JP2706150B2 - Control system of polygon mirror drive motor and its device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method of a polygon mirror driving motor of an image forming apparatus for forming a latent image on a photoreceptor such as a copying machine and visualizing the latent image by a developing unit, and the apparatus. Things.

[Prior Art] Conventionally, speed control in this type of device is performed by using a well-known phase locked loop (PLL).
P). In this case, the internal constant (gain) of the PLL control is switched between the control during the transition period such as when the motor is started and the target speed is switched and the control during the steady state after the target rotation speed is reached. By doing so, the supply current to the motor during the transition period is limited to suppress overshoot, and a smooth transition to the steady state is realized.

[Problems to be Solved by the Invention] However, since the supply current to the motor is limited during the transition period, the time required to reach the target rotation speed at the time of starting the motor or switching the target speed increases. In addition, there is a problem that the time required for the first copy time and the time required for copying requiring switching of the speed are increased.

The present invention has been made in view of the above points, and an object of the present invention is to improve control of a transition period. Specifically, during a transitional period in which the relationship between the state quantity and the control quantity is ambiguous, the control quantity is calculated and controlled by performing a fuzzy inference on the ambiguous relation, and a polygon mirror drive motor control method and apparatus therefor. Is to provide.

Further, in the control of the transition period, the load fluctuation due to the aging of the apparatus and the torque fluctuation due to the motor temperature rise have a great influence. When the function indicating the ambiguous relation used in the fuzzy inference is constant with respect to this fluctuation, there is a problem that the control state changes.

It is a further object of the present invention to provide a polygon mirror drive motor control method and apparatus for improving the control of the transition time using fuzzy inference with respect to the aforementioned fluctuation.

[Means for Solving the Problems] In order to solve this problem, a polygon mirror driving motor control method according to the present invention employs a polygon mirror in an image forming apparatus which forms a latent image on a photoreceptor and visualizes the latent image with a developing unit. A drive motor control method, wherein when the polygon motor is in a transitional period, at least one of a polygon motor speed detected by an encoder of the polygon motor, a plurality of target speeds of the polygon motor, and a moving angle amount of the polygon motor. One ambiguous relation is selected from the plurality of ambiguous relations between the state quantity and the speed control quantity corresponding to the required time of the transition period, and the speed control quantity is calculated by fuzzy inference. The polygon motor is controlled based on.

Here, the transition period is a period from when the polygon motor reaches a predetermined target speed after the start of driving of the polygon motor, until the polygon motor reaches the target speed after changing the target speed of the polygon motor.

In a steady state other than the transition period, the polygon motor speed is controlled by the PLL using the polygon motor speed detected by the polygon motor encoder and the target speed of the polygon motor.

The control device for a polygon mirror drive motor according to the present invention is a control device for a polygon mirror drive motor in an image forming apparatus for forming a latent image on a photoreceptor and visualizing the latent image by a developing means, and detects the detection by an encoder of the polygon motor. Using the polygon motor speed and the target speed of the polygon motor,
First polygon motor speed control means for controlling a polygon motor speed by a PLL; at least one of a polygon motor speed detected by an encoder of the polygon motor, a plurality of target speeds of the polygon motor, and a moving angle amount of the polygon motor; State quantity detection means for detecting a state quantity, function storage means for storing a plurality of functions representing the state quantity and the speed control amount by at least one vague set, and a plurality of functions stored in the function storage means A selecting means for selecting one function based on the required time, a rule storing means for storing a relationship between the state quantity and the speed control quantity as a qualitative rule, and A degree belonging to the set of speed control quantities is calculated from a degree belonging to the set of state quantities, and the most likely speed control quantity is inferred from the calculated degrees. An inference means, a second polygon motor speed control means for controlling a polygon motor speed based on the speed control amount inferred by the inference means, and at a predetermined timing, the first polygon motor speed control means Control switching means for switching between control and control by the second polygon motor speed control means.

Here, the selecting means selects the plurality of functions according to a time deviation from the start of driving the polygon motor to the time when the polygon motor reaches the target speed, and the switching means, when the polygon motor reaches the target speed. The control is switched from the control by the second polygon motor speed control means to the control by the first polygon motor speed control means.

The switching means switches from the control by the first polygon motor speed control means to the control by the second polygon motor speed control means when changing the target speed of the polygon motor.

Further, the selection means selects the plurality of functions in accordance with a time deviation from when the target speed of the polygon motor is changed to when the target speed is reached, and after the change means changes the target speed of the polygon motor, When the polygon motor reaches the target speed, the control by the second polygon motor speed control means is switched to the control by the first polygon motor speed control means.

Example An example of the present invention will be described below in detail with reference to the drawings.

<Example of Configuration> FIG. 2 is a simplified cross-sectional view of the copying apparatus of the present embodiment. Reference numeral 110 denotes a platen glass on which a document to be copied is placed; 112, an optical system having an illumination lamp for illuminating the document; 108, a home sensor for detecting that the optical system is at a reference position;
Is an image sensor for detecting that the optical system advances and is the leading edge of the document. Further, a detection signal from the image sensor is generated even when the optical system moves backward. 111 is a photosensitive drum. 120
Is a hexahedral polygon mirror for operating a well-known laser beam on the photosensitive drum, and 106 is a motor for driving the polygon mirror 120.

FIG. 1 is a basic block diagram of the polygon motor control unit of the copying apparatus according to the present embodiment. 106 is a motor for driving the polygon mirror 120. 105 is a driver for the motor 106. 107 is an encoder connected to the motor 106,
A signal synchronized with the rotation of 106 is output. Reference numeral 100 denotes a well-known PLL control unit.When the motor 106 is rotated at a desired speed, a reference frequency FS corresponding to the desired speed is input so that the phase angle with the encoder signal FG from the motor 106 is changed. A pulse width modulation signal P1 serving as a speed control signal for the motor 106 is output so as to have a constant angle.

101 is a motor speed control based on fuzzy inference described later, an output of a reference frequency FS required for performing the motor speed control by the PLL, a drive stop control by ON / OFF of the drive stop control signal, and a PLL control of the motor speed control. CP for calculation and control that performs switching control between manual and fuzzy control
A U, and has counter d _C, counter t _C, the timer T _S, and a timer T _E. A ROM 103 stores a program to be controlled by the CPU 101 and a fuzzy rule 103a and a membership function 103b, which will be described later. Where membership function 1
03b has a plurality of membership functions such as a membership function 1, a membership function 2, and so on. Reference numeral 102 denotes a RAM used as a work area when performing control and fuzzy inference, and a previous required time 102a for storing a required time of the previous fuzzy control.
have. 104 is a speed control signal P1 output by PLL and a speed control signal P2 output by fuzzy inference (where P
1 and P2 are pulse width modulation signals), and can be switched by the signal SW of the CPU 101 described above.

In this embodiment, at the same magnification and at the time of magnification copying, the rotation speed of the photoconductor drive motor (not shown) is 180 rpm, the rotation speed of the polygon mirror drive motor is 8600 rpm, and the reference frequency FS is 1
The rotation speed of the photoconductor drive motor (not shown) at the time of reduction is 130 rpm, the rotation speed of the polygon mirror drive motor is 6200 rpm, and the reference frequency is 722 Hz.

<Operation Example> Next, an operation example of speed control by fuzzy inference of the polygon motor of the present embodiment will be described. This operation example will be described with reference to FIGS.

The CPU 101 calculates the rotation speed of the polygon mirror 120 by counting the number of pulses output from the encoder 107 of the polygon motor for a certain period of time, and further calculates the difference between the calculated speed and the target speed as a speed deviation. I do. By comparing the number of pulses required for movement between the current position and the target position with the number of pulses input from the encoder after the current position, a distance deviation that is the number of movement pulses of the polygon motor 106 to the target position is calculated. I do.

 In order to make this fuzzy inference, the speed deviation of the target speed from the current speed and the distance deviation of the target position from the current position are used as two state quantities.

The polygon motor speed control amount is used as the control amount for controlling the speed of the polygon motor.

3A to 3C show a fuzzy set called a membership function of the above-mentioned state quantities and control quantities.

The speed deviation, the distance deviation and the polygon motor control amount are largely divided into several sets. For example, in the case of a speed deviation, 1) S _S ... The speed deviation is small.

Moderate 2) M _S ... speed deviation.

3) L _S : Speed deviation is large.

In the case of a distance deviation, 1) S _d ... The distance deviation is small.

2) M _d ... Distance deviation is medium.

3) a large L _d ... distance deviation.

And The degree belonging to each set is represented by a value from 0 to 1. Fig. 3A shows the membership function of the speed deviation, Fig. 3B
The figure shows the membership function of the distance deviation, and FIG. 3C shows the membership function of the polygon motor control amount. In this embodiment,
In addition to FIGS. 3A to 3C, a member function of the polygon motor control amount obtained by rewriting FIG. 3C as shown in FIG. 9 is prepared, and the function is selected according to the required time.

Next, a method of calculating the control amount of the polygon optical motor from the state amounts of the speed deviation and the distance deviation will be described. For determining the polygon motor control amount, for example, the following fuzzy rule is used.

(Rule 1) If, if the speed deviation = L _S and distance deviation = M _d, the polygon motor control amount = M _C (Rule 2) If, if the speed deviation = M _S and distance deviation = M _d, polygon motor control Amount = S _C Thus, the fuzzy rules are set as required. No.
4A and 4B show the fuzzy rule used in this embodiment.

FIG. 5 is an example of calculating the control amount of the polygon motor by performing fuzzy inference using the above (rule 1) and (rule 2). As an example, let us consider a case where speed deviation = x and distance deviation y.

In (Rule 1), in the set of L _S the degree of mu _X with respect to the input x by Menbashitsupu function of the speed deviation, the set of M _d at the degree of mu _y for the input y by Menbashitsupu function of distance deviation include. After that, the minimum value of μ _x and μ _y is obtained, and the value is defined as the degree to which the condition part of (rule 1) is satisfied. The value and the MIN (minimum value) between Menbashitsupu function M _C of the controlled variable of the polygon motor Taking operation becomes trapezoid indicated by the shaded area in S. The same calculation is performed in (rule 2), and the shape shown by the shaded portion of T comes out.

Thereafter, the sum of the set of S and the set of T is calculated, and a new set of U indicated by the hatched portion is created. The center of gravity P of this set is set as the control amount of the polygon motor obtained by the fuzzy inference. In the case of the speed deviation = L _S and distance deviation = S _d, in the case of the speed deviation = M _S and distance deviation = S _d is not shown.

As described above, for all the fuzzy rules shown in FIG. 4, the degree of belonging to the fuzzy set of the control quantity is calculated from the degree to which the state quantity belongs to the fuzzy set in accordance with each of the fuzzy rules by the method described above, and the degree of belonging to each rule is calculated. The sum of the sets is calculated, the most likely control amount is calculated by obtaining the center of gravity, and the center of gravity is set as the control amount of the polygon motor. Then, the polygon motor is controlled according to the set polygon motor control amount. This control amount is the duty of the PWM output of the polygon motor.

<At the time of starting the polygon motor> Next, the procedure of the fuzzy inference at the time of starting the polygon mirror driving motor will be described with reference to the flowcharts of FIGS.

The routine of FIG. 6 is executed each time the polygon motor moves a predetermined number (d) due to an encoder interrupt. This encoder interrupt routine is used until the polygon motor reaches the target speed. On the other hand, the routine is provided separately from Figure 7 Time measurement interrupt routine in step S20 in the, counts up-counter t _C in a predetermined time interval. The counter t _C is a step in the routine of FIG.
Cleared to zero in S13. Accordance connexion, the rotational speed of the polygon motor at that time from the value of the counter d _C and t _C is obtained.

First to count up-counter d _C at step S11. Step obtains a rotational speed-S12 the value of the counter t _C, calculates the speed deviation. Counter t _C is, step S12
After the processing of (1) is completed, it is cleared to zero in step S13. Calculating the distance deviation from the value of the counter d _C at step S14.

Next, in step S21, the deviation between the previous required time for starting and the target value is positively determined based on the required time for starting the previous polygon motor driving (the time from the start of the motor to the end of the control based on the fuzzy inference). Is prepared in advance so as to correct, for example, the time required for the previous start is 400 mse
If it is less than c, control is performed by using the control amount membership function shown in FIG. 3C, and if it is 400 msec or more, control is performed by using the control amount membership function shown in FIG.

Next, in steps S15 and S16, the degree of belonging to the fuzzy set of the state for each of the moving distance and the moving speed is determined, and the degree of belonging to the fuzzy set of the control amount is determined from the value based on the fuzzy rule of FIG. 4A. . When this operation is completed for all rules to be considered, the process proceeds from step S15 to S17, where the sum of sets belonging to each rule is calculated,
In step S18, the most likely control amount is calculated by obtaining the center of gravity, and in step S19, the center of gravity is set as PWM data for controlling the polygon mirror driving motor.

When the rotation speed of the polygon motor reaches the set value, the speed control of the polygon mirror drive motor is switched to PLL. At the same time, the time required from the start of the polygon motor to that time is stored. This value is referred to at the next correction of the fuzzy rule.

<At the time of shifting the polygon motor> Next, with reference to the flowcharts of FIGS. 6 and 7, the procedure of the fuzzy inference at the time of shifting the rotation speed of the polygon mirror driving motor will be described.

The routine of FIG. 6 is executed each time the polygon motor moves a predetermined number (d) due to an encoder interrupt. This encoder interrupt routine is used from the time the gear shift command of the polygon motor is received until the rotational speed reaches a certain set value (second speed). On the other hand, the present routine is provided separately from the seventh view of a time measurement interrupt routine, the counter t _C
Is performed at regular intervals. Hereinafter, the processing of each step is the same as that at the time of starting except that the fuzzy rule shown in FIG. 4A is used for acceleration and FIG. 4B is used for deceleration. Note that, when shifting, based on the shift required time (from the start of motor shift until the rotation speed of the polygon motor reaches the target speed) at the time of the previous polygon motor shift, for example, when the previous shift required time is less than 399 msec. Uses the control amount membership function shown in FIG. 3C, and when the time is longer than 300 msec, control is performed by using the control amount membership function shown in FIG.

When the rotation speed of the polygon motor reaches the set value, the speed control of the polygon mirror drive motor is switched to PLL. At the same time, the time required from the start of the polygon motor shift to that time is stored. This value is referred to at the next correction of the fuzzy rule.

<Switching Between Fuzzy Control and PLL Control> Next, referring to the flowchart of FIG. 8, the speed of the polygon mirror driving motor by the fuzzy speed control and the PLL speed control at the time of starting the polygon mirror driving motor and at the time of shifting. Control switching will be described.

First, in steps S30 and S40, it is determined whether to start or shift. In the case of startup, the process proceeds from step S30 to step S31, where the target frequency corresponding to the target speed of the polygon motor is set.
Output FS (1KHz) to PLL. In step S32, switches the speed control of the polygon motor to fuzzy velocity control, reset to zero the timer T _E at step S32a. In step S33, the polygon motor is rotated. Step S
At 34, it is determined whether or not the polygon motor has reached the target speed. If the speed has not reached, the process waits for reaching the target speed while performing fuzzy control at step S34 every predetermined rotation.
In step S35 the speed control of the polygon motor with switched to PLL velocity control, and stores the value of the timer T _E as the last required time at step S35a.

In the case of shifting, the process proceeds from step S40 to step S41, where the target frequency FS corresponding to the target speed of the polygon motor is set.
(722Hz) is output to the PLL. In step S42, switches the speed control of the polygon motor to fuzzy velocity control, reset to zero the timer T _E at step S42a. In step S43, the rotation of the polygon motor is reduced. In step S44, it is determined whether or not the polygon motor has reached the target speed. If not, the process waits for the target speed to be reached while performing fuzzy control in step S44 every predetermined rotation. In step S45, the speed control of the polygon motor is
Switch to LL speed control and set a timer in step S45a.
Stores the value of T _E as the previous duration.

If it is not during driving or shifting, P is set in step S50.
Continue control by LL.

[Effects of the Invention] As described above, according to the present invention, at the time of excessive control such as starting of the polygon mirror driving motor, switching of the rotation speed, etc., switching to speed control by fuzzy inference is performed. Can be shortened, and the time required for copying that requires switching of the first copy time and speed can be shortened.

Furthermore, since the time is reduced and a smooth transition to the steady state is realized, there is an effect that the image quality can be stabilized.

In addition, the time required is measured at the time of transition control such as when the polygon motor is started and when shifting, and a plurality of membership functions indicating an ambiguous relationship used in the fuzzy inference are switched according to the data, thereby changing over time. Thus, stable control can be performed even with respect to load fluctuations due to motor and torque fluctuations due to motor temperature rise.

[Brief description of the drawings]

FIG. 1 is a basic block diagram of a polygon motor control unit of the copying apparatus of this embodiment, FIG. 2 is a simplified cross-sectional view of the copying apparatus of this embodiment, and FIG. 3A shows an example of a membership function of a speed deviation. FIG. 3B is a diagram showing an example of a membership function of a distance deviation. FIG. 3C is a diagram showing an example of a membership function of a polygon motor control amount. FIGS. 4A and 4B are diagrams showing a fuzzy rule of the present embodiment. FIG. 5 is a diagram showing an example of fuzzy inference of this embodiment. FIG. 6 is a flowchart showing the procedure of an encoder interrupt routine. FIG. 7 is a flowchart showing the procedure of a timer interrupt routine. FIG. 9 is a flowchart showing a procedure for switching between speed control and PLL speed control. FIG. 9 is a diagram showing an example of a membership function in which FIG. 3C is rewritten in accordance with the required time in this embodiment. In the figure, 100: PLL control unit, 101: CPU, 102: RAM, 10
3 ROM, 103a Fuzzy rule, 103b Membership function, 104 Switching switch, 105 Driver, 106
…… Motor, 107 …… Encoder, 108 …… Home sensor, 109 …… Image sensor, 110 …… Origin platen glass, 111…
.., Photosensitive drum, 112, optical system, 120, polygon mirror.

Claims (7)

(57) [Claims] 1. A polygon mirror drive motor control method in an image forming apparatus for forming a latent image on a photoreceptor and visualizing the latent image by a developing means, wherein when the polygon motor is in a transitional period, an encoder of the polygon motor is used. A plurality of ambiguous relationships between at least one state quantity and a speed control amount among the detected polygon motor speed, a plurality of target speeds of the polygon motor, and a moving angle amount of the polygon motor correspond to the required time of the transition period. A speed control amount is calculated by fuzzy inference, and the polygon motor is controlled based on the speed control amount. 2. The method according to claim 1, wherein the transition period is a period from when the polygon motor reaches a predetermined target speed until the polygon motor reaches a predetermined target speed after the start of driving of the polygon motor, and before the polygon motor reaches the target speed. 2. A control method for a polygon mirror driving motor according to claim 1, wherein 3. The polygon motor speed is controlled by a PLL using a polygon motor speed detected by an encoder of the polygon motor and a target speed of the polygon motor during a steady state other than the transition period. The control method of the polygon mirror drive motor according to claim 1. 4. A control device for a polygon mirror driving motor in an image forming apparatus for forming a latent image on a photosensitive member and visualizing the latent image by a developing means, comprising: a polygon motor speed detected by a polygon motor encoder; Using the target speed and PL
First polygon motor speed control means for controlling the polygon motor speed by L; at least one of a polygon motor speed detected by an encoder of the polygon motor, a plurality of target speeds of the polygon motor, and a moving angle amount of the polygon motor; State quantity detection means for detecting a state quantity; function storage means for storing a plurality of functions representing the state quantity and the speed control amount by at least one vague set; and a plurality of functions stored in the function storage means A selecting means for selecting one function based on a required time; a rule storing means for storing a relation between the state quantity and the speed control quantity as a qualitative rule; A degree belonging to the set of speed control quantities is calculated from a degree belonging to the set of state quantities, and the most likely speed control quantity is inferred from the calculated degrees. Second polygon motor speed control means for controlling a polygon motor speed based on the speed control amount inferred by the inference means; and at a predetermined timing, the first polygon motor speed control means And a control switching unit for switching between control by the second polygon motor speed control unit and control by the second polygon motor speed control unit. 5. The method according to claim 1, wherein the selecting means selects the plurality of functions in accordance with a time deviation from the start of driving the polygon motor to the time when the polygon motor reaches the target speed. 5. The polygon mirror drive motor control device according to claim 4, wherein the control is switched from the control by the second polygon motor speed control means to the control by the first polygon motor speed control means. 6. The switching means switches the control by the first polygon motor speed control means to the control by the second polygon motor speed control means when changing the target speed of the polygon motor. 5. A control device for a polygon mirror driving motor according to claim 4. 7. The method according to claim 1, wherein the selecting means selects the plurality of functions in accordance with a time deviation from when the target speed of the polygon motor is changed to when the target speed is reached. 7. The method according to claim 6, wherein when the changed polygon motor reaches a target speed, the control by the second polygon motor speed control means is switched to the control by the first polygon motor speed control means. Control device for polygon mirror drive motor.