JPH04318536A - Optical system control method for image forming device - Google Patents

Abstract

PURPOSE:To carry out control of the optical system with high reliability by preventing runaway or overshooting of the optical system and by reducing the rising time of the optical system. CONSTITUTION:An electric motor 8 is turned OFF when an interruption controller of a speed detection means is in a multiple interruption state. Furthermore, control voltage at an initial driving of the optical system 11 is compared with the present control voltage. When the difference exceeds a specified amount, prescanning of the optical system 11 is newly carried out and calculation of state quantity X0 is carried out again.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an optical system of an image forming apparatus (speed control, abnormality detection control) using a microcomputer.

0002

2. Description of the Related Art FIG. 3 is a speed control block diagram of an optical system of a copying machine.
M) 3 and random access memory (RAM) 4 are connected to each other via a bus. 5 is a command generation circuit that outputs a state command signal that commands the state of the electric motor 8;
Generates speed command signals, etc. The output of this command generation circuit 5 is also connected to the bus. A detection interface circuit 10 processes the output of the incremental encoder 9 and converts it into a digital value, and is provided with a counter that counts the output pulses of the incremental encoder 9. Reference numeral 6 denotes a driving interface circuit, which converts the digital value of the calculation result of the microcomputer 1 into a pulse-like signal (control signal) for operating a power semiconductor, such as a transistor, forming the driving circuit 7. The drive circuit 7 operates based on the pulsed signal and controls the voltage applied to the electric motor 8.

As a result, the electric motor 8 rotates at a desired speed. The rotational speed of the electric motor 8 is detected by an incremental encoder 9 and an interface circuit 10, and is input into the microcomputer 1. Reference numeral 11 denotes an optical system of the copying machine attached to the electric motor 8. Further, the interface circuit 10 determines the rotational direction of the electric motor 8 and determines the home position sensor HPS. Although the above circuit is a description of a discrete type microcomputer, a microcomputer in which the command generation circuit 5, drive interface circuit 6, and interface circuit 10 are integrated into one chip can also perform the same functions. Of course.

Next, a conventional example of detecting the speed using an interrupt will be described. A processing method of the interface circuit 10 by processing the output of the incremental encoder 9 shown in FIG. 3 will be described. The interface circuit 10 connects the output of the incremental encoder 9 to the interrupt of the microprocessor (interrupt controller) 2, and also includes a counter for counting the reference clock (CLK). The description will start from the state immediately before the edge (109) in FIG. 4 arrives. 0B is the output pulse of the incremental encoder 9, and CLK is the reference clock of the detection interface circuit 10. The counter measures the pulse period of Tn-1 by C
Count number given based on the LK signal, e.g. 0FF
Decrement count is executed from FFH. When edge 109 reaches the interrupt of microprocessor 2, execution of the interrupt routine of FIG. 5 begins.

First, the decremented count value of the counter is latched into a storage register built into the interface circuit 10 by P1. Next, the latched decrement count value is stored in the RAM 4 of FIG. 3 by P2. Then, by P3, the count number 0FFFFH for counting the pulse period Tn is given to the counter, and the counter starts decrementing the count from the initial value (0FFFFH) again, and ends the interrupt processing. When the edge (110) is reached again, the above process is repeated. Further, the conversion of the speed ω(k) is as shown in the following equation. TCLK; CLK cycle NE; Incremental encoder division number n; CLK
Count number = 0FFFFH - Decrement count number k; Unit conversion constant K to rotation speed; Constant ω(k) = {k/(TCLK ・NE )}・
(1/n)=K・(1/n)

[0006] Here, when the microprocessor 2 is detecting the speed and another interrupt occurs, this is called multiple interrupts, but when the pulse of the encoder 9 of the motor 8 is input to the microprocessor 2, another interrupt occurs. In this case, noise may enter the signal line input from the encoder 9 to the microprocessor 2. In addition, the pulse interval of the encoder 9 is short,
If the next pulse is input during interrupt processing, the pulse interval may become short even if the motor 8 rotates at the desired speed if the motor 8 rotates at an abnormally high speed or the division accuracy of the incremental encoder 9 is not achieved. .

Conventionally, in the speed control method of the optical system 11, when the power is turned on, the optical system is pre-scanned at least once, and the state quantity X0 corresponding to the target speed is calculated from the data taken in by this pre-scan. 11
A technique has been proposed to prevent overshoot during startup.

[0008]

[Problem to be solved by the invention] Among the above conventional techniques,
If noise enters the signal line, if the noise is recognized as an encoder pulse, erroneous speed detection will occur, which will interfere with control calculations. The same applies when the division accuracy is not achieved. Next, if the motor 8 is rotating at an abnormally high speed, if multiple interrupts are enabled, interrupts will occur one after another during interrupt processing, and there is a risk that the motor 8 will run out of control because it will not be able to exit from the interrupt routine. Ta.

[0009] Furthermore, due to the pre-scan when the power is turned on,
In the conventional technology that suppresses overshoot when the optical system 11 starts up, when the environment (temperature, humidity) changes compared to when the power is turned on, the frictional force of the optical system 11 and the parameters (resistance, torque constant) of the electric motor 8 change. Therefore, if the state quantity X0 obtained from the data obtained from the pre-scan when the power is turned on is used, there is a problem that the overshoot at startup becomes large and it takes a long time to reach the target value.

The present invention was made based on this background, and it is possible to control the optical system with high reliability by preventing runaway and overshoot of the optical system and shortening the start-up time of the optical system. An object of the present invention is to provide a method for controlling an optical system of an image forming apparatus.

[0011]

[Means for Solving the Problems] The above object is to provide a driving means for driving an electric motor, a state commanding means for outputting a state command signal for commanding the operating state of the electric motor, a speed detection means for detecting the speed of the electric motor, It has a microprocessor, a random access memory, and a read-only memory in which processing procedures of the microprocessor are stored, and inputs the state command signal and a signal for detecting the speed of the electric motor to the drive means. In a method for controlling an optical system of an image forming apparatus in which an electric motor for driving an optical system of the image forming apparatus is controlled by a digital control device comprising a microcomputer that calculates a control signal to be applied, an interrupt controller of the speed detecting means is in a multiple interrupt state. This is achieved by the first means, which turns off the electric motor when the In addition, the above purpose uses a software servo system based on an integral type optimal regulator method, performs a pre-scan of the optical system at least once when the power is turned on, and calculates the steady speed, state quantity, and control voltage during forward and backward movements. Store it in the memory, calculate the state quantity X0 according to the target speed during image formation,
In an optical system control method for an image forming apparatus, in which a control calculation is performed using the state quantity X0 as a new initial value when the motor starts up and reaches a desired speed, the target speed is the same and the optical system is moving forward. If the difference between the initial control voltage and the current control voltage exceeds a predetermined value, a new pre-scan is performed,
A second step that stores the steady speed, state quantity, and control voltage during forward and backward movement of the optical system in memory, and recalculates the state quantity X0.
This is accomplished by the following means.

0012

[Operation] In the first means, when multiple interrupts are applied to the interrupt controller, the motor is immediately stopped to prevent runaway of the motor, runaway of the program, and eventually runaway of the optical system. . In addition, in the second means, whether the environment has changed or not is determined by comparing the initial (Vi) and current (Vt) of the control voltage during steady state when the target speed is the same.
) When the control voltage becomes larger than the desired value, prescan is performed again to eliminate overshoot and shorten the rise time even if the environment changes. Note that if the user does not press the copy button after the pre-scan, the optical system may be free-run once to measure the current control voltage Vt.

[0013]

Embodiments Each embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart of an optical system control (abnormality detection control) method according to a first embodiment corresponding to claim 1. The processes of P21, P22, and P23 are the processes of P1 and P23 shown in FIG.
Since this is the same as the processing of P2 and P3, it will be omitted. In the process P24, a bit in the interrupt request control register of the microprocessor 2 containing an interrupt request is checked. If there is no interrupt request, it is normal interrupt operation, so P2
At 5, the interrupt ends. P if there is an interrupt request
At 26, the electric motor 8 is turned off. Next, in P27, interrupts are masked so that no new interrupts occur. and P
At step 28, the interrupt abnormality data is stored in the RAM 4. Finally, the interrupt is terminated at P29.

FIG. 2 is a flowchart of an optical system control (speed control) method according to a second embodiment corresponding to claims 2 and 3. After the power is turned on, a pre-scan mode is implemented in the process of P31, and the steady state quantity X0 according to the target value is calculated. X0 is the integral value of the deviation between the target value and the output of the integral type optimal regulator. In the process of P32, it is determined whether the scan mode is immediately after pre-scan. If the user does not press the copy button after pre-scanning, the optical system 11 may be free run in the same magnification mode once. The reason why the 1x mode is used is that it is considered to be the mode that users use most often, but it is of course not necessary to use the 1x mode, and several types of modes may be used. If it is determined in the process of P32 that it is immediately after the pre-scan, the process of P33 is performed. In the process of P33, the steady state control voltage (during original reading) Vi is changed to R
Save to AM4. If you want to try several different modes,
Of course, the mode Mx and the control voltage Vi must be associated with each other. Further, the control voltage Vi may be determined by reading the control voltage during steady state several times and taking the average value. Alternatively, you may read it several times, discard the maximum and minimum values, and take the average of the several data in between. Next, in the process of P34, the document scan is finished, and the process returns to P32. If it is determined that it is not immediately after the pre-scan, the process moves to P35. In the process of P35, the control voltage Vt during normal operation (during document reading) is stored in the RAM 4. If several types of modes are being tried in the process of P33, it goes without saying that the mode Mx and the control voltage Vt should be associated with each other. Of course, the data on the control voltage Vt may also be averaged in the same way as the data on the control voltage Vi. P
In step 36, the document scan is finished, and the process moves to step P37.

In the process P37, the control voltage Vi immediately after the pre-scanning is compared with the current control voltage Vt. When testing multiple modes, the control voltages Vi and Vt corresponding to the modes are compared. Vx indicates a voltage difference that does not affect the rise time of the optical system 11,
If the voltage is higher than Vx, there will be an effect. If No in the process of P37, the process returns to P32 and executes the processes in the order of P35, P36, and P37. If Yes in the process of P37, that is, if the control voltage has changed by more than Vx compared to the initial state,
This is a case where the parameters and sliding friction of the electric motor 8 are changed. In that case, return to P31 and re-execute the pre-scan. Then, the state quantity X0 is recalculated at P31, and then the processes at P32, P33, and P34 are performed, and the new control voltage Vi is stored.

The control voltages Vi and Vt are calculated by the microcomputer 1, and there is no need for sensors or A/D converters for measuring the control voltages Vi and Vt, so the cost does not increase. Stable scanning becomes possible. The control voltage Vt in the steady state is detected when the user presses the copy button, but it may of course be detected by free running once at a predetermined interval.

[0017]

According to the invention as set forth in claim 1, since multiple interrupts to the interrupt controller are checked, malfunctions due to noise can be prevented, and runaway of the motor can be prevented when the encoder division accuracy is not achieved. Can be done. Furthermore, it is possible to prevent a phenomenon in which it becomes impossible to escape from the interrupt routine when the pulse interval of the encoder becomes short. According to the invention described in claims 2 and 3, the frictional force of the sliding surface of the optical system and the parameter fluctuation of the electric motor are monitored by comparing the initial control voltage and the current control voltage,
When the control voltage changes by more than a predetermined value, a new pre-scan of the optical system is performed and the state quantity X0 is recalculated, so that overshoot of the optical system and delay in the rise time can be prevented.

[Brief explanation of drawings]

FIG. 1 is a flowchart of an optical system control method according to a first embodiment of the present invention.

FIG. 2 is a flowchart of an optical system control method according to a second embodiment of the present invention.

FIG. 3 is a speed control block diagram of the optical system of the copying machine.

FIG. 4 is a timing chart of encoder output pulses and reference clock.

FIG. 5 is a flowchart of the interrupt routine.

[Explanation of symbols]

1 Microcomputer 7 Drive circuit (drive means) 8 Electric motor 9 Speed encoder (speed detection means) 11 Optical system Vi Initial control voltage Vt Current control voltage

Claims (3)

[Claims] 1. A drive means for driving an electric motor, a state command means for outputting a state command signal for commanding the operating state of the electric motor, a speed detection means for detecting the speed of the electric motor, a microprocessor, a random access memory, and a microcomputer having a read-only memory in which processing procedures of the microprocessor are stored, and inputting the state command signal and a signal for detecting the speed of the electric motor to calculate a control signal to be applied to the drive means. In the method for controlling an optical system of an image forming apparatus, the electric motor for driving the optical system of the image forming apparatus is controlled by a digital control apparatus comprising: when the interrupt controller of the speed detection means enters a multiple interrupt state, A method for controlling an optical system of an image forming apparatus, characterized in that the optical system is turned off. [Claim 2] A software servo system based on an integral type optimal regulator method is used, and when the power is turned on, at least one
At the same time, pre-scan the optical system, store the steady speed, state quantity, and control voltage during forward and backward movements in memory, calculate the state quantity X0 according to the target speed during image formation, and start the motor. When the desired speed is reached, the state quantity X
In an optical system control method for an image forming apparatus in which control calculations are performed using 0 as a new initial value, the target speed is the same and the difference between the initial control voltage and the current control voltage when the optical system moves forward is a predetermined value. If the value is exceeded, a new pre-scan is performed, the steady speed, state quantity, and control voltage during forward and backward movement of the optical system are stored in memory, and the state quantity X0 is recalculated. A method for controlling the optical system of the device. 3. The optical system of an image forming apparatus according to claim 2, wherein when the user does not press a copy button, the optical system performs a free run once in a predetermined period and measures the current control voltage. System control method.