Patent Publication Number: US-2020276716-A1

Title: Robot apparatus, control method for robot apparatus, method of manufacturing article using robot apparatus, communication device, communication method, control program, and recording medium

Description:
BACKGROUND 
     Field 
     The present disclosure relates to a robot apparatus that uses wireless communication. 
     Description of the Related Art 
     In recent years, robot apparatuses including an articulated robot arm have been used on production lines for manufacturing products. A robot arm of this type is provided with a gripping device, such as a robot hand, or a tool or the like, as an end effector at a leading end thereof, and operates a workpiece to manufacture an article such as an industrial product or a part thereof. 
     A robot hand functioning as the end effector is provided with a finger portion for gripping a workpiece. The robot hand converts torque from a motor incorporated in the robot hand into a linear motion using a gear and transmits the linear motion to the finger portion, to grip the workpiece. 
     The robot arm includes a joint that connects a link with another link. The robot arm also includes, as a joint mechanism, for example, a motor, such as an alternate current (AC) servomotor or a direct current (DC) brushless servomotor, and a reduction gear provided at an output side, and controls a link operation. 
     Heretofore, in a case where control signals for controlling a motor incorporated in the end effector and the motor incorporated in the robot arm are transmitted to the motors, the control signals have generally been transmitted via a communication cable wired in the robot arm. 
     However, the robot arm is constantly moving, and thus the communication cable used in the robot arm is required to have an inflection resistance. In addition, in order to control motors provided in each joint of the robot arm and the robot hand, the number of communication cables increases. This causes the inflection resistance of each communication cable to deteriorate, and the robot arm needs to be thickened to secure a space for the communication cable. 
     To solve the above-described problem, various wireless communication methods are proposed for the robot apparatus to realize wireless communication in the robot apparatus. 
     Examples of the wireless communication methods include methods using protocols such as (Ethernet for Control Automation Technology) EtherCAT, Control &amp; Communication (CC)-Link Industrial Ethernet (IE), (Process Field Bus Decentralized Periphery) PROFIBUS-DP, and Mechatrolink-III, which are capable of establishing high-speed communication, in addition to a Controller Area Network (CAN) and Recommended Standards (RS)-485, which have been heretofore used. 
     In addition, Japanese Patent Application Laid-Open No. 2005-217799 discusses a method in which various electronic devices wirelessly send data that require multiplexing, such as high-speed data which cannot be easily transmitted by a wired connection, or data to be transmitted via a bus line in order to reduce the number of communication cables, while the various electronic devices send, via a wire, data for which high-speed large-amount data transfer is not required. With this method, the number of communication cables for transmitting data necessary for multiplexing can be reduced. 
     However, the robot arm can take various orientations depending on an operation to be executed. Depending on the orientation of the robot arm, a peripheral device or a link of the robot arm is disposed between a control device and a communication target device, which may make the wireless communication unstable. 
     In addition, generally-used wireless transmission methods (e.g., Wireless Fidelity (Wi-Fi) Institute of Electrical and Electronics Engineers (IEEE) 802.1, 4G, and 5G) use a frequency of 1 GHz or higher and a high rectilinear advancing property. Accordingly, even if the communication target deviates only slightly from a communicable area depending on the orientation of the robot arm, the communication can be interrupted. 
     The method discussed in Japanese Patent Application Laid-Open No. 2005-217799 assumes an electronic device in which no shielding material is disposed between a transmission target and a reception target, like in a laptop personal computer (PC), and thus wireless communication can be stably performed while preventing the transmission target and the reception target from deviating from the communicable area. Therefore, it is difficult for the method to deal with the above-described interruption of wireless connection that may occur during a great motion performed by the robot arm. 
     SUMMARY 
     In view of the above-described issues, the present disclosure is directed to providing a robot apparatus capable of performing a stable wireless communication. 
     According to an aspect of the present disclosure, a robot apparatus includes a robot arm including a link, a first control device disposed in the robot arm, a second control device, and a wireless communication unit configured to enable the first control device and the second control device to communicate with each other wirelessly. The wireless communication unit is disposed in the link. 
     Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view illustrating a schematic configuration of a robot apparatus according to an exemplary embodiment of the present disclosure. 
         FIG. 2  is a block diagram illustrating the robot apparatus according to the exemplary embodiment. 
         FIGS. 3A   3 B, and  3 C are explanatory diagrams each illustrating an antenna according to the exemplary embodiment. 
         FIG. 4  is a flowchart illustrating control processing according to the exemplary embodiment. 
         FIGS. 5A and 5B  are plan views each illustrating a combination of antennas to be used depending on an orientation of a robot arm body according to the exemplary embodiment. 
         FIG. 6  is a plan view illustrating a case where the combination of antennas to be used is changed according to the exemplary embodiment. 
         FIG. 7  is a plan view illustrating an advantageous effect according to the exemplary embodiment. 
         FIG. 8  is a plan view illustrating another advantageous effect according to the exemplary embodiment. 
         FIG. 9  is a plan view illustrating a case where installation positions of antennas to be used are changed according to the exemplary embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments for carrying out the present disclosure will be described below with reference to the accompanying drawings. Configurations described below are merely examples, and details thereof can be appropriately modified by one skilled in the art within the scope of the present disclosure. In addition, numerical values mentioned in exemplary embodiments are values merely for reference and should not limit the present disclosure. 
     A first exemplary embodiment will be described below.  FIG. 1  is a plan view illustrating a robot apparatus  100  according to the first exemplary embodiment as viewed in a certain direction. In the drawings described below, arrows X, Y, and Z represent a coordinate system of the entire robot apparatus  100 . In a general robot system using a robot apparatus, not only a global coordinate system representing an overall installation environment, but also a local coordinate system representing a position of a robot hand, a finger portion, or the like is used, as needed, as an XYZ three-dimensional coordinate system, depending on a control operation or the like to be executed. In the present exemplary embodiment, the coordinate system of the entire robot apparatus  100  is represented by XYZ, and a local coordinate system is represented by xyz. 
     As illustrated in  FIG. 1 , the robot apparatus  100  includes an articulated robot arm body  200 , a robot hand body  300 , and a control device  400  that controls an overall operation of the robot apparatus  100 . 
     The robot apparatus  100  also includes an external input device  500  as a teaching device that transmits teaching data to the control device  400 . An example of the external input device  500  is a teaching pendant, which is used for an operator to designate the positions of the robot arm body  200  and the robot hand body  300 . 
     The present exemplary embodiment illustrates a case where a robot hand is provided as an end effector at a distal end of the robot arm body  200 . However, the end effector is not limited to a robot hand, but instead a tool or the like may be used. 
     A link  201  which is a proximal end of the robot arm body  200  is disposed on a base  210 . 
     The robot hand body  300  grips an object such as a part or a tool. The robot hand body  300  according to the present exemplary embodiment uses a drive mechanism (not illustrated) and a motor  311  to open or close two finger portions to thereby grip or release a workpiece. The robot hand body  300  may grip the workpiece while preventing the workpiece from being displaced relatively to the robot arm body  200 . 
     The present exemplary embodiment illustrates an example where two finger portions are configured to grip an object. However, the finger portions may be provided with a pneumatic mechanism or an adhesive mechanism to hold the workpiece by adsorbing the workpiece. 
     A hand motor driver  301  that controls driving of the motor  311  is incorporated in the robot hand body  300 . 
     The robot hand body  300  is connected to a link  204 . The robot hand body  300  can be rotated by the rotation of the link  204 . 
     The robot arm body  200  includes a plurality of joints, such as four joints (four axes). The robot arm body  200  also includes a plurality of (four) motors  211  to  214  that rotationally drive joints J 1  to J 4 , respectively, about the corresponding rotation axis. 
     The motors  211  to  214  connect links  201  to  204  directly or via a transmission member such as a belt, a bearing, or the like (not illustrated). 
     If torque for driving the links  201  to  204  is insufficient, a reduction gear (not illustrated) may be disposed at the rotation axis of each of the motors  211  to  214  to amplify the torque. 
     In the robot arm body  200 , the plurality of links  201  to  204  is rotatably connected to each other in the joints J 1  to J 4 . In this case, the links  201  to  204  are sequentially connected in series in a direction from the proximal end of the robot arm body  200  to the distal end thereof. 
     The motors  211  to  214 , which are disposed in the joints J 1  to J 4 , respectively, are each provided with an arm motor driver  50  that controls the corresponding motor. 
     In the present exemplary embodiment, a node control system in which a driver for controlling a motor in each joint is disposed at each axis is adopted as a method for controlling the robot arm. 
     The node control system is operated when power and control signals are sent to the arm motor drivers  50 , which are disposed in the joints J 1  to J 4 , respectively. Accordingly, in the node control system, plane-wave method (PWM) noise is not likely to occur and the length of a sensor wire can be reduced when a sensor or the like is placed, which leads to a reduction in the noise effects coming from the sensor. 
     Thus, the noise that occurs in each device can be prevented from adversely affecting wireless communication. 
     As illustrated in  FIG. 1 , the base  210  and the link  201  of the robot arm body  200  are connected with the joint J 1 . The rotation axis of the joint J 1  matches an X-axis direction in a state illustrated in  FIG. 1 . 
     The link  201  and the link  202  of the robot arm body  200  are connected with the joint J 2 . The rotation axis of the joint J 2  matches a Y-axis direction in the state illustrated in  FIG. 1 . 
     The link  202  and the link  203  of the robot arm body  200  are connected with the joint J 3 . The rotation axis of the joint J 3  matches the Y-axis direction in the state illustrated in  FIG. 1 . 
     The link  203  and the link  204  of the robot arm body  200  are connected with the joint J 4 . The rotation axis of the joint J 4  matches the Y-axis direction in the state illustrated in  FIG. 1 . 
     With the configuration described above, the robot arm body  200  can direct the end effector (robot hand body  300 ) of the robot arm body  200  in arbitrary three-direction orientations, at any three-dimensional positions, within a movable range. 
     A leading end of a hand portion of the robot arm body  200  corresponds to the robot hand body  300  in the present exemplary embodiment. In a case where robot hand body  300  grips an object, the robot hand body  300  and an object (e.g., a part or a tool) gripped by the robot hand body  300  are collectively referred to as the leading end of the hand portion of the robot arm body  200 . 
     In other words, the robot hand body  300  functioning as the end effector is referred to as the leading end of the hand portion, regardless of whether the robot hand body  300  is gripping an object or not. 
     With the configuration described above, the robot arm body  200  can cause the robot hand body  300  to operate at any position to perform a desired operation. Examples of the desired operation include an operation of gripping the workpiece, and assembling the gripped workpiece to a predetermined workpiece, to manufacture an article. 
     The robot hand body  300  may be, for example, an end effector such as an air hand using a pneumatic driving method. 
     The robot hand body  300  can be attached to the link  204  by a semi-fixing means such as fixation with a screw, or by an attachment/detachment means such as latching. 
     In particular, if the robot hand body  300  is detachably mountable, the following system can also be employed. That is, the robot arm body  200  is controlled to attach/detach or replace various types of robot hand bodies  300  disposed at a supply position by the operation of the robot arm body  200  itself. 
     A plurality of antennas  13 , each of which serves as a wireless communication unit, is provided as illustrated in  FIG. 1  to establish wireless communication among the control device  400 , the hand motor driver  301  incorporated in the robot hand body  300 , and the arm motor drivers  50 . 
     In the present exemplary embodiment, six antennas  13  are installed in the robot apparatus  100 . The antenna disposed on the control device  400  is referred to as an antenna  13 - 0 , and the antenna disposed on the base  210  is referred to as an antenna  13 - 1 . Similarly, the antenna disposed in the vicinity of the joint J 2  is referred to as an antenna  13 - 2 , the antenna disposed in the vicinity of the joint J 3  is referred to as an antenna  13 - 3 , the antenna disposed in the vicinity of the joint J 4  is referred to as an antenna  13 - 4 , and the antenna disposed on the robot hand body  300  is referred to as an antenna  13 - 5 . 
     In the present exemplary embodiment, generally-used wireless transmission methods (e.g., Wireless Fidelity (Wi-Fi) Institute of Electrical and Electronics Engineers (IEEE) 802.1, 4G, and 5G) are adopted for the antennas  13  to be used. 
     By wireless communication via the antennas  13 , operation data used to cause the robot hand body  300  to operate is transmitted from the control device  400  to the hand motor driver  301  through a wireless communication path  12 . Similarly, the wireless communication path  12  is also used for transmitting data to the arm motor drivers  50  corresponding to the joints J 1  to J 4 , respectively. 
     The antennas  13  described above enable wireless communication. The antennas  13  will be described in detail below. 
     The control device  400  according to the present exemplary embodiment also functions as a power supply device for supplying power to the robot apparatus  100 . 
     The power to the motor  311  is supplied to the motor  311  from the control device  400  through a power supply cable  1 . 
       FIG. 2  is a block diagram illustrating a configuration example of the robot apparatus  100  according to the present exemplary embodiment. The robot arm control device  400  is composed of a computer, and includes a central processing unit (CPU)  401  as a control unit (processing unit). 
     The control device  400  also includes, as storage units, a read-only memory (ROM)  402 , a random access memory (RAM)  403 , and a hard disk drive (HDD)  404 . The control device  400  also includes a recording disk drive  405  and various interfaces  406  to  409  and  411 . 
     The CPU  401  is connected to each of the ROM  402 , the RAM  403 , the HDD  404 , the recording disk drive  405 , and the various interfaces  406  to  409  and  411  via a bus  410 . 
     The ROM  402  stores a program  430  for causing the CPU  401  to execute arithmetic processing. The CPU  401  executes each process of a robot control method based on the program (recorded) stored in the ROM  402 . 
     The RAM  403  is a storage device that temporarily stores various data such as arithmetic processing results obtained by the CPU  401 . 
     The HDD  404  is a storage device that stores arithmetic processing results obtained by the CPU  401 , various data externally acquired, and the like. 
     The recording disk drive  405  can read out various data, programs, and the like recorded on a recording disk  431 . 
     The external input device  500  is connected to the interface  406 . The CPU  401  receives teaching data from the external input device  500  via the interface  406  and the bus  410 . 
     The motors  211  to  214  that drive the joints J 1  to J 4 , respectively, include sensor units  221  to  224 , which are connected to the motors  211  to  214 , respectively. The motor  311  that drives the finger portions of the robot hand body  300  includes a sensor unit  321  which is connected to the motor  311 . 
     The term “sensor” used herein refers to an angular sensor for detecting a rotational angle of the rotation axis of each of the motors  211  to  214  and the sensor unit  321 . Examples of the sensor include a magnetic encoder and an optical encoder. 
     The encoders have, for example, an absolute encoder function and an increment encoder function as their functions. The increment encoder can detect an angle of a motor in one rotation, and the absolute encoder can count the number of rotations of a motor when the motor rotates a plurality of times. 
     The robot arm according to the present exemplary embodiment includes a joint that is rotated 360° or more, and, therefore, the absolute encoder is used for the robot arm in the present exemplary embodiment. 
     The arm motor driver  50  is connected to the interface  409 . The CPU  401  acquires detection results from the sensor units  221  to  224  via the interface  409  and the bus  410 . Further, the CPU  401  outputs command values data for the respective joints to an arm motor driver  50  via the bus  410  and the interface  409  at a predetermined time interval. 
     Similarly, the hand motor driver  301  is connected to the interface  411  so that the hand motor driver  301  can communicate with the CPU  401  via the bus  410 . The CPU  401  acquires a detection result from the sensor unit  321  via the hand motor driver  301 , the bus  410 , and the interface  411 . Further, the CPU  401  outputs the command value data of the respective finger portions to the hand motor driver  301  via the bus  410  and the interface  411  at a predetermined time interval. 
     The interface  407  is connected to a monitor  421 . Various images are displayed on the monitor  421  under control of the CPU  401 . The interface  408  is configured to be connectable with an external storage device  422 . The external storage device  422  is a storage unit such as a rewritable nonvolatile memory or an external HDD. 
     The present exemplary embodiment illustrates a case where the HDD  404  is used as a computer-readable recording medium and the program  430  is stored in the HDD  404 . However, the program  430  is not limited to this example. The program  430  may be recorded on any type of recording medium, as long as the recording medium is a computer-readable recording medium. 
     As a recording medium for supplying the program  430 , for example, the ROM  402 , the recording disk  431 , or the external storage device  422  may be used. Specifically, the examples of the recording medium may include a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a compact disc (CD)-ROM, CD-Recordable (CD-R), a magnetic tape, a nonvolatile memory, and a ROM. 
     Next, the antennas  13  serving as the wireless communication unit used in the present exemplary embodiment will be described in detail with reference to  FIG. 3 . Assume that all the antennas  13 - 0  to  13 - 5  have the same configuration.  FIG. 3A  is a perspective view illustrating the antenna  13  as viewed in a predetermined direction. FIGS.  3 B and  3 C each illustrate a radiation pattern of the antenna  13 . 
     Referring to  FIG. 3A , the antenna  13  is composed of a chip antenna, and includes a chip  14 , a turntable  15 , and an antenna control device  16 . 
     The chip  14  is mounted on the turntable  15  as illustrated in  FIG. 3A , and the turntable  15  is configured to be rotated by a motor (not illustrated). 
     Driving of the motor for driving the turntable  15  is controlled by the antenna control device  16  so that the motor can be arbitrarily rotated. The antenna control device  16  acquires command values, such as a driving amount of the turntable  15 , from the control device  400 . 
     Each antenna control device  16  includes a controller for performing a wireless communication control including data modulation and demodulation. The controller included in the antenna control device  16  includes a radio wave intensity measurement unit that measures a radio wave intensity state of each antenna  13 . The controller can measure a radio wave intensity in a current state. 
     Each antenna  13  is used for data communication about at least one axis of the joints J 1  to J 4  of the robot arm body  200 . A single antenna  13  enables data communication corresponding to a plurality of axes such as two axes or three axes. 
     Each antenna  13  has different communication frequency bands in order to prevent interference among channels used for each antenna control device  16 . 
     The number of the antennas  13  used in the present exemplary embodiment is six. However, the number of the antennas  13  to be used may be increased or decreased as needed. 
     Referring to  FIG. 3B , when the chip  14  of the antenna  13  is installed on an XY plane with a radiation surface of the chip  14  facing upward, a large radio wave is radiated in a Z-axis direction as indicated by a radiation pattern “a” as illustrated in  FIG. 3C . When the radiation surface of the chip  14  is rotated by the turntable  15 , the radio wave can be radiated in a predetermined direction. 
     In the present exemplary embodiment, the radiation surface of the chip  14  is changed by the turntable  15  and the motor. However, instead of using this configuration, another configuration can be applied to the apparatus as long as the radiation surface of the chip  14  can be changed. 
     In the present exemplary embodiment, if a metallic object is disposed at a position where the radio wave radiated from the antenna  13  is blocked, the radio wave intensity is lowered. Accordingly, peripheral members are appropriately selected, arranged, and designed to prevent the metallic object other than the links of the robot arm body  200 , from being disposed at the position where the radio wave radiated from the antenna  13  is blocked. Depending on the orientation of the robot arm, each link is inevitably disposed at the position where the radio wave radiated from the antenna  13  is blocked. In such a case, the radial radio wave from the antennas  13  is diffracted to perform communication. 
     Next, a wireless transmission control method depending on the orientation of the robot arm body  200  according to the present exemplary embodiment will be described with reference to a flowchart illustrated in  FIG. 4 . 
     A control processing flow illustrated in  FIG. 4  is executed by the CPU  401  of the control device  400  by reading out the program  430 . 
     Referring to  FIG. 4 , first, in step S 101 , it is determined whether a teaching operation for the robot arm body  200  is already executed. 
     If the teaching operation is not executed (NO in step S 101 ), the processing proceeds to step S 102 . In step S 102 , the teaching operation is executed. In the present exemplary embodiment, the external input device  500  executes the teaching operation for the robot arm body  200 . If the teaching operation is already executed (YES in step S 101 ), the processing proceeds to step S 104 . 
     After that, when the teaching operation is completed, the processing proceeds to step S 103 . In step S 103 , a combination of the antennas  13  to be used for wireless communication is selected based on information about the orientation of the robot arm body  200  set by the teaching operation and positional information about each antenna  13  in each orientation. 
     The radio wave intensity state under a standard environment of each antenna  13  is stored in advance in the information about all orientations of the robot arm body  200 . 
     In step S 103 , a combination of the antennas  13  in which the radio wave intensity enables communication among the antennas  13 , is selected based on the stored data of the radio wave intensity of each antenna  13  according to the orientation information about the robot arm body  200  subjected to the teaching operation. 
       FIGS. 5A and 5B  each illustrate a combination of the antennas  13  to be used depending on the orientation of the robot arm body  20 X).  FIGS. 5A and 5B  each illustrate a case where wireless data is transmitted from the antenna  13 - 0  to the antenna  13 - 5 .  FIG. 5A  illustrates a case where the distance between the antenna  13 - 0  and the antenna  13 - 5  is relatively small.  FIG. 5B  illustrates a case where the distance between the antenna  13 - 0  and the antenna  13 - 5  is large. 
     The antenna  13 - 0  is a basic antenna that transmits command data created by the control device  400 . Therefore, the antenna  13 - 0  is installed at a position where the location of the antenna is not changed depending on the orientation of the robot arm body  200 . With this configuration, the command data indispensable for controlling the robot arm body  200  can be reliably transmitted. 
     Similarly, the antenna  13 - 1  is installed in the base  210  at a position where the location of the antenna is not changed depending on the orientation of the robot arm body  200 . 
     In the present exemplary embodiment, a transmission form will be described using the antenna  13 - 0 . However, depending on the intended use of the robot apparatus  100 , the antenna  13 - 0  may be omitted. The antenna  13 - 1  and the control device  400  may be communicably connected with the power supply cable  1 , and the antenna  13 - 1  may be used as the basic antenna. 
     Referring to  FIG. 5A , in the case of transmitting wireless data from the antenna  13 - 0  to the antenna  13 - 5 , a combination of the antennas  13 - 0 ,  13 - 3 ,  13 - 4 , and  13 - 5  is selected and the antenna  13 - 3  and the antenna  13 - 4  are used as relays. 
     Referring to  FIG. 5B , in the case of transmitting wireless data from the antenna  13 - 0  to the antenna  13 - 5 , a combination of the antennas  13 - 0 ,  13 - 2 ,  13 - 3 ,  13 - 4 , and  13 - 5  is selected and the antenna  13 - 2 , the antenna  13 - 3 , and the antenna  13 - 4  are used as relays. 
     As described above, in step S 103 , in the case of transmitting wireless data from a certain antenna to a certain antenna, a combination of antennas, including the antennas  13  to be used as relays, is selected depending on the orientation of the robot arm body  200  as described above. 
     In the present exemplary embodiment, a combination of antennas is selected depending on the orientation of the robot arm body  20 X). However, a combination of antennas may be selected depending on a distance between a transmitting antenna and a receiving antenna. 
     Next, in step S 104 , the robot arm body  200  is driven to measure the current radio wave intensity of each antenna  13 . 
     Next, in step S 105 , the stored data on the radio wave intensity is compared with the radio wave intensity measured in an actual environment in step S 104 , and it is determined whether the difference between the radio wave intensities is more than or equal to a predetermined range. 
     This is because, in the process of driving the robot arm body  200  in step S 104 , the radio wave intensity measured in the actual environment may be different from the stored data on the radio wave intensity depending on the installation environment of the robot apparatus  100 . 
     In this case, even if a combination of the antennas  13  in which the radio wave intensity enables communication when the robot arm body  200  is in a predetermined orientation, is selected based on the stored data of the radio wave intensity, the radio wave intensity may be insufficient in the actual environment. 
     If the radio wave intensity is smaller than an assumed value (YES in step S 105 ), the processing proceeds to step S 106 . In step S 106 , the radio wave intensity is optimized to an intensity that enables communication, according to the state of the radio wave intensity in the actual environment. 
     As a method for optimizing the radio wave intensity, the number of the antennas  13  used as relays is increased based on the radio wave intensity kept by the combination of the antennas  13  currently selected. 
       FIG. 6  illustrates a case where the radio wave intensity is optimized to an intensity that enables communication if in the combination of the antennas  13  illustrated in  FIG. 5A , the radio wave intensity is not sufficient. 
     Referring to  FIG. 6 , the antenna  13 - 2  is also used as a relay to optimize the radio wave intensity. 
     In the case of increasing the number of the antennas  13  to be used as relays, when data about driving of the robot arm body  200  is transmitted from the antenna  13 - 0 , transmission order data indicating the name and order of antennas to be used as relays is transmitted together. 
     In the case of  FIG. 6 , the antenna  13 - 2  that is not used in the case of  FIG. 5A  is added as a relay. Accordingly, the transmission order data is transmitted together so that the data on driving of the robot arm body  200  is transmitted in the order of the antenna  13 - 2 , the antenna  13 - 3 , the antenna  13 - 4 , and the antenna  13 - 5 . 
     Thus, the data on driving of the robot arm body  200  can be transmitted through the wireless communication path  12  illustrated in  FIG. 6 , and the radio wave intensity can be optimized. 
     A direction of generating radio waves by the antenna  13 - 2 , the antenna  13 - 3 , and the antenna  13 - 4 , which are used as relays, may be changed as needed. 
     After completion of the optimization of the radio wave intensity in step S 106 , the processing returns to step S 105 . In step S 105 , the current radio wave intensity of each antenna  13  is measured, and the stored data about the radio wave intensity is compared with the radio wave intensity measured in the actual environment, and then it is determined whether the difference between the radio wave intensities is more than or equal to the predetermined range. 
     In step S 105 , if the difference between the stored data about the radio wave intensity and the radio wave intensity measured in the actual environment is smaller than the predetermined range, it is determined that the optimization of the radio wave intensity is completed (NO in step S 105 ) and then the processing flow is terminated. 
     As described above, in the present exemplary embodiment, a combination of the antennas  13  to be used for communication is selected or changed, as needed, based on the orientation of the robot arm body  200  and the state of the radio wave between the antennas  13 , thereby changing the wireless communication path as a transmission path for data transmission. 
     In other words, it is possible to switch a communication method from directly transmitting the data to a target antenna, to increasing the antennas  13  as the relays and indirectly transmitting the data. 
     Consequently, even when the wireless communication is interrupted for various reasons, the occurrence of an erroneous operation and a real-lime loss can be reduced, and thus a stable wireless communication can be achieved. 
     Further, the communication path is changed depending on the orientation of the robot arm body  200 , and the number of the antennas  13  to be used is changed. Thus, a time required for data transmission can be changed depending on the orientation of the robot arm body  200 , so that an efficient communication can be achieved. 
     The present embodiment described above illustrates an example where the radio wave from each antenna  13  is a wave that is likely to be diffracted. On the other hand, a case will be considered where wireless communication using a system with a frequency of 1 GHz or higher and a high rectilinear advancing property. In this case, when data communication is performed using the antennas  13 - 0  to  13 - 5 , as illustrated in  FIG. 7 , a plurality of links is located in the robot arm body  200 , which makes it difficult to perform communication in a state where the radio wave is diffracted. 
     However, a communication path can be formed along each link as illustrated in  FIG. 8  by providing antennas at a plurality links of the robot arm body  200  and by using the links as antenna relays for the respective joints. Accordingly, it is possible to prevent each link of the robot arm body  200  from interfering with the communication. In particular, the links of the robot arm body  200  is not deformed if no impact is applied to the links. Therefore, the position of each antenna  13  is stabilized, and thus the above-described method is suitable for wireless communication in a system with a high rectilinear advancing property. 
     The method for optimizing the radio wave intensity executed in step S 106  is not limited to the method described above. For example, a method can be employed and carried out in which each antenna  13  is configured to change the installation position of each antenna  13  with a motor or the like (not illustrated). 
       FIG. 9  illustrates a case there the positions of the antennas  13 - 3 ,  13 - 4 , and  13 - 5  are changed to optimize the radio wave intensity. Referring to  FIG. 9 , the positions of the antennas  13 - 3 ,  13 - 4 , and  13 - 5  are changed so as to approach the antenna  13 - 0 . 
     As a method for causing the antennas  13 - 3 ,  13 - 4 , and  13 - 5  to approach the antenna  13 - 0 , a linear guide or the like is disposed at a predetermined position of each link, thereby enabling each antenna  13  to travel along the linear guide. 
     Further, each antenna  13  is connected to a motor with a belt. When the motor is driven, the antenna  13  can be moved on the linear guide by the belt. 
     By changing the installation position of each antenna  13  as described above, the radio wave intensity can be optimized with a combination of originally used antennas. It is also possible to prevent each link of the robot arm body  200  from standing in the communication path as illustrated in  FIG. 9 , which leads to a further improvement in stability of communication. 
     Although it will not be described in detail, the direction of the radio wave radiated from each antenna  13  may be changed, as needed, by a beamforming technique depending on the orientation of the robot arm, and the ratio wave intensity may be optimized to an intensity that enables communication. 
     In the exemplary embodiment described above, the antennas  13  provided on the robot arm body  200  are used as relays. However, depending on the operation of the robot arm body  200 , only the antenna  13 - 1 , which is provided on the base  210 , may be used as a relay. If the robot arm body  200  has a small operation range, only the antenna  13 - 1  disposed on the base  210 , which is a basal portion of the robot arm body  200 , can cover the range. In that case, the data may be sent from the control device  400  to the antenna  13 - 1 , and the data may also be sent to each unit based on the antenna  13 - 1 . 
     The first exemplary embodiment described above illustrates a specific example where the processing procedure is executed by the control device  400 . However, a control program of software for executing the above-described functions, and a medium recording the program may be loaded in the external input device  500  to carry out the program. 
     Accordingly, the control program of software for executing the above-described functions, the recording medium recording the control program, and a communication device constitute the present disclosure. 
     The exemplary embodiment described above illustrates a case where a ROM or RAM is used as a computer-readable recording medium, and the control program is stored in the ROM or RAM. However, the present disclosure is not limited to this configuration. 
     The control program for carrying out the present disclosure may be recorded on any recording medium, as long as the recording medium is a computer-readable recording medium. Examples of the recording medium for supplying the control program may include an HDD, an external storage device, and a recording disk. 
     OTHER EMBODIMENTS 
     Embodiment(s) of the present disclosure can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     In the exemplary embodiment described above, the antennas  13  are provided on the control device  400  to perform communication, but instead the antennas  13  may be installed at locations other than the control device  400  to perform communication. 
     The exemplary embodiment described above illustrates an example where the robot hand body  300  is used as a data communication target. However, the data communication target is not limited to this example. For example, the antennas  13 - 1  to  13 - 4  may be used to communicate with the motors  211  to  214  for driving the joints J 1  to J 4  of the robot arm body  200 . In this case, the present disclosure can be carried out by employing a configuration in which an antenna is provided on each arm motor drivers  50  to enable data transmission and reception. 
     The exemplary embodiment described above illustrates an example where the antennas  13  each serving as the wireless communication unit can generate a radio wave. However, the wireless communication unit is not limited to this example. For example, in the robot arm body  200 , some of the wireless communication units may be connected by a wired connection, and wireless communication units that cannot generate any radio wave may be used. 
     In the exemplary embodiment described above, wireless communication is performed using the antennas  13 . However, the wireless communication is not limited to this example. For example, an information terminal, such as a smartphone or a personal computer (PC), which includes a wireless communication function, such as Wi-Fi, may be used as the control device  400  and the information terminal or PC may wirelessly communicate with the robot apparatus  100 . 
     The various exemplary embodiments described above illustrate a case where the robot apparatus  100  uses an articulated robot arm including a plurality of joints. However, the number of joints is not limited to this example. A vertical multiaxial configuration is illustrated as a form of the robot apparatus  100 . However, a configuration similar to the configuration described above can be carried out using joints of different forms such as parallel link type joints. 
     The various exemplary embodiments described above illustrate configuration examples of the robot apparatus  100  with reference to the drawings illustrating the respective exemplary embodiments. However, the present disclosure is not limited to these examples. The design of the robot apparatus  100  according to the present disclosure can be arbitrarily changed by one skilled in the art. Each motor provided in the robot apparatus  100  is not limited to the above-described configuration, but instead a device, such as an artificial muscle, or the like may be used as a drive source for driving each joint. 
     The various exemplary embodiments described above can be applied to any machine capable of automatically performing expansion and contraction, bending and stretching, moving upward or downward, moving leftward or rightward, or turning operation, or a combination of these operations, based on information stored in the storage device provided in the control device  400 . 
     While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2019-036673, filed Feb. 28, 2019, which is hereby incorporated by reference herein in its entirety.