JP2019185654A - Control system, control method and program - Google Patents

Abstract

To provide a control system capable of positioning an object at a high speed and with high accuracy.SOLUTION: A positioning part positions an estimated position of an object in each control cycle based on an image photographed in each photographing cycle and position related information provided from a moving mechanism. A feedback control part updates a movement command for adjusting the estimated position with a target position every second cycle. When deviation between the estimated position and the target position is less than a threshold value, a stop control part stops the update of the movement command. When a measurement result obtained from an image photographed after determination that movement in accordance with a final movement command has completed satisfies a predetermined condition, a determination part determines that the positioning of the object has ended.SELECTED DRAWING: Figure 1

Description

  The present technology relates to a control system, a control method, and a program using a visual sensor.

  In FA (Factory Automation), various techniques (positioning techniques) for aligning the position of an object with a target position have been put into practical use. At this time, as a method for measuring the deviation (distance) between the position of the object and the target position, there is a method using an image captured by a visual sensor.

  Japanese Patent Laid-Open No. 2017-24134 (Patent Document 1) discloses a vision in which a movable table, a driving mechanism for moving the movable table, and a workpiece placed on the movable table are repeatedly imaged and the position of the workpiece is repeatedly detected. A workpiece positioning device provided with a sensor is disclosed. The workpiece positioning device calculates the difference between the detected position and the target position every time the position is detected by the visual sensor, and moves the movable base when it is determined that the difference is within the allowable range. Stop. The workpiece positioning device calculates the difference between the position detected by the visual sensor after the movable table stops moving and the target position, and determines whether the calculated difference is within an allowable range. If it is determined that the difference is outside the allowable range, the moving direction of the movable base that reduces the difference is determined, and the drive mechanism is controlled to move the movable base in the determined moving direction.

JP 2017-24134 A

  It takes a certain amount of time to detect the position by the visual sensor. Therefore, even if the difference between the position detected by the visual sensor and the target position is within the allowable range and the movement of the movable table is stopped, the current position of the workpiece is detected by the movement of the movable table during the position detection time by the visual sensor. The difference between the target position and the target position may be outside the allowable range. Therefore, in the technique described in Patent Document 1, the frequency at which the difference between the position detected by the visual sensor after the movement of the movable base stops and the target position is determined to be outside the allowable range increases, and the positioning speed decreases. Cheap. By expanding the allowable range, the frequency decreases, but in this case, the positioning accuracy decreases.

  The present invention has been made in view of the above problems, and an object thereof is to provide a control system, a control method, and a program capable of positioning an object at high speed and with high accuracy.

  According to an example of the present disclosure, an object control system includes a moving mechanism for moving an object, a visual sensor for imaging the object, a position determination unit, a feedback control unit, and a stop control unit. And an imaging command unit and a determination unit. The position determination unit determines the estimated position of the target object for each second period shorter than the first period, based on the image captured by the visual sensor for each first period and the position related information from the moving mechanism. . The feedback control unit updates a movement command for adjusting the estimated position to the target position of the target object every second period and outputs the updated movement command to the movement mechanism. The stop control unit stops the update of the movement command by the feedback control unit when the first deviation between the estimated position and the target position is less than the first threshold. When the update of the movement command is stopped, the imaging command unit determines whether the movement according to the final movement command is completed, determines that the movement according to the final movement command is completed, and then issues an imaging command to the visual sensor. Output. The determination unit determines to end the positioning of the object when the measurement result from the image captured in response to the imaging command satisfies a predetermined condition.

  According to this disclosure, the feedback control unit updates the movement command for adjusting the estimated position to the target position every second period and outputs the updated movement command to the movement mechanism. Thereby, the positioning according to the state of the object can be performed with an accuracy that can be visually recognized by the visual sensor. Therefore, robustness against disturbance is improved and positioning accuracy is improved.

  The estimated position is determined for each second period based on the image captured by the visual sensor for each first period and the position related information from the moving mechanism. Visual sensors generally have low responsiveness. For this reason, if feedback control is performed using an image obtained from a visual sensor, overshoot and vibration are likely to occur, so the gain of feedback control cannot be increased very much. However, by using the estimated position determined based on the position related information from the moving mechanism, the gain in the feedback control can be increased and the estimated position can be brought close to the target position at high speed.

  Further, when the first deviation between the estimated position and the target position is less than the first threshold, the update of the movement command is stopped, and after it is determined that the movement according to the final movement command is completed, the imaging command is output to the visual sensor. Is done. When the measurement result from the image captured in accordance with the imaging command satisfies a predetermined condition, it is determined that the positioning is to be ended. That is, the position of the object is reconfirmed by the image obtained after the movement of the object in accordance with the final movement command is completed. Then, even if the movement according to the final movement command is taken into account, the positioning is ended when the measurement result satisfies a predetermined condition. Thereby, positioning of a target object can be performed with high precision.

  Furthermore, as described above, since the responsiveness of the visual sensor is low, the difference between the position of the target obtained from the image captured by the visual sensor and the current position of the moving target tends to increase. On the other hand, the estimated position is determined based on the position related information from the moving mechanism every second period shorter than the first period. Therefore, the estimated error of the estimated position is smaller than the error of the position measured based only on the image captured every first period. As a result, the frequency at which the measurement result does not satisfy the predetermined condition due to the movement according to the final movement command after the first deviation between the estimated position and the target position is less than the first threshold is low. Thereby, it can position at high speed.

  Thus, according to the control system of the present disclosure, the object can be positioned at high speed and with high accuracy.

  In the above disclosure, when the measurement result does not satisfy a predetermined condition, the feedback control unit resumes the update of the movement command. According to this disclosure, the update of the movement command can be resumed even when the measurement result does not satisfy the predetermined condition due to the movement according to the final movement command.

  In the above disclosure, the imaging command unit completes the movement according to the final movement command when the second deviation between the position command value indicated by the final movement command and the position indicated by the position related information is less than the second threshold value. It is determined that Alternatively, the imaging command unit may determine that the movement according to the final movement command is completed when the speed indicated by the position related information is less than the third threshold. According to these disclosures, it is possible to reliably determine whether or not the movement according to the final movement command is completed.

  Alternatively, the imaging command unit may determine that the movement according to the final movement command has been completed when the elapsed time after the update of the movement command is stopped by the stop control unit exceeds the fourth threshold value. According to this disclosure, it is possible to easily determine whether or not the movement according to the final movement command is completed without using the position related information.

  In the above disclosure, the measurement result indicates the measurement position of the object measured from the image captured in accordance with the imaging command. The predetermined condition is a condition that the third deviation between the measurement position and the target position is less than the fifth threshold value. According to this disclosure, the position of the object can be accurately positioned at the target position.

  According to an example of the present disclosure, the control system includes a moving mechanism for moving the object and a visual sensor for imaging the object. The control method in the object control system includes the following first to fifth steps. In the first step, the estimated position of the object is determined for each second period shorter than the first period, based on the image captured by the visual sensor for each first period and the position related information from the moving mechanism. It is a step to do. The second step is a step in which a movement command for adjusting the estimated position to the target position of the object is updated every second period and output to the movement mechanism. The third step is a step of stopping the update of the movement command when the first deviation between the estimated position and the target position is less than the first threshold value. In the fourth step, when the update of the movement command is stopped, it is determined whether the movement according to the final movement command is completed, and after determining that the movement according to the final movement command is completed, the imaging command is sent to the visual sensor. Is a step of outputting. The fifth step is a step of determining that the positioning of the object is to be ended when the measurement result from the image captured in accordance with the imaging command satisfies a predetermined condition. According to this disclosure, the object can be positioned at high speed and with high accuracy.

  According to an example of the present disclosure, a program for causing a computer to execute a control method in an object control system causes the computer to execute the first to fifth steps. According to this disclosure, the object can be positioned at high speed and with high accuracy.

  According to the present invention, an object can be positioned at high speed and with high accuracy.

It is a schematic diagram which shows the outline | summary of the control system which concerns on this Embodiment. It is a perspective view which shows an example of the stage apparatus which comprises the control system which concerns on this Embodiment. It is a schematic diagram which shows the hardware constitutions of the image process part which comprises the control system which concerns on this Embodiment. It is a schematic diagram which shows the hardware constitutions of the controller which comprises the control system which concerns on this Embodiment. It is a flowchart which shows an example of the flow of a process of a controller. It is a flowchart which shows the processing content of the subroutine of the estimated position determination process shown in FIG. It is a flowchart which shows the processing content of the subroutine of the estimation process of the encoder value at the time of imaging shown in FIG.

  Embodiments of the present invention will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are denoted by the same reference numerals and description thereof will not be repeated.

§1 Application example An example of a scene to which the present invention is applied will be described with reference to FIG. FIG. 1 is a schematic diagram showing an outline of a control system according to the present embodiment. The control system 1 shown in FIG. 1 performs positioning using image processing. The positioning typically means a process of placing an object (hereinafter also referred to as “work W”) at an original position of the production line in the manufacturing process of an industrial product. For example, the control system 1 positions the glass substrate with respect to the exposure mask before the circuit pattern printing process (exposure process) on the glass substrate in the production line of the liquid crystal panel.

  As shown in FIG. 1, the control system 1 includes a stage device 10, a servo driver 20, a visual sensor 30, and a controller 40.

  The stage apparatus 10 moves the workpiece W to be placed. The stage device 10 operates under operation control from the servo driver 20.

  The servo driver 20 controls the operation of the stage apparatus 10 using the movement command MV received every control cycle Tc. The servo driver 20 acquires the encoder value PVm of the motor included in the stage device 10 and outputs it to the controller 40. At this time, the servo driver 20 outputs the encoder value PVm to the controller 40 at the same cycle as the control cycle Tc.

  The stage device 10 and the servo driver 20 constitute a moving mechanism for moving the workpiece W.

  The visual sensor 30 images a region including the workpiece W placed on the stage device 10 and performs processing on the image obtained by the imaging, whereby a position of a specific point on the workpiece W (hereinafter, a measurement position PVv). Measure). The specific point is, for example, a mark marked on the workpiece W, a corner of the workpiece W, or the like.

  The visual sensor 30 includes an imaging unit 31 and an image processing unit 32. The imaging unit 31 performs an imaging process of capturing an image of a subject existing in the imaging field and generating image data, and images the workpiece W. The imaging unit 31 is a camera, for example. The imaging unit 31 performs imaging in accordance with imaging triggers TR1 and TR2 from the controller 40. The image processing unit 32 performs image analysis on the image data generated by the imaging unit 31 and measures the measurement position PVv.

  The controller 40 is a PLC (programmable logic controller), for example, and performs various FA controls. The controller 40 includes, for example, a first imaging command unit 41, a position determination unit 42, a feedback control unit 43, a stop control unit 44, a second imaging command unit 45, and a determination unit 46.

  The first imaging command unit 41 outputs an imaging trigger TR1 to the visual sensor 30 at a predetermined imaging cycle Tp. The imaging cycle Tp is set longer than the total time of the time required for the imaging processing by the imaging unit 31 and the time required for measurement of the measurement position PVv by the image processing unit 32, and is longer than the control cycle Tc.

  When receiving the stop signal SS from the stop control unit 44, the first imaging command unit 41 stops the output process of the imaging trigger TR1. When receiving the restart signal RS from the determination unit 46 in a state where the output process of the imaging trigger TR1 is stopped, the first imaging command unit 41 restarts the output process of the imaging trigger TR1.

  The position determination unit 42 calculates the estimated position PV of the workpiece W for each control cycle Tc based on the measurement position PVv measured for each imaging cycle Tp by the visual sensor 30 and the encoder value PVm output for each control cycle Tc. decide.

  The feedback control unit 43 uses the target position SP and the estimated position PV determined by the position determination unit 42 to update a movement command MV for adjusting the estimated position PV to the target position SV every control cycle Tc. Output to the driver 20. Feedback control unit 43 includes a subtraction unit 431 and a PID calculation unit 432.

  The subtraction unit 431 outputs a deviation (distance) | Lm1 | between the estimated position PV and the target position SV. The PID calculation unit 432 performs PID calculation so that the distance | Lm1 | converges to 0, and calculates a movement command MV for each control cycle Tc. The PID calculation unit 432 outputs a movement command MV to the servo driver 20. The movement command MV is, for example, a position command or a speed command.

  When receiving the stop signal SS from the stop control unit 44, the feedback control unit 43 stops updating the movement command MV. When the feedback control unit 43 receives the restart signal RS from the determination unit 46 while the update of the movement command MV is stopped, the feedback control unit 43 restarts the update of the movement command MV.

  The stop control unit 44 compares the distance | Lm1 | between the estimated position PV and the target position SV with a threshold Th1, and outputs a stop signal SS when the distance | Lm1 | is less than the threshold Th1. The stop control unit 44 stops the update of the movement command MV by the feedback control unit 43 by outputting a stop signal SS to the feedback control unit 43. Furthermore, the stop control unit 44 stops the output process of the imaging trigger TR1 by the first imaging command unit 41 by outputting a stop signal SS to the first imaging command unit 41.

  When the update of the movement command is stopped by the stop signal SS, the second imaging command unit 45 determines whether or not the movement of the work W accompanying the final movement command at the time of the update stop is completed. The second imaging command unit 45 outputs the imaging trigger TR2 to the visual sensor 30 after determining that the movement of the work W accompanying the final movement command is completed.

  The determination unit 46 determines whether or not the measurement position PVv from the image captured in accordance with the imaging trigger TR2 satisfies a predetermined condition. This condition is a condition for determining the end of positioning. The determination unit 46 determines that the positioning of the workpiece W is finished when the measurement position PVv satisfies a predetermined condition, and outputs an end signal FS. When the end signal FS is output, the controller 40 ends the movement control of the stage apparatus 10.

  The determination unit 46 outputs a restart signal RS to the first imaging command unit 41 and the feedback control unit 43 when the measurement position PVv does not satisfy a predetermined condition. When the restart signal RS is output, the first imaging command unit 41 resumes the output process of the imaging trigger TR1, and the feedback control unit 43 resumes the update of the movement command MV.

<Action and effect>
As described above, in the present embodiment, the feedback control unit 43 updates the movement command for adjusting the estimated position PV to the target position SP of the workpiece W for each control cycle Tc and outputs it to the servo driver 20. Thereby, the positioning according to the state of the workpiece | work W can be performed with the precision which can be visually recognized by the visual sensor 30. FIG. Therefore, robustness against disturbance is improved and positioning accuracy is improved.

  The estimated position PV is determined for each control period Tc based on an image captured by the visual sensor 30 for each imaging period Tp and an encoder value PVm that is position-related information from the stage apparatus 10. The imaging cycle Tp of the visual sensor 30 is longer than the control cycle Tc. Since the measurement position PVv is position information with a long update cycle and a delay, if feedback control is performed using the measurement position PVv instead of the estimated position PV, overshoot and vibration are likely to occur. The control gain cannot be increased too much. However, the estimated position PV is determined based on the encoder value PVm that is position-related information from the stage apparatus 10, and the gain in feedback control can be increased by using the estimated position PV, and the estimated position PV is set to the target position SP. Can approach high speed.

  However, there is a possibility that the workpiece W slightly moves due to the movement command after the distance | Lm1 | between the estimated position PV and the target position SP is less than the threshold Th1, and the position of the workpiece W moves away from the target position. Therefore, the stop control unit 44 stops the update of the movement command by the feedback control unit 43 when the distance | Lm1 | between the estimated position PV and the target position SP is less than the threshold Th1. When the update of the movement command is stopped, the second imaging command unit 45 determines whether or not the movement according to the final movement command at the time of the update stop is completed, and after determining that the movement according to the final movement command is completed The imaging trigger TR2 is output to the visual sensor 30. When the measurement position PVv from the image imaged in accordance with the imaging trigger TR2 satisfies a predetermined condition, the determination unit 46 determines to end the positioning of the workpiece W. Thereby, the workpiece W can be positioned with high accuracy.

  Since the responsiveness of the visual sensor 30 is low, the difference between the measurement position PVv of the work W obtained from the image captured by the visual sensor 30 and the current position of the moving work W tends to increase. On the other hand, the estimated position PV is determined based on the image captured at each imaging cycle Tp and the encoder value PVm output at each control cycle Tc. Therefore, the estimation error of the estimated position PV is smaller than the error between the measurement position PVv and the current position measured based only on the image captured at each imaging cycle Tp. As a result, the frequency at which the measurement position PVv does not satisfy the predetermined condition due to the movement according to the final movement command after the distance | Lm1 | between the estimated position PV and the target position SP becomes less than the threshold Th1 is low. Thereby, it can position at high speed.

  Thus, according to the control system of the present embodiment, the workpiece W can be positioned at high speed and with high accuracy.

§2 Specific example Next, an example of a control system according to the present embodiment will be described.

<2-1. Stage and Motor>
FIG. 2 is a perspective view showing an example of a stage apparatus constituting the control system 1 according to the present embodiment. In the example illustrated in FIG. 2, the stage apparatus 10 includes an X stage 11, a Y stage 13, a θ stage 15, and servo motors 12, 14, and 16. The X stage 11 moves along the X direction by driving the servo motor 12. The Y stage 13 moves along the Y direction by driving the servo motor 14. The θ stage 15 is rotated in the θ direction by driving the servo motor 16.

  Each of the servo motors 12, 14, 16 is provided with an encoder. The encoder detects the rotational position of the corresponding motor and outputs an encoder value PVm as a detection result.

<2-2. Hardware configuration of image processing unit>
FIG. 3 is a schematic diagram illustrating a hardware configuration of the image processing unit 32 configuring the control system 1 according to the present embodiment. The image processing unit 32 typically has a structure according to a general-purpose computer architecture, and implements various types of image processing as will be described later by the processor executing a preinstalled program.

  More specifically, the image processing unit 32 includes a processor 310 such as a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit), a RAM (Random Access Memory) 312, a display controller 314, a system controller 316, and the like. , An I / O (Input Output) controller 318, a hard disk 320, a camera interface 322, an input interface 324, a controller interface 326, a communication interface 328, and a memory card interface 330. These units are connected to each other so as to be capable of data communication with a system controller 316 as a center.

  The processor 310 exchanges programs (codes) and the like with the system controller 316 and executes them in a predetermined order, thereby realizing the target arithmetic processing.

  The system controller 316 is connected to the processor 310, the RAM 312, the display controller 314, and the I / O controller 318 via buses, and performs data exchange with each unit and the entire processing of the image processing unit 32. To manage.

  The RAM 312 is typically a volatile storage device such as a DRAM (Dynamic Random Access Memory), a program read from the hard disk 320, an image (image data) captured by the imaging unit 31, and an image corresponding to the image. Holds processing results and work data. The processing result for the image includes the exposure start time and the exposure end time when the image is captured, and the measurement position PVv.

  The display controller 314 is connected to the display unit 70, and outputs signals for displaying various information to the display unit 70 in accordance with internal commands from the system controller 316.

  The I / O controller 318 controls data exchange with a recording medium connected to the image processing unit 32 and an external device. More specifically, the I / O controller 318 is connected to the hard disk 320, the camera interface 322, the input interface 324, the controller interface 326, the communication interface 328, and the memory card interface 330.

  The hard disk 320 is typically a nonvolatile magnetic storage device, and stores various setting values in addition to programs executed by the processor 310.

  The camera interface 322 corresponds to an input unit that receives image data generated by shooting the workpiece W, and mediates data transmission between the processor 310 and the imaging unit 31. The camera interface 322 includes an image buffer for temporarily storing image data from the imaging unit 31.

  The input interface 324 mediates data transmission between the processor 310 and an input device such as a keyboard 334, a mouse, a touch panel, and a dedicated console.

  The controller interface 326 mediates data transmission between the processor 310 and the controller 40.

  The communication interface 328 mediates data transmission between the processor 310 and another personal computer or server device (not shown). The communication interface 328 typically includes Ethernet (registered trademark), USB (Universal Serial Bus), or the like.

  The memory card interface 330 mediates data transmission between the processor 310 and the recording medium 50.

<2-3. Controller hardware configuration>
FIG. 4 is a schematic diagram showing a hardware configuration of a controller constituting the control system according to the present embodiment. As shown in FIG. 4, the controller 40 includes a main control unit 410 and a plurality of servo units 422, 424, 426. The controller 40 according to the present embodiment includes the same number of servo units 422, 424, 426 as the servo motors 12, 14, 16 included in the stage device 10.

  The main control unit 410 governs overall control of the controller 40. The main control unit 410 is connected to the servo units 422, 424, and 426 via the internal bus 419, and exchanges data with each other. The servo units 422, 424, and 426 output control commands (typically drive pulses and the like) to the servo drivers 22, 24, and 26, respectively, in accordance with internal commands from the main control unit 410 and the like. The servo drivers 22, 24, and 26 are drivers that drive the connected servo motors 12, 14, and 16, respectively.

  The main control unit 410 includes a chip set 411, a processor 412, a nonvolatile memory 413, a main memory 414, a system clock 415, a memory card interface 416, a communication interface 417, and an internal bus controller 418. The chip set 411 and other components are coupled via various buses.

  The processor 412 and the chipset 411 typically have a configuration according to a general-purpose computer architecture. That is, the processor 412 interprets and executes instruction codes sequentially supplied from the chipset 411 according to the internal clock. The chip set 411 exchanges internal data with various connected components and generates instruction codes necessary for the processor 412. The system clock 415 generates a system clock having a predetermined period and provides it to the processor 412. The chip set 411 caches data obtained as a result of execution of arithmetic processing by the processor 412.

  The main control unit 410 has a nonvolatile memory 413 and a main memory 414 as storage means. The nonvolatile memory 413 holds data definition information, log information, and the like in addition to the OS and the control program 430 executed by the processor 412. The control program 430 is distributed while being stored in the recording medium 51 or the like. The main memory 414 is a volatile storage area, holds various programs to be executed by the processor 412, and is also used as a working memory when executing the various programs.

  The main control unit 410 has a communication interface 417 and an internal bus controller 418 as communication means. These communication circuits transmit and receive data. The communication interface 417 exchanges data with the visual sensor 30. The communication interface 417 receives from the visual sensor 30 the exposure start time and the exposure end time when capturing an image, and the measurement position PVv. The internal bus controller 418 controls data exchange through the internal bus 419. The internal bus controller 418 receives the encoder value PVm from the servo drivers 22, 24 and 26. The internal bus controller 418 includes a buffer memory 481, a DMA (Dynamic Memory Access) control circuit 482, and an internal bus control circuit 483.

  The memory card interface 416 connects the recording medium 51 detachably attached to the main control unit 410 and the processor 412. The recording medium 51 stores information such as a program by an electrical, magnetic, optical, mechanical, or chemical action so that the information such as a program recorded by a computer or other device or machine can be read. It is a medium to do. The recording medium 51 is distributed in a state where a control program 430 executed by the controller 40 is stored, and the memory card interface 416 reads the control program from the recording medium 51. The recording medium 51 is a general-purpose semiconductor storage device such as SD (Secure Digital), a magnetic recording medium such as a flexible disk, or an optical recording medium such as a CD-ROM (Compact Disk Read Only Memory). Become. Alternatively, a program downloaded from a distribution server or the like may be installed in the controller 40 via the communication interface 417.

<2-4. Second imaging command unit>
For example, the second imaging command unit 45 determines whether or not the movement of the workpiece W accompanying the final movement command is completed as follows.

  When the movement command MV is a position command, the second imaging command unit 45 compares the deviation (distance) | Lm2 | between the position command value and the actually measured position and the threshold value Th2 for each of the servo motors 12, 14, and 16. To do. The second imaging command unit 45 may acquire the measured positions from the encoder values PVm from the servo motors 12, 14, and 16, respectively. When the distance | Lm2 | between the position command value and the actually measured position is less than the threshold Th2 in all of the servo motors 12, 14, and 16, the second imaging command unit 45 has completed the movement of the workpiece W accompanying the final movement command. And the imaging trigger TR2 is output.

  When the movement command MV is a speed command, the second imaging command unit 45 may compare the rotation speed and the threshold value Th <b> 2 for each of the servo motors 12, 14, and 16. The second imaging command unit 45 may acquire the respective rotation speeds from the encoder values PVm from the servo motors 12, 14, 16. When the rotation speed is lower than the threshold Th2 in all of the servo motors 12, 14, 16, the second imaging command unit 45 determines that the movement of the workpiece W accompanying the final movement command is completed, and outputs the imaging trigger TR2. .

<2-5. Judgment part>
The determination unit 46 determines whether or not to end the positioning of the workpiece W depending on whether or not the measurement position PVv satisfies a predetermined condition. The condition is appropriately determined according to the accuracy required for positioning the workpiece W.

  For example, the predetermined condition is that the deviation (distance) | Lm3 | between the measurement position PVv and the target position SV is less than the threshold Th3. In this case, the determination unit 46 calculates the distance | Lm3 | between the measurement position PVv and the target position SV, and compares the calculated distance | Lm3 | with the threshold Th3. The determination unit 46 outputs the end signal FS when the distance | Lm3 | is less than the threshold Th3, and outputs the restart signal RS when the distance | Lm3 | is equal to or greater than the threshold Th3. The threshold value Th3 may be the same as or different from the threshold value Th1.

§3 Example of operation <3-1. Controller processing flow>
An example of the processing flow of the controller 40 will be described with reference to FIG. FIG. 5 is a flowchart illustrating an example of a process flow of the controller 40.

  First, the controller 40 initializes the estimated position PV and the encoder value PVm (step S1). Next, the first imaging command unit 41 starts output processing of the imaging trigger TR1 for each imaging cycle Tp (step S2). When the output of the measurement position PVv from the visual sensor 30 and the encoder value PVm from each of the servo drivers 22, 24, 26 is started, the position determination unit 42 determines the estimated position PV (step S3). Details of the process of determining the estimated position PV will be described later.

  Next, the feedback control unit 43 performs feedback control based on the estimated position PV and the target position SV (step S4). Specifically, the feedback control unit 43 calculates a movement command MV for adjusting the estimated position PV to the target position SV and outputs it to the servo drivers 22, 24, and 26.

  The stop control unit 44 compares the distance | Lm1 | between the estimated position PV and the target position SV with a threshold Th1, and determines whether the distance | Lm1 | is less than the threshold Th1 (step S5). If the distance | Lm1 | is not less than the threshold value Th1 (NO in step S5), the process returns to step S3. Thereby, step S3 and step S4 are repeatedly performed. As a result, the movement command MV is updated by feedback control, and the operation of the stage device 10 for adjusting the estimated position PV to the target position SV is continued. Steps S3 and S4 are executed every control cycle Tc.

  If the distance | Lm1 | is less than the threshold Th1 (YES in step S5), the stop control unit 44 outputs a stop signal SS to the feedback control unit 43 and the first imaging command unit 41. As a result, the feedback control unit 43 stops updating the movement command MV. Further, the first imaging command unit 41 stops the output process of the imaging trigger TR1 for each imaging cycle Tp (step S6).

  Next, the second imaging command unit 45 compares the distance | Lm2 | between the position command value indicated by the final movement command at the time of updating stop and the measured position and the threshold Th2, and the distance | Lm2 | is less than the threshold Th2. It is determined whether or not there is (step S7). If the distance | Lm2 | is not less than the threshold Th2 (NO in step S7), the process returns to step S7. If the distance | Lm2 | is less than the threshold Th2 (YES in step S7), the second imaging command unit 45 outputs the imaging trigger TR2 to the visual sensor 30 (step S8).

  Next, the determination unit 46 acquires the measurement position PVv measured from the image captured according to the imaging trigger TR2 from the visual sensor 30 (step S9). The determination unit 46 compares the distance | Lm3 | between the measurement position PVv and the target position SV and the threshold value Th3, and determines whether the distance | Lm3 | is less than the threshold value Th3 (step S10). When the distance | Lm3 | is not less than the threshold Th3 (NO in step S10), the restart signal RS is output from the determination unit 46, and the process returns to step S2. If the distance | Lm3 | is less than the threshold Th3 (YES in step S10), the determination unit 46 outputs an end signal FS and ends the positioning process (step S11).

  When the positioning process is completed, a predetermined process is performed on the positioned workpiece W. For example, when positioning the work W with respect to the exposure mask before the circuit pattern printing process (exposure process) on the work W that is a glass substrate, the controller 40 prints when the end signal FS is output from the determination unit 46. Drive control of the apparatus which performs processing.

<3-2. Estimated position determination process>
The position determination unit 42 calculates the estimated position PV by performing a process as shown in the flowchart of FIG. 6, for example. FIG. 6 is a flowchart showing the processing contents of the subroutine of the estimated position determination processing shown in FIG.

  The position determination unit 42 detects whether or not the measurement position PVv from the visual sensor 30 is obtained (step S21). If it is the time when the measurement position PVv is obtained (YES in step S21), the position determination unit 42 detects whether or not the measurement position PVv is a normal value (step S22). For example, the position determining unit 42 determines that the measured position PVv is a normal value if the measured position PVv is a value within a predetermined range. If the measurement position PVv is a normal value (YES in step S22), the position determination unit 42 receives an input of the measurement position PVv (step S23).

  When the position determination unit 42 receives the input of the measurement position PVv, the position determination unit 42 estimates the encoder value PVms at the imaging time that is the basis of calculation of the measurement position PVv (step S24). A specific method of this estimation will be described later. When the exposure time of the imaging unit 31 is long, the imaging time is, for example, an exposure start time (time when the shutter of the imaging unit 31 is opened) and an exposure end time (time when the shutter of the imaging unit 31 is closed). It is set by the middle time.

  The position determination unit 42 calculates the estimated position PV using the measurement position PVv and encoder value PVm at the same time and the encoder value PVms at the imaging time that is the calculation source of the measurement position PVv (step S25). Specifically, in step S25, the position determination unit 42 calculates the estimated position PV using the following (Equation 1).

PV = PVv + (PVm−PVms) (Formula 1)
The position determination unit 42 outputs the calculated estimated position PV to the feedback control unit 43 (S26). Further, the position determination unit 42 updates and stores the estimated position PV as the reference estimated position PVp and the encoder value PVm at this time as the reference encoder value PVmp.

  If it is time when the measurement position PVv from the visual sensor 30 is not obtained (NO in step S21), the position determination unit 42 detects whether or not the output of the measurement position PVv is one or more times (step S27). ). Further, if the measurement position PVv is not a normal value (NO in step S22), the position determination unit 42 similarly detects whether or not the output of the measurement position PVv is one or more times (step S27).

  If the output of the measurement position PVv is one or more times (YES in step S27), the position determination unit 42 calculates the estimated position PV using the encoder value PVm, the reference estimated position PVp, and the reference encoder value PVmp. (S28). Specifically, in step S28, the position determination unit 42 calculates the estimated position PV using the following (Expression 2).

PV = PVp + PVm−PVmp (Formula 2)
If the output of the measurement position PVv is not even once (NO in step S27), the position determination unit 42 maintains the estimated position PV as the initial value. After step S28 and if NO at step S27, the process proceeds to step S26. After step S26, the process returns to step S4 shown in FIG.

  By executing such processing, the controller 40 calculates the estimated position PV using the high-accuracy measurement position PVv at the time when the high-accuracy measurement position PVv by image processing is input. Positioning control can be realized. Here, the time interval at which the measurement position PVv is input is the imaging cycle Tp, and is longer than the control cycle Tc at which the encoder value PVm is input. However, between the input times of the measurement positions PVv adjacent on the time axis, the position determination unit 42 calculates the estimated position PV and performs position control for each input time of the encoder value PVm having a short input cycle. Thereby, positioning control with high accuracy and a short cycle becomes possible. Further, the position determination unit 42 performs processing using the above-described simple four arithmetic operations. Therefore, high-speed and high-accuracy positioning can be realized with a simple configuration and processing.

  Calculation of the measurement position PVv requires time for imaging by the visual sensor 30 and image processing. Therefore, the imaging cycle Tp is long. Even if the measurement position PVv is obtained at the calculation time tn of the estimated position PV, the measurement position PVv is based on the image captured at the imaging time tv1 past the calculation time tn, and the workpiece W at the imaging time tv1 Is calculated with high accuracy.

  The time (tn−tv1) has elapsed from the imaging time tv1 to the calculation time tn, and the workpiece W is moving. Therefore, the movement of the workpiece W must be corrected.

  Here, the encoder value PVm is updated at a control cycle Tc that is shorter than the imaging cycle Tp. Using this, the position determination unit 42 performs the calculation shown in (Equation 1). Specifically, the position determination unit 42 acquires the encoder value PVms at the imaging time tv1 and the encoder value PVm at the calculation time tn. The position determination unit 42 calculates the estimated position PV at the calculation time tn by adding the change ΔPVm (PVm−PVms) of the encoder value PVm for the time (tn−tv1) to the measurement position PVv. At this time, the estimated position PV becomes discontinuous at the calculation time tn. In this case, the time change of the estimated position PV can be smoothed by using a smoothing process (for example, moving averaging process) on the estimated position PV. More preferable.

  By using this processing, the estimated position PV reflects the position of the workpiece W at the calculation time tn with high accuracy. Therefore, highly accurate positioning control is possible.

  Further, the position determination unit 42 calculates the encoder value PVms at the imaging time using the following process. FIG. 7 is a flowchart showing the processing contents of a subroutine for estimation processing of the encoder value at the time of imaging shown in FIG.

  As illustrated in FIG. 7, the position determination unit 42 acquires an imaging time (S31). The position determination unit 42 acquires encoder values PVm at a plurality of times close to the imaging time (S32). The position determination unit 42 calculates an interpolation value of the encoder values PVm at a plurality of times and sets it as the encoder value PVms at the imaging time (S33). If the imaging time matches the encoder value calculation time, this encoder value may be used as it is.

  Specifically, the position determination unit 42 acquires the encoder value PVm (n) at the calculation time tn for calculating the estimated position PV. The position determination unit 42 acquires an imaging time tvi that is past the calculation time tn. The position determination unit 42 includes two times close to the imaging time tvi, for example, a past calculation time t (n−k) and a past calculation time t (n−k + 1) sandwiching the imaging time tvi on the time axis. Is detected.

  The position determination unit 42 acquires the encoder value PVm (nk) at the calculation time t (n−k) and the encoder value PVm (n−k + 1) at the calculation time t (n−k + 1). The past encoder values are stored in the storage unit of the controller 40 (for example, the nonvolatile memory 413 or the main memory 414 (see FIG. 3)).

  The position determination unit 42 calculates an encoder value PVms (ni) at the imaging time tvi by using an interpolation value of the encoder value PVm (n−k) and the encoder value PVm (n−k + 1). Specifically, the position determination unit 42 calculates the encoder value PVms (ni) at the imaging time tvi using the following (Equation 3).

PVms (ni) = PVm (n−k) + Kk * (PVm (n−k + 2) −PVm (n−k + 1)) (Expression 3)
Here, Kk is an interpolation coefficient. When the control cycle is Tc, the transmission delay time of the encoder value PVm is Ted, the transmission delay time of the imaging trigger TR1 is Tsd, and Tc−Ted ≦ Tsd <2Tc−Ted, the interpolation coefficient Kk is Calculated using Equation 4).

Kk = {Tsd- (Tc-Ted)} / Tc (Formula 4)
By using such a method for calculating the interpolation value, the encoder value PVms (ni) at the imaging time tvi can be calculated with high accuracy. As a result, the estimated position PV with higher accuracy can be calculated, and positioning control with higher accuracy becomes possible.

§4 Modification The second imaging command unit 45 may determine that the movement according to the final movement command is completed when the elapsed time after the stop signal SS is output from the stop control unit 44 exceeds the threshold Th4. . The threshold value Th4 is determined in advance so as to be longer than the time required to complete the movement according to the final movement command. For example, the time required to complete the movement according to the final movement command is confirmed by a preliminary experiment, and a time longer than the maximum value of the time is determined as the threshold Th4.

  The stop control unit 44, the second imaging command unit 45, and the determination unit 46 may be configured by a comparator circuit. For example, stop control unit 44 includes a comparator circuit that compares a voltage value corresponding to distance | Lm1 | with a voltage value corresponding to threshold value Th1. The comparator circuit outputs a stop signal SS that becomes active when the distance | Lm1 | is less than the threshold Th1. The second imaging command unit 45 includes a comparator circuit that compares a voltage value corresponding to the distance | Lm2 | and a voltage value corresponding to the threshold Th2. The comparator circuit outputs an imaging trigger TR2 that becomes active when the distance | Lm2 | is less than the threshold Th2. The determination unit 46 includes a comparator circuit that compares the voltage value corresponding to the distance | Lm3 | with the voltage value corresponding to the threshold Th3. The comparator circuit outputs an end signal FS that becomes active when the distance | Lm3 | is less than the threshold Th3, and outputs a restart signal RS that becomes active when the distance | Lm3 | is equal to or greater than the threshold Th3.

§5 Appendix As described above, the present embodiment and the modified example include the following disclosure.

(Configuration 1)
A control system (1) for an object (W),
A moving mechanism (10, 20) for moving the object (W);
A visual sensor (30) for imaging the object (W);
Based on the image captured by the visual sensor (30) for each first period and the position related information from the moving mechanism (10, 20), the target for each second period shorter than the first period. A position determining unit (42) for determining an estimated position of the object (W);
A feedback control unit (43) that updates a movement command for adjusting the estimated position to a target position of the object (W) every second cycle and outputs the movement command to the movement mechanism (10, 20);
A stop control unit (44) for stopping the update of the movement command by the feedback control unit (43) when a first deviation between the estimated position and the target position is less than a first threshold;
When the update of the movement command is stopped, it is determined whether the movement according to the final movement command is completed, and after determining that the movement according to the final movement command is completed, the imaging command is sent to the visual sensor (30). An imaging command section (45) for outputting
A control system (1) comprising: a determination unit that determines to end positioning of the object (W) when a measurement result from an image captured in accordance with the imaging command satisfies a predetermined condition.

(Configuration 2)
The control system (1) according to Configuration 1, wherein the feedback control unit (43) resumes the update of the movement command when the measurement result does not satisfy the predetermined condition.

(Configuration 3)
The imaging command unit (45) moves in accordance with the final movement command when a second deviation between a position command value indicated by the final movement command and a position indicated by the position related information is less than a second threshold value. The control system (1) according to Configuration 1 or 2, wherein it is determined that is completed.

(Configuration 4)
The control system according to Configuration 1 or 2, wherein the imaging command unit (45) determines that the movement according to the final movement command is completed when the speed indicated by the position-related information is less than a third threshold. 1).

(Configuration 5)
The imaging command unit (45) determines that the movement according to the final movement command is completed when the elapsed time since the update of the movement command is stopped by the stop control unit (44) exceeds a fourth threshold value. The control system (1) according to configuration 1 or 2.

(Configuration 6)
The measurement result indicates a measurement position of the object (W) measured from an image captured according to the imaging command,
The control system (1) according to any one of configurations 1 to 5, wherein the predetermined condition is a condition that a third deviation between the measurement position and the target position is less than a fifth threshold value.

(Configuration 7)
A control method in a control system (1) for an object (W),
The control system (1)
A moving mechanism (10, 20) for moving the object (W);
A visual sensor (30) for imaging the object (W),
The control method is:
Based on the image captured by the visual sensor (30) for each first period and the position related information from the moving mechanism (10, 20), the target for each second period shorter than the first period. Determining an estimated position of the object (W);
Updating a movement command for adjusting the estimated position to a target position of the object (W) every second period, and outputting it to the movement mechanism (10, 20);
Stopping the update of the movement command when a first deviation between the estimated position and the target position is less than a first threshold;
When the update of the movement command is stopped, it is determined whether the movement according to the final movement command is completed, and after determining that the movement according to the final movement command is completed, the imaging command is sent to the visual sensor (30). A step of outputting
And a step of determining that the positioning of the object (W) is to be ended when a measurement result from an image captured in response to the imaging command satisfies a predetermined condition.

(Configuration 8)
A program (430) for causing a computer to execute a control method in a control system (1) for an object (W),
The control system (1)
A moving mechanism (10, 20) for moving the object (W);
A visual sensor (30) for imaging the object (W),
The control method is:
Based on the image captured by the visual sensor (30) for each first period and the position related information from the moving mechanism (10, 20), the target for each second period shorter than the first period. Determining an estimated position of the object (W);
Updating a movement command for adjusting the estimated position to a target position of the object (W) every second period, and outputting it to the movement mechanism (10, 20);
Stopping the update of the movement command when a first deviation between the estimated position and the target position is less than a first threshold;
When the update of the movement command is stopped, it is determined whether the movement according to the final movement command is completed, and after determining that the movement according to the final movement command is completed, the imaging command is sent to the visual sensor (30). A step of outputting
And a step of determining that the positioning of the object (W) is to be ended when a measurement result from an image captured in response to the imaging command satisfies a predetermined condition.

  Each embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. In addition, the invention described in the embodiment and each modification is intended to be implemented alone or in combination as much as possible.

  DESCRIPTION OF SYMBOLS 1 Control system, 10 stage apparatus, 11, 13, 15 stage, 12, 14, 16 Servo motor, 20, 22, 24, 26 Servo driver, 30 Visual sensor, 31 Imaging part, 32 Image processing part, 40 Controller, 41 First imaging command unit, 42 Position determination unit, 43 Feedback control unit, 44 Stop control unit, 45 Second imaging command unit, 46 Determination unit, 50, 51 Recording medium, 70 Display unit, 310, 412 Processor, 312 RAM, 314 Display Controller, 316 System Controller, 318 I / O Controller, 320 Hard Disk, 322 Camera Interface, 324 Input Interface, 326 Controller Interface, 328, 417 Communication Interface, 330, 416 Memory Card Interface, 334 keyboard, 410 main control unit, 411 chipset, 413 non-volatile memory, 414 main memory, 415 system clock, 418 internal bus controller, 419 internal bus, 422, 424, 426 servo unit, 430 control program, 431 Subtraction unit, 432 PID operation unit, 481 buffer memory, 482 control circuit, 483 internal bus control circuit, W work.

Claims (8)

An object control system,
A moving mechanism for moving the object;
A visual sensor for imaging the object;
A position for determining an estimated position of the object for each second period shorter than the first period, based on an image captured by the visual sensor for each first period and position-related information from the moving mechanism. A decision unit;
A feedback control unit that updates a movement command for adjusting the estimated position to a target position of the object every second period and outputs the movement command to the movement mechanism;
A stop control unit that stops updating the movement command by the feedback control unit when a first deviation between the estimated position and the target position is less than a first threshold;
When updating of the movement command is stopped, it is determined whether or not the movement according to the final movement command is completed, and after determining that the movement according to the final movement command is completed, the imaging command is output to the visual sensor. An imaging command section;
A control system comprising: a determination unit that determines to end positioning of the object when a measurement result from an image captured in accordance with the imaging command satisfies a predetermined condition.   The control system according to claim 1, wherein the feedback control unit resumes updating the movement command when the measurement result does not satisfy the predetermined condition.   When the second deviation between the position command value indicated by the final movement command and the position indicated by the position related information is less than a second threshold, the imaging command unit has completed the movement according to the final movement command The control system according to claim 1 or 2, wherein   The control system according to claim 1, wherein the imaging command unit determines that the movement according to the final movement command is completed when a speed indicated by the position related information is less than a third threshold value.   The imaging command unit determines that the movement according to the final movement command is completed when an elapsed time from when the update of the movement command is stopped by the stop control unit exceeds a fourth threshold value. 2. The control system according to 2. The measurement result indicates a measurement position of the object measured from an image captured according to the imaging command,
The control system according to any one of claims 1 to 5, wherein the predetermined condition is a condition that a third deviation between the measurement position and the target position is less than a fifth threshold value. A control method in an object control system, comprising:
The control system is
A moving mechanism for moving the object;
A visual sensor for imaging the object,
The control method is:
Determining an estimated position of the object for each second period shorter than the first period, based on an image captured by the visual sensor for each first period and position-related information from the moving mechanism. When,
Updating a movement command for adjusting the estimated position to a target position of the object every second period and outputting the movement command to the movement mechanism;
Stopping the update of the movement command when a first deviation between the estimated position and the target position is less than a first threshold;
When updating of the movement command is stopped, it is determined whether or not the movement according to the final movement command is completed, and after determining that the movement according to the final movement command is completed, the imaging command is output to the visual sensor. Steps,
And determining to end positioning of the object when a measurement result from an image imaged in accordance with the imaging command satisfies a predetermined condition. A program for causing a computer to execute a control method in an object control system,
The control system is
A moving mechanism for moving the object;
A visual sensor for imaging the object,
The control method is:
Determining an estimated position of the object for each second period shorter than the first period, based on an image captured by the visual sensor for each first period and position-related information from the moving mechanism. When,
Updating a movement command for adjusting the estimated position to a target position of the object every second period and outputting the movement command to the movement mechanism;
Stopping the update of the movement command when a first deviation between the estimated position and the target position is less than a first threshold;
When updating of the movement command is stopped, it is determined whether or not the movement according to the final movement command is completed, and after determining that the movement according to the final movement command is completed, the imaging command is output to the visual sensor. Steps,
And a step of determining that the positioning of the object is to be terminated when a measurement result from an image captured in response to the imaging command satisfies a predetermined condition.

Images