying a current value given by the microcomputer 21 by a motor torque constant Kt (DC motor torque constant) and obtaining a motor shaft equivalent equivalent moment of inertia. After calculating the angular acceleration of the motor 16 by dividing by J,
This angular acceleration is calculated by 1 / s ² , that is, the second-order integration. The encoder 17 is provided with such a motor 1
6, the position output x is detected, and the detected position output x is fed back to the microcomputer 21.

The photoelectric conversion unit 9 in the image reading device
In the position control described above, when the motor 16 is in a steady state, stable position control can be performed only by the robust controller Kr. However, in a transient state such as when the motor 16 starts up, overshoot occurs,
As a result, the tip of the read image expands and contracts. In the image reading apparatus according to the first embodiment, as shown in FIG. 3, a feedforward loop is added, and a torque required at the time of startup is set as a feedforward amount.
6, overshoot can be suppressed, the accuracy of position control for the photoelectric conversion unit 9 equipped with the scanning optical system can be improved, and high-quality images can be read.

That is, according to the image reading apparatus of the first embodiment, the original 10 is optically scanned a plurality of times to perform the position control by the robust controller incorporating the target position shift due to disturbance or the like into the design. Even when the image data is read, the positional deviation of the image reading position can be reduced, and a high-quality image can be read. In addition, since the necessary torque at the time of rising is given to the motor 16 as the feedforward amount, overshoot at the leading edge of the document can be suppressed, and high-quality images can be read with a short approach distance.

[Second Embodiment] Next, an image reading apparatus according to a second embodiment will be described. Note that the configuration of the image reading apparatus according to the second embodiment is the same as that of the image reading apparatus according to the first embodiment shown in FIGS.

FIG. 4 is a block diagram for explaining position control of the photoelectric conversion unit in the image reading apparatus according to the second embodiment. The operation of the image reading apparatus according to the second embodiment will be described with reference to FIG.

The microcomputer 21 calculates a feedforward amount for giving a necessary torque to the motor 16 at the time of startup from a target position function Ref_posi as a state command signal output from the state command unit 22.

The target position function Ref_posi is given by, for example, the following quartic function. Ref_posi (t) = a14 × t ⁴ + a13 × t ³
+ A12 × t ²

Then, the given target position function Ref_
When pos is differentiated by s ² , that is, second-order differentiation, the obtained second-order differential value AC (t) is obtained by AC (t) = 12 × a14 × t ² +
6 × a13 × t + 2 × a12.

Subsequently, the obtained second-order differential value AC (t) is multiplied by the equivalent inertia moment J of the motor 16 (DC servo motor) and the image reading device, and the motor torque constant Kt (DC motor torque constant) ) To obtain a current value as a feedforward amount.

The microcomputer 21 calculates the position output x detected by the encoder 17 and the target position function Ref_po.
and a current value as a pulse-like drive control signal obtained by multiplying the position error e by the gain Kt of the robust controller.
The current value as the feedforward amount obtained as described above is added, and given to the drive circuit 24 via the interface 23.

The other operations are the same as those described in the first embodiment with reference to FIG. 3, and the description thereof is omitted here.

In this way, since the required torque is applied to the motor 16 at the time of starting, the deviation e (Ref_Ref_
pos-x) shows a response as shown by the solid line in FIG. That is, by providing the feedforward amount obtained as described above to the motor 16, the motor 16
Overshoot can be suppressed. On the other hand, FIG.
The middle dashed line shows the response of the deviation e (Ref_posi-x) when there is no feedforward FF, and it can be seen that the motor has overshoot.

As described above, in the image reading device according to the second embodiment, the target position function is second-order differentiated, and the obtained second-order differential value is multiplied by the equivalent moment of inertia J between the motor 16 and the image reading device 1. And the torque constant Kt of the motor 16
Therefore, even when the target position function changes, the required torque at the time of startup can be given to the motor 16 as the feedforward amount even when the target position function changes. Therefore, even at the time of zooming, overshoot at the leading edge of the document can be suppressed, and high-quality images can be read.

Here, the target position function Ref_pos
i (t) will be described in more detail. In the image reading apparatus 1 according to the second embodiment, the target position function Ref given to the microcomputer 21 from the state command unit 22
_Posi (t) is the fourth or higher order in which the acceleration becomes 0 and the speed becomes constant before the reading position of the document 10.

Now, the target position function Ref_posi
(T) is calculated by Ref_posi (t) = a14 × t ⁴ + a13 × t ³
+ A12 × t ² . Here, a14, a13, and a12 can be obtained from the following simultaneous equations.

[0051]

(Equation 3)

Here, t is t = tau / delta1.
, Tau indicates the actual time, q1 indicates the approach distance until the photoelectric conversion unit 9 reaches the image reading position of the document 10, and delta1
Indicates an approach time required for the photoelectric conversion unit 9 to travel the approach distance q1. That is, the target position function Ref_posi (t) is calculated by the photoelectric conversion unit 9.
Is operated, when the time delta1 required to travel the approach distance q1 has elapsed, the photoelectric conversion unit 9
Is zero, and the speed thereafter is constant.

The target position function at the actual time is represented by Posit.
If ion (tau), Position (tau) = a14 × (tau / de
lta1) ⁴ + a13 × (tau / delta1) ³ + a
It is 12 × (tau / delta1) ² .

The acceleration Acc (tau) obtained by second-order differentiation of the position (tau) is given by: Acc (tau) = (12 × a14 × (tau / del)
ta1) ² + 6 × a13 × (tau / delta1) +
2 × a12) / (delta1 ² ).

Therefore, the value at the time of the rise of Acc (tau) becomes 0 before the leading edge of the image, and the overshoot can be suppressed.

Here, the normalization of t is defined as delta1 = 10
0 ms, q1 = 9.35 rad, Ref_speed
Under the condition of d = 123.5 rad / s, a14, a13,
6 and 7 show the relationship between t obtained by obtaining a12 and the target position trajectory and acceleration trajectory. Also, q1 = 9.35ra
d, Ref_speed = 123.5 rad / s, de
FIGS. 8 and 9 show the relationship between tau and the target position trajectory and the acceleration trajectory when lta1 = 100 ms. As can be seen from these figures, by giving the target position function as described above, the acceleration of the photoelectric conversion unit 9 becomes zero at q1 and delta1, and the speed thereafter becomes constant.

As described above, in the image reading apparatus according to the second embodiment, the target position function Ref_posi is
Since the acceleration becomes 0 before the reading position of 0 and the speed is constant, the feed forward amount at the document reading start position becomes 0, and the position vibration such as overshoot is suppressed. And a high-quality image can be read from the leading edge of the document.

Next, a case will be described in which the image reading apparatus 1 according to the second embodiment reads an image of the document 10 at a variable magnification.

In the image reading apparatus 1 according to the second embodiment, in the target position function Ref_posi (t), Ref_s
When speed is multiplied by N (N is a positive real number),
the a1 multiplied by N, ^two times N the q1. For example, Ref_s
When speed = 123.5 rad / s is doubled,
Double delta1 = 100ms, q1 = 9.35r
Ad is multiplied by 2 squared. FIGS. 10 and 11 show the relationship between tau and the target position trajectory and acceleration trajectory in this case. Note that the acceleration value on the normalized time axis is shown in FIG.
Will be the same as shown in

As described above, the target position function Ref_pos
In i (t), when Ref_speed is multiplied by N (N is a positive real number), delta1 is multiplied by N and q1 is changed by N
^The target position function Ref_posi should be doubled.
Is a coefficient of (t) a14, a13, a12 also may be respectively N ² multiplied by. Therefore, since it is not necessary to have a table for each magnification, it is possible to read a high-quality image with a small amount of memory.

Further, in the image reading apparatus 1 according to the second embodiment, the normalized target position function value and the second derivative of the target position function are tabulated in advance and stored in a memory such as the ROM 27 or the RAM 28 in advance. .

For example, q1 = 9.35 rad, Ref_
speed = 123.5 rad / s, delta1 = 1
In the case of 00 ms, t, f1 (t), and the second derivative of f1 (t) are stored in the memory of the microcomputer 21 in advance. Then, the microcomputer 21 calculates a target position trajectory based on the stored data. For example, when Ref_speed = 123.5 rad / s, which is twice, delta1 is delta1 = 100 ms = 2
It becomes 200 ms twice.

When the actual time tau is 40 ms, t =
From tau / delta1 = 40/200, t = 0.2
become. As the target position trajectory, f1 (0.2) may be read from the table. The second order differential value for feedforward may be read from the second order differential table of f1 (0.2). The values in the table are stored in the microcomputer 21
Can be created in accordance with the sampling period.

FIGS. 12, 13 and 14 show examples of the above-mentioned tables. Here, FIG. 12 shows the normalized time t
FIG. 4 is an explanatory diagram showing a table of target positions and target accelerations for = tau / delta1. FIG. 13 shows the actual time ta.
It is explanatory drawing which shows the table of the target position when u, delta1 = 0.1. FIG. 14 shows the real time tau,
FIG. 9 is an explanatory diagram showing a table of target positions when delta1 = 0.2.

When delta1 is twice, Ref_s
peed twice as much, q1 will 2 ² times. Therefore, the coefficients a14, a13, and a12 are quadrupled. That is, f1 (tau) in FIG. 14 is 4 of f1 (tau) in FIG.
Doubled.

As described above, according to the image reading apparatus of the second embodiment, since the normalized target position function value and the second derivative of the target position function are tabulated, the target position function
It is possible to eliminate the need to execute the calculation of the second derivative for each control sampling. As a result, the microcomputer 2
1 can shorten the processing time and improve control performance. In addition, since it is not necessary to store all of the target position trajectory and the feedforward amount in the magnification mode in a memory, the amount of memory can be reduced,
As a result, the cost of the device can be reduced.

[Third Embodiment] Next, an image reading apparatus according to a third embodiment will be described. Note that the configuration of the image reading apparatus according to the third embodiment is the same as that described in the first embodiment with reference to FIGS. 1 and 2, and a description thereof will be omitted.

FIG. 15 is a block diagram for explaining position control of the photoelectric conversion unit in the image reading apparatus according to the third embodiment. Embodiment 3 will be described with reference to FIG.
The operation of the image reading apparatus will be described.

When the photoelectric conversion unit 9 of the image reading apparatus 1 is driven, a friction torque (Tf) is generally generated. Therefore, when the motor 16 starts up, the position output x lags behind the target value. Therefore, in the image reading apparatus 1 according to the third embodiment, in addition to the feedforward FF described in the first and second embodiments, a friction torque correction feedforward loop is used in combination to correct the friction torque. Is added to the pulse-like drive control signal, and the resultant value is supplied to the drive circuit 24.

The other operations are the same as those in the second embodiment, and a description thereof will not be repeated.

As described above, since the feedforward amount for correcting the friction torque is given to the motor 16, the deviation e (Ref_posi-x) shows a response as shown in FIG. As can be seen from FIG. 16, the delay of the position output x with respect to the target value is corrected.

As described above, according to the image reading apparatus of the third embodiment, a feedforward loop for friction torque is added to the image reading apparatus of the second embodiment.
It is possible to suppress the target position following delay due to the friction torque. Therefore, the overshoot can be suppressed, the photoelectric conversion unit 9 can accurately follow the target position, and the occurrence of expansion and contraction at the tip of the read image can be prevented, and a high-quality image can be read. .

[0073]

As described above, according to the image reading apparatus of the present invention (claim 1), the detecting means for detecting the rotation angle of the motor, and the scanning generated when the scanning optical system is moved by the motor. A robust controller that incorporates target position deviations due to parameter fluctuations and disturbances of the optical system into its design is configured, and the motor is robustly controlled based on the detection result of the detection means, so that the scanning optical system follows the target position. Control means, wherein the control means optically scans the original document a plurality of times to read the image data of a plurality of colors in order to provide the motor with a necessary torque at the time of startup of the motor as a feedforward amount. Also,
The positional deviation of the image reading position can be reduced, and high-quality image reading can be performed. In addition, since the necessary torque is given to the motor at the time of rising as a feedforward amount, overshoot at the leading edge of the document can be suppressed, and high-quality images can be read with a short approach distance.

Further, the image reading apparatus of the present invention (claim 2)
According to the image reading apparatus of the first aspect, the control means performs second-order differentiation of a function that gives a target position trajectory of position tracking control for the motor, and obtains a second-order differential value between the motor and the image reading apparatus. In addition to multiplying by the equivalent moment of inertia and dividing by the torque constant of the motor to obtain the feedforward amount, the obtained feedforward amount is given to the motor. To the motor as a feedforward amount. Therefore, at the time of zooming, overshoot at the leading edge of the document can be suppressed, and high-quality images can be read.

Further, the image reading apparatus of the present invention (claim 3)
According to the image reading apparatus of the second aspect, since the control means further supplies the motor with a feedforward amount for correcting the friction torque, a delay in following the target position due to the friction torque can be suppressed. Accordingly, it is possible to suppress the overshoot and to cause the scanning optical system to accurately follow the target position, to prevent the leading end of the read image from expanding and contracting, and to read a high-quality image.

An image reading apparatus according to the present invention (claim 4)
According to the second aspect of the present invention, in the image reading apparatus according to the second or third aspect, the control means determines that the acceleration is zero before the reading position of the document as a function for giving a target position trajectory at the time of starting the motor.
Then, since a fourth-order or higher function with a constant speed is used, positional vibration such as overshoot at the document reading start position can be suppressed, and a high-quality image can be read from the leading edge of the document.

An image reading apparatus according to the present invention (claim 5)
According to this, in the image reading device according to any one of claims 2 to 4, the function for giving the target position trajectory is a relation between the approach distance q1, the target document scan speed Ref_speed, and the time delta1 spent for the approach, expressed by the following equation. In the case of having

(Equation 4) Ref_speed to case (the N is a positive real number) N times to, for delta1 together with the N times, q1 is ² times N, the coefficients of the target position function a14, a13,
a12 also may be each N ² multiplied by. Therefore, since it is not necessary to have a table for each magnification, it is possible to read a high-quality image with a small amount of memory.

An image reading apparatus according to the present invention (claim 6)
According to this, in the image reading device according to any one of claims 2 to 5, the control means includes a function value that gives a normalized target position trajectory and a second derivative value of a function that gives the target position trajectory. Is stored in advance, and a function value that gives a predetermined target position trajectory and a second derivative of a function that gives the target position trajectory are selected from the storage unit in accordance with a change in the target position trajectory, and the motor is selected. Is robustly controlled, it is not necessary to execute the calculation of the target position function and the second derivative for each control sampling. As a result, the processing time of the control means can be reduced, and control performance can be improved. In addition, since it is not necessary to store the entire target position trajectory and the feedforward amount in the magnification mode in a memory, the amount of memory can be reduced, and as a result,
The cost of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a configuration of an image reading device according to a first embodiment;

FIG. 2 is a block diagram of the image reading apparatus according to the first embodiment;

FIG. 3 is a block diagram for explaining position control of a photoelectric conversion unit in the image reading apparatus according to the first embodiment;

FIG. 4 is a block diagram for explaining position control of a photoelectric conversion unit in the image reading apparatus according to the second embodiment.

FIG. 5 illustrates a deviation e (Ref_pos) in the position control of the photoelectric conversion unit in the image reading apparatus according to the second embodiment.
It is explanatory drawing which shows the response of ix).

FIG. 6 is a diagram illustrating an image reading apparatus according to a second embodiment, in which t is normalized by delta1 = 100 ms, and Ref_spe
It is explanatory drawing which shows the relationship between t obtained as a result of having calculated a14, a13, and a12 on condition of ed = 123.5 rad / s and q1 = 9.35 rad, and a target position locus.

FIG. 7 is a diagram illustrating an image reading apparatus according to a second embodiment, where t is normalized as delta1 = 100 ms, and Ref_spe
FIG. 9 is an explanatory diagram showing a relationship between t and acceleration trajectory obtained as a result of obtaining a14, a13, and a12 under the conditions of ed = 123.5 rad / s and q1 = 9.35 rad.

FIG. 8 illustrates an image reading apparatus according to a second embodiment.
9.35 rad, Ref_speed = 123.5 rad
ta when d / s, delta1 = 100 ms
FIG. 7 is an explanatory diagram showing a relationship between u and a target position trajectory.

FIG. 9 illustrates an image reading apparatus according to a second embodiment, where q1 =
9.35 rad, Ref_speed = 123.5 rad
ta when d / s, delta1 = 100 ms
FIG. 9 is an explanatory diagram illustrating a relationship between u and an acceleration trajectory.

FIG. 10 illustrates an image reading apparatus according to a second embodiment.
f_speed = 123.5 rad / s is doubled, and de
Double lta1 = 100 ms, q1 = 9.35 rad
FIG. 9 is an explanatory diagram showing a relationship between tau and a target position trajectory when is multiplied by 2 squares.

FIG. 11 illustrates an image reading apparatus according to a second embodiment.
f_speed = 123.5 rad / s is doubled, and de
Double lta1 = 100 ms, q1 = 9.35 rad
FIG. 9 is an explanatory diagram showing a relationship between tau and an acceleration trajectory when is multiplied by 2 squares.

FIG. 12 is an explanatory diagram showing a table of a target position and a target acceleration with respect to a normalized time t = tau / delta1 in the image reading apparatus according to the second embodiment.

FIG. 13 is an explanatory diagram showing a table of target positions when the real time tau and delta1 = 0.1 in the image reading apparatus according to the second embodiment;

FIG. 14 is an explanatory diagram showing a table of target positions when the real time tau and delta1 = 0.2 in the image reading apparatus according to the second embodiment;

FIG. 15 is a block diagram for explaining position control of a photoelectric conversion unit in the image reading apparatus according to the third embodiment.

FIG. 16 illustrates a deviation e (Ref_po) in the position control of the photoelectric conversion unit in the image reading apparatus according to the third embodiment.
FIG. 9 is an explanatory diagram showing a response of (si-x).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image reading device 2 Main body case 3 Contact glass 4 Fluorescent lamp 5 First mirror 6 Second mirror 7 Lens 8 CCD 9 Photoelectric conversion unit 10 Document 11 Optical axis 12 Wire 13, 14 Pulley 15 Power transmission mechanism 16 Motor 17 Encoder 21 Micro Computer 22 State command unit 23, 25 Interface 24 Drive circuit 26 Microprocessor 27 ROM 28 RAM 29 Bus Ref_pos Target position function Kr Robust controller gain Kt Motor torque constant (DC motor torque constant) J Motor shaft converted equivalent inertia moment s Laplace calculation Child x position output FF feed forward

Claims (6)

[Claims] 1. An image reading apparatus, comprising: a scanning optical system that irradiates a document with light to perform main scanning, moves the scanning optical system in a sub-scanning direction by a motor to perform sub-scanning, and reads an image of the document. Detecting means for detecting the rotation angle of the motor, and a robust controller incorporating in its design target position deviations caused by parameter fluctuations and disturbances of the scanning optical system generated when the scanning optical system is moved by the motor. And control means for making the scanning optical system follow a target position by robustly controlling the motor based on the detection result of the detection means, wherein the control means is required when the motor starts up. An image reading device for applying a high torque to the motor as a feedforward amount. 2. The method according to claim 1, wherein the control unit performs second-order differentiation on a function that provides a target position trajectory of position following control for the motor,
The obtained second derivative is multiplied by the equivalent moment of inertia of the motor and the image reading device, and the divided value is divided by a torque constant of the motor to obtain the feedforward amount. The image reading apparatus according to claim 1, wherein 3. The image reading apparatus according to claim 2, wherein the control unit further supplies a feedforward amount for correcting a friction torque to the motor. 4. The control means uses a function of the fourth or higher order in which acceleration becomes zero and a speed becomes constant before the reading position of the document as a function for giving the target position trajectory when the motor starts up. 4. The image reading device according to claim 2, wherein 5. When the function that gives the target position trajectory has the following formula, where the approach distance q1, the target document scan speed Ref_speed, and the time delta1 spent for the approach are: When the Ref_speed is multiplied by N (N is a positive real number), the delta1 is multiplied by N and the q1
The image reading apparatus according to claim 2, wherein N is multiplied by N ² . 6. The target position trajectory according to claim 6, wherein the control unit includes a storage unit in which a function value that gives the normalized target position trajectory and a second derivative of the function that gives the target position trajectory are stored in advance. A function value for giving the predetermined target position trajectory and a second derivative of a function for giving the target position trajectory are selected from the storage means, and the motor is robustly controlled. The image reading device according to claim 2.