JP2018171806A - Image formation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the technique capable of maintaining the state of the sheet properly even in a case where the external force acts.SOLUTION: A system 1 includes an image formation device 30, a sheet conveyance device 60, a motor 53 driving the conveyance device and a controller 10. The controller determines whether or not the stop condition is satisfied, stops the image formation processing when determining that the stop condition is satisfied, and executes the virtual compliance control to the motor so as to follow the external force transmitted from the sheet to the motor. The controller is configured to determine whether or not the resumption condition is satisfied, stop the virtual compliance control to resume the image formation processing when determining the resumption condition is satisfied.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an image forming system.

  An ink jet printer is conventionally known as an image forming system. In a general ink jet printer, paper is conveyed by the rotation of a roller. The roller is rotationally driven by a motor. An ink jet printer that applies a predetermined hold current to a motor in order to hold the position of a temporarily stopped sheet is also known (see, for example, Patent Document 1).

JP 2005-247488 A

  In the image forming system described above, maintaining the paper pause state is important for ensuring the quality of the image formed on the paper. However, in the conventional control method, in a case where an external force acts on the paper due to factors such as the user pulling the paper, slipping occurs between the roller and the paper, so that the paper is properly maintained in a paused state. I can't.

  Therefore, according to one aspect of the present disclosure, there is provided a technology capable of appropriately maintaining the seat pause state by suppressing the occurrence of slippage even when an external force is applied to the seat due to a user's pulling or the like. It is desirable to be able to do it.

  An image forming system according to an aspect of the present disclosure includes an image forming device, a transport device, a motor, and a controller. The image forming device is configured to form an image on a sheet. The transport device is configured to transport the sheet to the discharge area. The motor drives the transport device. The controller is configured to control the motor and the image forming device.

  According to an aspect of the present disclosure, the controller performs an image forming process for controlling the image forming device to form an image on the sheet and controlling the transport device to transport the sheet on which the image is formed to the discharge area. Run. The controller further determines whether the stop condition is satisfied. When it is determined that the stop condition is satisfied, the controller stops the image forming process and executes virtual compliance control for the motor so as to follow the external force transmitted from the sheet to the motor. The controller determines whether the restart condition is satisfied. If it is determined that the restart condition is satisfied, the controller stops the virtual compliance control and restarts the image forming process.

  According to this image forming system, the virtual compliance control can appropriately control the motor according to the external force acting on the sheet. Accordingly, even when an external force is applied by a user operation or the like, it is possible to prevent the sheet from slipping at the point of application of the force between the conveying device and the sheet, and appropriately maintain the temporary stop state of the sheet. Can do.

The transport device described above may be configured to include a roller at the boundary with the discharge area and discharge the sheet to the discharge area by rotation of the roller. In this case, the controller may be configured to adjust the strength of the virtual compliance control by adjusting the design value of the control system in the virtual compliance control in accordance with the positional relationship between the sheet and the roller.

  When an external force is generated by a user's pulling operation or the like, the sheet may come off the roller. In order to suppress such a possibility, virtual compliance control may be strengthened. On the other hand, if the virtual compliance control is strengthened, the possibility of slipping and the possibility of the sheet breaking are increased. Adjusting the strength of the virtual compliance control in accordance with the positional relationship between the sheet and the roller is effective for suppressing the slipping and slipping of the sheet from the roller.

  For example, the controller may adjust the design value so that the virtual compliance control is strengthened as the distance from the upstream end of the sheet in the conveyance direction of the sheet is reduced. Such adjustment of the strength of the virtual compliance control can appropriately suppress the possibility of the sheet coming off the roller due to an external force.

  According to one aspect of the present disclosure, the virtual compliance control system may include a virtual spring-mass-damper system including a mass element, a spring element, and a damper element. In this case, the design value to be adjusted can be at least one of the mass of the mass element, the spring constant of the spring element, and the damper constant of the damper element.

  According to one aspect of the present disclosure, the image forming system may include a measurement device that measures a physical quantity related to rotation of the motor. In this case, the controller may be configured to calculate an operation amount for the motor based on a deviation between the physical quantity measured by the measurement device and the target value of the physical quantity. The controller may be further configured to estimate an external force acting on the motor from the relationship between the operation amount and the physical amount, and correct the operation amount on the motor based on the estimated external force.

  According to one aspect of the present disclosure, the controller is configured to estimate an external force during execution of the virtual compliance control, and to cause the output device to output an alarm on the condition that the estimated external force exceeds a threshold value. Also good. The alarm can be output to the user, for example. In this case, it is possible to prompt the user to cancel the sheet pulling operation before the sheet is removed.

  According to one aspect of the present disclosure, the controller may determine that the stop condition is satisfied when a predetermined amount of image formation on the sheet is completed after starting the image forming process based on the start instruction. The controller may determine that the restart condition is satisfied when a restart instruction from the user is input. Such an operation may provide the user with an opportunity to confirm whether the image formation progress is correct.

  According to an aspect of the present disclosure, the controller discharges a sheet when a predetermined amount of image formation is completed when the image represented by the designated image data is formed on the sheet in the forward direction in the image forming process. You may estimate the length of the site | part located in a conveyance direction upstream from an area | region. The controller controls the image forming device to form the image represented by the image data on the sheet in the forward direction when the estimated length is greater than or equal to the reference, and when the estimated length is less than the reference The image forming device may be controlled so that the image represented by the image data is formed on the sheet in the reverse direction.

The predetermined amount of image formation is meaningful in providing the user with an opportunity to confirm whether the image formation progress is correct. However, in an environment where various image data exists, if a predetermined amount of image is formed on the sheet in the forward direction based on the image data, the sheet length sufficient to hold the position of the subsequent sheet is set inside the discharge area. May not be retained. When the length of the part located upstream in the transport direction from the sheet discharge area is less than the reference, according to the method of forming the image represented by the image data on the sheet in the reverse direction, when forming an image based on such image data However, when stopping, a length sufficient to hold the position of the sheet can be secured inside the discharge area.

1 is a diagram illustrating a mechanical configuration of an image forming system. 1 is a block diagram illustrating an electrical configuration of an image forming system. 6 is a flowchart illustrating print control processing executed by a controller. It is a block diagram showing the structure of a control system. It is a block diagram showing the structure of a virtual compliance controller. It is a flowchart showing the setting process which a controller performs. It is explanatory drawing regarding image rotation. It is a graph showing the change of the position deviation with respect to external force, and the operation amount (electric current). It is a block diagram showing the structure of the control system of a modification.

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
The image forming system 1 of the present embodiment is configured as an ink jet printer. As shown in FIG. 1, the image forming system 1 includes an inkjet head 31 in a housing 6. The inkjet head 31 includes a nozzle group that ejects ink droplets on the lower surface. The ink-jet head 31 is disposed above the platen 61 that constitutes the transport path of the paper Q while being mounted on the carriage 35.

  The carriage 35 is provided so as to be able to reciprocate in the main scanning direction (the normal direction of the paper surface in FIG. 1) perpendicular to the conveyance direction of the paper Q. The inkjet head 31 reciprocates in the main scanning direction together with the carriage 35. The inkjet head 31 forms an image on the paper Q passing over the platen 61 by ejecting ink droplets in the process of this reciprocation.

  The paper Q is transported from upstream to downstream along the platen 61 by the rotation of the transport roller 63 and the paper discharge roller 65. The conveyance roller 63 is provided upstream of the platen 61 and is disposed to face the pinch roller 64. The paper discharge roller 65 is provided downstream of the platen 61 and is disposed to face the spur roller 66.

  The conveyance roller 63 conveys the paper Q downstream by rotating in a state where the paper Q is sandwiched between the conveyance roller 63 and the pinch roller 64. The paper discharge roller 65 conveys the paper Q downstream by rotating in a state where the paper Q is sandwiched between the paper discharge roller 65 and the spur roller 66. The paper Q conveyed downstream from the paper discharge roller 65 is discharged to the paper discharge tray 69. The paper discharge tray 69 supports the paper Q conveyed from the paper discharge roller 65 from below.

  As shown in FIG. 2, the image forming system 1 includes a controller 10, a communication interface 20, a user interface 25, a recording unit 30, a paper feeding unit 40, and a paper conveying unit 50. A paper transport mechanism 60 including a platen 61, a transport roller 63, a pinch roller 64, a paper discharge roller 65, and a spur roller 66 is provided in the paper transport unit 50.

The controller 10 controls each part of the image forming system 1. The controller 10 includes a CPU 11, a ROM 13 and a RAM 15. The CPU 11 executes a process according to a program stored in the ROM 13. The RAM 15 is used as a working memory when the CPU 11 executes processing. The controller 10 can include a dedicated circuit (not shown) for controlling each unit in the image forming system 1.

  The communication interface 20 realizes communication between the controller 10 and an external device. When the controller 10 receives a print command from an external device via the communication interface 20, the controller 10 forms an image based on the print target image data on the paper Q based on the print target image data received together with the print command. The recording unit 30, the paper feeding unit 40, and the paper transport unit 50 are controlled.

  The user interface 25 includes a display for displaying information to the user, a speaker for outputting a warning sound, and an input device for receiving a command from the user.

  The recording unit 30 includes the inkjet head 31 and the carriage 35 described above. The recording unit 30 forms an image based on the image data to be printed on the paper Q by causing the carriage 35 to reciprocate in the main scanning direction according to an instruction from the controller 10 and causing the ink jet head 31 to eject ink droplets. . The paper feed unit 40 supplies the paper Q to the transport mechanism 60 in accordance with an instruction from the controller 10.

  The paper transport unit 50 includes a motor driving circuit 51, a transport motor 53, an encoder 55, and a signal processing circuit 57 together with the transport mechanism 60. The motor drive circuit 51 drives the carry motor 53 with a drive current corresponding to the operation amount U input from the controller 10. The motor drive circuit 51 can drive the transport motor 53 by PWM.

  The carry motor 53 is driven by the motor drive circuit 51 to drive the carry roller 63 to rotate. The paper discharge roller 65 is connected to the transport roller 63 via a power transmission mechanism (not shown), and rotates in synchronization with the transport roller 63.

  The encoder 55 is a rotary encoder that outputs a pulse signal corresponding to the rotation of the transport motor 53. The encoder 55 is provided at a position where the rotational motion of the transport motor 53 can be observed directly or indirectly. The encoder 55 outputs an A-phase signal and a B-phase signal as the pulse signal as in the known rotary encoder. Hereinafter, the A-phase signal and the B-phase signal are expressed as encoder signals.

  The encoder signal output from the encoder 55 is input to the signal processing circuit 57. The signal processing circuit 57 measures the rotation amount X and the rotation speed V of the transport motor 53 based on the encoder signal, and inputs information on the measured rotation amount X and rotation speed V to the controller 10. The controller 10 controls the conveyance motor 53 based on the information about the rotation amount X and the rotation speed V input from the signal processing circuit 57.

  Next, details of processing executed by the controller 10 will be described. When a print command is input, the controller 10 executes processing for forming image data to be printed on the paper Q. Specifically, when a print command in the trial print mode is input, the controller 10 executes the print control process shown in FIG. When this print control process is started, the controller 10 executes a setting process (S110). The controller 10 sets the strength of virtual compliance control in the setting process (details will be described later).

Thereafter, the controller 10 starts an image forming process for forming an image based on the image data to be printed on the paper Q (S120). Specifically, the paper feed unit 40 is controlled to supply the paper Q from the paper feed tray to the paper transport unit 50. Further, the controller 10 controls the paper transport unit 50 so that the paper Q is transported toward the paper discharge tray 69 by the rotation of the transport roller 63 and the paper discharge roller 65. Furthermore, the controller 10 controls the recording unit 30 so that an image based on the image data to be printed is formed in accordance with the conveyance of the paper Q.

  The controller 10 continues the image forming process (S120), and determines whether a predetermined amount of image is formed on the paper Q by the image forming process (S130). If it is determined that a predetermined amount of image has been formed (Yes in S130), the image forming process is temporarily stopped, and the paper Q is sent to the discharge tray 69 side to a position where the user can visually recognize the predetermined amount of image. Next, the transport motor 53 is controlled (S140). This operation is performed to present the initial print result to the user.

  Thereafter, the controller 10 executes position holding control according to the control system 100 shown in FIG. 4 in order to hold the position of the paper Q (S150). The position holding control includes virtual compliance control for generating a torque of the transport motor 53 so as to follow an external force acting on the transport motor 53 from the paper Q. Examples of the external force include an external force generated when the user pulls the paper Q exposed on the paper discharge tray 69 from the paper discharge roller 65.

  The control system 100 shown in FIG. 4 calculates the operation amount U for the transport motor 53 based on the deviation E = Xr−X between the rotation amount X and the target value Xr, and supplies the drive current corresponding to the operation amount U to the transport motor 53. , The conveyance motor 53 is controlled so that the rotation amount X is maintained at the target value Xr.

  Specifically, the control system 100 includes a position commander 110, a subtractor 120, a position corrector 130, a position controller 140, an adder 150, a disturbance compensator 160, a disturbance observer 170, a virtual compliance. And a controller 180.

  The position commander 110 inputs the target value Xr to the subtracter 120. The target value Xr is the rotation amount or rotation position X of the transport motor 53 at the start of position holding control. The subtractor 120 inputs the position deviation E = Xr−X between the target value Xr and the rotation amount X input from the signal processing circuit 57 to the position corrector 130.

  The position corrector 130 corrects the position deviation E from the subtractor 120 with the position correction amount Xc input from the virtual compliance controller 180, and the corrected position deviation Ec = E−Xc is sent to the position controller 140. input.

  The position controller 140 calculates an operation amount U1 for the transport motor 53 based on the corrected position deviation Ec, and inputs the calculated operation amount U1 to the adder 150. The position controller 140 is configured as a proportional derivative controller. That is, the position controller 140 calculates the sum (Up + Ud) of the operation amount Up obtained by inputting the position deviation Ec to the proportional device and the operation amount Ud obtained by inputting the position deviation Ec to the differentiator (Up + Ud). This is input to the adder 150 as U1.

  The adder 150 adds the disturbance compensation amount U5 from the disturbance compensator 160 to the operation amount U1 from the position controller 140, and inputs the operation amount U = U1 + U5 after the addition to the motor drive circuit 51. This manipulated variable U corresponds to a current command value. The motor drive circuit 51 drives the carry motor 53 so as to apply a drive current corresponding to the input operation amount U to the carry motor 53. For example, the motor drive circuit 51 can perform PWM control on the transport motor 53 according to the operation amount U.

The disturbance observer 170 is based on the operation amount U input from the adder 150 to the motor drive circuit 51 and the measured rotational speed V input from the signal processing circuit 57.
Estimate the external force acting on.

As shown in FIG. 5, the disturbance observer 170 includes an inverse model calculator 171, subtracters 173 and 179, a low-pass filter 175, and a friction estimator 177.
The inverse model calculator 171 uses the inverse model H ⁻¹ of the transfer function model H that represents the relationship between the manipulated variable U and the rotational speed V, and operates when the observed rotational speed V is assumed to have no disturbance. Convert to quantity U0. The subtractor 173 subtracts the operation amount U input to the motor drive circuit 51 by the operation amount U0 from the inverse model calculator 171 to calculate a disturbance estimated value τ = U−U0. A proportional relationship is established between the current applied to the conveyance motor 53 and the torque. Therefore, the disturbance estimated value τ corresponds to a force component that is not considered in the transfer function model H. The estimated disturbance value τ includes a component of a force acting on the transport motor 53 from the paper Q and a frictional force component generated on the rotation shaft of the transport motor 53.

The low-pass filter 175 corrects the disturbance estimated value τ so as to remove the high-frequency component and outputs the corrected value. The corrected disturbance estimated value τ is input to the subtracter 179.
The friction estimator 177 calculates the estimated value F of the friction force component using the rotational speed V, and inputs this estimated friction force value F to the subtracter 179. This frictional force estimated value F includes a dynamic friction component and a viscous friction component depending on the rotational speed V.

  The subtracter 179 subtracts the estimated frictional force F from the friction estimator 177 from the estimated disturbance τ input from the low-pass filter 175, so that the estimated value of the external force mainly acting on the transport motor 53 from the paper Q is obtained. R = τ−F is calculated and input to the disturbance compensator 160 and the virtual compliance controller 180. The disturbance compensator 160 calculates a disturbance compensation amount U5 = K · R by applying a predetermined gain K to the external force estimated value R, and inputs this to the adder 150.

  The virtual compliance controller 180 is a virtual spring-mass-damper system controller. The virtual compliance controller 180 includes subtracters 181 and 182, gain amplifiers 183, 186 and 187, and integrators 184 and 185. The gain amplifier 183 corresponds to a virtual mass element, the gain amplifier 186 corresponds to a virtual damper element, and the gain amplifier 187 corresponds to a virtual spring element.

  The subtractor 181 subtracts the estimated external force value R by the spring component Kv · Xc input from the gain amplifier 187 and inputs the value after subtraction (R−Kv · Xc) to the subtractor 182. The subtractor 182 subtracts the input value (R−Kv · Xc) from the subtractor 181 by the damper component Dv · Vc input from the gain amplifier 186 to obtain the mass component (R−Kv · Xc−Dv · Vc). ) And the mass component is input to the gain amplifier 183.

  The gain amplifier 183 has a gain 1 / M corresponding to the virtual mass M, and the acceleration of the virtual spring-mass-damper system Ac = (R−Kv · Xc−Dv) corresponding to the mass component input from the subtractor 182. Convert to Vc) / M. The acceleration Ac is input to the integrator 184 and converted into the velocity Vc, and further input into the integrator 185 and converted into the position Xc.

  The gain amplifier 186 has a gain Dv corresponding to the damper constant Dv of the virtual damper element, converts the speed Vc input from the integrator 184 into a force damper component (Dv · Vc), and inputs it to the subtractor 182. To do. The damper constant Dv may be understood as the damping coefficient of the virtual damper element.

  The gain amplifier 187 has a gain Kv corresponding to the spring constant Kv of the virtual spring element, converts the position Xc input from the integrator 185 into a force spring component (Kv · Xc), and inputs the force to the subtractor 181. To do. The spring constant Kv may be understood as the elastic coefficient of the virtual spring element.

  The position Xc of the virtual spring-mass damper system is input to the position corrector 130 as the position correction amount Xc. By correcting the position deviation E input to the position corrector 130 by the position correction amount Xc, the operation amount U is calculated so that torque following the external force acting on the paper Q is generated from the transport motor 53.

  In S150, the controller 10 repeatedly executes the operation amount U calculation operation according to the control system 100 and the operation amount U input operation to the motor drive circuit 51 at a predetermined control period until a restart instruction is input. . As a result, a torque that follows the external force is generated in the transport motor 53, and the rotational position (X) of the transport motor 53 is corrected to the position (Xr) at the start of the position holding control.

  In addition to the process of S150, the controller 10 repeatedly executes a process (S160) for determining whether the estimated external force value R exceeds a predetermined alarm threshold value at a predetermined control cycle until a restart instruction is input. . When it is determined that the external force estimated value R exceeds the warning threshold value (Yes in S160), the controller 10 controls the user interface 25 to cause the user interface 25 to output a warning for the user (S170). The warning is in the form of sound and / or display. The warning may be a warning prompting to stop the pulling operation of the paper Q.

  The controller 10 repeatedly executes the above-described processing of S150 to S170 at a predetermined control cycle, and further determines whether an instruction to resume image forming processing is input from the user interface 25 (S180). If it is determined that a restart instruction has been input (Yes in S180), the position holding control is stopped and the image forming process temporarily stopped in S140 is restarted (S190).

  Specifically, the transport motor 53 is controlled so that the paper Q sent out in S140 is retracted to the position before the sending, that is, the position at the time of stopping the image forming process. Then, the recording unit 30 is controlled so that image formation on the paper Q is resumed from this position. Further, the controller 10 controls the paper transport unit 50 so that the paper Q is transported downstream, and the recording unit 30 so that an image based on the image data to be printed is formed in accordance with the transport of the paper Q. To control. When the image forming process ends, the print control process shown in FIG. 3 ends.

  Although not shown, the controller 10 discharges the paper Q to the paper discharge tray without restarting the image forming process (S190) when the interruption command is input from the user through the user interface 25 without the restart command being input. Can be executed.

  Next, details of the setting process executed by the controller 10 in S110 will be described with reference to FIG. In the setting process (S110), the controller 10 analyzes the image data to be printed, temporarily forms a predetermined amount of image on the paper Q, and stops the image forming process in S140 with respect to the paper discharge roller 65. Determine the relative position. Specifically, the distance L from the contact point of the paper Q with the paper discharge roller 65 to the trailing edge of the paper, that is, the edge on the upstream side in the transport direction of the paper Q is determined. The paper size is specified from the paper type information input together with the print command.

  The controller 10 further determines whether or not the distance L is greater than a predetermined first threshold TH (S220). If the distance L is greater than the first threshold TH, the virtual compliance control is set to the “weak” level (S230), and the setting process is terminated. Setting the virtual compliance control to the “weak” level means that the virtual mass M, the spring coefficient Kv, and the damper constant Dv, which are variable parameters of the virtual compliance controller 180, are values for the predefined “weak” level. Corresponds to setting to. The value of the variable parameter for setting the virtual compliance control to the “weak” level is stored in the ROM 13.

  The values of the virtual mass M, the spring coefficient Kv, and the damper constant Dv for setting the virtual compliance control to the “weak” level are the virtual mass M, the spring coefficient Kv for setting the virtual compliance control to the “strong” level. And relatively smaller than the value of the damper constant Dv.

  When the controller determines that the distance L is equal to or less than the first threshold value TH (No in S220), the controller determines whether the distance L is greater than a second threshold value TL that is smaller than the first threshold value TH (S240). ). If it is determined that the distance L is greater than the second threshold TL (Yes in S240), the virtual compliance control is set to the “strong” level (S250), and the setting process is terminated. Setting the virtual compliance control to the “strong” level means that the virtual mass M, the spring coefficient Kv, and the damper constant Dv, which are variable parameters of the virtual compliance controller 180, are values for the predefined “strong” level. Corresponds to setting to. The value of the variable parameter for setting the virtual compliance control to the “strong” level is stored in the ROM 13.

  As described above, when the distance L from the position of the paper Q nipped by the paper discharge roller 65 to the rear edge of the paper is long, the controller 10 sets the virtual compliance control to the “weak” level and the distance L is short. In this case, the virtual compliance control is set to the “strong” level. This suppresses the possibility of slippage between the paper discharge roller 65 and the paper Q, and further suppresses the possibility of the paper Q coming out of the paper discharge roller 65. That is, the controller 10 realizes virtual compliance control with an appropriate sensitivity according to the positional relationship between the paper Q and the paper discharge roller 65.

  In addition, if the controller 10 determines that the distance L is equal to or smaller than the second threshold value TL (No in S240), the controller 10 executes the processes after S260. In the present embodiment, when the distance L is equal to or smaller than the second threshold TL, the paper Q comes out of the paper discharge roller 65 due to the user pulling the paper Q even if the virtual compliance control is set to the “strong” level. Corresponding to the case where the possibility is high.

  In the case where the distance L is equal to or less than the second threshold TL, as shown in the upper part of FIG. 7, there is no image formed on the leading end side of the paper Q in the image data to be printed, as shown in the lower left part of FIG. When a predetermined amount of image formation is performed based on this image data, image formation is performed after the second half of the paper Q, and the distance L becomes short.

  In this case, the controller 10 reverses the orientation of the image with respect to the paper Q by rotating the image data to be printed by 180 degrees. As a result, an environment is formed in which the distance L is long when a predetermined amount of image is formed.

  That is, when the controller 10 determines that the distance L is equal to or smaller than the second threshold TL (No in S240), the image data to be printed is rotated 180 degrees (S260), and the virtual compliance control is set to the “weak” level. (S270). In S270, an embodiment in which the virtual compliance control is set to the “strong” level is also conceivable. Thereafter, the controller 10 ends the setting process (S110) and executes the processes after S120. When the 180 degree rotation process of the image data is executed in S260, the controller 10 executes the image forming process (S120) based on the image data after the 180 degree rotation process.

The middle part of FIG. 8 is a graph showing the change in the positional deviation E = X−Xr when the virtual compliance control is set to the “strong” level and when it is set to the “weak” level. The lower part of FIG. 8 shows a change in the corresponding operation amount (current command value) U by a graph. The middle stage and the lower stage in FIG. 8 show changes in the position deviation E and the operation amount U when an external force is temporarily applied as shown in the upper stage of FIG.

  As can be understood from FIG. 8, when the virtual compliance control is performed at the “weak” level, the variation of the position deviation E becomes large. This increases the possibility that the paper Q will slip out of the paper discharge roller 65 due to the pulling force from the user when the distance L is short, while the paper Q slips at the contact point with the paper discharge roller 65. It shows that the possibility can be reduced. As can be understood from the middle part of FIG. 8, when the external force applied to the paper Q disappears, the controller 10 controls the transport motor 53 so that the virtual compliance control returns to the position before the external force is applied.

  As described above, the image forming system 1 according to the present embodiment has been described. However, according to the present embodiment, the conveyance motor 53 can be controlled to follow an external force typified by a pulling force from the user. The once stopped image forming process can be resumed with high accuracy from the stop position. Therefore, according to the image forming system 1 of the present embodiment, a high-quality image can be formed on the paper Q even in a case where image formation is temporarily stopped, such as trial printing.

  In particular, according to the present embodiment, the strength of the virtual compliance control is appropriately adjusted by changing the virtual mass M, the spring constant Kv, and the damper constant Dv according to the positional relationship between the paper Q and the roller. Accordingly, it is possible to realize appropriate sheet Q position holding control while suppressing the removal of the sheet Q due to external force.

  The present disclosure is not limited to the above embodiments, and can take various forms. In the above embodiment, the virtual spring-mass damper system is adopted, but the virtual compliance controller 180 may be configured with a virtual first-order lag system. For example, the virtual compliance controller 180 may be configured by a controller having a transfer characteristic represented by a transfer function kv / (Tv · s + 1) having variable parameters kv and Tv. Here, s is a Laplace operator. In this case, the strength of the virtual compliance control can be realized by adjusting the variable parameters kv and Tv.

  In the above embodiment, the virtual compliance control is adjusted in two stages of “strong” and “weak”, but the virtual compliance control may be adjusted in three or more stages such as “strong”, “medium”, and “weak”. Good. In this case, the variable parameter of the virtual compliance controller 180 can be adjusted so that the virtual compliance control becomes stronger as the distance L becomes shorter.

  An appropriate value of the variable parameter can be determined by the designer of the image forming system 1 based on the test result. In addition, the position holding control (S150) may be realized according to the control system 200 shown in FIG. The control system 200 is obtained by replacing the position controller 140 in the control system 100 with another position controller 240.

  Similar to the position controller 140, the position controller 240 includes a proportional device 241 and a differentiator 242. The proportional device 241 and the differentiator 242 respectively output an operation amount Up and an operation amount Ud corresponding to the corrected position deviation Ec input from the position corrector 130. The position controller 240 includes a speed corrector 243. The speed corrector 243 corrects the operation amount Ud output from the differentiator 242 with the speed correction amount Vc input from the virtual compliance controller 180, and outputs the corrected operation amount Ud1 = Ud−Vc.

Further, the position controller 240 includes an adder 244 that outputs an addition value Upd = (Up + Ud1) between the corrected operation amount Ud1 and the operation amount Up output from the proportional device 241. Further, the position controller 240 corrects the addition value Upd with the acceleration correction amount Ac input from the virtual compliance controller 180, and sets the corrected operation amount (Upd−Ac) as the operation amount U1 to the adder 150. An input acceleration corrector 245 is provided. Such a position controller 240 can also appropriately control the position holding of the paper Q in a form including virtual compliance control.

  In addition, the control systems 100 and 200 may be realized by software or hardware. For example, the control systems 100 and 200 may be realized by information processing by the CPU 11 or may be realized by a dedicated circuit incorporated in the controller 10. The above-described control systems 100 and 200 are examples, and it goes without saying that various control systems can be adopted. The present disclosure may be applied to position holding control of the paper Q that is temporarily exposed to the outside during duplex printing.

  The functions of one constituent element in the above embodiment may be distributed among a plurality of constituent elements. Functions of a plurality of components may be integrated into one component. A part of the configuration of the above embodiment may be omitted. At least a part of the configuration of the embodiment may be added to or replaced with the configuration of the other embodiment. Any aspect included in the technical idea specified from the wording of the claims is an embodiment of the present disclosure.

DESCRIPTION OF SYMBOLS 1 ... Image forming system, 10 ... Controller, 11 ... CPU, 13 ... ROM, 25 ... User interface, 30 ... Recording part, 31 ... Inkjet head, 35 ... Carriage, 40 ... Paper feed part, 50 ... Paper conveyance part, 51 DESCRIPTION OF SYMBOLS Motor drive circuit 53 ... Conveyance motor 55 ... Encoder 57 ... Signal processing circuit 60 ... Conveyance mechanism 63 ... Conveyance roller 65 ... Discharge roller 69 ... Discharge tray 100 ... Control system 110 ... Position Commander 120 ... Subtractor 130 ... Position corrector 140 ... Position controller 150 ... Adder 160 ... Disturbance compensator 170 ... Disturbance observer 180 ... Virtual compliance controller 181 ... Subtractor 182 ... Subtractor, 183 ... gain amplifier, 184 ... integrator, 185 ... integrator, 186 ... gain amplifier, 187 ... gain amplifier, 200 ... control System, 240 ... position controller, 241 ... proportional unit, 242 ... differentiator, 243 ... speed corrector, 244 ... adder, 245 ... acceleration corrector, Q ... paper.

Claims (8)

An imaging device configured to form an image on a sheet;
A transport device configured to transport the sheet to a discharge area;
A motor for driving the transport device;
A controller configured to control the motor and the image forming device;
With
The controller is
Controlling the image forming device to form an image on the sheet, and further performing an image forming process for controlling the transport device to transport the sheet on which the image is formed to the discharge area,
Determine whether the stop condition is satisfied,
If it is determined that the stop condition is satisfied, the image forming process is stopped,
Performing virtual compliance control on the motor to follow the external force transmitted from the seat to the motor;
Determine if the restart condition is satisfied,
An image forming system that stops the virtual compliance control and restarts the image forming process when it is determined that the restart condition is satisfied. The transport device includes a roller at a boundary with the discharge area, and is configured to discharge the sheet to the discharge area by rotation of the roller.
The image forming system according to claim 1, wherein the controller adjusts the strength of the virtual compliance control by adjusting a design value of a control system in the virtual compliance control in accordance with a positional relationship between the sheet and the roller. .   The controller adjusts the design value so that the virtual compliance control is strengthened as the distance from the upstream end of the sheet in the conveyance direction of the application point of the force from the roller in the sheet is shorter. 2. The image forming system according to 2. The control system includes a virtual spring-mass-damper system including a mass element, a spring element, and a damper element;
The image forming system according to claim 2, wherein the design value to be adjusted is at least one of a mass of the mass element, a spring constant of the spring element, and a damper constant of the damper element. A measuring device for measuring a physical quantity related to rotation of the motor;
The controller calculates, as the virtual compliance control, an operation amount for the motor based on a deviation between a physical quantity measured by the measurement device and a target value of the physical quantity, and from a relationship between the operation quantity and the physical quantity, The image forming system according to claim 1, wherein an external force acting on the motor is estimated, and an operation amount for the motor is corrected based on the estimated external force.   6. The controller according to claim 1, wherein the controller estimates the external force during execution of the virtual compliance control, and causes an output device to output an alarm on condition that the estimated external force exceeds a threshold value. The image forming system according to one item.   The controller, after starting the image forming process based on a start instruction from a user, determines that the stop condition is satisfied when a predetermined amount of image formation is completed on the sheet, and a restart instruction from the user is received. The image forming system according to claim 1, wherein when the input is performed, it is determined that the restart condition is satisfied.   The controller conveys from the discharge area of the sheet when the predetermined amount of image formation is completed when the image represented by the designated image data is formed on the sheet in the forward direction in the image forming process. Estimating the length of a portion located upstream in the direction, and if the length is greater than or equal to the reference, the image forming device is controlled to form an image represented by the image data in the positive direction on the sheet, The image forming system according to claim 7, wherein when the length is less than the reference, the image forming device is controlled to form an image represented by the image data on the sheet in a reverse direction.