JP4732085B2 - Servo control device, image forming apparatus, and program - Google Patents

Description

The present invention is related to servo control apparatus and an image forming apparatus, and program.

  As various image forming apparatuses such as printers, facsimiles, copying machines, plotters, printer / fax / copier multifunction machines, etc., recording heads (printing heads) constituted by droplet discharging heads that discharge recording liquid (for example, ink) droplets are used. ) Is mounted on a carriage, and the carriage is referred to as a recording medium (hereinafter referred to as “paper”, but the material is not limited to paper, and is also referred to as recording medium, recording paper, recording paper, transfer material, etc.) )) Is serially scanned in a direction orthogonal to the conveyance direction, and the recording medium is intermittently conveyed according to the recording width, and an image is formed (recorded) by alternately repeating conveyance and recording. , Printing, printing, and printing are also used synonymously.) There is a serial type image forming apparatus.

  As described above, in the serial type image forming apparatus, in order to form a high-quality image by ejecting recording liquid droplets from a recording head mounted on a carriage to a predetermined position on a sheet, carriage movement scanning control is performed. In general, a DC servo motor is used as the drive motor for moving and scanning the carriage, the moving speed and moving position of the carriage are detected by a linear encoder, and the detected speed (speed detection value) and target speed (speed target) are detected. The control value is calculated based on the difference from the value), and the DC servo motor is driven and controlled by PWM control based on the control value.

As a conventional servo motor control apparatus or method, for example, Patent Document 1 discloses a drive unit that controls a motor to stop a controlled body (driven body) that is driven in a predetermined state, and controls digital calculation results. In a motor control system including an arithmetic control unit that controls the drive unit based on a target value, the arithmetic control unit is configured to determine the current speed and angular velocity of the controlled object obtained at each sampling time and the target of the controlled object. A control target value obtained by adding a target speed value or an offset value obtained based on the current speed and angular speed to a control value calculated based on the difference from the speed value is calculated, and the drive unit is controlled by the control target value. It is described that the controlled object is controlled to stop.
JP 2004-357374 A

Further, in Patent Document 2, in order to suppress the occurrence of vibration due to fluctuations in the moving speed of the carriage drive motor and to realize stable drive motor control, the control unit includes control values obtained by servo control (PI control). It is described that the offset value determined for each of the acceleration interval, constant velocity interval, and deceleration interval of the carriage moving speed is summed, and the drive motor that drives the carriage is controlled using the total value as a control value. Has been.
JP 2004-351778 A

Further, Patent Document 3 discloses that feedforward provided in a servo control system of a hard disk drive that provides a feedforward value for reducing current control noise during servo control is based on a speed command value by a speed command device of the servo control system. And a means for obtaining a speed difference before that, and a calculation based on the speed difference thereby, and generating an adaptive feedforward value that changes according to a current command value instructing a speed reduction in a servo control deceleration section A feedforward calculating means for obtaining a speed difference, a delay means for delaying the speed command value to the next command, a previous speed command value that has passed through the delay means, and a current speed command value by the speed command device; It is described that it comprises an adding means for adding.
Japanese Patent Laid-Open No. 10-055637

  As described in the above-mentioned patent document, when the driven body is driven by servo control, feed control is added to lower the control gain in order to suppress reaction to disturbance. Yes.

  However, in the motor stop control method described in Patent Document 1 described above, the deceleration feedforward value obtained based on the current speed or the target speed is added to the drive output value (control value) as the control target value. Yes.

  However, when the control target value is calculated in this way, the driving load increases due to mechanical variations, environment, changes with time, etc., and the driving output value at constant speed is obtained from the value indicated by line A in FIG. 10B, for example. Even when the value is changed to the value indicated by the line B, the deceleration feedforward value FF remains the value indicated by the line C in FIG. FIG. 10A is a diagram for explaining the change in the target speed Vtar with respect to the control step n.

The present invention has been made in view of the above problems, and an object thereof is to be able to cope with load fluctuations.

In order to solve the above-described problem, a servo control device according to the present invention provides:
A drive output value for driving the drive motor is calculated based on a speed detection value and a speed target value of the drive motor that moves the driven body, and the drive motor is driven according to the calculated drive output value. In the servo control device,
When driving the driven body at a reduced speed,
During the period from the control step for starting the deceleration to the predetermined number of control steps, the calculated drive output value is divided into values corresponding to the difference from the previous control step of the speed target value for each step of servo control. Add a predetermined value as a deceleration feed forward,
In the control step after the predetermined number of control steps, a value corresponding to the difference from the previous control step of the speed target value is added to the calculated drive output value as a deceleration feed forward for each servo control step. The configuration.

An image forming apparatus according to the present invention includes a servo control device according to the present invention that drives and controls a drive motor for moving and scanning a carriage on which a recording head is mounted.
The program according to the present invention is:
A drive output value for driving the drive motor is calculated based on a speed detection value and a speed target value of the drive motor that moves the driven body, and the drive motor is driven according to the calculated drive output value. A program for causing a computer to execute servo control processing,
When driving the driven body at a reduced speed,
During the period from the control step for starting the deceleration to the predetermined number of control steps, the calculated drive output value is divided into values corresponding to the difference from the previous control step of the speed target value for each step of servo control. Add a predetermined value as a deceleration feed forward,
In the control step after the predetermined number of control steps, a value corresponding to the difference from the previous control step of the speed target value is added to the calculated drive output value as a deceleration feed forward for each servo control step. The computer is configured to execute processing.

According to the servo control device according to the present invention and the program according to the present invention, when the driven body is driven to decelerate , the calculated drive output value is calculated from the control step for starting the deceleration to the control step for a predetermined number of times. For each step of servo control, the value corresponding to the difference from the previous control step of the speed target value and the divided predetermined value are added as deceleration feed forward, and the calculation is performed in the control steps after the predetermined number of control steps . Since the value corresponding to the difference from the previous control step of the speed target value for each step of servo control is added to the drive output value as deceleration feed forward , even when there is load fluctuation, there is load fluctuation However, it is possible to perform deceleration control with appropriate feedforward, and to perform stable deceleration control that is resistant to load fluctuations. Kill.

According to the image forming apparatus according to the present invention is provided with the servo control apparatus according to the present invention, it is possible to perform scanning movement stable carriage even if there is a load change, thereby improving the image quality be able to.

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, it will be described with reference to the functional block diagram of FIG. 1 for the servo control device according to the present invention. In the following description, it is assumed that the drive motor moves the carriage in the main scanning direction using the carriage of the image forming apparatus as a driven body.

The servo control apparatus includes a driving motor (DC motor) 2 for moving the driven body 1, an encoder 3 for outputting a detection pulse corresponding to the moving speed distance and the moving speed of the driven body 1, the encoder 3 A speed / position measuring unit 4 that processes a detection signal to calculate a detected speed value and a detected movement value, a speed profile storing unit 5 that stores a speed profile that gives a target speed (speed target value), and a speed / position measuring unit 4 for calculating the deviation between the speed detection value from 4 and the speed target value from the speed profile storage unit 5, and PI for controlling the drive of the drive motor 2 based on the deviation calculated by the comparison calculation unit 6. A drive output value calculation unit 7 for calculating a (proportional integral) value (drive output value), and the calculated drive output value output from the drive output value calculation unit 7 include a speed target value for each step of servo control. Last time From a feedforward (FF) addition unit 9 that adds a value corresponding to the difference from the control step as a deceleration feedforward value and outputs a value obtained by adding the feedforward value as a drive output value; And a driver 10 that drives the drive motor 2 in accordance with the output drive output value.

  Here, the calculation method of the drive output value (motor output value) by the comparison calculation unit 6, the drive output value calculation unit 7, and the feedforward addition unit 9 is a control step from the start of servo control based on a general PI control equation. The feedforward value, where n is the number, the motor output (drive output value) is M (n), the carriage speed (speed of the driven body 1) is V (n), and the target speed (speed target value) is Vtar (n). When FF (n) is assumed, the following equation (1) is used.

At this time,
ΔM (n) = M (n) −M (n−1)
ΔFF (n) = FF (n) −FF (n−1)
Then, the expression (1) can be expressed as the expression (2).

  Here, assuming that k is a proportional constant, ΔFF (n) is obtained by the following equation (3) after the start of deceleration of the carriage. Accordingly, as shown in FIG. 2, when the drive output value at the constant speed is changed from the value indicated by the line D to the value indicated by the line E, FF (n) is also the value indicated by the line G from the value indicated by the line F. Therefore, it is possible to use effective deceleration feedforward even when the load fluctuates.

  In other words, when driving at a reduced speed, a value corresponding to the difference from the previous control step of the speed target value is added to the drive output value for each step of the servo control as a deceleration feedforward value, Deceleration control can be performed by appropriate feedforward, and stable deceleration control strong against load fluctuation can be performed.

  Although equation (3) has a linear function relationship, it may be a higher order function.

Here, a certain motor output M When V is the speed when sufficient time has elapsed after adding the fix, M Assuming that the relationship between fix and V is M_fix = f (V), it is preferable that the relationship of equation (3) is made based on the relationship of f (V). That is, when f (V) can be expressed by a substantially linear function, if the slope is k ′, the slope k in equation (3) is set to about 1.0 to 1.5 times k ′. It shows that.

Next, a description of another embodiment of servo control system according to the present invention.
As described above, after starting the deceleration of the main scanning carriage, if ΔFF (n) is obtained by the equation (3), it takes time until the carriage actually starts deceleration when the inertia of the carriage is large. The actual speed is indicated by a line K with respect to the target speed indicated by the line J in FIG.

  Therefore, in the control step for starting the deceleration of the carriage, a predetermined constant is D, and ΔFF (n) is calculated by the following equation (4), and is obtained by the following equation (3) in the subsequent control steps.

  At this time, when the motor output at constant speed is indicated by a line H in FIG. 3, FF (n) is indicated by a line L, and the time until the carriage actually starts deceleration is shortened, as shown in FIG. Thus, the actual speed when the line M is set as the target speed is as indicated by the line N, and the followability is improved.

  In this way, in the control step for starting deceleration, the followability can be improved by adding a predetermined value to the deceleration feedforward.

Next, still another embodiment will be explained the servo control device according to the present invention.
As described above, in the control step in which the carriage starts to decelerate, ΔFF (n) is calculated by equation (4), and in the subsequent control steps, it is calculated by (3). Depending on the value of the constant D, It is considered that the motor output value is suddenly changed and vibration is generated.

  In such a case, if the control step at which the carriage starts decelerating is m, the number of times the constant D is divided is 1, and the constant D is expressed by the following equation (5), when Dm ≦ n <m + 1, In the equation (6), when m + l ≦ n, the following equation (7) is used.

  In this way, by dividing the predetermined value and adding it to the deceleration feedforward from the control step for starting the deceleration to the predetermined number of control steps, the motor output value can be obtained as shown by the line O in FIG. In contrast to the abrupt change, the motor output value can be moderately changed as indicated by the line P, and the vibration generated in the carriage can be reduced.

Next, an example of an image forming apparatus according to the present invention comprises a servo control apparatus according to the present invention with reference to FIGS. FIG. 7 is an explanatory side view for explaining the overall configuration of the image forming apparatus, and FIG. 8 is an explanatory plan view of a main part of the apparatus.

  In this image forming apparatus, a carriage 103 is slidably held in a main scanning direction by a guide rod 101 and a guide rail 102 that are horizontally mounted on left and right side plates (not shown), and a driving pulley 106A is driven by a main scanning motor 104. 8 and the driven pulley 106 </ b> B through the timing belt 105 to move and scan in the direction indicated by the arrow (main scanning direction) in FIG. 8.

  For example, four independent ink jet recording liquid droplets (ink droplets) of black (K), cyan (C), magenta (M), and yellow (Y) are recorded on the carriage 103. The recording head 107 composed of the liquid ejection heads 107k, 107c, 107m, and 107y is arranged in a direction along the main scanning direction, and is mounted with the droplet ejection direction facing downward. In addition, although the independent liquid discharge head is used here, it is also possible to employ a configuration in which one or a plurality of heads having a plurality of nozzle rows for discharging recording liquid droplets of each color are used. Further, the number of colors and the arrangement order are not limited to this.

  The carriage 103 is equipped with a sub tank 108 for each color for supplying each color ink to the recording head 107. Ink is supplied to the sub tank 108 from a main tank (ink cartridge) (not shown) via an ink supply tube 109.

  On the other hand, as a sheet feeding unit for feeding a recording medium (sheet) 112 loaded on a sheet stacking unit (pressure plate) 111 such as a sheet feeding cassette 110, the sheets 112 are separated and fed from the sheet stacking unit 111 one by one. Opposite to the half-moon roller (feed roller) 113 and the feed roller 113 to be fed, a separation pad 114 made of a material having a large friction coefficient is provided, and this separation pad 114 is urged toward the feed roller 113 side.

  As a transport unit for transporting the paper 112 fed from the paper feed unit below the recording head 107, a transport belt 121 for electrostatically attracting and transporting the paper 112, and a paper feed unit A counter roller 122 for transporting the paper 112 fed through the guide 115 while sandwiching it between the transport belt 121 and the paper 112 fed substantially vertically upward is changed by about 90 ° and copied on the transport belt 121. A conveying guide 123 for adjusting the pressure and a tip pressure roller 125 urged toward the conveying belt 121 by a pressing member 124. In addition, a charging roller 126 that is a charging unit for charging the surface of the conveyance belt 121 is provided.

  Here, the conveyance belt 121 is an endless belt, and is stretched between the conveyance roller 127 and the tension roller 128, and the conveyance roller 127 rotates from the sub-scanning motor 131 via the timing belt 132 and the timing roller 133. By doing so, it is configured to circulate in the belt conveyance direction (sub-scanning direction) of FIG. A guide member 129 is disposed on the back side of the conveyance belt 121 in correspondence with the image forming area formed by the recording head 107.

  As shown in FIG. 8, a slit disk 134 is attached to the shaft of the transport roller 127, and a sensor 135 that detects the slit of the slit disk 134 is provided. An encoder 136 is configured.

  The charging roller 126 is arranged so as to contact the surface layer of the conveyor belt 121 and rotate following the rotation of the conveyor belt 121, and applies 2.5N to both ends of the shaft as a pressing force.

  Further, as shown in FIG. 7, an encoder scale 142 having slits is provided on the front side of the carriage 103, and an encoder sensor comprising a transmissive photosensor that detects the slits of the encoder scale 142 on the front side of the carriage 103. The encoder 144 for detecting the position of the carriage 103 in the main scanning direction is configured by these.

  Further, as a paper discharge unit for discharging the paper 112 recorded by the recording head 107, a separation unit for separating the paper 112 from the conveying belt 121, a paper discharge roller 152 and a paper discharge roller 153, and paper discharge A paper discharge tray 154 for stocking the paper 112 to be printed.

  A double-sided paper feeding unit 155 is detachably mounted on the back. The double-sided paper feeding unit 155 takes in the paper 112 returned by the reverse rotation of the transport belt 121, reverses it, and feeds it again between the counter roller 122 and the transport belt 121.

  Further, as shown in FIG. 8, a maintenance / recovery mechanism 156 for maintaining and recovering the state of the nozzles of the recording head 107 is arranged in a non-printing area on one side of the carriage 103 in the scanning direction.

  The maintenance / recovery machine 156 includes a cap 157 for capping each nozzle surface of the recording head 107, a wiper blade 158 which is a blade member for wiping the nozzle surface, and a discharge unit for discharging the thickened recording liquid. An empty discharge receiver 159 for receiving droplets when performing empty discharge for discharging droplets that do not contribute to recording is provided.

  In the image forming apparatus configured as described above, the sheets 112 are separated and fed one by one from the sheet feeding unit, and the sheet 112 fed substantially vertically upward is guided by the guide 115, and includes the conveyance belt 121 and the counter roller 122. The leading end is guided by the transporting guide 123 and pressed against the transporting belt 121 by the leading end pressing roller 125, and the transporting direction is changed by approximately 90 °.

  At this time, a positive output and a negative output are alternately repeated from the AC bias supply unit (high-voltage power supply) to the charging roller 126 by a control circuit (not shown), that is, alternating voltages are applied, and the conveyor belt 121 alternates. In the charging voltage pattern, that is, in the sub-scanning direction that is the circumferential direction, plus and minus are alternately charged in a band shape with a predetermined width. When the paper 112 is fed onto the conveyance belt 121 charged alternately with plus and minus, the paper 112 is attracted to the conveyance belt 121 by electrostatic force, and the paper 112 is conveyed in the sub-scanning direction by the circular movement of the conveyance belt 121. Is done.

  Therefore, by driving the recording head 107 according to the image signal while moving the carriage 103 in the forward and backward directions, ink droplets are ejected onto the stopped paper 112 to record one line, and the paper 112 is After transporting a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the paper 112 has reached the recording area, the recording operation is finished, and the paper 112 is discharged onto the paper discharge tray 154.

  In the case of double-sided printing, when recording on the front surface (surface to be printed first) is completed, the recording belt 112 is fed into the double-sided paper feeding unit 155 by rotating the conveyor belt 121 in the reverse direction. The paper 112 is reversed (with the back surface being the printing surface), and is fed again between the counter roller 122 and the conveyor belt 121. The timing is controlled, and the sheet is conveyed onto the conveyor bell 121 as described above. After recording on the back side, the sheet is discharged to the discharge tray 154.

  Further, during printing (recording) standby, the carriage 103 is moved to the maintenance / recovery mechanism 155 side, and the nozzle surface of the recording head 107 is capped by the cap 157 so that the nozzles are kept in a wet state. To prevent. In addition, the recording liquid is sucked from the nozzle in a state where the recording head 107 is capped by the cap 157 (referred to as “nozzle suction” or “head suction”), and a recovery operation is performed to discharge the thickened recording liquid or bubbles. Wiping is performed by the wiper blade 158 in order to clean and remove ink adhering to the nozzle surface of the recording head 107 by this recovery operation. In addition, an idle ejection operation for ejecting ink not related to recording is performed before the start of recording or during recording. Thereby, the stable ejection performance of the recording head 107 is maintained.

Next, an outline of the control unit of the image forming apparatus will be described with reference to the block diagram of FIG.
The control unit 200 also serves as means for constituting each part of the servo control device according to the present invention. The CPU 211 controls the entire device, a program executed by the CPU 211, a ROM 202 for storing other fixed data, and image data. RAM 203 for temporarily storing data, rewritable nonvolatile memory 204 for holding data even while the apparatus is powered off, image processing for performing various signal processing, rearrangement, etc. on image data and other devices And an ASIC 205 for processing input / output signals for overall control.

  The control unit 200 includes a print control unit 207 including an I / F 206 for transmitting and receiving data and signals to and from the host side, a data transfer unit for controlling the drive of the recording head 107, and a drive signal generating unit. A head driver (driver IC) 208 for driving the recording head 107 provided on the carriage 103 side, a motor drive unit 210 for driving the main scanning motor 4 and the sub-scanning motor 31 which are drive motors in the present invention, An AC bias supply unit 212 that supplies an AC bias to the charging roller 34 and an I / O 213 for inputting detection signals from various sensors such as a temperature sensor 215 that detects the temperature of the sub-scanning motor 31 are provided. The control unit 200 is connected to an operation panel 214 for inputting and displaying information necessary for the apparatus.

  Here, the control unit 200 transmits print data from the host side such as an information processing device such as a personal computer, an image reading device such as an image scanner, an imaging device such as a digital camera, etc. via an I / F 206 via a cable or a network. Receive.

  Then, the CPU 201 of the control unit 200 reads and analyzes the print data in the reception buffer included in the I / F 206, performs necessary image processing, data rearrangement processing, and the like in the ASIC 205, and this image data is head-driven. The data is transferred from the control unit 207 to the head driver 208. Note that generation of dot pattern data for outputting an image is performed by a printer driver on the host side.

  The print control unit 207 transfers the image data described above as serial data, and outputs a transfer clock, a latch signal, a control signal, and the like necessary for the transfer of the image data and confirmation of the transfer to the head driver 208. Including a D / A converter for D / A converting D / A conversion of drive pulse pattern data stored in the ROM, a voltage signal amplifier, a current amplifier, and the like, and a drive signal or a plurality of drive pulses Is output to the head driver 208.

  The head driver 208 selectively selects a drive pulse that constitutes a drive signal provided from the head drive control unit 207 based on image data corresponding to one row of the print head 7 input serially. The recording head 7 is driven by applying it to a driving element (for example, a piezoelectric element) that generates energy for discharging the ink. At this time, by selecting a driving pulse constituting the driving signal, for example, dots having different sizes such as a large droplet, a medium droplet, and a small droplet can be sorted.

  The CPU 201 also detects a speed detection value and a position detection value obtained by sampling a detection pulse from the encoder sensor 143 constituting the linear encoder, and a speed target value and a position target value obtained from a previously stored speed / position profile. Based on this, a drive output value (control value) for the main scanning motor 104 is calculated, and the main scanning motor 104 is driven via the motor driving unit 210. Similarly, based on a speed detection value and a position detection value obtained by sampling a detection pulse from the encoder sensor 135 constituting the rotary encoder, and a speed target value and a position target value obtained from a previously stored speed / position profile. The driving output value (control value) for the sub-scanning motor 131 is calculated and the sub-scanning motor 131 is driven via the motor driving unit 210 and the motor driver.

  Here, when the carriage 103 is driven to decelerate, the CPU 201 drives and controls the main scanning motor 104 by adding a feedforward value to the drive output value calculated based on the speed deviation and outputting it as a drive output value.

Since the in the image forming apparatus is provided with a servo control apparatus according to the present invention, strong against load fluctuation, you can perform main scanning movement stable carriage 103, image quality improves.

  In the above embodiment, the present invention has been described with the serial type image forming apparatus having a printer configuration. However, the present invention is not limited to this, and the present invention is not limited to this. Can also be applied.

An embodiment of the servo control apparatus according to the present invention is a block diagram showing functional. It is explanatory drawing with which it uses for description of an effect | action of the same control apparatus. It is explanatory drawing with which it uses for operation | movement description of other embodiment of the same control apparatus. It is explanatory drawing with which it uses for description of the comparative example of the embodiment. It is explanatory drawing with which it uses for operation | movement description of the same embodiment. It is explanatory drawing with which it uses for operation | movement description of other embodiment of the same control apparatus. 1 is an explanatory side view illustrating an overall configuration of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the apparatus. It is a block diagram explaining the outline | summary of the control part of the apparatus. It is explanatory drawing with which it uses for description of how to apply the conventional feedforward.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Driven body 2 ... Drive motor 3 ... Encoder 4 ... Speed / position measurement part 5 ... Speed profile storage part 6 ... Comparison calculation part 7 ... Drive output value calculation part 8 ... Feed forward addition part 103 ... Carriage 107 ... Recording head 200 ... Control unit 207 ... Print control unit 210 ... Motor drive unit

Claims (3)

A drive output value for driving the drive motor is calculated based on a speed detection value and a speed target value of the drive motor that moves the driven body, and the drive motor is driven according to the calculated drive output value. In the servo control device,
When driving the driven body at a reduced speed,
During the period from the control step for starting the deceleration to the predetermined number of control steps, the calculated drive output value is divided into values corresponding to the difference from the previous control step of the speed target value for each step of servo control. Add a predetermined value as a deceleration feed forward,
In the control step after the predetermined number of control steps, a value corresponding to the difference from the previous control step of the speed target value is added to the calculated drive output value as a deceleration feed forward for each servo control step. A servo control device characterized by that. The servo control device according to claim 1, wherein the drive motor is driven and controlled in an image forming apparatus that forms an image by moving and scanning a carriage mounted with a recording head for discharging a recording liquid by a servo-controlled drive motor. An image forming apparatus comprising: A drive output value for driving the drive motor is calculated based on a speed detection value and a speed target value of the drive motor that moves the driven body, and the drive motor is driven according to the calculated drive output value. A program for causing a computer to execute servo control processing,
When driving the driven body at a reduced speed,
During the period from the control step for starting the deceleration to the predetermined number of control steps, the calculated drive output value is divided into values corresponding to the difference from the previous control step of the speed target value for each step of servo control. Add a predetermined value as a deceleration feed forward,
In the control step after the predetermined number of control steps, a value corresponding to the difference from the previous control step of the speed target value is added to the calculated drive output value as a deceleration feed forward for each servo control step. A program that causes a computer to execute processing.

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