JP2019215634A - Control system, control unit, and program - Google Patents

Abstract

To provide a control system that can prevent a reduction in the accuracy of determination of the position of an object.SOLUTION: A control system comprises: a visual sensor; a movement control unit; an estimation unit; and an imaging control unit. The estimation unit estimates the speed of movement of a feature portion at a next imaging scheduled timing, on the basis of the latest position of the feature portion specified by the visual sensor from an image picked up at the latest imaging timing, and reference information including at least one of information from a movement mechanism and information generated by the movement control unit. The imaging control unit controls the visual sensor to pick up an image at the imaging scheduled timing when the movement speed is less than a threshold, and not to pick up an image at the imaging scheduled timing when the movement speed exceeds the threshold.SELECTED DRAWING: Figure 6

Description

  The present technology relates to a control system, a control device, and a program for positioning an object.

  In FA (Factory Automation), various technologies (positioning technology) for adjusting the position of an object to a target position have been put to practical use. At this time, as a method of measuring the deviation of the position of the object from the target position, there is a method of using an image obtained by imaging the object.

  Japanese Patent Laying-Open No. 2014-203365 (Patent Literature 1) discloses that an image of an object is captured while moving a moving mechanism that changes the position of the object, image data is acquired, and the position of a characteristic portion included in the image data is acquired. A control system for positioning an object at a target position based on the object is disclosed.

JP 2014-203365 A

  According to the technique disclosed in Patent Document 1, the position of the characteristic portion is specified using image data obtained by imaging a moving target, so that the positioning can be speeded up. However, image blur occurs because the moving target is imaged. When the position of the characteristic portion is specified using an image with a large image blur amount, the position accuracy of the characteristic portion is reduced. For this reason, the positioning accuracy of the target object decreases.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a control system, a control device, and a program that can suppress a decrease in positioning accuracy of an object.

  According to an example of the present disclosure, a control system that controls a moving mechanism that moves an object to position the object includes a visual sensor, a movement control unit, an estimation unit, and an imaging control unit. The visual sensor acquires an image by imaging the object at each imaging timing, and specifies the position of a characteristic portion of the object based on the image. The movement control unit controls the movement mechanism based on the position of the characteristic portion specified by the visual sensor so that the position of the target object approaches the target position. The estimating unit includes the latest position of the characteristic portion specified by the visual sensor from the image captured at the latest imaging timing, and reference information including at least one of the information from the moving mechanism and the information generated by the moving control unit. , The moving speed of the characteristic portion at the next scheduled imaging timing is estimated. The imaging control unit controls the visual sensor so that the imaging is performed at the scheduled imaging timing when the moving speed is lower than the threshold, and is not performed at the scheduled imaging timing when the moving speed exceeds the threshold.

  According to the present disclosure, it is possible to avoid capturing an image having a large image blurring amount, and to suppress a decrease in positioning accuracy due to the image.

  According to an example of the present disclosure, the moving mechanism includes a motor driven to move the object. The reference information includes information indicating the driving amount of the motor from the latest imaging timing.

  The information indicating the driving amount of the motor from the latest imaging timing directly indicates the moving amount of the moving mechanism from the latest imaging timing. Therefore, according to this disclosure, the estimating unit can accurately estimate the moving speed of the characteristic portion.

  According to an example of the present disclosure, the movement control unit generates a movement command for the movement mechanism in each control cycle. The reference information includes information indicating a movement command generated by the movement control unit after the latest imaging timing.

  The movement command is a command for moving the moving mechanism, and is directly related to the movement of the moving mechanism. Therefore, according to this disclosure, the estimating unit can accurately estimate the moving speed of the characteristic portion.

  According to an example of the present disclosure, the movement control unit determines the target trajectory of the moving mechanism based on the latest position, and controls the moving mechanism to move according to the determined target trajectory. The reference information includes information indicating the target trajectory.

  The target trajectory indicates a trajectory to be moved by the moving mechanism, and is directly related to the movement of the moving mechanism. Therefore, according to this disclosure, the estimating unit can accurately estimate the moving speed of the characteristic portion.

  According to an example of the present disclosure, the control device obtains an image by capturing an image of the moving object that moves the object, and identifies a position of a characteristic portion of the object based on the image. The visual sensor is controlled to position the object. The control device includes a movement control unit, an estimation unit, and an imaging control unit. The movement control unit controls the movement mechanism based on the position of the characteristic portion specified by the visual sensor so that the position of the target object approaches the target position. The estimating unit includes the latest position of the characteristic portion specified by the visual sensor from the image captured at the latest imaging timing, and reference information including at least one of the information from the moving mechanism and the information generated by the moving control unit. , The moving speed of the characteristic portion at the next scheduled imaging timing is estimated. The imaging control unit controls the visual sensor so that the imaging is performed at the scheduled imaging timing when the moving speed is lower than the threshold, and is not performed at the scheduled imaging timing when the moving speed exceeds the threshold.

  According to an example of the present disclosure, a program for controlling a moving mechanism that moves an object and supporting a control system that positions the object causes a computer to execute first to third steps. The control system includes a visual sensor for acquiring an image by capturing an image of the object, and identifying a position of a characteristic portion of the object based on the image. The first step is a step of controlling the moving mechanism based on the position of the characteristic portion specified by the visual sensor so that the position of the target object approaches the target position. The second step is a reference including at least one of the latest position of the characteristic portion specified by the visual sensor from the image captured at the latest imaging timing, information from the moving mechanism, and information generated by the controlling step. This is a step of estimating the moving speed of the characteristic portion at the next scheduled imaging timing based on the information. The third step is a step of controlling the visual sensor so that the image is captured at the scheduled imaging timing when the moving speed is lower than the threshold, and not captured at the scheduled imaging timing when the moving speed exceeds the threshold.

  According to these disclosures, it is possible to avoid capturing an image having a large image blurring amount, and to suppress a decrease in positioning accuracy due to the image.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the positioning accuracy of an object can be suppressed.

FIG. 1 is a schematic diagram illustrating an overall configuration of a control system according to the present embodiment. FIG. 2 is a schematic diagram illustrating a hardware configuration of an image processing apparatus included in the control system according to the present embodiment. FIG. 2 is a schematic diagram illustrating a hardware configuration of a motion controller included in the control system according to the embodiment. FIG. 2 is a block diagram illustrating a functional configuration of the control system illustrated in FIG. 1. FIG. 4 is a diagram illustrating a method for estimating a movement amount of a work from an imaging timing to a first intermediate timing. It is a flowchart which shows an example of the flow of the positioning process of a control system. 9 is a flowchart illustrating an example of a flow of a control process of a moving mechanism by a movement control unit. FIG. 9 is a diagram illustrating a method for estimating moving speeds Va and Vb in a first modification. FIG. 13 is a block diagram illustrating a functional configuration of a control system 1A according to a third modification. It is a figure showing an example of target trajectories TGX, TGY, and TGθ. 9 is a flowchart illustrating a flow of a process in a target trajectory determination unit.

  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 First, an application example of the control system according to the present embodiment will be described. FIG. 1 is a schematic diagram illustrating an overall configuration of a control system 1 according to the present embodiment. The control system 1 shown in FIG. 1 performs alignment using image processing. The alignment typically means a process of arranging an object (hereinafter, also referred to as “work”) at an original position of a production line in a manufacturing process of an industrial product or the like. As an example of such alignment, the control system 1 controls the positioning of the work 2 with respect to the exposure mask 4 before the circuit pattern is printed on the work 2 which is a glass substrate in a liquid crystal panel production line. The workpiece 2 is provided with marks 5a and 5b, which are characteristic portions for positioning, at predetermined positions. The control system 1 captures the marks 5a and 5b provided on the work 2, and performs image processing on the image obtained by the imaging, thereby realizing the positioning of the work 2.

  The control system 1 includes a moving mechanism 100, a driver unit 200, a visual sensor 300, and a motion controller 400.

  The moving mechanism 100 moves the work 2. The moving mechanism 100 may have any degree of freedom as long as the mechanism can arrange the work 2 at the target position. The moving mechanism 100 is, for example, an XYθ stage that can apply horizontal translational movement and rotational movement to the work 2.

  The moving mechanism 100 of the example shown in FIG. 1 includes an X stage 110X, a Y stage 110Y, a θ stage 110θ, and servomotors 120X, 120Y, 120θ. In the example shown in FIG. 1, each of the servomotors 120X, 120Y, and 120θ is constituted by a rotary motor. The servo motor 120X translates and drives the X stage 110X along the X-axis direction. The servo motor 120Y translates and drives the Y stage 110Y along the Y-axis direction. The servo motor 120θ drives the θ stage 110θ to rotate about an axis parallel to the Z axis.

  Driver unit 200 performs feedback control on moving mechanism 100 according to a moving command received at each control cycle Ts. As shown in FIG. 1, the driver unit 200 includes servo drivers 200X, 200Y, and 200θ. Servo driver 200X performs feedback control on servo motor 120X such that the movement amount of X stage 110X approaches the movement command. The servo driver 200Y performs feedback control on the servomotor 120Y so that the movement amount of the Y stage 110Y approaches the movement command. The servo driver 200θ performs feedback control on the servomotor 120θ so that the movement amount of the θ stage 110θ approaches the movement command.

  The visual sensor 300 acquires an image by imaging the work 2 at each imaging timing, and specifies the positions of the marks 5a and 5b of the work 2 based on the image. The imaging timing is determined by a predetermined imaging cycle Tb. The visual sensor 300 performs image processing on one or more cameras (cameras 302a and 302b in the example of FIG. 1) and the images captured by the cameras 302a and 302b, thereby forming marks 5a and 5b included in the images. And an image processing device 304 for specifying the position of the image.

  The motion controller 400 is, for example, a PLC (programmable logic controller), and performs various FA controls. The motion controller 400, which is a control device, controls the moving mechanism 100 based on the positions of the marks 5a and 5b specified by the visual sensor 300 so that the position of the work 2 approaches the target position. Specifically, the motion controller 400 generates a movement command for bringing the position of the work 2 closer to the target position for each control cycle Ts, and outputs the generated movement command to the driver unit 200.

  The motion controller 400 converts the latest positions of the marks 5a and 5b specified by the visual sensor 300 from the image captured at the latest imaging timing and a movement command that is information generated when controlling the moving mechanism 100. Based on this, the moving speed of the marks 5a and 5b at the next scheduled imaging timing of the visual sensor 300 is estimated.

  The motion controller 400 controls the visual sensor 300 so that an image is captured at the scheduled imaging timing when the estimated moving speed is lower than the threshold, and not captured at the scheduled imaging timing when the estimated moving speed exceeds the threshold.

  Accordingly, it is possible to avoid capturing an image having a large image blurring amount, and to suppress a decrease in positioning accuracy due to the image.

§2 Specific Example Next, a specific example of the control system 1 according to the present embodiment will be described.

<2-1. Hardware configuration of image processing device>
FIG. 2 is a schematic diagram illustrating a hardware configuration of an image processing apparatus included in the control system according to the present embodiment. Referring to FIG. 2, image processing apparatus 304 typically has a structure according to a general-purpose computer architecture, and executes various programs described below by executing a program installed in advance by a processor. Implement image processing.

  More specifically, the image processing device 304 includes a processor 310 such as a CPU (Central Processing Unit) and an MPU (Micro-Processing Unit), a RAM (Random Access Memory) 312, a display controller 314, and a system controller 316. , An I / O (Input Output) controller 318, a hard disk 320, a camera interface 322, an input interface 324, a motion controller interface 326, a communication interface 328, and a memory card interface 330. These units are connected to each other so as to enable data communication with the system controller 316 at the 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 intended 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, respectively, exchanges data with each unit, and performs processing of the entire image processing apparatus 304. Govern

  The RAM 312 is typically a volatile storage device such as a DRAM (Dynamic Random Access Memory), and includes programs read from the hard disk 320, images (image data) acquired by the cameras 302a and 302b, images , And the work data, etc. are retained.

  The display controller 314 is connected to the display unit 332, and outputs a signal for displaying various information to the display unit 332 according to an internal command from the system controller 316.

  The I / O controller 318 controls data exchange between a recording medium connected to the image processing apparatus 304 and an external device. More specifically, the I / O controller 318 is connected to the hard disk 320, camera interface 322, input interface 324, motion controller interface 326, communication interface 328, and memory card interface 330.

  The hard disk 320 is typically a nonvolatile magnetic storage device, and stores various setting values in addition to the control program 350 executed by the processor 310. The control program 350 installed on the hard disk 320 is distributed while being stored in a memory card 336 or the like. Instead of the hard disk 320, a semiconductor storage device such as a flash memory or an optical storage device such as a DVD-RAM (Digital Versatile Disk Random Access Memory) may be employed.

  The camera interface 322 corresponds to an input unit that receives image data generated by photographing a workpiece, and mediates data transmission between the processor 310 and the cameras 302a and 302b. The camera interface 322 includes image buffers 322a and 322b for temporarily storing image data from the cameras 302a and 302b, respectively. Although a single image buffer that can be shared between cameras may be provided for a plurality of cameras, it is preferable to independently arrange a plurality of cameras in association with each camera in order to speed up processing.

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

  Motion controller interface 326 mediates data transmission between processor 310 and motion controller 400.

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

  The memory card interface 330 mediates data transmission between the processor 310 and the memory card 336 as a recording medium. The memory card 336 distributes the control program 350 executed by the image processing device 304 in a stored state, and the memory card interface 330 reads the control program from the memory card 336. The memory card 336 includes a general-purpose semiconductor storage device such as SD (Secure Digital), a magnetic recording medium such as a flexible disk (Flexible Disk), and 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 image processing device 304 via the communication interface 328.

  When using a computer having a structure according to the general-purpose computer architecture as described above, an OS for providing basic functions of the computer in addition to an application for providing functions according to the present embodiment (Operating System) may be installed. In this case, the control program according to the present embodiment executes a process by calling necessary modules in a predetermined order and / or timing among program modules provided as a part of the OS. Is also good.

  Further, the control program according to the present embodiment may be provided by being incorporated in a part of another program. Even in such a case, the program itself does not include a module included in another program to be combined as described above, and the process is executed in cooperation with the other program. That is, the control program according to the present embodiment may be a form incorporated in such another program.

  Alternatively, part or all of the functions provided by executing the control program may be implemented as a dedicated hardware circuit.

<2-2. Hardware Configuration of Motion Controller>
FIG. 3 is a schematic diagram illustrating a hardware configuration of the motion controller 400 included in the control system according to the embodiment. The motion controller 400 includes a chipset 412, a processor 414, a nonvolatile memory 416, a main memory 418, a system clock 420, a memory card interface 422, a communication interface 428, an internal bus controller 430, and a field bus controller. 438. The chipset 412 and other components are respectively connected via various buses.

  The processor 414 and the chipset 412 typically have a configuration according to a general-purpose computer architecture. That is, the processor 414 interprets and executes the instruction codes sequentially supplied from the chipset 412 according to the internal clock. The chipset 412 exchanges internal data with various connected components and generates an instruction code necessary for the processor 414. The system clock 420 generates a system clock having a predetermined cycle and provides the system clock to the processor 414. The chip set 412 has a function of caching data and the like obtained as a result of execution of arithmetic processing by the processor 414.

  The motion controller 400 has a nonvolatile memory 416 and a main memory 418 as storage means. The non-volatile memory 416 non-volatilely stores data definition information, log information, and the like, in addition to the control program 440 executed by the processor 414. The control program 440 is distributed while being stored in the recording medium 424 or the like. The main memory 418 is a volatile storage area that holds various programs to be executed by the processor 414 and is also used as a working memory when executing various programs.

  The motion controller 400 has a communication interface 428 and an internal bus controller 430 as communication means. These communication circuits transmit and receive data.

  The communication interface 428 exchanges data with the image processing device 304. The internal bus controller 430 controls data exchange. More specifically, the internal bus controller 430 includes a buffer memory 436, a DMA (Dynamic Memory Access) control circuit 432, and an internal bus control circuit 434.

  The memory card interface 422 connects the recording medium 424 detachable to the motion controller 400 and the processor 414.

  The fieldbus controller 438 is a communication interface for connecting to a field network. The motion controller 400 is connected to the servo drivers 200X, 200Y, 200θ via the fieldbus controller 438. For the field network, for example, EtherCAT (registered trademark), EtherNet / IP (registered trademark), CompoNet (registered trademark), or the like is employed.

<2-3. Functional Configuration of Image Processing Device>
FIG. 4 is a block diagram showing a functional configuration of the control system shown in FIG. As shown in FIG. 4, the image processing device 304 includes an image acquisition unit 32 and a position identification unit 34.

  Upon receiving the imaging trigger TR from the motion controller 400, the image acquiring unit 32 controls the cameras 302a and 302b to capture an image, and acquires an image of a predetermined size from the cameras 302a and 302b.

  The position specifying unit 34 specifies the position of the mark 5a (hereinafter, referred to as “measurement position PSa”) included in the image captured by the camera 302a. The position specifying unit 34 specifies the position of the mark 5b (hereinafter, referred to as “measurement position PSb”) included in the image captured by the camera 302b. The position specifying unit 34 recognizes the marks 5a and 5b from the image using a known pattern recognition technique, and measures the coordinates of the recognized marks 5a and 5b. The coordinates are indicated in the local coordinate system of each of the cameras 302a and 302b. The position specifying unit 34 outputs the coordinates of the measured position PSa of the specified mark 5a and the coordinates of the measured position PSb of the specified mark 5b to the motion controller 400.

<2-4. Functional Configuration of Motion Controller>
As illustrated in FIG. 4, the motion controller 400 includes a movement control unit 41, an estimation unit 45, and an imaging control unit 46. The movement control unit 41, the estimation unit 45, and the imaging control unit 46 are realized by the processor 414 illustrated in FIG.

  Further, as shown in FIG. 4, the moving mechanism 100 includes an encoder 130. The encoder 130 generates a pulse signal corresponding to the amount of movement of each of the servomotors 120X, 120Y, 120θ. Encoder 130 counts the number of pulses included in the pulse signal corresponding to servo motor 120X, and measures the translation amount of X stage 110X in the X direction from the initial position as encoder value PVmX. The count value of the number of pulses and the movement amount are related by a predetermined coefficient. Therefore, the encoder 130 can measure the movement amount by multiplying the count value of the number of pulses by the coefficient. Similarly, encoder 130 measures the translation amount of Y stage 110Y in the Y direction from the initial position as encoder value PVmY, and measures the rotational movement amount of θ stage 110θ from the initial position as encoder value PVmθ. The encoder 130 measures and outputs the encoder values PVmX, PVmY, PVmθ at the same cycle as the control cycle Ts.

<2-4-1. Movement control section>
The movement control unit 41 moves the moving mechanism 100 based on the latest measurement position PSa of the mark 5a and the latest measurement position PSb of the mark 5b specified by the visual sensor 300 such that the position of the work 2 approaches the target position SP. Control.

  The target position SP of the work 2 is determined in advance for each production process. For example, the midpoint between the mark 5a and the mark 5b is located at a predetermined coordinate, and an angle between a straight line connecting the mark 5a and the mark 5b and the X axis or the Y axis is a predetermined angle. Such a position of the work 2 is set as the target position SP.

  Alternatively, the cameras 302a and 302b may image two target marks provided on the exposure mask 4 (see FIG. 1) together with the marks 5a and 5b of the work 2. In this case, the target position SP is set according to the positions of the two target marks included in the captured image. For example, the position of the work 2 where the mark 5a matches one of the two target marks and the mark 5b matches the other of the two target marks is set as the target position SP.

  The movement control unit 41 generates a movement command for bringing the position of the work 2 closer to the target position SP based on the latest measurement position PSa of the mark 5a and the latest measurement position PSb of the mark 5b specified by the visual sensor 300. I do.

  The cycle at which the measurement positions PSa and PSb are specified is at least the imaging cycle Tb. On the other hand, the movement command is generated for each control cycle Ts. As an example, the imaging cycle Tb is, for example, about 60 ms, and the control cycle Ts is, for example, 1 ms. Thus, the imaging cycle Tb is longer than the control cycle Ts. Therefore, if the moving mechanism 100 is controlled using only the measurement positions PSa and PSb specified by the visual sensor 300, overshoot and vibration are likely to occur. In order to avoid such overshoot and vibration, the movement control unit 41 determines the estimated position PV of the work 2 using the measured positions PSa and PSb and the encoder values PVmX, PVmY and PVmθ, and sets the estimated position PV as the estimated position PV. A control command is generated based on the control command. The encoder values PVmX, PVmY, PVmθ detected in the past are stored in the storage unit of the motion controller 400 (for example, the nonvolatile memory 416 or the main memory 418 (see FIG. 3)).

  As shown in FIG. 4, the movement control unit 41 includes a position determination unit 42, a subtraction unit 43, and a calculation unit 44.

  The position determination unit 42 calculates the estimated position PV of the work 2 based on the latest measurement position PSa of the mark 5a and the latest measurement position PSb of the mark 5b specified by the visual sensor 300 and the encoder values PVmX, PVmY, PVmθ. It is determined for each control cycle Ts. Details of the method of determining the estimated position PV will be described in an operation example described later.

  The subtraction unit 43 outputs a deviation of the estimated position PV from the target position SP. The calculation unit 44 performs calculations (for example, P calculation, PID calculation, and the like) so that the deviation of the estimated position PV from the target position SP converges to 0, and calculates the movement commands MVX, MVY, and MVθ for each control cycle Ts. The movement command MVX is a movement command for the X stage 110X. The movement command MVY is a movement command for the Y stage 110Y. The movement command MVθ is a movement command for the θ stage 110θ. The calculation unit 44 outputs the calculated movement commands MVX, MVY, MVθ to the servo drivers 200X, 200Y, 200θ, respectively. The movement commands MVX, MVY, MVθ are position commands or speed commands.

<2-4-2. Estimation part>
The estimating unit 45 calculates the moving speed of the mark 5a on the image at the next scheduled imaging timing tk based on the latest measured positions PSa and PSb and the moving commands MVX, MVY and MVθ generated by the moving control unit 41. Va and the moving speed Vb of the mark 5b are estimated. The scheduled imaging timing tk is determined in advance according to the imaging cycle Tb. The estimating unit 45 estimates the moving velocities Va and Vb at the first intermediate timing tm1 that is q times (q is an integer of 1 or more) the control cycle Ts before the scheduled imaging timing tk. Q is predetermined so that q times the control cycle Ts is sufficiently smaller than the imaging cycle Tb. q is 1, 2 or 3, for example. Hereinafter, a specific processing method of the estimation unit 45 will be described.

  First, the estimation unit 45 calculates the moving amount Δp1 of the work 2 from the latest imaging timing t (k−1) at which the visual sensor 300 images the work 2 to the first intermediate timing tm1 = (ΔX1, ΔY1, Δθ1). Is estimated. ΔX1 indicates the translation amount of the X stage 110X in the X direction. ΔY1 indicates the translation amount of the Y stage 110Y in the Y direction. Δθ1 indicates the amount of rotational movement of the θ stage 110θ.

  Note that the period from the imaging timing t (k−1) to the next scheduled imaging timing tk may coincide with the imaging period Tb, or may coincide with a period that is an integral multiple of 2 or more of the imaging period Tb. . This is because the visual sensor 300 may be controlled so as to stop imaging at the scheduled imaging timing.

  FIG. 5 is a diagram illustrating a method for estimating the movement amount of the work 2 from the imaging timing t (k−1) to the first intermediate timing tm1. As shown in FIG. 5, the estimating unit 45 calculates the moving amount based on the encoder value PVm (k-1) at the imaging timing t (k-1) and the encoder value PVm (m1) at the first intermediate timing tm1. Estimate Δp1. Note that PVm (i) at the timing ti is represented by (PVmθ (i), PVmX (i), PVmY (i)). PVmθ (i), PVmX (i), PVmY (i) are encoder values PVmθ, PVmX, PVmY output from the encoder 130 at the timing ti, respectively. Alternatively, when the timing ti is different from the detection time of the encoder 130, PVmX (i) is an interpolation value of the encoder value PVmX output from the encoder 130 at two detection times close to the timing ti. Similarly, PVmY (j) is an interpolation value of the encoder value PVmY output from the encoder 130 at two detection times close to the time tj. PVmθ (j) is an interpolation value of the encoder value PVmθ output from the encoder 130 at two detection times close to the time tj. The method of calculating the interpolation value will be described later.

  The estimation unit 45 calculates a difference between the encoder value PVm (k-1) at the imaging timing t (k-1) and the encoder value PVm (m1) at the first intermediate timing tm from the imaging timing t (k-1). It is estimated as the movement amount Δp1 of the work 2 until one intermediate timing tm1. That is, the estimation unit 45 estimates the movement amount Δp1 according to the following equation (1).

Δp1 = (ΔX1, ΔY1, Δθ1)
= (PVmX (m1) -PVmX (k-1), PVmY (m1) -PVmY (k-1), PVmθ (m1) -PVmθ (k-1)) Expression (1).

  Next, the estimating unit 45 estimates the position of the mark 5a (hereinafter, referred to as “estimated position PM1a”) and the position of the mark 5b (hereinafter, referred to as “estimated position PM1b”) at the first intermediate timing tm1. First, a method of estimating the estimated position PM1a will be described.

  The estimating unit 45 converts the coordinates of the measurement position PSa (the local coordinate system of the camera 302a) received from the image processing device 304 into the coordinates of the world coordinate system (the mechanical coordinate system of the moving mechanism 100). The estimating unit 45 obtains the XY coordinates (xsa, ysa) of the measurement position PSa in the world coordinate system using the first calibration data that associates the local coordinate system of the camera 302a with the world coordinate system.

  The estimating unit 45 obtains the coordinates of the estimated position PM1a in the world coordinate system using a conversion formula from the measured position PSa when the work 2 moves by the movement amount Δp1 = (ΔX1, ΔY1, Δθ1) to the estimated position PM1a. . The conversion equation is shown in the following equation (2).

Sa ′ = T (Ra (Sa)) Equation (2)
In the equation (2), Sa represents (xsa, ysa) ^T which is a transposed matrix of the X coordinate xsa and the Y coordinate ysa of the measurement position PSa in the world coordinate system. Ra () indicates a conversion formula corresponding to the rotational movement, and is based on the distance between the rotational center of the θ stage 110θ and the measurement position PSa and the rotational movement amount of the θ stage 110θ from the imaging timing t (k−1). Is determined. Here, Δθ1 is used as the amount of rotational movement. T () indicates a conversion equation corresponding to the translation, and is determined according to the translation amount of the X stage 110X and the Y stage 110Y from the imaging timing t (k−1). Here, ΔX1 and ΔY1 are used as the translation amounts. Sa ′ indicates the transposed matrix of the X coordinate and the Y coordinate of the position of the mark 5a in the world coordinate system when the work 2 is moved by the movement amount Δp1. Here, Sa ′ indicates (xm1a, ym1a) ^T which is a transposed matrix of the X coordinate xm1a and the Y coordinate ym1a of the estimated position PM1a.

  The estimating unit 45 uses the first calibration data to inversely transform the coordinates of the estimated position PM1a in the world coordinate system into coordinates in the local coordinate system corresponding to the camera 302a. Thereby, the estimating unit 45 can obtain the coordinates of the estimated position PM1a in the local coordinate system.

  By the same method, the estimation unit 45 predicts the estimated position PM1b of the mark 5b at the first intermediate timing tm1. That is, the estimation unit 45 converts the coordinates of the measurement position PSb (the local coordinate system of the camera 302b) received from the image processing device 304 into the coordinates of the world coordinate system. The estimating unit 45 obtains the XY coordinates (xsb, ysb) of the measurement position PSb in the world coordinate system using the second calibration data that associates the local coordinate system of the camera 302b with the world coordinate system.

  The estimating unit 45 obtains the coordinates of the estimated position PM1b in the world coordinate system using a conversion formula from the measured position PSb when the work 2 has moved by the movement amount Δp1 = (ΔX1, ΔY1, Δθ1) to the estimated position PM1b. . The conversion equation is shown in the following equation (3).

Sb ′ = T (Rb (Sb)) Equation (3)
In Expression (3), Sb represents (xsb, ysb) ^T which is a transposed matrix of the X coordinate xsb and the Y coordinate ysb of the measurement position PSb in the world coordinate system. Rb () indicates a conversion equation corresponding to the rotational movement, and is based on the distance between the rotational center of the θ stage 110θ and the measurement position PSb, and the rotational movement amount of the θ stage 110θ from the imaging timing t (k−1). Is determined. Here, Δθ1 is used as the amount of rotational movement. T () indicates a conversion equation corresponding to the translation, and is determined according to the translation amount of the X stage 110X and the Y stage 110Y from the imaging timing t (k−1). Here, ΔX1 and ΔY1 are used as the translation amounts. Sb ′ indicates a transposed matrix of the X coordinate and the Y coordinate of the position of the mark 5b in the world coordinate system when the work 2 is moved by the movement amount Δp1. Here, Sb ′ indicates (xm1b, ym1b) ^T which is a transposed matrix of the X coordinate xm1b and the Y coordinate ym1b of the estimated position PM1b.

  The estimating unit 45 uses the second calibration data to inversely transform the coordinates of the estimated position PM1b in the world coordinate system into coordinates in the local coordinate system corresponding to the camera 302b. Thereby, the estimation unit 45 can obtain the coordinates of the estimated position PM1b in the local coordinate system.

  The period from the first intermediate timing tm1 to the scheduled imaging timing tk is one to several times the control cycle Ts. Therefore, the change amount of the movement command is small during the period. That is, it may be considered that the movement command at the first intermediate timing tm1 is continued until the scheduled imaging timing tk.

  Therefore, the estimating unit 45 substitutes the X coordinate and the Y coordinate of the estimated position PM1a of the mark 5a at the first intermediate timing tm1 into Sa in the above equation (2), thereby obtaining the position at the scheduled imaging timing tk (hereinafter, “ Predicted position PEa ”). In this case, Ra () in Expression (2) is the distance between the rotation center of the θ stage 110θ and the estimated position PM1a at the first intermediate timing tm1, the movement command MVθ at the first intermediate timing tm1, and the first intermediate timing tm1. From the time t to the scheduled imaging timing tk. T () is determined according to the movement commands MVX and MVY at the first intermediate timing tm1 and the time from the first intermediate timing tm1 to the scheduled imaging timing tk.

  The estimating unit 45 uses the first calibration data to inversely transform the coordinates of the predicted position PEa in the world coordinate system into coordinates in the local coordinate system corresponding to the camera 302a. Thereby, the estimation unit 45 can obtain the coordinates of the predicted position PEa in the local coordinate system.

  Similarly, the estimating unit 45 substitutes the X coordinate and the Y coordinate of the estimated position PM1b of the mark 5b at the first intermediate timing tm1 into Sb of the above equation (3), thereby obtaining the position at the scheduled imaging timing tk (hereinafter, referred to as “Sb”) “Predicted position PEb”). In this case, Ra () in Equation (3) is the distance between the rotation center of the θ stage 110θ and the estimated position PM1b at the first intermediate timing tm1, the movement command MVθ at the first intermediate timing tm1, and the first intermediate timing tm1. From the time t to the scheduled imaging timing tk. T () is determined according to the movement commands MVX and MVY at the first intermediate timing tm1 and the time from the first intermediate timing tm1 to the scheduled imaging timing tk.

  The estimating unit 45 uses the second calibration data to inversely transform the coordinates of the predicted position PEb in the world coordinate system into coordinates in the local coordinate system corresponding to the camera 302b. Thereby, the estimating unit 45 can obtain the coordinates of the predicted position PEb in the local coordinate system.

  The estimating unit 45 estimates the moving speed Va of the mark 5a and the moving speed Vb of the mark 5b on the image at the scheduled imaging timing tk according to the following equations (4) and (5).

Va = (PEa−PM1a) / (tk−tm1) Equation (4)
Vb = (PEb−PM1b) / (tk−tm1) Equation (5)
In Expression (4), “PEa−PM1a” indicates the distance between the predicted position PEa and the estimated position PM1a, and is calculated based on the X coordinate and the Y coordinate in the local coordinate system between the predicted position PEa and the estimated position PM1a. . In Expression (5), “PEb−PM1b” indicates a distance between the predicted position PEb and the estimated position PM1b, and is calculated based on the X coordinate and the Y coordinate in the local coordinate system between the predicted position PEb and the estimated position PM1b. . “Tk−tm1” indicates the time from the first intermediate timing tm1 to the scheduled imaging timing tk.

  In this way, the estimating unit 45 estimates the moving speeds Va and Vb of the marks 5a and 5b on the image at the scheduled imaging timing tk at the first intermediate timing tm1 before the scheduled imaging timing tk.

<2-4-3. Imaging control unit>
The imaging control unit 46 controls the operation of the visual sensor 300. Upon receiving an instruction to start positioning processing from a higher-level control device, the imaging control unit 46 outputs an imaging trigger TR (imaging instruction) to the image processing device 304 in accordance with the imaging cycle Tb. Specifically, upon receiving an instruction to start the positioning process, the imaging control unit 46 outputs a first imaging trigger TR. Thereafter, the imaging control unit 46 outputs the second and subsequent imaging triggers TR every time the imaging period Tb elapses.

  However, the imaging control unit 46 determines whether or not to output the imaging trigger TR based on the moving speeds Va and Vb estimated by the estimation unit 45. The imaging control unit 46 outputs an imaging trigger TR at the next scheduled imaging timing tk when the moving speeds Va and Vb are less than the predetermined threshold Th1, and at least one of the moving speeds Va and Vb exceeds the threshold Th1. In this case, the imaging trigger TR is not output at the imaging scheduled timing tk. That is, the imaging control unit 46 performs imaging at the scheduled imaging timing tk when the moving speeds Va and Vb are less than the threshold Th1, and performs imaging at the scheduled imaging timing tk when at least one of the moving speeds Va and Vb exceeds the threshold Th1. The visual sensor 300 is controlled so as not to allow the visual sensor 300 to operate.

  The threshold value Th1 is experimentally or theoretically determined according to the allowable upper limit value of the measurement error of the measurement positions PSa and PSb caused by the blur due to the image blur. That is, the moving speed of the marks 5a and 5b on the image when the measurement error of the allowable upper limit value occurs is predetermined as the threshold Th1.

§3 Operation example <3-1. Flow of positioning process of control system>
An example of the flow of the positioning process of the control system 1 will be described with reference to FIG. FIG. 6 is a flowchart illustrating an example of the flow of the positioning process of the control system.

  First, in step S1, the motion controller 400 initializes the estimated position PV and the encoder values PVmX, PVmY, PVmθ. Next, when the work 2 is placed on the moving mechanism 100, the imaging control unit 46 outputs the first imaging trigger TR to the image processing device 304. Accordingly, in step S2, the cameras 302a and 302b capture an image of the workpiece 2 with the moving mechanism 100 stopped.

  Next, in step S3, the image processing device 304 specifies the measurement position PSa of the mark 5a included in the image captured by the camera 302a and the measurement position PSb of the mark 5b included in the image captured by the camera 302b. . Next, in step S4, the movement control unit 41 starts movement control of the movement mechanism 100.

  Next, in step S5, the movement control unit 41 determines whether the deviation of the estimated position PV from the target position SP is less than a threshold Th2. The threshold value Th2 is predetermined in accordance with the required positioning accuracy. When the deviation of the estimated position PV from the target position SP is smaller than the threshold Th2 (YES in step S5), the movement control unit 41 ends the movement control of the movement mechanism 100. Thus, the positioning process ends.

  If the deviation of the estimated position PV from the target position SP is not less than the threshold Th2 (NO in step S5), the processing in steps S6 to S12 is repeated for each imaging cycle Tb. Note that the movement control by the movement control unit 41 is also performed in parallel between steps S6 to S12.

  In step S6, the estimation unit 45 determines whether or not the current time is the first intermediate timing tm1 which is q times the control cycle Ts before the next scheduled imaging timing tk. If the current time is not the first intermediate timing tm1 (NO in step S6), the process returns to step S5.

  If the current time is the first intermediate timing tm1 (YES in step S6), in step S7, the estimating unit 45 estimates the moving speeds Va and Vb of the marks 5a and 5b on the image at the scheduled imaging timing tk.

  Next, in step S8, the imaging control unit 46 determines whether or not the moving speeds Va and Vb are less than the threshold Th1.

  If the moving speeds Va and Vb are less than the threshold Th1 (YES in step S8), the imaging control unit 46 outputs the imaging trigger TR to the image processing device 304 at the scheduled imaging timing tk (step S9). In step S10, the image acquisition unit 32 of the image processing device 304 controls the cameras 302a and 302b to capture images, and obtains images captured by the cameras 302a and 302b. In step S11, the position specifying unit 34 specifies the measurement positions PSa and PSb of the marks 5a and 5b included in the image, respectively.

  Next, in step S12, the next scheduled imaging timing is updated. Specifically, the motion controller 400 sets the time that has elapsed by the imaging cycle Tb from the imaging scheduled timing tk before the update as the next imaging scheduled timing tk. After step S12, the process returns to step S5.

  If at least one of the moving speeds Va and Vb is equal to or higher than the threshold Th1 (NO in step S8), the process proceeds to step S12. That is, at the scheduled imaging timing tk before the update, the imaging trigger TR is not output, and the visual sensor 300 does not image the work 2.

<3-2. Processing of movement control unit>
FIG. 7 is a flowchart illustrating an example of a flow of a control process of the moving mechanism by the movement control unit. First, in step S21, the position determination unit 42 acquires the latest measurement positions PSa and PSb specified by the image processing device 304. The position determining unit 42 uses the first calibration data and the second calibration data to convert the coordinates (local coordinate system) of the measurement positions PSa and PSb received from the image processing device 304 into coordinates of the world coordinate system, respectively. Convert.

  In step S22, the position determination unit 42 acquires the latest imaging time. The position determination unit 42 acquires, for example, the time at which the latest imaging trigger TR was output as the imaging time. Alternatively, in consideration of the delay time from when the imaging trigger TR is output to when the cameras 302a and 302b start exposure, the position determination unit 42 captures an image at a time that has elapsed by the delay time from the time at which the imaging trigger TR was output. You may acquire as time.

  Next, in step S23, the position determination unit 42 acquires the encoder values PVmX, PVmY, PVmθ at a plurality of times close to the imaging time.

  Next, in step S24, the position determination unit 42 calculates an interpolation value of the encoder values PVmX at a plurality of times, and sets the interpolation value as the encoder value PVmsX at the imaging time. Similarly, the position determination unit 42 calculates an interpolation value of the encoder value PVmY at a plurality of times, and sets the interpolation value as the encoder value PVmsY at the imaging time. The position determination unit 42 calculates an interpolation value of the encoder value PVmθ at a plurality of times, and sets the interpolation value as the encoder value PVmsθ at the imaging time.

  Specifically, the position determination unit 42 calculates an interpolation value as follows. The encoder value PVmX detected by the encoder 130 at the detection time t (n) is defined as an encoder value PVmX (n). The position determination unit 42 specifies two times close to the imaging time tvi, for example, a detection time t (nk) and a detection time t (nk + 1) sandwiching the imaging time tvi on the time axis.

  The position determination unit 42 acquires the encoder value PVmX (nk) at the detection time t (nk) and the encoder value PVmX (nk + 1) at the detection time t (nk + 1).

  The position determination unit 42 calculates the encoder value PVmsX (vi) at the imaging time tvi by using an interpolation value between the encoder value PVmX (nk) and the encoder value PVmX (nk + 1). Specifically, the position determination unit 42 calculates the encoder value PVmsX (vi) at the imaging time tvi using the following equation (6).

PVmsX (vi) = PVmX (n−k) + Kk * (PVmX (n−k + 1) −PVmX (nk)) (6)
Here, Kk is an interpolation coefficient. When the control cycle is Ts, the transmission delay time of the encoder value PVmX is Ted, and the transmission delay time of the imaging trigger TR is Tsd, and Ts−Ted ≦ Tsd <2Ts−Ted, the interpolation coefficient Kk is expressed by the following equation. It is calculated using (7).

Kk = {Tsd- (Ts-Ted)} / Ts (7)
By using such a method of calculating the interpolation value, the encoder value PVmsX (vi) at the imaging time tvi can be calculated with high accuracy. Similarly, encoder values PVmsY (vi) and PVmsθ (vi) at the imaging time tvi are calculated. If the imaging time matches the calculation time of the encoder value, the encoder value may be used as it is.

  Next, in step S25, the position determination unit 42 estimates using the latest measured positions PSa, PSa, the encoder values PVmX, PVmY, PVmθ after the imaging time, and the encoder values PVmsX, PVmsY, PVmsθ at the imaging time. The position PV is calculated.

  Specifically, the measurement position PSa is translated by (PVmX−PVmsX) in the X direction, translated by (PVmY−PVmsY) in the Y direction, and rotationally moved by (PVmθ−PVmsθ) in the Y direction. The position PSwa after the input and the affine transformation is calculated. Similarly, the measurement position PSb is input to the affine transformation equation, and the position PSwb after the affine transformation is calculated. The position determination unit 42 determines the position of the work 2 when the mark 5a is located at the position PSwa and the mark 5b is located at the position PSwb as the estimated position PV. That is, the position determination unit 42 determines the coordinates of the midpoint between the positions PSwa and PSwb, and the angle between the straight line connecting the positions PSwa and PSwb and the X axis or the Y axis, as information for specifying the estimated position PV. Is calculated as

  Next, in step S26, the calculation unit 44 generates movement commands MVX, MVY, MVθ by, for example, P calculation based on the deviation of the estimated position PV from the target position SP, and sends the movement commands to the servo drivers 200X, 200Y, 200θ, respectively. Output.

  By executing such processing, the motion controller 400 determines the estimated position PV using the high-precision measurement positions PSa and PSb at the time when the high-precision measurement positions PSa and PSb are input by the image processing. It is possible to calculate and realize high-accuracy positioning control. Here, the time interval at which the measurement positions PSa and PSb are input is the imaging period Tb, which is longer than the control period Ts at which the encoder values PVmX, PVmY, and PVmθ are input. However, between the input times of the adjacent measurement positions PSa and PSb on the time axis, the position determination unit 42 determines the estimated position PV for each input time of the encoder values PVmX, PVmY, and PVmθ having a short input cycle. The movement of the movement mechanism 100 is controlled. This enables high-accuracy and short-period positioning control. Further, the position determination unit 42 performs a process using the above-described simple four arithmetic operations. Therefore, high-speed and high-accuracy positioning by a simple configuration and processing can be realized.

<3-3. Action / Effect>
As described above, the control system 1 includes the visual sensor 300, the movement control unit 41, the estimation unit 45, and the imaging control unit 46. The visual sensor 300 acquires an image by imaging the work 2 at each imaging timing, and specifies the measurement positions PSa and PSb of the marks 5a and 5b of the work 2 based on the image. The movement control unit 41 controls the movement mechanism 100 based on the measurement positions PSa and PSb specified by the visual sensor 300 so that the position of the work 2 approaches the target position. Based on the latest measurement positions PSa and PSb specified from the image captured at the latest imaging timing t (k−1) and the reference information, the estimation unit 45 determines the marks 5a and 5a at the next scheduled imaging timing tk. The moving speeds Va and Vb of 5b are estimated respectively. The reference information includes information from the moving mechanism 100 and information generated by the movement control unit 41. The imaging control unit 46 performs imaging so as to perform imaging at the scheduled imaging timing tk when the moving speeds Va and Vb are less than the threshold Th1, and not to perform imaging at the scheduled imaging timing tk when the moving speeds Va and Vb exceed the threshold Th1. The sensor 300 is controlled.

  Accordingly, it is possible to avoid capturing an image having a large image blurring amount, and to suppress a decrease in positioning accuracy due to the image.

  The reference information includes encoder values PVmX, PVmY, and PVmθ indicating the drive amounts (here, the rotation amounts) of the servo motors 120X, 120Y, and 120θ from the imaging timing t (k-1). Further, the reference information includes the movement commands MVX, MVY, MVθ generated by the movement control unit 41 after the imaging timing t (k−1). Specifically, the reference information includes the movement commands MVX, MVY, MVθ generated at the first intermediate timing tm1.

  The encoder values PVmX, PVmY, PVmθ directly indicate the amount of movement of the moving mechanism 100. The moving mechanism 100 moves according to the movement commands MVX, MVY, MVθ. Therefore, the marks 5a and 5b of the work 2 also move according to the movement commands MVX, MVY and MVθ. Therefore, the estimating unit 45 can accurately estimate the moving speeds Va and Vb of the marks 5a and 5b at the scheduled imaging timing tk, respectively.

§4 Modification <4-1. Modification 1>
Based on the encoder values PVmX, PVmY, and PVmθ output from the imaging timing t (k-1) to the first intermediate timing tm1, the estimation unit 45 moves the marks 5a and 5b at the next scheduled imaging timing tk based on the moving speed Va of the marks 5a and 5b. , Vb may be estimated.

  FIG. 8 is a diagram illustrating a method for estimating the moving speeds Va and Vb according to the first modification. As illustrated in FIG. 8, the estimating unit 45 estimates the moving amount Δp2 of the work 2 from the imaging timing t (k−1) to the second intermediate timing tm2 = (ΔX2, ΔY2, Δθ2). The second intermediate timing tm2 is a timing preceding the first intermediate timing tm1 by a period r times (r is an integer of 1 or more) the control cycle Ts. r is 1, 2 or 3, for example. The method of estimating the movement amount Δp2 is the same as the method of estimating the movement amount Δp1. That is, the estimation unit 45 calculates the encoder value PVm (k-1) at the imaging timing t (k-1) and the encoder value PVm (m2) = (PVmX (m2), PVmY (m2), at the second intermediate timing tm2. PVmθ (m2)) is estimated as the movement amount Δp2.

  The estimating unit 45 estimates the position of the mark 5a (hereinafter, referred to as “estimated position PM2a”) and the position of the mark 5b (hereinafter, referred to as “estimated position PM2b”) at the second intermediate timing tm2.

  Specifically, the estimation unit 45 estimates the estimated position PM2a using the latest measured position PSa and the estimated movement amount Δp2 according to the above equation (2). At this time, Ra () is determined based on the distance between the rotation center of the θ stage 110θ and the measurement position PSa, and the rotational movement amount Δθ2 of the θ stage 110θ from the imaging timing t (k-1). T () is determined according to the translation amount ΔX2 of the X stage 110X and the translation amount ΔY2 of the Y stage 110Y from the imaging timing t (k−1).

  The estimation unit 45 estimates the estimated position PM2b using the latest measured position PSb and the estimated movement amount Δp2 according to the above equation (3). At this time, Ra () is determined based on the distance between the rotation center of the θ stage 110θ and the measurement position PSb, and the rotational movement amount Δθ2 of the θ stage 110θ from the imaging timing t (k-1). T () is determined according to the translation amount ΔX2 of the X stage 110X and the translation amount ΔY2 of the Y stage 110Y from the imaging timing t (k−1).

  The period from the first intermediate timing tm1 to the scheduled imaging timing tk is one to several times the control cycle Ts. Therefore, the moving speed of the marks 5a and 5b hardly changes during the period. Therefore, the estimating unit 45 estimates the moving speeds of the marks 5a and 5b on the image from the second intermediate timing tm2 to the first intermediate timing tm1 as the moving speeds Va and Vb on the image at the scheduled imaging timing tk. That is, the estimating unit 45 estimates the moving speed Va of the mark 5a and the moving speed Vb of the mark 5b on the image at the scheduled imaging timing tk according to the following equations (8) and (9).

Va = (PM1a-PM2a) / (tm1-tm2) (8)
Vb = (PM1b-PM2b) / (tm1-tm2) (9)
In Expression (8), “PM1a−PM2a” indicates a distance between the estimated position PM1a and the estimated position PM2a. In Expression (9), “PM1b−PM2b” indicates a distance between the estimated position PM1b and the estimated position PM2b. "Tm1-tm2" indicates the time from the second intermediate timing tm2 to the first intermediate timing tm1.

  In this way, the estimation unit 45 estimates the moving speeds Va and Vb of the marks 5a and 5b at the scheduled imaging timing tk at the first intermediate timing tm1 before the next scheduled imaging timing tk.

<4-2. Modification 2>
In the above description, the movement amount Δp1 of the work 2 from the imaging timing t (k−1) to the first intermediate timing tm1 has been estimated based on the encoder values PVmX, PVmY, PVmθ. However, based on the movement commands MVX, MVY, MVθ generated during the period from the imaging timing t (k−1) to the first intermediate timing tm1, the estimation unit 45 estimates the movement amount Δp1 of the work 2 during the period. May be.

  The moving mechanism 100 on which the work 2 is placed moves according to the movement commands MVX, MVY, MVθ. Therefore, the translation amount ΔX1 of the workpiece 2 in the X direction during the period from the imaging timing t (k−1) to the first intermediate timing tm1 is estimated from the movement command MVX generated during the period. Similarly, the translation amount ΔY1 of the work 2 in the Y direction during the period from the imaging timing t (k−1) to the first intermediate timing tm1 is estimated from the movement command MVY generated during the period. The rotational movement amount Δθ1 of the work 2 during the period from the imaging timing t (k−1) to the first intermediate timing tm1 is estimated from the movement command MVθ generated during the period.

  For example, assuming that the movement command MVX is a speed command and the value of the movement command MVX at time t is MVX (t), the estimating unit 45 calculates the translation movement amount ΔX1 according to the following equation (10). MVX (t) is constant during the control cycle Ts.

  Similarly, the estimating unit 45 calculates the translation amount ΔY1 in the Y direction and the rotational movement in the period from the imaging timing t (k−1) to the first intermediate timing tm1 according to the following equations (11) and (12). The quantity Δθ1 is calculated. In equation (11), MVY (t) indicates the value of the movement command MVY at time t. In equation (12), MVθ (t) indicates the value of the movement command MVθ at time t. The movement commands MVY and MVθ are speed commands, and MVY (t) and MVθ (t) are constant during the control cycle Ts.

  In this manner, the estimating unit 45 determines the marks 5a, 5a at the next scheduled imaging timing tk based on the movement commands MVX, MVY, MVθ generated from the imaging timing t (k-1) to the first intermediate timing tm1. The moving speeds Va and Vb of 5b may be estimated.

<4-3. Modification 3>
In the above description, the movement control unit 41 generates the movement commands MVX, MVY, MVθ so that the estimated position PV approaches the target position SP. However, the target trajectory of the moving mechanism 100 for moving the workpiece 2 more smoothly may be determined, and the moving mechanism 100 may be controlled according to the determined target trajectory. In this case, the moving speeds Va and Vb of the marks 5a and 5b on the image at the scheduled imaging timing tk may be estimated based on the determined target trajectory.

<4-3-1. Functional configuration of control system>
FIG. 9 is a block diagram illustrating a functional configuration of a control system 1A according to the third modification. As shown in FIG. 9, the control system 1A is different from the control system 1 shown in FIG. 4 in that a motion controller 400A is provided instead of the motion controller 400. The motion controller 400A is different from the motion controller 400 in that the motion controller 400A includes a movement control unit 41A and an estimation unit 45A instead of the movement control unit 41 and the estimation unit 45. The movement control unit 41A is different from the movement control unit 41 in that a target trajectory determination unit 47 and a calculation unit 44A are provided instead of the position determination unit 42, the subtraction unit 43, and the calculation unit 44.

<4-3-1-1. Target trajectory determination unit>
The target trajectory determination unit 47 determines a target trajectory of the moving mechanism 100 based on the measurement position PSa of the mark 5a and the measurement position PSb of the mark 5b specified by the image processing device 304 and the target position SP. Specifically, the target trajectory is determined as follows.

  The target trajectory determination unit 47 specifies the actual position of the work 2 at the imaging timing t (k-1) based on the latest measurement positions PSa and PSb. The target trajectory determination unit 47 calculates a required moving distance Lo of the moving mechanism 100 for moving the specified work 2 from the actual position to the target position SP. The target trajectory determination unit 47 divides the required moving distance Lo of the moving mechanism 100 into the required moving distance LX in the X-axis direction, the required moving distance LY in the Y-axis direction, and the required moving distance Lθ in the rotation direction.

  The target trajectory determining unit 47 determines a target trajectory TGX of the X stage 110X based on the required moving distance LX and the target position SPX of the X stage 110X. The target trajectory determination unit 47 determines a target trajectory TGY of the Y stage 110Y based on the required moving distance LY and the target position SPY of the Y stage 110Y. The target trajectory determination unit 47 determines the target trajectory TGθ of the θ stage 110θ based on the required moving distance Lθ and the target position SPθ of the θ stage 110θ.

  FIG. 10 is a diagram illustrating an example of the target trajectories TGX, TGY, and TGθ. The target trajectory TGX is determined so that the function LX (t) indicating the time change of the deviation between the position of the target trajectory TGX at time t and the target position SPX is a fifth-order or higher-order function. The function LX (t) is a function in which the required moving distance LX and the time t are at least explanatory variables. Similarly, the target trajectory TGY is determined such that the function LY (t) indicating the time change of the deviation between the position of the target trajectory TGY and the target position SPY at the time t is a fifth-order or higher-order function. The target trajectory TGθ is determined so that the function Lθ (t) indicating the time change of the deviation between the position of the target trajectory TGθ at time t and the target position SPθ is a multidimensional function of order 5 or higher.

  The target trajectory determination unit 47 calculates functions LX (t), LY (t), and Lθ (t) indicating the time change of the deviation between the determined target trajectories TGX, TGY, TGθ and the target positions SPX, SPY, SPθ, respectively. Output to the unit 44A. The functions LX (t), LY (t), Lθ (t) are information indicating the target trajectories TGX, TGY, TGθ, respectively.

  The target trajectory determination unit 47 determines the functions LX (t), LY (t), Lθ (t) according to the latest measurement positions PSa, PSb of the marks 5a, 5b specified by the image processing device 304 for each imaging cycle Tb. To update.

<4-3-1-2. Arithmetic unit>
The calculation unit 44A calculates the movement commands MVX, MVY, MVθ for each control cycle Ts based on the functions LX (t), LY (t), Lθ (t). Specifically, the arithmetic unit 44A calculates the deviation of the position of the current time t on the target trajectory TGX from the target position SPX by substituting the current time t into the function LX (t). Arithmetic unit 44A calculates movement command MVX by performing, for example, P operation on the calculated deviation. The calculation unit 44A calculates the movement commands MVY and MVθ by the same method.

<4-3-1-3. Estimation part>
The estimation unit 45A estimates the movement amount Δp1 of the work 2 from the imaging timing t (k−1) to the first intermediate timing tm1, based on the target trajectories TGX, TGY, and TGθ determined by the target trajectory determination unit 47. . Specifically, as illustrated in FIG. 10, the estimation unit 45A calculates the translation amount of the workpiece 2 in the X direction from the imaging timing t (k−1) to the first intermediate timing tm1 in the target trajectory TGX. It is calculated as the amount ΔX1. Similarly, the estimating unit 45A calculates the movement amount of the target trajectory TGY from the imaging timing t (k-1) to the first intermediate timing tm1 as the translation movement amount ΔY1 of the work 2 in the Y direction. The estimating unit 45A calculates the movement amount from the imaging timing t (k-1) to the first intermediate timing tm1 on the target trajectory TGθ as the rotation movement amount Δθ1 of the work 2.

  The estimating unit 45A estimates the estimated position PM1a of the mark 5a at the first intermediate timing tm1 according to the above equation (2) using the latest measured position PSa and the estimated movement amount Δp1. The estimating unit 45A estimates the estimated position PM1b of the mark 5b at the first intermediate timing tm1 according to the above equation (3) using the latest measured position PSb and the estimated movement amount Δp1.

  Further, the estimating unit 45A estimates the moving amount Δpk of the work 2 from the imaging timing t (k−1) to the scheduled imaging timing tk based on the target trajectories TGX, TGY, and TGθ. . Specifically, the estimating unit 45A calculates the movement amount from the imaging timing t (k-1) to the scheduled imaging timing tk on the target trajectory TGX as the translation movement amount ΔXk of the work 2 in the X direction. Similarly, the estimating unit 45A calculates the movement amount of the target trajectory TGY from the imaging timing t (k−1) to the scheduled imaging timing tk as the translation movement amount ΔYk of the workpiece 2 in the Y direction. The estimating unit 45A calculates the amount of movement from the imaging timing t (k-1) to the scheduled imaging timing tk on the target trajectory TGθ as the rotational movement amount Δθk of the work 2.

  The estimation unit 45A estimates the predicted position PEa of the mark 5a at the scheduled imaging timing tk by substituting the X coordinate xsa and the Y coordinate ysa of the latest measurement position PSa into the right side of the above equation (2). At this time, Ra () is determined based on the distance between the rotation center of the θ stage 110θ and the measurement position PSa, and the rotational movement amount Δθk of the θ stage 110θ from the imaging timing t (k-1). T () is determined according to the translation amount ΔXk of the X stage 110X and the translation amount ΔYk of the Y stage 110Y from the imaging timing t (k−1).

  Similarly, the estimation unit 45A estimates the predicted position PEb of the mark 5b at the scheduled imaging timing tk by substituting the X coordinate xsb and the Y coordinate ysb of the latest measurement position PSb into the left side of the above equation (3). . At this time, Ra () is determined based on the distance between the rotation center of the θ stage 110θ and the measurement position PSb, and the rotational movement amount Δθk of the θ stage 110θ from the imaging timing t (k-1). T () is determined according to the translation amount ΔXk of the X stage 110X and the translation amount ΔYk of the Y stage 110Y from the imaging timing t (k−1).

  The estimating unit 45A estimates the moving speed Va of the mark 5a and the moving speed Vb of the mark 5b at the scheduled imaging timing tk according to the above equations (4) and (5).

<4-3-2. Processing of target trajectory determination unit>
FIG. 11 is a flowchart illustrating a flow of processing in the target trajectory determination unit. The process shown in FIG. 11 is performed each time the measurement positions PSa and PSb of the marks 5a and 5b are specified by the image processing device 304.

  In step S31, the target trajectory determining unit 47 acquires the measurement positions PSa and PSb of the marks 5a and 5b from the image processing device 304.

  In step S32, the target trajectory determination unit 47 specifies the actual position of the work 2 based on the measurement positions PSa, PSb of the marks 5a, 5b. Then, the target trajectory determination unit 47 calculates the required movement distance LX in the X-axis direction, the required movement distance LY in the Y-axis direction, and the required movement distance in the rotation direction for moving the specified work 2 from the actual position to the target position SP. Lθ is calculated.

  In step S33, the target trajectory determination unit 47 corrects the required movement distances LX, LY, Lθ. The correction is performed in order to suppress the slip of the work 2 on the moving mechanism 100 and the residual vibration after the positioning of the moving mechanism 100. If the slip or the residual vibration of the work 2 is small enough to be ignored, step S33 may be omitted.

  The correction method in step S33 is as follows. The target trajectory determination unit 47 calculates, as an error, a position deviation En (t) between the actual position of the moving mechanism 100 determined based on the encoder value from the encoder 130 and the current time position on the target trajectory determined last time. . The position deviation En (t) is decomposed into a component EnX (t) in the X-axis direction, a component EnY (t) in the Y-axis direction, and a component Enθ (t) in the rotation direction.

  The target trajectory determination unit 47 calculates the required moving distance LXm after correction by correcting the necessary moving distance LX with the position deviation EnX (t). Similarly, the target trajectory determination unit 47 calculates the corrected required moving distance LYm by correcting the required moving distance LY with the position deviation EnY (t). The target trajectory determining unit 47 calculates the corrected required moving distance Lθm by correcting the required moving distance Lθ with the position deviation Enθ (t).

  In step S34, the target trajectory determination unit 47 initializes the measurement time t to zero. In step S35, the target trajectory determination unit 47 calculates the trajectory time T. The trajectory time T represents the time required to move the moving mechanism 100 from the start point to the end point of the target trajectories TGX, TGY, TGθ. As an example, the trajectory time T is calculated based on the following equation (13).

T = max {f (Amax), Tmin} (13)
“Amax” shown in the above equation (13) represents the maximum acceleration. “F ()” is a function for calculating the trajectory time required when the necessary moving distance is moved to the moving mechanism 100 at the maximum acceleration Amax. “Tmin” is a predetermined minimum trajectory time. “Max (α, β)” is a function for obtaining the maximum value from the numerical values α and β.

  According to the above equation (13), the orbit time T is determined so as not to be less than the minimum orbit time Tmin. If the minimum trajectory time Tmin is not provided, when the required moving distance Lo is very small, the moving mechanism 100 immediately reaches the target position, so that the time until the next imaging timing is wasted. Become. However, by providing the minimum trajectory time Tmin, when the required movement distance Lo is extremely small, the moving mechanism 100 moves at an acceleration lower than the maximum acceleration, and the moving mechanism 100 moves smoothly. Can be. As an example, the minimum trajectory time Tmin is calculated by multiplying the average imaging interval by a fixed ratio (for example, 50%).

  In step S36, the target trajectory determination unit 47 sets the target trajectories TGX, TGY, and TGθ on the basis of the required movement distances LXm, LYm, and Lθm obtained in step S33 and the trajectory time T calculated in step S35, respectively. decide.

  Specifically, the target trajectory determination unit 47 sets the target trajectory TGX such that a function LX (t) indicating a time change of the deviation between the position of the target trajectory TGX and the target position SPX is represented by the following equation (14). Determine TGX. The target trajectory determination unit 47 determines the target trajectory TGY such that a function LY (t) indicating the time change of the deviation between the position of the target trajectory TGY and the target position SPY is represented by the following equation (15). The target trajectory determination unit 47 determines the target trajectory TGθ such that a function Lθ (t) indicating the time change of the deviation between the position of the target trajectory TGθ and the target position SPθ is represented by the following equation (16).

LX (t) = LXm * [1- (t / T) ³ {10-15 (t / T) +6 (t / T) ² }] (14)
LY (t) = LYm * [1- (t / T) ³ {10-15 (t / T) +6 (t / T) ² }] (15)
Lθ (t) = Lθm * [1− (t / T) ³ {10−15 (t / T) +6 (t / T) ² }} (16)
As shown in Expressions (14) to (16), the functions LX (t), LY (t), and Lθ (t) use the required movement distances LXm, LYm, Lθm and time t at least as explanatory variables, and This is a multi-dimensional function using deviations from the positions SpX, SPY, and SPθ as objective variables.

  The functions LX (t), LY (t) and Lθ (t) shown in the above equations (14) to (16) are quintic functions, but the functions LX (t), LY (t) and Lθ (T) may be a sixth-order or higher order function.

  When the maximum acceleration Amax is given, the trajectory time T is calculated by the following equations (17) to (19). In equation (17), Lm is LXm, LYm, Lθm.

f (Amax) = C ₁ * Lm / Amax (17)
^{_{C 1 = 60C 2 (2C 2}} 2 -3C 2 +1) ··· (18)
^{_{C 2 = 0.5-3 1/2 / 6 ···}} (19)
In this manner, every time the measurement positions PSa and PSb are specified, the target trajectory determination unit 47 sets the functions LX indicating the target trajectories TGX, TGY, and TGθ until the moving mechanism 100 reaches the target position SP. (T), LY (t), and Lθ (t) are collectively calculated.

<4-4. Other variations>
In the above description, the moving mechanism 100 is an XYθ table. However, the moving mechanism 100 may be a θXY table, a UVW table, an XY table, an XYZ table, an articulated robot, or the like.

  In the above description, the work 2 is positioned using the marks 5a and 5b provided on the work 2 as characteristic portions of the work 2. However, the work 2 may be positioned using another part of the work 2 as a characteristic part of the work 2. For example, a screw or a screw hole provided in the work 2 may be used as a characteristic portion of the work 2. Alternatively, a corner of the work 2 may be used as a characteristic portion of the work 2.

  The servomotors 120X, 120Y, 120θ may be linear motors instead of rotary motors. Further, the encoder 130 may be a linear encoder. In this case, the estimation unit 45 may acquire information indicating the position of the linear axis as information indicating the drive amount of the motor, and estimate the movement amount Δp1 based on the acquired information.

§5 Supplement As described above, the present embodiment and modifications include the following disclosure.

(Configuration 1)
A control system (1, 1A) for controlling a moving mechanism (100) for moving an object (2) to position the object (2),
An image is acquired by imaging the object (2) at each imaging timing, and based on the image, a visual sensor (5) for specifying the position of a characteristic portion (5a, 5b) of the object (2). 300)
For controlling the moving mechanism (100) such that the position of the object (2) approaches a target position based on the position of the characteristic portion (5a, 5b) specified by the visual sensor (300). A movement control unit (41, 41A);
The latest position of the characteristic portion (5a, 5b) specified by the visual sensor (300) from the image captured at the latest imaging timing, information from the moving mechanism (100), and the movement control unit (41) An estimating unit (45, 45A) for estimating the moving speed of the characteristic portion (5a, 5b) at the next scheduled imaging timing based on the reference information including at least one of the information generated by ,
An imaging control for controlling the visual sensor (300) so that an image is captured at the scheduled imaging timing when the moving speed is less than a threshold and is not imaged at the scheduled imaging timing when the moving speed exceeds the threshold. A control system (1, 1A), comprising:

(Configuration 2)
The moving mechanism (100) includes a motor driven to move the object (2),
The control system (1) according to Configuration 1, wherein the reference information includes information indicating a driving amount of the motor from the latest imaging timing.

(Configuration 3)
The movement control unit (41, 41A) generates a movement command for the movement mechanism (100) for each control cycle,
The control system (1) according to configuration 1 or 2, wherein the reference information includes information indicating a movement command generated by the movement control unit (41, 41A) after the latest imaging timing.

(Configuration 4)
The movement control unit (41A) determines a target trajectory of the moving mechanism (100) based on the latest position, and controls the moving mechanism (100) to move according to the determined target trajectory;
The control system (1A) according to Configuration 1, wherein the reference information includes information indicating the target trajectory.

(Configuration 5)
A moving mechanism (100) for moving the object (2) and an image obtained by imaging the object (2), and based on the image, characteristic portions (5a, 5b) of the object (2) are obtained. A) a control device (400) for controlling the position of the object (2) by controlling a visual sensor (300) for specifying the position of the object (2);
For controlling the moving mechanism (100) such that the position of the object (2) approaches a target position based on the position of the characteristic portion (5a, 5b) specified by the visual sensor (300). A movement control unit (41, 41A);
The latest position of the characteristic portion (5a, 5b) specified by the visual sensor (300) from the image captured at the latest imaging timing, information from the moving mechanism (100), and the movement control unit (41) An estimating unit (45, 45A) for estimating the moving speed of the characteristic portion (5a, 5b) at the next scheduled imaging timing based on the reference information including at least one of the information generated by ,
An imaging control for controlling the visual sensor (300) so that an image is captured at the scheduled imaging timing when the moving speed is less than a threshold and is not imaged at the scheduled imaging timing when the moving speed exceeds the threshold. A control device (400), comprising: a unit (46).

(Configuration 5 ')
A control device (400) used in the control system (1, 1A) according to any one of Configurations 1 to 4,
Said movement control unit (41, 41A);
The estimation unit (45, 45A);
A control device, comprising: the imaging control unit (46).

(Configuration 6)
A program for controlling a movement mechanism (100) for moving an object (2) to support a control system (1, 1A) for positioning the object (2),
The control system (1, 1A) acquires an image by imaging the object (2), and specifies a position of a characteristic portion (5a, 5b) of the object (2) based on the image. A visual sensor (300) for performing
On the computer,
Controlling the movement mechanism (100) such that the position of the object (2) approaches a target position based on the position of the characteristic portion (5a, 5b) specified by the visual sensor (300); ,
Generated by the latest position of the characteristic portion (5a, 5b) specified by the visual sensor (300) from the image captured at the latest imaging timing, information from the moving mechanism (100), and the controlling step Estimating the moving speed of the characteristic portion (5a, 5b) at the next scheduled imaging timing based on the reference information including at least one of the information to be obtained;
Controlling the visual sensor (300) so that the image is captured at the scheduled imaging timing when the moving speed is less than the threshold, and not captured at the scheduled imaging timing when the moving speed exceeds the threshold. Let the program.

(Configuration 6 ')
A program for supporting the control system (1, 1A) according to any one of the configurations 1 to 4,
On the computer,
Controlling the movement mechanism (100) such that the position of the object (2) approaches a target position based on the position of the characteristic portion (5a, 5b) specified by the visual sensor (300); ,
Generated by the latest position of the characteristic portion (5a, 5b) specified by the visual sensor (300) from the image captured at the latest imaging timing, information from the moving mechanism (100), and the controlling step Estimating the moving speed of the characteristic portion (5a, 5b) at the next scheduled imaging timing based on the reference information including at least one of the information to be obtained;
Controlling the visual sensor (300) so that the image is captured at the scheduled imaging timing when the moving speed is less than the threshold, and not captured at the scheduled imaging timing when the moving speed exceeds the threshold. Let the program.

  The embodiments disclosed this time should be considered in all respects as illustrative 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. Further, it is intended that the inventions described in the embodiments and the respective modified examples are implemented alone or in combination as much as possible.

  1, 1A control system, 2 work, 4 exposure mask, 5a, 5b mark, 32 image acquisition unit, 34 position identification unit, 41, 41A movement control unit, 42 position determination unit, 43 subtraction unit, 44, 44A calculation unit, 45, 45A estimation unit, 46 imaging control unit, 47 target trajectory determination unit, 100 moving mechanism, 110X X stage, 110Y Y stage, 110θ θ stage, 120X, 120Y, 120θ servo motor, 130 encoder, 200 driver unit, 200X, 200Y, 200θ Servo driver, 300 visual sensor, 302a, 302b camera, 304 image processing device, 310,414 processor, 312 RAM, 314 display controller, 316 system controller, 318 I / O controller, 320 hard disk , 322 camera interface, 322a, 322b image buffer, 324 input interface, 326 motion controller interface, 328, 428 communication interface, 330, 422 memory card interface, 332 display unit, 334 keyboard, 336 memory card, 350, 440 control program, 400, 400A motion controller, 412 chipset, 416 nonvolatile memory, 418 main memory, 420 system clock, 424 recording medium, 430 internal bus controller, 432 DMA control circuit, 434 internal bus control circuit, 436 buffer memory, 438 field bus controller.

Claims (6)

A control system that controls a moving mechanism that moves the object, and positions the object,
A visual sensor for acquiring an image by imaging the object at each imaging timing, and identifying a position of a characteristic portion of the object based on the image;
Based on the position of the characteristic portion specified by the visual sensor, a movement control unit for controlling the movement mechanism so that the position of the object approaches a target position,
The latest position of the characteristic portion specified by the visual sensor from the image captured at the latest imaging timing, and reference information including at least one of the information from the moving mechanism and the information generated by the movement control unit. Based on the estimating unit for estimating the moving speed of the characteristic portion at the next imaging scheduled timing,
An imaging control unit for controlling the visual sensor, so that the imaging is performed at the scheduled imaging timing when the moving speed is less than the threshold, and the imaging is not performed at the scheduled imaging timing when the moving speed exceeds the threshold. Equipped with control system. The moving mechanism includes a motor driven to move the object,
The control system according to claim 1, wherein the reference information includes information indicating a driving amount of the motor from the latest imaging timing. The movement control unit generates a movement command for the movement mechanism for each control cycle,
The control system according to claim 1, wherein the reference information includes information indicating a movement command generated by the movement control unit after the latest imaging timing. The movement control unit determines a target trajectory of the moving mechanism based on the latest position, and controls the moving mechanism to move according to the determined target trajectory,
The control system according to claim 1, wherein the reference information includes information indicating the target trajectory. A moving mechanism for moving the object, and acquiring an image by imaging the object, based on the image, controlling a visual sensor for specifying the position of a characteristic portion of the object, A control device for positioning an object,
Based on the position of the characteristic portion specified by the visual sensor, a movement control unit for controlling the movement mechanism so that the position of the object approaches a target position,
The latest position of the characteristic portion specified by the visual sensor from the image captured at the latest imaging timing, and reference information including at least one of the information from the moving mechanism and the information generated by the movement control unit. Based on the estimating unit for estimating the moving speed of the characteristic portion at the next imaging scheduled timing,
An imaging control unit for controlling the visual sensor, so that the imaging is performed at the scheduled imaging timing when the moving speed is less than the threshold, and the imaging is not performed at the scheduled imaging timing when the moving speed exceeds the threshold. A control device. A program for controlling a moving mechanism for moving an object, and supporting a control system for positioning the object,
The control system acquires an image by imaging the object, and includes a visual sensor for identifying the position of a characteristic portion of the object based on the image,
On the computer,
Based on the position of the characteristic portion specified by the visual sensor, controlling the moving mechanism so that the position of the object approaches the target position,
The latest position of the characteristic portion specified by the visual sensor from the image captured at the latest imaging timing, and reference information including at least one of the information from the moving mechanism and the information generated by the controlling step. Estimating the moving speed of the characteristic portion at the next imaging scheduled timing based on
Controlling the visual sensor so that the image is captured at the scheduled imaging timing when the moving speed is less than the threshold, and is not captured at the scheduled imaging timing when the moving speed exceeds the threshold. .