Patent Publication Number: US-11021333-B2

Title: Conveyor tracking system and calibration method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of Japan patent application serial no. 2018-026357, filed on Feb. 16, 2018. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to calibration in a conveyor tracking system. 
     Description of Related Art 
     In the factory automation (FA) field, technology for controlling various processes using image processing is frequently used for labor saving. As an application example of such image processing technology, there is an operation process of conveying workpieces according to a conveyance device such as a conveyor belt and tracking and picking up workpieces being conveyed using a robot. Such an operation process is called conveyor tracking and the like. 
     In this conveyor tracking technology, the position of each workpiece is identified by capturing images of workpieces on a conveyance device using a camera and performing image analysis such as pattern matching or binarization processing on the images obtained according to image capturing. Then, a robot tracks and picks up each workpiece on the basis of the identified position of each workpiece using an image processing device. 
     Conventionally, the position of a workpiece identified according to image analysis performed on a camera image is coordinate values of a coordinate system based on camera images (hereinafter referred to as “camera coordinate system”) and cannot be used for robot control as it is. Accordingly, it is necessary to perform a process of transforming coordinate values calculated in the camera coordinate system into coordinate values on a coordinate system for robot control (hereinafter referred to as “robot coordinate system”). 
     A relationship in which such coordinate values of the camera coordinate system are correlated to coordinate values of the robot coordinate system is determined according to an operation called calibration. For example, Japanese Laid-open No. 2012-187651 (Patent Document 1) discloses a method for calculating parameters set for transforming coordinate values within an imaging range of an imaging unit into coordinate values of a coordinate system of a moving machine using a sheet including a pattern for calibration. 
     In the method disclosed in Patent Document 1, it is necessary to correctly locate the tip of a hand of a robot on the pattern for calibration. To correctly locate the tip of a hand of a robot on the pattern, a certain degree of experience is required. The position of the tip of the hand of the robot may be measured by imaging the position with a camera using a technology as disclosed in Japanese Laid-open No. 2009-290852 (Patent Document 2), for example, such that users with little experience are also able to perform correct calibration. 
     However, providing a new camera for calibration is not practical and calibration of a newly provided camera itself is also required. 
     Accordingly, the disclosure provides a method for allowing even users with little experience in operation of robots to be able to perform correct calibration. 
     SUMMARY 
     According to one embodiment of the disclosure, a conveyor tracking system is provided. The conveyor tracking system includes a conveyance device that conveys workpieces; a robot that is disposed in association with the conveyance device and picks up the workpieces conveyed by the conveyance device; an image capturing part that has an imaging visual field on a conveyance route of the conveyance device; a visual sensor that performs an image measurement on images captured by the image capturing part; a control device that generates an operation command for the robot using a parameter set that is previously calculated based on an image measurement result obtained by the visual sensor; and a mobile device which has a touch panel used for a process of calculating the parameter set. The mobile device includes a display part which displays one or more patterns at predetermined positions; and a transmission part which transmits, according to a fact of being touched in a state in which the one or more patterns are displayed, information indicating a touch position being touched to the control device. The control device includes a calculation part which calculates that parameter set based on the image measurement result obtained by the visual sensor when the mobile device is disposed in the imaging visual field in a state in which the one or more patterns are displayed, the touch position when the mobile device is touched by the robot, and a distance between a position of the mobile device when the mobile device is disposed in the imaging visual field and a position when the mobile device is touched by the robot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing the overall configuration of a conveyor tracking system according to the present embodiment. 
         FIG. 2  is a diagram for describing an example of a calibration process in the conveyor tracking system according to the present embodiment. 
         FIG. 3  is a schematic diagram showing an example of a hardware configuration of a device for identifying a position of a workpiece included in the conveyor tracking system according to the present embodiment. 
         FIG. 4  is a schematic diagram showing an example of a hardware configuration of a device for pickup of a workpiece included in the conveyor tracking system according to the present embodiment. 
         FIG. 5  is a schematic diagram showing an example of a hardware configuration of a mobile device used in the conveyor tracking system according to the present embodiment. 
         FIG. 6  is a diagram for describing coordinate transformation and tracking in the conveyor tracking system according to the present embodiment. 
         FIG. 7  is a schematic diagram for describing a calibration process (1) according to the present embodiment. 
         FIG. 8  is a flowchart showing a processing procedure of the calibration process (1) according to the present embodiment. 
         FIG. 9  is a flowchart showing a processing procedure of step S 9  of  FIG. 8 . 
         FIG. 10  is a diagram for describing a process of calculating a parameter set according to the calibration shown in  FIG. 9 . 
         FIG. 11  is a schematic diagram for describing a calibration process (2) according to the present embodiment. 
         FIG. 12  is a figure showing a processing procedure of the calibration process (2) according to the present embodiment. 
         FIG. 13  is a diagram showing an example of a user interface screen provided in a mobile device according to the present embodiment. 
         FIG. 14  is a diagram showing another example of a user interface screen provided in the mobile device according to the present embodiment. 
         FIG. 15  is a diagram showing yet another example of a user interface screen provided in the mobile device according to the present embodiment. 
         FIG. 16  is a diagram showing yet another example of a user interface screen provided in the mobile device according to the present embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present disclosure will be described in detail with reference to the drawings. Meanwhile, the same or corresponding parts in the figures are denoted by the same reference signs and description thereof will not be repeated. 
     &lt;A. Example of Application&gt; 
     First, an example of a situation to which the present disclosure is applied will be described with reference to  FIGS. 1 and 2 . 
       FIG. 1  is a schematic diagram showing the overall configuration of a conveyor tracking system  1  according to the present embodiment. Referring to  FIG. 1 , the conveyor tracking system  1  includes a conveyor  10  which is an example of a conveyance device for conveying workpieces W. The conveyor  10  is driven and rotated by driving rollers  12  and  14  to sequentially convey workpieces W supplied at any timing from the left to the right on the paper. 
     A robot  300  disposed near the conveyor  10  picks up the workpieces W on the conveyor  10  and places the workpieces W on a different line which is not shown, or the like (a pickup and place operation). The robot  300  is disposed in association with the conveyor  10  and picks up the workpieces W conveyed by the conveyor  10 . The robot  300  may align an orientation of the workpieces W in a previously designated direction when picking up the workpieces W. Typically, foods such as candy, various tablets and the like may be conceived as the workpieces W. 
     A camera  250  which is an imaging part having an imaging visual field is disposed on a conveyance route of the conveyor  10 . The imaging visual field of the camera  250  is set at the upstream side of the conveyor  10 . Images captured by the camera  250  are output to a visual sensor  200 . Although  FIG. 1  shows a configuration example in which the visual sensor  200  and the camera  250  are independent of each other, a configuration in which both are integrated may be employed. 
     The visual sensor  200  performs image measurement on images captured by the camera  250 . In the present embodiment, the visual sensor  200  measures the position (more specifically, the position of a center of gravity) of each workpiece W on the conveyor  10  by performing an image measurement process such as pattern matching on images sequentially captured by the camera  250 . 
     An encoder  450  is provided in the conveyer  10  and outputs pulse signals according to a movement amount of the conveyor  10 . The pulse signals from the encoder  450  are received by a counter  400  and a value indicating the movement amount of the conveyor  10  and/or a value indicating a movement speed are calculated. 
     A programmable logic controller (PLC)  100  which is an example of a control device is in charge of processes in the conveyor tracking system  1 . The PLC  100  is connected to the visual sensor  200  and the counter  400  through a field network  18 . 
     The PLC  100  generates an operation command for the robot  300  using a parameter set calculated in advance based on an image measurement result obtained by the visual sensor  200 . More specifically, the PLC  100  acquires the position of each workpiece W measured by the visual sensor  200  and a value indicating a movement amount of the conveyor  10  (and/or a value indicating a movement speed) calculated by the counter  400 . The PLC  100  appropriately updates the position of each workpiece W present on the conveyor  10  according to movement of the conveyor  10  and outputs an operation command for the robot  300  on the basis of the updated position of each workpiece W. 
     The robot  300  picks up a workpiece W which is a target on the conveyor  10  according to an operation command from the PLC  100  and moves and places the workpiece W at a designated position. Although  FIG. 1  illustrates a parallel robot as a typical example, the robot is not limited thereto and a scalar robot, a vertical articulated robot and the like may be used. 
     A robot controller  350  receives an operation command from the PLC  100  and drives each axis constituting the robot  300  according to the received operation command. The robot controller  350  is connected to the PLC  100  through an information system network  20 . 
     A teaching pendant  380  for manually operating the robot  300  is connected to the robot controller  350 . When a user operates the teaching pendant  380 , the robot  300  operates according to the operation (teaching) of the user. 
     A human machine interface (HMI)  700  may be connected to the information system network  20  in addition to the PLC  100  and the robot controller  350 . The HMI  700  presents information managed by the PLC  100  and the like to the user, and receives an operation from the user and outputs the operation to the PLC  100 . 
     A support device  600  for performing source code editing, object code conversion, debugging and the like with respect to a user program executed in the PLC  100  is connectable to the PLC  100 . 
     As shown in  FIG. 1 , a coordinate system (hereinafter referred to as a “camera coordinate system”) based on the imaging visual field of the camera  250  is defined in the conveyor tracking system  1 . The camera coordinate system may be regarded as a two-dimensional coordinate system having an apex of an image captured by the camera  250  as a base. In the example shown in  FIG. 1 , a coordinate system with an Xc axis and a Yc axis having the left top of an image as a base is designated. That is, when the position of a workpiece W is measured according to pattern matching or the like for images output by imaging the imaging visual field through the camera  250 , the measured position of the workpiece W is output as coordinate values of the camera coordinate system (coordinate system with the Xc axis and the Yc axis). 
     In addition, in the conveyor tracking system  1 , a coordinate system (hereinafter referred to as a “robot coordinate system”) for designating the position of the tip of the hand (picking) position of the robot  300  is defined. In the example shown in  FIG. 1 , an Xrb axis and a Yrb axis are defined along a surface parallel with a conveying surface of the conveyor  10 . It is assumed that the Xrb axis is parallel with the conveying direction of the conveyor  10  and the Yrb axis is perpendicular to the conveying direction of the conveyor  10 . Further, a Zrb axis is defined in a direction perpendicular to the conveying surface of the conveyor  10 . Accordingly, the robot coordinate system is configured by three axes including the Xrb axis, the Yrb axis and the Zrb axis. However, since the Xc axis and the Yc axis constituting the camera coordinate system are also parallel with the conveying surface of the conveyor  10 , it is possible that the calibration between the camera coordinate system and the robot coordinate system focuses on only the relationship between the Xc axis and the Yc axis of the camera coordinate system and the Xrb axis and the Yrb axis of the robot coordinate system. 
     Calibration according to the present embodiment includes determination of a parameter set for realizing transformation between coordinate values of the camera coordinate system and coordinate values of the robot coordinate system. 
       FIG. 2  is a diagram for describing an example of a calibration process in the conveyor tracking system  1  according to the present embodiment. Referring to  FIG. 2 , in the present embodiment, the calibration is implemented using a mobile device  500  having a touch panel. The mobile device  500  has the touch panel and calculates a parameter set using a detection result obtained by the touch panel, and the like. As the mobile device  500 , for example, a tablet, a notebook computer, a smartphone and the like are conceivable. 
     Specifically, one or more patterns  550  for the calibration which have been defined in advance are displayed on the touch panel of the mobile device  500  and the mobile device  500  is disposed in the imaging visual field of the camera  250 . In this manner, the mobile device  500  has a function of displaying one or more patterns at predetermined positions. 
     In this state, the visual sensor  200  measures the positions of the patterns  550  with respect to images captured by the camera  250  and the measured positions (coordinate values of the camera coordinate system) are transmitted to the PLC  100 . 
     In one or some exemplary embodiments, data is exchanged between the mobile device  500  and the PLC  100  through wireless communication. Specifically, an interface for performing wireless communication with the mobile device  500  may be provided in the PLC  100 . Alternatively, an interface for performing wireless communication with the mobile device  500  may be provided in the field network  18  or the information system network  20  and the PLC  100  may exchange data with the mobile device  500  through the interface. 
     Subsequently, the mobile device  500  moves on the conveyer  10  to the downstream side by a predetermined distance L. Here, the patterns  550  for the calibration displayed on the touch panel of the mobile device  500  are maintained to be uniform. Then, the user locates the tip of the hand of the robot  300  on each pattern  550  displayed on the touch panel of the mobile device  500  by operating the robot  300 . 
     Here, the mobile device  500  may detect a position at which the tip of the hand of the robot  300  is located on the touch panel. The mobile device  500  transmits the position (coordinate values of the robot coordinate system) on the touch panel at which the tip of the hand of the robot  300  is located to the PLC  100 . In this manner, the mobile device  500  has a function of transmitting information representing a touch position to the PLC  100  according to touching applied to the touch position in a state in which one or more patterns  550  have been displayed. 
     The PLC  100  may acquire a distance L by which the conveyor  10  has moved (or a count number corresponding to the distance L) through the encoder  450  and the counter  400 . 
     The PLC  100  determines a parameter set with respect to the calibration using the positions (coordinate values of the camera coordinate system) of the patterns  550 , the distance L by which the mobile device  500  has moved, and the position (coordinate values of the robot coordinate system) of the tip of the hand detected by the mobile device  500 . 
     In this manner, the PLC  100  calculates a parameter set based on an image measurement result obtained by the visual sensor  200  when the mobile device  500  is disposed in the imaging visual field in a state in which one or a plurality of patterns has been displayed, a touch position when the mobile device  500  is touched by the robot  300 , and the distance L between the position of the mobile device  500  in the state in which the mobile device  500  is disposed in the imaging visual field and the position when the mobile device  500  is touched by the robot  300 . 
     As will be described later, capturing an image of the mobile device  500  by the camera  250  and touching the mobile device  500  by the robot  300  may be implemented in any order. In the following description, an example of implementing capturing of an image of the mobile device  500  in advance and an example of touching the mobile device  500  in advance by the robot  300  will be respectively described. 
     In the present embodiment, the PLC  100  performs determination of a parameter set for transforming a measurement result (coordinate values) of the camera coordinate system into the robot coordinate system and arithmetic operations for coordinate transformation between the camera coordinate system and the robot coordinate system using the parameter set. By employing this configuration, arithmetic operations necessary for conveyor tracking may be executed at once in the PLC  100 . 
     &lt;B. Hardware Configuration&gt; 
     Next, a hardware configuration of each device constituting the conveyor tracking system  1  according to the present embodiment will be described. 
     (b1: PLC  100 ) 
       FIG. 3  is a schematic diagram showing an example of a hardware configuration of a device for identifying a position of a workpiece W included in the conveyor tracking system  1  according to the present embodiment. Referring to  FIG. 3 , the PLC  100  is a kind of computer and realizes various processes by executing various programs through a processor. 
     The PLC  100  includes a processor  102 , a main memory  104 , a field network interface  106 , a wireless network interface  108 , a local communication interface  110 , an information system network interface  112 , and a storage  120 . These components are connected to a bus  140 . 
     The processor  102  reads programs stored in the storage  120  and the like to the main memory  104  and executes the programs. For example, the processor  102  may be composed of a central processing unit (CPU), a micro-processing unit (MPU), a graphics processing unit (GPU) or the like. For the processor  102 , a configuration having a plurality of cores may be employed or a plurality of processors  102  may be provided. 
     The main memory  104  is composed of a volatile storage device such as a dynamic random access memory (DRAM) and a static random access memory (SRAM), and the like. 
     The field network interface  106  is a controller which exchanges data with the visual sensor  200  and the counter  400  through the field network  18 . For example, it is possible to employ a fixed-cycle network such as EtherCAT (registered trademark) as the field network  18 . 
     The wireless network interface  108  is a controller which exchanges data with the mobile device  500  through wireless communication. For example, a wireless local area network (LAN), Bluetooth (registered trademark) or the like which conforms to IEEE 802.11 may be used as wireless communication. 
     The local communication interface  110  is a controller which exchanges data with the support device  600  and the like. For example, a universal serial bus (USB) and the like may be used for local communication. 
     The information system network interface  112  is a controller which exchanges data with the robot controller  350 , the HMI  700  and the like through the information system network  20 . For example, the Ethernet (registered trademark) and EtherNet/IP (registered trademark) which are general network protocols, and the like may be used for the information system network  20 . 
     The storage  120  stores programs executed in the PLC  100  and various types of data in a nonvolatile manner. For example, the storage  120  may be composed of a nonvolatile storage device such as a flash memory and a hard disk. 
     In the configuration shown in  FIG. 3 , the storage  120  includes a PLC system module  122 , a user program  124 , a tracking program  126 , calibration parameters  128 , a calibration program  130  and a robot position command generation program  132 . 
     The PLC system module  122  includes a library and the like and provides a basic control function realized according to execution of the user program  124 . The user program  124  is a program arbitrarily created according to a control target of the PLC  100  and includes a sequence program, a motion program and the like. 
     The tracking program  126  includes code for realizing a process of sequentially updating positions of workpieces W for realizing conveyor tracking. When the tracking program  126  is executed, a tracking record  105  which manages the position of each workpiece W is generated in the main memory  104 . The calibration parameters  128  are a parameter set with respect to the calibration, which are determined according to a procedure which will be described later. The calibration program  130  includes code for realizing the procedure which will be described later. The robot position command generation program  132  generates commands necessary for the robot  300  (e.g., a workpiece following speed, a pickup operation start position, a movement destination of workpieces W, and the like) on the basis of the position of each of workpiece W managed by executing the tracking program  126 . 
     Although  FIG. 3  shows an example of a configuration in which the processor  102  executes programs to provide necessary processes, some or all of the provided processes may be mounted using a dedicated hardware circuit (e.g., an application specific integrated circuit (ASIC)) or a field-programmable gate array (FPGA) or the like). 
     (b2: Visual Sensor  200  and Camera  250 ) 
     Referring to  FIG. 3 , the visual sensor  200  is a kind of computer and measures the position of each workpiece W on the conveyor  10  by performing an image measurement process such as pattern matching on images sequentially captured by the camera  250 . 
     More specifically, the visual sensor  200  includes an object recognition engine  202 , a camera interface  204  and a field network interface  206 . 
     The object recognition engine  202  performs an image measurement process such as pattern matching on input images from the camera  250 . The object recognition engine  202  outputs coordinate values (Xc1, Yc1) of the camera coordinate system as the position of a recognized workpiece. The camera interface  204  acquires images from the camera  250  and applies various settings for the camera  250 . The field network interface  206  is a controller which exchanges data (coordinate values of workpieces Win this example) with the PLC  100  through the field network  18 . 
     The visual sensor  200  may be realized by a processor executing a program and may be mounted using a dedicated hardware circuit (e.g., an ASIC, an FPGA or the like). 
     The camera  250  includes an optical system such as lenses and an aperture, and a light-receiving element such as a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor. The camera  250  captures images according to a command from the visual sensor  200  and outputs the captured images to the visual sensor  200 . 
     (b3: Robot  300  and Robot Controller  350 ) 
       FIG. 4  is a schematic diagram showing an example of a hardware configuration of a device for pickup of a workpiece W included in the conveyor tracking system  1  according to the present embodiment. Referring to  FIG. 4 , the robot controller  350  causes the robot  300  to perform designated operations by driving motors  310 - 1 ,  310 - 2 , . . . ,  310 - n  constituting the robot  300 . 
     The robot controller  350  includes an information system network interface  352 , a position controller  354  and drivers  356 - 1 ,  356 - 2 , . . . ,  356 - n.    
     The information system network interface  352  is a controller which exchanges data (operation commands in this example) with the PLC  100  through the information system network  20 . The position controller  354  outputs a position command (e.g., a number of pulses according to a movement amount) for the drivers  356 - 1 ,  356 - 2 , . . . ,  356 - n  according to an operation command from the PLC  100 . The drivers  356 - 1 ,  356 - 2 , . . . ,  356 - n  generates a power signal for driving the motors  310 - 1 ,  310 - 2 , . . . ,  310 - n  of the robot  300  according to a command from the position controller  354 . 
     The robot controller  350  may be realized by a processor executing a program or may be mounted using a dedicated hardware circuit (e.g., an ASIC or an FPGA). 
     (b4: Counter  400  and Encoder  450 ) 
     Referring back to  FIG. 3 , the counter  400  detects a movement amount of a detection target (the conveyor  10  in the present embodiment) of the encoder  450  by counting pulse signals output from the encoder  450 . 
     More specifically, the counter  400  includes a pulse counter  402 , an arithmetic operation processing unit  404  and a field network interface  406 . 
     The pulse counter  402  receives input of pulse signals from the encoder  450  and integrates the number of times of generation of rising edges and falling edges of the pulse signals. The arithmetic operation processing unit  404  calculates a movement amount of the detection target (conveyor  10 ) by multiplying a count number obtained by the pulse counter  402  by a predetermined coefficient. Alternatively, the arithmetic operation processing unit  404  may output a count number obtained by the pulse counter  402  as it is. The field network interface  406  is a controller which exchanges data (a count number in this example) with the PLC  100  through the field network  18 . 
     (b5: Mobile Device  500 ) 
       FIG. 5  is a schematic diagram showing an example of a hardware configuration of the mobile device  500  used in the conveyor tracking system  1  according to the present embodiment. Referring to  FIG. 5 , the mobile device  500  includes a processor  502 , a main memory  504 , a storage  510 , a wireless network interface  516  and a touch panel  520 . These components are connected to a bus  518 . 
     The processor  502  reads programs such as an operating system (OS)  512  and a calibration application  514  stored in the storage  510  to the main memory  504  and executes the programs. For example, the processor  502  may be composed of a CPU, an MPU, a GPU or the like. As the processor  502 , a configuration having a plurality of cores may be employed or a plurality of processors  502  may be provided. For example, the main memory  504  may be composed of a volatile storage device such as a DRAM and an SRAM. For example, the storage  510  may be composed of a nonvolatile storage device such as a flash memory or a hard disk. 
     The wireless network interface  516  is a controller which exchanges data with the PLC  100  through wireless communication. 
     The touch panel  520  receives an external touch operation and detects a position touched according thereto. The touch panel  520  includes a display  522  for displaying various types of information and a position detection device  524  for detecting a touch position. Further, a known device such as a capacitive device, a pressure sensitive device or ultrasonic device may be used as the position detection device  524 . 
     The calibration application  514  realizes processes of displaying patterns for the calibration on the display  522 , detecting a position touched by the robot  300  or the like and transmitting the position to the PLC  100 , as will be described later. 
     (b6: Support Device  600 ) 
     The support device  600  provides functions such as source code editing, object code conversion and debugging with respect to the user program executed in the PLC  100 . Typically, the support device  600  is realized by executing a support program through a general-purpose computer conforming to a known architecture. Since a hardware configuration of the general-purpose computer is known, detailed description thereof is not performed. 
     (b7: HMI  700 ) 
     The HMI  700  presents information managed by the PLC  100  and the like to a user, receives an operation from the user and outputs the operation to the PLC  100 . Typically, the HMI device  700  is realized by executing a support program through a general-purpose computer conforming to a known architecture. Since a hardware configuration of the general-purpose computer is known, detailed description thereof is not performed. 
     &lt;C. Coordinate Transformation and Calibration&gt; 
     Next, coordinate transformation and calibration therefor in the conveyor tracking system  1  according to the present embodiment will be described. 
       FIGS. 6A and 6B  are diagrams for describing coordinate transformation and calibration in the conveyor tracking system  1  according to the present embodiment. Referring to  FIG. 6A , it is assumed that the position of a workpiece W is measured in the camera coordinate system (coordinate system with the Xc axis and the Yc axis) set in the imaging visual field of the camera  250 . The measured position may be represented as coordinate values (Xc1, Yc1) of the camera coordinate system. A process of representing the coordinate values (Xc1, Yc1) of the camera coordinate system as coordinate values (Xrb1, Yrb1) of the robot coordinate system (coordinate system with the Xrb axis and the Yrb axis) is coordinate transformation. Coordinate transformation according to the present embodiment may also include, in addition to the process of transforming the coordinate values (Xc1, Yc1) of the camera coordinate system into the coordinate values (Xrb1, Yrb1) of the robot coordinate system, a process of inverse transformation thereof. 
     As an example of coordinate transformation, for example, a transformation formula represented by the following formulas (1-1) and (1-2) may be used.
 
 Xrb 1= A·Xc 1+ B·Yc 1+ C   (1-1)
 
 Yrb 1= D·Xc 1+ E·Yc 1+ F   (1-2)
 
     In the above formulas, coefficients A, B, C, D, E and F correspond to a parameter set with respect to the calibration. 
     Meanwhile, a coordinate transformation formula is not limited to the aforementioned transformation formula and any transformation formula may be used. It is assumed that the parameter set with respect to the calibration depends on a used transformation formula. 
     Referring to  FIG. 6B , when the workpiece W is conveyed on the conveyor  10 , the position thereof changes by the conveyed distance, and thus the position of the workpiece W at an arbitrary time t may be calculated according to a transformation formula represented by the following formulas (2-1) and (2-2) when a movement amount (movement speed) of the conveyer  10  per unit count number is represented by each component of the camera coordinate system (coordinate system with the Xc axis and the Yc axis) as dX and dY.
 
 Xrb 1( t )= Xrb 1(0)+ dX·En   C ( t )  (2-1)
 
 Yrb 1( t )= Yrb 1(0)+ dY·En   C ( t )  (2-2)
 
     Here, En C (t) denotes a count number increment from a count number at a timing (time t 0 ) when the position of the workpiece W is measured. 
     In the conveyor tracking system  1 , the PLC  100  saves a count number at a timing when the position of any workpiece W has been measured by the visual sensor  200  as an initial count number of the workpiece W. In addition, the PLC  100  sequentially updates (i.e., tracks) the positions of workpieces W based on a count number increment with respect to each workpiece W. 
     The PLC  100  outputs an operation command for the robot  300  based on the position of each workpiece W which is sequentially updated according to conveyance of the conveyor  10 . 
     The processes in the conveyor tracking system  1  according to the present embodiment are summarized as follows. 
     Workpieces W which are conveyance targets are sequentially conveyed from the upstream side of the conveyor  10 . When the camera  250  disposed at the upstream side of the conveyor  10  captures images of the workpieces W, the visual sensor  200  measures the positions of the workpieces W (generally the positions of centers of gravity of the workpieces W) which are conveyance targets. The PLC  100  transforms the positions of the workpieces W (coordinate values of the camera coordinate system) measured by the visual sensor  200  into coordinate values of the robot coordinate system, sequentially updates the positions of the respective workpieces W according to a movement amount of the conveyor  10  and gives an operation command to the robot  300 . 
     The robot  300  picks up and conveys workpieces W entering a predetermined tracking range (operation range) in order according to the operation command from the PLC  100 . 
     In the conveyor tracking system  1  according to the present embodiment, the calibration is performed using the mobile device  500  having a touch panel. A calibration procedure and the like will be described below. 
     &lt;D. Calibration Process (1)&gt; 
     First, a calibration process (1) will be described. In this calibration process (1), the mobile device  500  is used instead of a sheet including the conventional patterns for the calibration. 
     (d1: Overview) 
       FIG. 7  is a schematic diagram for describing the calibration process (1) according to the present embodiment.  FIG. 8  is a flowchart showing a processing procedure of the calibration process (1) according to the present embodiment. 
     Referring to  FIGS. 7 and 8 , first, the mobile device  500  is set to a state in which the mobile device  500  displays one or more patterns  550  for the calibration (step S 1 ), and the mobile device  500  is disposed in the imaging visual field of the camera  250  on the conveyor  10  in this state (step S 2 ). 
     Subsequently, the camera  250  captures an image of the mobile device  500  displaying the one or more patterns  550  (step S 3 ) and the visual sensor  200  measures the position (e.g., the position of the center or the position of center of gravity) of each pattern  550  by performing pattern matching or the like on the captured image (step S 4 ). 
     Thereafter, the conveyor  10  is driven to convey the mobile device  500  within a tracking range (the operation range of the robot  300 ) (step S 5 ). Then, a user locates the tip  320  of the hand of the robot  300  at a pattern  550  displayed on the mobile device  500  using the teaching pendant  380  or the like (step S 6 ). In this manner, the mobile device  500  is disposed in the imaging visual field where an image thereof is captured by the camera  250  and then receives a touch operation performed by the robot  300 . 
     The mobile device  500  detects the position at which the tip  320  of the hand of the robot  300  has been located and transmits information representing the position to the PLC  100  (step S 7 ). 
     Then, it is determined whether locating at a predetermined number of patterns  550  has been performed (step S 8 ). If locating at the predetermined number of patterns  550  has not been performed (NO in step S 8 ), step S 6  and subsequent processes are repeated. If locating at the predetermined number of patterns  550  has been performed (YES in step S 8 ), step S 9  and subsequent processes are repeated. 
     Meanwhile, although a locating destination of the tip  320  of the hand of the robot  300  may be only one pattern  550 , in one or some exemplary embodiments, locating is performed with respect to three patterns  550 . 
     The PLC  100  calculates a parameter set with respect to the calibration based on (1) a result of measurement of the positions of patterns  550  displayed on the display of the mobile device  500 , (2) a display position of each pattern  550  on the display of the mobile device  500 , (3) the position of the tip  320  of the hand detected in the mobile device  500 , (4) a result of teaching of the robot  300  (the position of the tip  320  of the hand in the robot coordinate system) and (5) a movement amount of the conveyor  10  (step S 9 ). In addition, the PLC  100  stores the calculated parameter set (step S 10 ). The calibration is completed according to the above-described procedure. 
     (d2: Calculation of Parameter Set) 
     Next, the procedure for calculating the parameter set with respect to the calibration shown in step S 9  of  FIG. 8  will be described in more detail. 
       FIG. 9  is a flowchart showing a processing procedure of step S 9  in  FIG. 8 .  FIG. 10  is a diagram for describing the process of calculating the parameter set with respect to the calibration shown in  FIG. 9 . Each step shown in  FIG. 9  is typically realized by the processor  102  of the PLC  100  which executes the calibration program  130  (refer to  FIG. 3 ). 
     Referring to  FIG. 9 , the PLC  100  calculates an inclination θt of the mobile device  500  with respect to the conveyor  10  based on (1) a result of measurement of the positions of patterns  550  displayed on the display of the mobile device  500  (step S 91 ). Meanwhile, the inclination θt of the mobile device  500  with respect to the conveyor  10  may be processed by the visual sensor  200 . In this case, the PLC  100  acquires the inclination θt of the mobile device  500  with respect to the conveyor  10  from the visual sensor  200 . 
     As shown in  FIG. 10 , the inclination θt of the mobile device  500  with respect to the conveyor  10  is calculated as an inclination of the mobile device  500  with respect to the conveyor  10  on the basis of positional relationships between patterns  550  measured by capturing an image of the mobile device  500  through the visual sensor  200 . 
     Meanwhile, coordinate values (Xc1, Yc1) of a pattern  550  which is a locating destination in the camera coordinate system is also acquired. 
     Referring back to  FIG. 9 , the PLC  100  subsequently calculates a deviation amount from the pattern  550  which is a locating destination based on (2) a display position of each pattern  550  on the display of the mobile device  500  (coordinate values on the display of the mobile device  500  and (3) the position of the tip  320  of the hand detected in the mobile device  500  (coordinate values on the display of the mobile device  500 ) (step S 92 ). The calculated deviation amount is defined as a difference between coordinate values in the display of the mobile device  500 . For a process which will be described later, the deviation amount is defined as a combination of two axial components defined according to a display region of the display of the mobile device  500  (diff_x and diff_y in  FIG. 10 ). 
     More specifically, since the mobile device  500  knows the positions at which the patterns  550  are displayed on the display and thus may cause the PLC  100  to be aware of coordinate values (Xd1′, Yd1′) of the pattern  550  which is a locating destination on the display, as shown in  FIG. 10 . In addition, the mobile device  500  may cause the PLC  100  to be aware of coordinate values (Xd1, Yd1) on the display at which the tip  320  of the hand of the robot  300  touches the mobile device  500 . 
     The PLC  100  calculates a parameter set further based on a deviation amount between one pattern  550  which is a locating destination among the one or more patterns  550  displayed on the mobile device  500  and the touch position. 
     More specifically, the PLC  100  corrects the deviation amount acquired from the mobile device  500  based on the direction of the mobile device  500  with respect to the conveyor  10  and then calculates the parameter set. Hereinafter, this processing procedure will be represented. 
     The PLC  100  calculates a deviation amount vector diff_L(diff_x, diff_y) which links the pattern  550  which is a locating destination with the tip  320  of the hand on the basis of the coordinate values (Xd1′, Yd1′) of the pattern  550  which is a locating destination and the coordinate values (Xd1, Yd1) of the tip  320  of the hand. In addition, the PLC  100  calculates an inclination θ1 (=a tan(diff_y/diff_x)[rad]) of the deviation amount vector diff_L with respect to the display of the mobile device  500 . 
     Referring back to  FIG. 9 , the PLC  100  transforms the deviation amount calculated in step S 92  into a deviation amount in the robot coordinate system based on the inclination θt calculated in step S 91  (step S 93 ). 
     More specifically, as shown in  FIG. 10 , the PLC  100  calculates a deviation amount vector (ΔXrb1, ΔYrb1 (robot coordinate system)) between the pattern  550  which is a locating destination and the tip  320  of the hand according to relational formulas represented by the following formulas (3-1) and (3-2) using the inclination θt and the inclination θ1.
 
Δ Xrb 1= k ×diff_ L× cos(θ t+θ 1)  (3-1)
 
Δ Yrb 1= k ×diff_ L× sin(θ t+θ 1)  (3-2)
 
     Here, the coefficient k is a correction coefficient for adapting the magnitudes of pixel values of the display of the mobile device  500  to the magnitude of the robot coordinate system and is acquired in advance based on the size and resolution of the display. 
     Referring back to  FIG. 9 , the PLC  100  calculates a robot coordinate system of the pattern  550  which is a locating destination by correcting (4) the result (Xrb1, Yrb1) of teaching of the robot  300  using the deviation amount in the robot coordinate system (step S 94 ). In addition, the PLC  100  (5) calculates a movement amount of the pattern  550  which is a locating destination in the robot coordinate system on the basis of a movement amount of the conveyor  10  (step S 95 ). Then, the PLC  100  (1) determines relational formulas for the calibration with respect to the pattern  550  which is a locating destination using coordinate values of the robot coordinate system which are obtained by transforming the result of measurement of the position of the pattern  550  displayed on the display of the mobile device  500  (coordinate values of the camera coordinate system) and the movement amount calculated in step S 95  (step S 96 ). The relational formulas determined in step S 96  are represented by the following formulas (4-1) and (4-2) using transformation functions Fx and Fy. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
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     Here, Enc denotes a count number counted when the mobile device  500  is moved. 
     Referring back to  FIG. 9 , the PLC  100  determines whether the calculation of parameter sets for the calibration with respect to all patterns  550  which are locating destinations is completed (step S 97 ). When there are remaining patterns  550  which are locating designations, for which the calculation of parameter sets for the calibration is not completed (NO in step S 97 ), the PLC  100  repeats step S 92  and subsequent processes for other patterns  550  which are locating destinations. 
     On the other hand, when calculation of parameter sets for the calibration with respect to all patterns  550  which are locating destinations is completed (YES in step S 97 ), the PLC  100  calculates a parameter set for the calibration based on the relational formulas (the aforementioned formulas (4-1) and (4-2)) determined in step S 96  for each pattern  550  which is a locating destination (step S 98 ). The calculation of parameter sets is to solve simultaneous linear equations. 
     According to the above-described process, calculation of parameter sets for the calibration is completed and the process returns to step S 10  in  FIG. 8 . 
     &lt;E. Calibration Process (2)&gt; 
     Next, the calibration process (2) will be described. In the calibration process (2), the position of the tip  320  of the hand of the robot  300  is detected by the mobile device  500  first, and then an image of the detected position is captured by the camera  250  to calculate a parameter set for the calibration. 
     (e1: Overview) 
       FIG. 11  is a schematic diagram for describing the calibration process (2) according to the present embodiment.  FIG. 12  is a figure showing a processing procedure of the calibration process (2) according to the present embodiment. 
     Referring to  FIGS. 11 and 12 , first, the mobile device  500  is disposed in the tracking range (the operation range of the robot  300 ) (step S 11 ). Then, the user causes the tip  320  of the hand of the robot  300  to touch any position on the mobile device  500  using the teaching pendant  380  or the like (step S 12 ). The mobile device  500  detects the position at which the tip  320  of the hand of the robot  300  has been located and displays a pattern  550  at the position (step S 13 ). 
     Thereafter, the conveyor  10  is driven in a reverse direction to convey the mobile device  500  to the imaging visual field of the camera  250  (step S 14 ). Subsequently, the camera  250  captures an image of the mobile device  500  displaying the pattern  550  (step S 15 ) and the visual sensor  200  measures the position (e.g., the position of the center or the position of center of gravity) of the pattern  550  by performing pattern matching or the like on the captured image (step S 16 ). 
     In this manner, the mobile device  500  displays at least one pattern  550  according to the position touched by the robot  300 . In addition, the mobile device  500  receives a touch operation of the robot  300  and then is disposed in the imaging visual field. A parameter set is calculated based on an image measurement result acquired by capturing an image of the mobile device  500  disposed in the imaging visual field using the camera  250 . 
     The PLC  100  calculates a parameter set with respect to the calibration based on (1) a result of measurement of the position of the pattern  550  displayed on the display of the mobile device  500 , (2) the position of the tip  320  of the hand detected in the mobile device  500 , (3) a result of teaching of the robot  300  (the position of the tip  320  of the hand in the robot coordinate system) and (4) a movement amount of the conveyor  10  (step S 17 ). Then, the PLC  100  stores the calculated parameter set (step S 18 ). The calibration is completed according to the above-described procedure. 
     (e2: Calculation of Parameter Set) 
     Next, a procedure for calculating a parameter set with respect to the calibration represented in  FIG. 10  will be described in more detail. 
     Referring to  FIG. 11 , the mobile device  500  detects a position at which the tip of the hand of the robot  300  touches the touch panel and displays a pattern  550  at the detected position. A result (Xrb1, Yrb1) of teaching of the robot  300  corresponds to the displayed pattern  550 . 
     Thereafter, although the mobile device  500  is moved to the imaging visual field of the camera  250 , the movement amount Enc (a count number counted when the mobile device  500  is moved) is known. 
     In a state in which the mobile device  500  has been disposed in the imaging visual field of the camera  250 , the visual sensor  200  may acquire the position (Xc1, Yc1) of the pattern  550  by capturing an image of the mobile device  500 . 
     Finally, the following formulas (5-1) and (5-2) are obtained using the transformation functions Fx and Fy.
 
 Fx ( Xc 1)+ dX·Enc=Xrb 1  (5-1)
 
 Fy ( Xc 1)+ dY·Enc=Yrb 1  (5-2)
 
     The PLC  100  calculates a parameter set with respect to the calibration based on the formulas (5-1) and (5-2). 
     &lt;F. User Interface&gt; 
     Next, an example of a user interface provided in the mobile device  500  according to the present embodiment will be described. 
     (f1: Leading to Touch Position) 
     In the mobile device  500 , a pattern  550  to be touched among one or more patterns  550  may be displayed in a different form from other patterns  550 . 
       FIG. 13  is a diagram showing an example of a user interface screen provided in the mobile device  500  according to the present embodiment. Referring to  FIG. 13 , the display of the mobile device  500  displays one or more patterns  550  for the calibration. In addition to display of these patterns  550 , a pattern  550  at which the tip  320  of the hand of the robot  300  will be located in each stage of the calibration may be displayed in an emphasized manner. That is, an emphasis mark  560  indicating a locating destination is added to a pattern  550  which is a locating destination. 
     The user locates the tip  320  of the hand of the robot  300  according to the emphasis mark  560 . When the tip  320  of the hand of the robot  300  needs to be sequentially located at a plurality of patterns  550 , display positions of the emphasis mark  560  are sequentially switched. 
     Complicatedness of a calibration operation performed by the user can be reduced using the emphasis mark  560  indicating which pattern  550  is desirable to be touched by the tip  320  of the hand of the robot  300 . That is, a situation in which the user touches a wrong pattern  550  with the tip  320  of the hand of the robot  300  can be avoided. 
     Accordingly, a user with little experiment is able to appropriately perform the calibration. 
     (f2: Checking of Touch Position) 
     In the mobile device  500 , a touch position which is actually touched may be displayed with one or more patterns  550 . 
       FIG. 14  is a diagram showing another example of a user interface screen provided in the mobile device  500  according to the present embodiment. Referring to  FIG. 14 , the display of the mobile device  500  displays one or more patterns  550  for the calibration. In addition to these patterns  550 , a touch position mark  570  indicating a position at which the tip  320  of the hand of the robot  300  is located and the mobile device  500  detects a touch of the tip  320  of the hand may be provided. 
     Although  FIG. 14  exemplifies the circular touch position mark  570  as an example, any shape such as a dot, an oval, a polygon, an asterisk and a circular slit may be used. In addition, any color may be employed as a display color of the touch position mark  570  and flickering or change of a display color may be employed in order to improve visibility. 
     The user is able to check whether the tip  320  of the hand of the robot  300  has been correctly located at a pattern  550  which is a locating destination by locating the tip  320  of the hand of the robot  300  and then referring to the touch position mark  570 . In addition, the user is able to find out a habit or disposition of the robot  300  by recognizing a difference between the pattern  550  which is a locating destination and the touch position mark  570  which is an actually touched position and thus can improve the skill of operating the robot  300  for the calibration. 
     (f3: Display of Calibration Accuracy) 
     In the calibration according to the present embodiment, the calibration accuracy may be calculated based on a deviation from a regression equation in a parameter set calculation process. Typically, the calibration accuracy is calculated in the PLC  100 . The calibration accuracy calculated in the PLC  100  may be transmitted to the mobile device  500 . When such a configuration is employed, the user may be notified of the calibration accuracy through the mobile device  500 . 
     That is, the mobile device  500  may display the accuracy of a parameter set calculated by the PLC  100 . 
     In the conveyor tracking system  1  according to the present embodiment, a touch position detected by the mobile device  500  is transmitted to the PLC  100  according to wireless communication or the like. In addition, a parameter set with respect to the calibration is calculated in the PLC  100  and the calibration accuracy of the calculated calibration is also calculated. Further, the calculated calibration accuracy is returned to the mobile device  500  and thus the user is able to immediately check a calibration operation result. If it is determined that sufficient calibration accuracy has not been acquired, the user is able to immediately resume the calibration operation. 
       FIG. 15  is a diagram showing yet another example of a user interface screen provided in the mobile device  500  according to the present embodiment. Referring to  FIG. 15 , the display of the mobile device  500  displays a numerical value of the calibration accuracy received from the PLC  100  (numerical value indication  580 ) and also displays a message  582  for asking resumption of the calibration. 
     For the message  582 , the user selects a “YES” button  584  if the calibration is resumed and selects a “NO” button  586  if not. 
     Alternatively, when the calibration accuracy does not reach a predetermined value, the intent of resumption of the calibration may be indicated to the user. 
     As described above, according to the mobile device  500  according to the present embodiment, when a calibration operation is performed, the calibration accuracy can be immediately checked and thus it is possible to reliably determine whether the calibration has been appropriately performed. In addition, the user can think of the cause when the calibration has been appropriately performed and thus can improve the skill of operating the robot  300  for the calibration. 
     (f4: Support of Robot Operation) 
     In the conveyor tracking system  1  according to the present embodiment, since a difference between the position of a displayed pattern  550  and a position actually touched by the tip  320  of the hand can be calculated in the mobile device  500 , a habit or disposition of the user performing a calibration operation may be acquired on the basis of the calculated difference. A method of operating the robot  300  may be supported for the user according to such habit or disposition of the user. 
       FIG. 16  is a diagram showing yet another example of a user interface screen provided in the mobile device  500  according to the present embodiment. Referring to  FIG. 16 , the display of the mobile device  500  may display details of an acquired habit or disposition of the user with respect to a calibration operation and a support message  590  including a guidance according to the habit or disposition, for example. 
     Specifically, the support message  590  presents a disposition of a user operation and a skill of the user to operate the tip  320  of the hand of the robot  300 . By presenting the support message  590  to the user, the user is able to locate the tip  320  of the hand of the robot  300  more appropriately when the user resumes the calibration, for example. It is possible to improve the skill of operating the robot  300  for the calibration by presenting the support message  590  to the user. 
     &lt;G. Supplementary Notes&gt; 
     The present embodiment described above includes the following technical ideas. 
     [Configuration 1] 
     A conveyor tracking system including a conveyance device  10  which conveys workpieces W; 
     a robot  300  which is disposed in association with the conveyance device and picks up the workpieces conveyed by the conveyance device; 
     an image capturing part  250  which has an imaging visual field on a conveyance route of the conveyance device; 
     a visual sensor  200  which performs an image measurement on images captured by the image capturing part; 
     a control device  100  which generates an operation command for the robot using a previously calculated parameter set based on an image measurement result obtained by the visual sensor; and 
     a mobile device  500  which has a touch panel  520  used in a process of calculating the parameter set, 
     wherein the mobile device includes: 
     a display part  520  which displays one or a plurality of patterns  550  at predetermined positions; and 
     a transmission part  516  which transmits, according to a fact of being touched in a state in which the one or the plurality of the patterns is displayed, information indicating a touch position being touched to the control device, and 
     the control device includes a calculation part  130  which calculates the parameter set based on the image measurement result obtained by the visual sensor when the mobile device is disposed in the imaging visual field in a state in which the one or the plurality of the patterns is displayed, the touch position when the mobile device is touched by the robot, and a distance between a position of the mobile device when the mobile device is disposed in the imaging visual field and a position when the mobile device is touched by the robot. 
     [Configuration 2] 
     The conveyor tracking system disclosed in configuration 1, wherein, after the mobile device is disposed in the imaging visual field and is captured by the imaging capturing part, the mobile device receives a touch operation performed by the robot. 
     [Configuration 3] 
     The conveyor tracking system disclosed in configuration 1 or 2, wherein the control device calculates the parameter set further based on the a deviation amount between one of the one or the plurality of the patterns displayed on the mobile device and the touch position. 
     [Configuration 4] 
     The conveyor tracking system disclosed in configuration 3, wherein the control device corrects the deviation amount based on a direction of the mobile device with respect to the conveyance and then calculates the parameter set. 
     [Configuration 5] 
     The conveyor tracking system disclosed in configuration 1, wherein the mobile device displays at least one pattern according to the touch position touched by the robot and is disposed in the imaging visual field after receiving a touch operation performed by the robot. 
     [Configuration 6] 
     The conveyor tracking system disclosed any one of configurations 1 to 5, wherein the mobile device displays a pattern to be touched among the one or the plurality of the patterns in a different form  560  from other patterns. 
     [Configuration 7] 
     The conveyor tracking system disclosed any one of configurations 1 to 6, wherein the mobile device displays the touch position  570  along with the one pattern or the plurality of the patterns. 
     [Configuration 8] 
     The conveyor tracking system disclosed any one of configurations 1 to 7, wherein the mobile device displays an accuracy  580  of the parameter set calculated by the control device. 
     [Configuration 9] 
     The conveyor tracking system disclosed any one of configurations 1 to 8, wherein data is exchanged between the control device and the mobile device through wireless communication. 
     [Configuration 10] 
     A calibration method in a conveyor tracking system  1  including a conveyance device  10  which conveys workpieces W; a robot  300  which is disposed in association with the conveyance device and picks up the workpieces conveyed by the conveyance device; an image capturing part  250  which has an imaging visual field on a conveyance route of the conveyance device; a visual sensor  200  which performs an image measurement on images captured by the image capturing part; and a control device  100  which generates an operation command for the robot using a previously calculated parameter set based on an image measurement result obtained by the visual sensor, 
     the calibration method including: 
     displaying one or a plurality of patterns at predetermined positions on a display of a mobile device having a touch panel (S 1 ); 
     disposing the mobile device in the imaging visual field in a state in which the one or the plurality of the patterns are displayed on the display of the mobile device and acquiring the image measurement result with respect to an image obtained by capturing an image of the mobile device according to the visual sensor (S 2  to S 4 ); 
     acquiring a touch position when the mobile device is touched by the robot in a state in which the one or the plurality of the patterns are displayed on the display of the mobile device (S 5  to S 7 ); and 
     calculating the parameter set based on the image measurement result, the touch position and a distance between a position of the mobile device in a state in which the mobile device is disposed in the imaging visual field and a position when the mobile device is touched by the robot (S 9 ). 
     &lt;H. Other Configurations&gt; 
     According to one embodiment of the disclosure, a conveyor tracking system is provided. The conveyor tracking system includes a conveyance device that conveys workpieces; a robot that is disposed in association with the conveyance device and picks up the workpieces conveyed by the conveyance device; an image capturing part that has an imaging visual field on a conveyance route of the conveyance device; a visual sensor that performs an image measurement on images captured by the image capturing part; a control device that generates an operation command for the robot using a parameter set that is previously calculated based on an image measurement result obtained by the visual sensor; and a mobile device which has a touch panel used for a process of calculating the parameter set. The mobile device includes a display part which displays one or more patterns at predetermined positions; and a transmission part which transmits, according to a fact of being touched in a state in which the one or more patterns are displayed, information indicating a touch position being touched to the control device. The control device includes a calculation part which calculates that parameter set based on the image measurement result obtained by the visual sensor when the mobile device is disposed in the imaging visual field in a state in which the one or more patterns are displayed, the touch position when the mobile device is touched by the robot, and a distance between a position of the mobile device when the mobile device is disposed in the imaging visual field and a position when the mobile device is touched by the robot. 
     According to this embodiment of the disclosure, since positions at which one or a plurality of patterns is displayed and a touch position actually touched by the robot may be detected in the mobile device, it is possible to correct a position deviation therebetween and then calculate a parameter set for calibration even when a user has a low operation skill. 
     In the above-described embodiment of the disclosure, after the mobile device is disposed in the imaging visual field and captured by the imaging capturing part, the mobile device may receive a touch operation performed by the robot. 
     According to this embodiment of the disclosure, it is possible to calculate a parameter set for calibration by conveying the mobile device instead of workpieces in the conveyance device. 
     In the above-described embodiment of the disclosure, the control device may calculate the parameter set further based on a deviation amount between one of the one or the plurality of the patterns displayed on the mobile device and the touch position. 
     According to this embodiment of the disclosure, a user having a low operation skill can also realize calibration with little error. 
     In the above-described embodiment of the disclosure, the control device may correct the deviation amount based on a direction of the mobile device with respect to the conveyance device and then calculate a parameter set. 
     According to this embodiment of the disclosure, it is possible to appropriately calculate a parameter set even when the mobile device is disposed being inclined with respect to the conveyance device. 
     In the above-described embodiment of the disclosure, the mobile device may display at least one pattern according to the touch position touched by the robot and may be disposed in the imaging visual field after receiving a touch operation of the robot. 
     According to this embodiment of the disclosure, since a pattern may be displayed at a position according to a touch position, a deviation amount between the pattern and the touch position is not generated and thus a calibration error can be reduced. 
     In the above-described embodiment of the disclosure, the mobile device displays a pattern to be touched among the one or the plurality of the patterns in a different form from other patterns. 
     According to this embodiment of the disclosure, a user with little experience can also realize calibration without an operation mistake. 
     In the above-described embodiment of the disclosure, the mobile device may display the touch position along with the one or the plurality of the patterns. 
     According to this embodiment of the disclosure, since a user may check the position of the mobile device touched by actually operating the robot, the user can objectively ascertain the accuracy of operation thereof and the like and thus can improve in operation skill. 
     In the above-described embodiment of the disclosure, the mobile device may display an accuracy of the parameter set calculated by the control device. 
     According to this embodiment of the disclosure, after a parameter set for calibration is calculated, the user can recognize the accuracy of the calculated parameter and thus can objectively ascertain a necessity of resumption of calibration. 
     In the above-described embodiment of the disclosure, data may be exchanged between the control device and the mobile device through wireless communication. 
     According to this embodiment of the disclosure, a series of calibration processes can be concluded in a state in which the mobile device has been disposed on the conveyance device. 
     According to another embodiment of the disclosure, a calibration method in a conveyor tracking system is provided. The conveyor tracking system includes a conveyance device which conveys workpieces; a robot which is disposed in association with the conveyance device and picks up the workpieces conveyed by the conveyance device; an image capturing part which has an imaging visual field on a conveyance route of the conveyance device; a visual sensor which performs an image measurement on images captured by the image capturing part; and a control device which generates an operation command for the robot using a parameter set that is previously calculated, based on the an image measurement result obtained by the visual sensor. The calibration method includes displaying one or a plurality of patterns at predetermined positions on a display of a mobile device having a touch panel; disposing the mobile device in the imaging visual field in a state in which the one or the plurality of the patterns is displayed on the display of the mobile device and acquiring the image measurement result with respect to an image obtained by capturing an image of the mobile device according to the visual sensor; acquiring a touch position when the mobile device is touched by the robot in a state in which the one or the plurality of the patterns is displayed on the display of the mobile device; and calculating the parameter set based on the image measurement result, the touch position and a distance between a position of the mobile device in a state in which the mobile device is disposed in the imaging visual field and a position when the mobile device is touched by the robot. 
     According to this embodiment of the disclosure, since positions at which one or a plurality of patterns is displayed and a touch position actually touched by the robot may be detected in the mobile device, it is possible to correct a position deviation therebetween and then calculate a parameter set for calibration even when a user has a low operation skill. 
     According to the embodiments of the disclosure, it is possible to provide a method by which even a user with little experience in robot operation is able to perform correct calibration. 
     &lt;I. Conclusion&gt; 
     In operation of conveyor tracking according to the present embodiment, a parameter set is calculated for performing transformation between the camera coordinate system and the robot coordinate system according to calibration. 
     In a conventional calibration method, a sheet including patterns for calibration is disposed on a conveyor and an image thereof is captured using a camera to acquire the positions of center of gravity of the patterns as coordinate values of the camera coordinate system. Then, the conveyor is operated to move the patterns for calibration to a position at which a robot picks up workpieces. In addition, the tip of the hand of the robot is located at the position of center of gravity of each pattern for calibration to teach the position (coordinate values of the robot coordinate system). Finally, the parameter set is calculated based on the coordinate values (a measurement result obtained by the camera) of the camera coordinate system, the coordinate values (a result of teaching of the robot) of the robot coordinate system, and a movement distance of the conveyor. Here, teaching of the robot requires at least three points. 
     In the above-described conventional method, a coordinate transformation formula includes an error if a robot teaching position is not correctly aligned with a pattern for calibration. When a command for performing a pickup operation is generated using the coordinate transformation formula including such an error, the robot fails to adsorb and grip the workpieces. 
     On the contrary, in the present embodiment, the position of center of gravity of each pattern is acquired by capturing an image of the mobile device  500  using the camera in a state in which patterns for calibration are displayed on the display of the mobile device  500  by using the mobile device  500  having the touch panel. 
     In addition, the mobile device  500  is touched with the tip  320  of the hand of the robot  300  to acquire a teaching position at that time and the positions of patterns for calibration displayed on the display of the mobile device  500 . Such information acquired by the mobile device  500  is transmitted to the PLC  100  such that the PLC  100  calculates a parameter set for calibration. 
     According to the present embodiment, since information of a teaching position for the robot  300  (coordinate values of the robot coordinate system) and coordinate values actually detected by the mobile device  500  at that time can be acquired, an error in the teaching position can be corrected. Accordingly, calibration accuracy can be improved compared to cases in which the conventional sheet including patterns for calibration is used. 
     Furthermore, according to the present embodiment, restrictions that the robot needs to be taught at three points or more, which are required in the conventional method, can be mitigated. Accordingly, a time required for calibration can be reduced. 
     In the present embodiment, an actually touched position, calibration accuracy of a calculated parameter set, and the like can be displayed on the mobile device  500 , and thus user operability with respect to calibration can be improved. 
     The embodiments disclosed herein are to be construed in all aspects as illustrative and not restrictive. The scope of the disclosure should be determined by the appended claims and their legal equivalents, not by the above description, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.