Patent Publication Number: US-2021167701-A1

Title: Automatic device and communications system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is the U.S. national stage of application No. PCT/JP2018/039143, filed on Oct. 22, 2018, and priority under 35 U.S.C. § 119(a) and 35 U.S.C. § 365(b) is claimed from Japanese Application No. 2017-233088, filed on Dec. 5, 2017. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates to an automatic device and a communications system. 
     BACKGROUND 
     Conventionally, a technique of giving instruction information from a control terminal to a plurality of motor modules provided in one robot by wireless communication has been known. 
     In wireless communication, however, not all motor modules can receive instruction information due to a propagation loss. In addition, a plurality of motor modules may receive instruction information at different timings depending on the propagation path or the wireless communications system. Therefore, operations of a plurality of motor modules may fail to synchronize. 
     SUMMARY 
     An automatic device according to one exemplary aspect of the present disclosure includes: a support; a first motor attached to the support; a second motor attached to the support; a first motor drive unit configured to drive the first motor; a second motor drive unit configured to drive the second motor; a first control unit configured to control the first motor drive unit; and a second control unit configured to control the second motor drive unit. The first control unit and the second control unit are communicably wired with each other. The first control unit transmits instruction information on the second motor to the second control unit by wired communication, and the second control unit receives the instruction information on the second motor from the first control unit by wired communication, and performs operation regarding the second motor according to the instruction information on the second motor. 
     A communications system according to one exemplary aspect of the present disclosure includes: the above automatic device; and the external control device. 
     The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a moving body that is an automatic device according to an embodiment of the present disclosure; 
         FIG. 2  is a front view of a rotating base unit of the moving body according to the embodiment; 
         FIG. 3  is a side view of a moving device according to the embodiment of the present disclosure; 
         FIG. 4  is a perspective view of the moving device according to the embodiment; 
         FIG. 5  is a block diagram of a control system including the moving body according to the embodiment; 
         FIG. 6  is a sequence diagram showing an example of operation of controlling a plurality of motors in the control system according to the embodiment; 
         FIG. 7  is a diagram showing an example of a control command transmitted from an external computer of the control system according to the embodiment; 
         FIG. 8  is a sequence diagram showing another example of operation of controlling the plurality of motors in the control system according to the embodiment; 
         FIG. 9  is a sequence diagram showing an example of operation of measuring and reporting each condition in the control system according to the embodiment; 
         FIG. 10  is a diagram showing an example of a measurement command transmitted from the external computer of the control system according to the embodiment; 
         FIG. 11  is a diagram showing an example of a condition report transmitted inside the moving body according to the embodiment; 
         FIG. 12  is a diagram showing an example of a condition report transmitted from the moving body of the control system to the external computer according to the embodiment; and 
         FIG. 13  is a sequence diagram showing another example of operation of measuring and reporting each condition in the control system according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure will be described below with reference to the accompanying drawings. 
       FIG. 1  is a perspective view showing an automatic device according to an embodiment of the present disclosure. In the present embodiment, the automatic device is a moving body  1 . The moving body  1  includes a vehicle body (chassis, support)  2  and two wheels  4 A,  4 B supported by the vehicle body  2  in a rotatable manner. The vehicle body  2  is a substantially horizontal frame provided at a lower portion of the moving body  1 . The wheels  4 A,  4 B are of the same shape and size, and are arranged concentrically. 
     The vehicle body  2  includes two wheel motors  6 A,  6 B for respectively driving the wheels  4 A,  4 B mounted thereon. The vehicle body  2  also includes a battery case  8  mounted thereon that accommodates a battery that is a power supply for driving the wheel motors  6 A,  6 B. Further, the vehicle body  2  is equipped with printed boards  10 A,  10 B,  12 A,  12 B on which circuits for driving the wheel motors  6 A,  6 B are arranged. The printed boards  12 A,  12 B are connected to each other with a cable  13  for wired communication described later. 
     Further, the vehicle body  2  is equipped with a plurality of columns  14 , and the columns  14  support a rotating base unit  16 . The rotating base unit  16  includes a support base  18  and a rotating base  20  having the same diameter. The support base  18  is fixed to the upper ends of the columns  14 . The rotating base  20  is disposed above the support base  18  and concentrically with the support base  18 . 
     As shown in  FIG. 2 , the support base  18  is equipped with a bearing  22 , and in the bearing  22 , a rotating-base-metal-fitting  24  that is attached to the rotating base  20  is inserted. The bearing  22  may be attached to the rotating base  20 , and the rotating-base-metal-fitting  24  may be attached to the support base  18  and inserted in the bearing  22 . In either case, the rotating base  20  is rotatable with respect to the support base  18  about a substantially vertical axis. 
     The moving body  1  is provided with a measuring device for measuring the rotation angle of the rotating base  20  of the rotating base unit  16 . The measuring device is not limited, but may be a photo sensor  26 , for example. Specifically, the support base  18  is equipped with a bracket  28 , and the bracket  28  supports the photo sensor  26 , as shown in  FIG. 1 . The photo sensor  26  has two photo reflectors  29   a ,  29   b , for example. 
     The outer circumferential surface of the rotating base  20  has a plurality of white portions and a plurality of black portions that are provided in an alternate manner. The plurality of white portions are arranged at equal angular intervals, and the plurality of black portions are also arranged at equal angular intervals. The white portions and the black portions may be provided by coloring, or may be provided by attaching pieces of white tape and black tape to the rotating base  20 . 
     Each of the photo reflectors  29   a ,  29   b  has a light-emitting element (e.g., a light-emitting diode) and a light-receiving element (e.g., a phototransistor), and the light-receiving element receives the light that has been emitted from the light-emitting element and reflected on the outer circumferential surface of the rotating base  20 . The light-receiving element outputs an electric signal corresponding to the intensity of the received light. The level of the electric signal output from the light-receiving element varies depending on whether the light-receiving element faces the white portion or the black portion. Therefore, the rotation angle of the rotating base  20  can be measured by grasping the number of times the level of the electric signal has changed since the rotating base  20  has been positioned at a reference angle. 
     In the present embodiment, the two photo reflectors  29   a ,  29   b  have different angular positions with respect to the rotating base  20 . Since the different angular positions cause a difference in the output phases of the two photo reflectors  29   a ,  29   b , which makes it possible to determine the rotation direction of the rotating base  20 . 
       FIGS. 3 and 4  show a moving device  30  according to the embodiment. The moving device  30  includes a connecting carrier  32  that joins the rotating bases  20  of the rotating base units  16  of the two moving bodies  1 . 
     Specifically, a groove or a recess  34  is formed at the center of each rotating base  20 , and two protrusions  36  are formed or attached to the lower surface of the connecting carrier  32 . Each of the protrusions  36  is fitted into the recess  34 . The connecting carrier  32  does not rotate with respect to the rotating base  20  of each of the moving bodies  1 . 
     The connecting carrier  32  has a flat upper surface, and can carry a load  38  on the upper surface. 
     The moving body  1  alone can also carry the load  38 . In this case, the load  38  is placed on the rotating base  20  of the rotating base unit  16  without using the connecting carrier  32 . 
     However, the moving device  30  formed by joining a plurality of moving bodies  1  with the connecting carrier  32  can carry a heavy load  38 . In this case, the rotating bases  20  of the rotating base units  16  of the plurality of moving bodies  1  connected by the connecting carrier  32  rotate according to the respective travelling directions of the moving bodies  1 , which does not hamper travelling of the moving bodies  1 . 
     In the moving device  30  shown in the figures, two moving bodies  1  are joined together, but three or more moving bodies  1  may be joined together by connecting the rotating bases  20  of their rotating base units  16  with one another. 
       FIG. 5  is a block diagram of a control system including the moving body  1  according to the embodiment of the present disclosure. The moving body  1  can communicate with an external computer (external control device)  40  configured to remotely operate the moving body  1  by wireless communication. Therefore, the control system shown in  FIG. 5  can be considered as a communications system. The wireless communication method is not limited, but Wi-Fi (registered trademark) may be employed, for example. 
     The moving body  1  includes two motor units, that is, a first motor unit  42 A and a second motor unit  42 B. The motor units  42 A,  42 B respectively correspond to the wheel motors  6 A,  6 B. 
     The motor units  42 A,  42 B are powered by a power supply  43 . The power supply  43  is a battery accommodated in the battery case  8  (see  FIG. 1 ). The photo sensor  26  is also powered by the power supply  43 . 
     The first motor unit  42 A includes the wheel motor  6 A, a wireless communication circuit  44 A, a main control unit  46 A, a memory  48 A, a motor drive control unit  50 A, a drive circuit  52 A, and a speed sensor  54 A. The second motor unit  42 B includes the wheel motor  6 B, a wireless communication circuit  44 B, a main control unit  46 B, a memory  48 B, a motor drive control unit  50 B, a drive circuit  52 B, and a speed sensor  54 B. Hereinafter, the wheel motor  6 A may be referred to as a first wheel motor  6 A, and the wheel motor  6 B may be referred to as a second wheel motor  6 B. 
     The wireless communication circuit  44 A, the main control unit  46 A, the memory  48 A, and the motor drive control unit  50 A are mounted on the printed board  12 A (see  FIG. 1 ) as a main control circuit. The drive circuit  52 A includes an inverter and a motor driver, and is mounted on the printed board  10 A (see  FIG. 1 ). The wireless communication circuit  44 B, the main control unit  46 B, the memory  48 B, and the motor drive control unit  50 B are mounted on the printed board  12 B (see  FIG. 1 ) as a main control circuit. The drive circuit  52 B includes an inverter and a motor driver, and is mounted on the printed board  10 B (see  FIG. 1 ). 
     The wireless communication circuits  44 A,  44 B are configured to wirelessly communicate with the external computer  40 . However, in the present embodiment, only the wireless communication circuit  44 A of the first motor unit  42 A is normally used. The wireless communication circuit  44 B of the second motor unit  42 B can be used as a backup in case of a failure of the wireless communication circuit  44 A. Alternatively, the wireless communication circuit  44 B of the second motor unit  42 B can be used as an auxiliary circuit. For example, the wireless communication circuit  44 A can be used for reception from the external computer  40 , and the wireless communication circuit  44 B can be used for transmission to the external computer  40 . 
     Each of the main control units  46 A,  46 B is a processor, and operates by reading and implementing a program stored in a recording medium (not shown). Therefore, the program (program code) itself read from the recording medium implements the function of the embodiment. Further, the recording medium storing the program can constitute the present disclosure. 
     The main control unit  46 A wirelessly communicates with the external computer  40  using the wireless communication circuit  44 A. The main control unit  46 A controls the motor drive control unit  50 A to control driving of the wheel motor  6 A. Further, the main control unit  46 A is communicably wired to the main control unit  46 B of the second motor unit  42 B. 
     The main control unit  46 B controls the motor drive control unit  50 B to control driving of the wheel motor  6 B. Further, the main control unit  46 B can wirelessly communicate with the external computer  40  using the wireless communication circuit  44 B as necessary. 
     The memories  48 A,  48 B are configured to store data necessary for the respective main control units  46 A,  46 B to perform processing. The main control units  46 A,  46 B are configured to read necessary data from the respective memories  48 A,  48 B. The memories  48 A,  48 B are volatile memories, but may be nonvolatile memories. Further, each of the memories  48 A,  48 B may include both a volatile memory and a nonvolatile memory. 
     The motor drive control unit  50 A is configured to control driving (for example, the rotational speed) of the wheel motor  6 A according to a command from the main control unit  46 A. The motor drive control unit  50 B is configured to control driving (for example, the rotational speed) of the wheel motor  6 B according to a command from the main control unit  46 B. Each of the motor drive control units  50 A,  50 B, for example, can perform proportional-integral-differential (PID) control or vector control, for example, and is formed of a microprocessor, an application specific integrated circuit (ASIC), or a digital signal processor (DSP), for example. 
     The drive circuit  52 A is configured to drive the wheel motor  6 A under the control of the motor drive control unit  50 A. The drive circuit  52 B is configured to drive the wheel motor  6 B under the control of the motor drive control unit  50 B. 
     The speed sensors  54 A,  54 B are configured to output electric signals indicating the rotational speeds of the wheel motors  6 A,  6 B, respectively. The speed sensors  54 A,  54 B are, for example, Hall sensors that are mounted inside the wheel motors  6 A,  6 B, respectively, and are configured to convert a magnetic field into an electric signal. The motor drive control unit  50 A determines the rotational speed of the wheel motor  6 A based on the output signal of the speed sensor  54 A. That is, the motor drive control unit  50 A measures the rotational speed of the wheel motor  6 A. The motor drive control unit  50 B determines the rotational speed of the wheel motor  6 B based on the output signal of the speed sensor  54 B. That is, the motor drive control unit  50 B measures the rotational speed of the wheel motor  6 B. The measured value of the rotational speed of the wheel motor  6 A is notified to the main control unit  46 A, and the main control unit  46 A uses the value of the rotational speed of the wheel motor  6 A to provide a command for controlling driving of the wheel motor  6 A to the motor drive control unit  50 A. The measured value of the rotational speed of the wheel motor  6 B is notified to the main control unit  46 B and the main control unit  46 B uses the value of the rotational speed of the wheel motor  6 B to provide a command for controlling driving of the wheel motor  6 B to the motor drive control unit  50 B. 
     Further, the motor drive control unit  50 A calculates the torque of the wheel motor  6 A with a publicly known calculation method based on the current value of the drive circuit  52 A. That is, the motor drive control unit  50 A measures the torque of the wheel motor  6 A. The motor drive control unit  50 B calculates the torque of the wheel motor  6 B with a publicly known calculation method based on the current value of the drive circuit  52 B. That is, the motor drive control unit  50 B measures the torque of the wheel motor  6 B. The measured value of the torque of the wheel motor  6 A is notified to the main control unit  46 A, and the main control unit  46 A uses the value of the torque of the wheel motor  6 A to provide a command for controlling driving of the wheel motor  6 A to the motor drive control unit  50 A. The measured value of the torque of the wheel motor  6 B is notified to the main control unit  46 B, and the main control unit  46 B uses the value of the torque of the wheel motor  6 B to provide a command for controlling driving of the wheel motor  6 B to the motor drive control unit  50 B. 
     The output signals of the two photo reflectors  29   a ,  29   b  of the photo sensor  26  are supplied to the main control unit  46 A of the first motor unit  42 A. According to the above configuration, the main control unit  46 A determines the rotation direction of the rotating base  20  and also the rotation angle of the rotating base  20  based on the output signals of the photo reflectors  29   a ,  29   b . That is, the main control unit  46 A measures the rotation angle of the rotating base  20 . 
     With reference to  FIGS. 6 and 7 , the description will be given of an example of operation of controlling the wheel motors  6 A,  6 B of the motor units  42 A,  42 B performed based on a control command from the external computer  40 . This operation is individually performed for each moving body  1  in the moving device  30  including a plurality of moving bodies  1  (see  FIGS. 3 and 4 ). 
     As shown in  FIG. 6 , the external computer  40  transmits a control command for all the motor units  42 A,  42 B to the first motor unit  42 A by wireless communication. The control command for all the motor units  42 A,  42 B is a control command for controlling driving of both the wheel motors  6 A,  6 B. 
     As shown in  FIG. 7 , a format of the control command includes, for example, a field indicating a command type, a field indicating a target achievement time, and a field indicating a first device ID (a device ID for the first motor unit  42 A), a field indicating a target speed for the first wheel motor  6 A, a field indicating a second device ID (a device ID for the second motor unit  42 B), and a field indicating a target speed for the second wheel motor  6 B. The field indicating a command type includes a bit string indicating that the transmitted command is a control command for setting a target speed. The field indicating a target achievement time includes a bit string indicating a time period until the wheel motors  6 A,  6 B reach a target speed after the control command is received. The field indicating a device ID includes a bit string indicating an ID for the motor unit having the wheel motor to be controlled by the control command. That is, the two fields indicating the device IDs each include a bit string indicating the device ID for the first motor unit  42 A or a bit string indicating the device ID for the second motor unit  42 B. The field indicating a target speed immediately after the field indicating the device ID of the first motor unit  42 A includes a bit string indicating a target speed for the first wheel motor  6 A. The field indicating a target speed immediately after the field indicating the device ID of the second motor unit  42 B includes a bit string indicating a target speed for the second wheel motor  6 B. 
     It is assumed that, for example, this control command specifies 100 ms as the target achievement time, 100 rpm as the target speed for the first wheel motor  6 A, and 200 rpm as the target speed for the second wheel motor  6 B. In this case, according to the control command, the first motor unit  42 A should adjust the rotational speed of the wheel motor  6 A to reach 100 rpm, and the second motor unit  42 B should adjust the rotational speed of the wheel motor  6 B to reach 200 rpm in 100 ms after the control command is received. 
     Referring back to  FIG. 6 , in the first motor unit  42 A, the main control unit  46 A creates a control plan for the first wheel motor  6 A and the second wheel motor  6 B when the wireless communication circuit  44 A receives the control command. Specifically, the main control unit  46 A determines instantaneous target speeds for the first wheel motor  6 A and the second wheel motor  6 B for each moment until the target achievement time has elapsed. Each of the moments is separated from one another by a constant control cycle. 
     The determination may be made by interpolation based on the current rotational speed of each motor, the target speed for each motor specified in the control command, and the target achievement time specified in the control command. For example, in the case where the wheel motors  6 A,  6 B are stopped (in the case where the rotational speeds are 0 rpm) when the control command of the above assumed example is received, the main control unit  46 A determines the instantaneous target speed for the first wheel motor  6 A for each moment of every 1 ms so as to increase the rotational speed of the first wheel motor  6 A by 1 rpm for each moment of every 1 ms. Further, the main control unit  46 A determines the instantaneous target speed for the second wheel motor  6 B for each moment of every 1 ms so as to increase the rotational speed of the second wheel motor  6 B by 2 rpm for each moment of every 1 ms. Thus, after a lapse of 100 ms, the rotational speed of the wheel motor  6 A reaches 100 rpm, and the rotational speed of the wheel motor  6 B reaches 200 rpm. In this example, the main control unit  46 A uses linear interpolation in determining the instantaneous target speeds for the wheel motors  6 A,  6 B, but may use another interpolation algorithm. 
     When the wireless communication circuit  44 A receives the control command, the main control unit  46 A stores the received control command in the memory  48 A before creating a control plan, and then creates a control plan using the control command read from the memory  48 A. 
     Once determining the instantaneous target speeds for the wheel motors  6 A,  6 B as described above, the main control unit  46 A stores the instantaneous target speeds for the wheel motors  6 A,  6 B in the memory  48 A. 
     Thereafter, the main control unit  46 A controls the motor drive control unit  50 A to adjust the rotational speed of the first wheel motor  6 A according to the control plan. That is, the main control unit  46 A reads the instantaneous target speed for the first wheel motor  6 A from the memory  48 A at each moment, and repeats, in a constant control cycle (for example, every 1 ms), controlling of the motor drive control unit  50 A so that the rotational speed of the first wheel motor  6 A reaches the instantaneous target speed. Further, the main control unit  46 A transmits control instruction information on control of driving of the second wheel motor  6 B to the second motor unit  42 B by wired communication according to the control plan. That is, the main control unit  46 A reads the instantaneous target speed of the second wheel motor  6 B from the memory  48 A at each moment, and repeats, in a constant control cycle (for example, every 1 ms), transmitting of the control instruction information indicating the instantaneous target speed of the second wheel motor  6 B to the second motor unit  42 B by wired communication. 
     In the second motor unit  42 B, the main control unit  46 B repeatedly receives the control instruction information indicating the instantaneous target speed for the second wheel motor  6 B from the first motor unit  42 A in a constant control cycle (for example, every 1 ms). Every time the main control unit  46 B receives the control instruction information, the main control unit  46 B controls the motor drive control unit  50 B according to the control instruction information so that the rotational speed of the second wheel motor  6 B reaches the instantaneous target speed. 
     In the first motor unit  42 A, when the wireless communication circuit  44 A receives a new control command, the main control unit  46 A creates a new control plan for the first wheel motor  6 A and the second wheel motor  6 B based on the current rotational speed of each motor, the target speed for each motor specified in the new control command, and the target achievement time specified in the new control command. The creation of the new control plan is implemented even when the current rotational speed of each motor has not reached the target speed specified in the immediately preceding control command. 
     Thereafter, the main control unit  46 A controls the motor drive control unit  50 A to adjust the rotational speed of the first wheel motor  6 A according to the new control plan, and transmits the control instruction information on control of driving of the second wheel motor  6 B to the second motor unit  42 B by wired communication according to the new control plan. In this way, the rotational speeds of the wheel motors  6 A,  6 B are synchronized and adjusted repeatedly. 
     In the above example, the control cycle of each motor is 1 ms, but is not limited to 1 ms and may be 5 ms, for example. 
       FIG. 8  is a sequence diagram showing another example of operation of controlling the plurality of motors in the control system according to the embodiment. The external computer  40 , the first motor unit  42 A, and the second motor unit  42 B may operate according to the sequence diagram shown in  FIG. 8 . 
     As shown in  FIG. 8 , the external computer  40  transmits a control command for all the motor units  42 A,  42 B to the first motor unit  42 A by wireless communication in the same manner as described above. In the first motor unit  42 A, when the wireless communication circuit  44 A receives the control command, the main control unit  46 A stores the received control command in the memory  48 A. 
     The main control unit  46 A creates a control plan (first control plan) for the first wheel motor  6 A. Specifically, the main control unit  46 A determines an instantaneous target speed for the first wheel motor  6 A for each moment until the target achievement time has elapsed. Each of the moments is separated from one another by a constant control cycle C 1  (for example, 1 ms). The determination may be made by interpolation, for example linear interpolation, based on the current rotational speed of the motor  6 A, the target speed for the motor  6 A specified in the control command, and the target achievement time specified in the control command in the same manner as described above. Once determining the instantaneous target speed for the wheel motor  6 A for each control cycle C 1 , the main control unit  46 A stores the instantaneous target speed for the wheel motor  6 A in the memory  48 A. 
     Further, the main control unit  46 A determines the instantaneous target speed for the second wheel motor  6 B for each control cycle C 2  (for example, 5 ms) that is longer than the control cycle C 1 , based on the control command. The determination may be made by interpolation, for example, linear interpolation, based on the current rotational speed of the motor  6 B, the target speed for the motor  6 B specified in the control command, and the target achievement time specified in the control command. Once determining the instantaneous target speed for the wheel motor  6 B for each control cycle C 2 , the main control unit  46 A stores the instantaneous target speed for the wheel motor  6 B in the memory  48 A. 
     Next, the main control unit  46 A reads the instantaneous target speed for the second wheel motor  6 B from the memory  48 A, and transmits control instruction information indicating the instantaneous target speed for the second wheel motor  6 B to the second motor unit  42 B by wired communication. The main control unit  46 A repeats, in the longer control cycle C 2 , reading out of the instantaneous target speed for the second wheel motor  6 B and transmitting of the control instruction information to the second motor unit  42 B by wired communication. 
     Upon receiving the control instruction information from the first motor unit  42 A, the main control unit  46 B of the second motor unit  42 B creates a control plan (second control plan) for the second wheel motor  6 B. Specifically, the main control unit  46 B determines the instantaneous target speed for the second wheel motor  6 B for each moment of each shorter control cycle C 1 . The determination may be made by interpolation, for example, linear interpolation, based on the current rotational speed of the motor  6 B, the target speed of the motor  6 B indicated by the control instruction information, and the length of the control cycle C 2 . Once determining the instantaneous target speed for the wheel motor  6 B for each control cycle C 1 , the main control unit  46 B stores the instantaneous target speed for the wheel motor  6 B in the memory  48 B. 
     Thereafter, the main control unit  46 A controls the motor drive control unit  50 A to adjust the rotational speed of the first wheel motor  6 A according to the first control plan. That is, the main control unit  46 A repeats, in the control cycle C 2 , reading of the instantaneous target speed for the first wheel motor  6 A from the memory  48 A at each moment, and controlling of the motor drive control unit  50 A so that the rotational speed of the first wheel motor  6 A reaches the instantaneous target speed. 
     Further, the main control unit  46 B controls the motor drive control unit  50 B to adjust the rotational speed of the second wheel motor  6 B according to the second control plan. That is, the main control unit  46 B repeats, in the control cycle C 2 , reading of the instantaneous target speed for the second wheel motor  6 B from the memory  48 B at each moment, and controlling of the motor drive control unit  50 B so that the rotational speed of the second wheel motor  6 B reaches the instantaneous target speed. In this way, the rotational speeds of the wheel motors  6 A,  6 B are synchronized and adjusted repeatedly. In this case, even when the control instruction information cannot be transmitted from the first motor unit  42 A to the second motor unit  42 B in the shorter control cycle C 1 , the rotational speed of the wheel motor  6 B can be adjusted in the shorter control cycle C 1 . 
     In the first motor unit  42 A, when the wireless communication circuit  44 A receives a new control command, the main control unit  46 A creates a new first control plan for the first wheel motor  6 A, and determines an instantaneous target speed for the second wheel motor  6 B in the longer control cycle C 2 . The creation of the new first control plan and determination of the instantaneous target speed for the wheel motor  6 B are implemented even when the current rotational speed of each motor has not reached the target speed specified in the immediately preceding control command. 
     Thereafter, the main control unit  46 A transmits control instruction information on control of driving of the second wheel motor  6 B to the second motor unit  42 B by wired communication, and controls the motor drive control unit  50 A to adjust the rotational speed of the first wheel motor  6 A according to the new first control plan. The main control unit  46 B creates a new second control plan for the second wheel motor  6 B, and controls the motor drive control unit  50 B to adjust the rotational speed of the second wheel motor  6 B according to the new second control plan. 
     As described above, the control command transmitted by wireless communication includes information indicating the target achievement time for driving the wheel motors  6 A,  6 B. The target achievement time may be constant at all times (for example, 100 ms). However, arrival time of a signal may vary depending on the propagation path in wireless communication. In view of this, it is preferable that the external computer  40  determines the target achievement time for driving the wheel motors  6 A,  6 B according to the wireless propagation delay between the external computer  40  and the wireless communication circuit  44 A. Specifically, the longer the wireless propagation delay, the longer the target achievement time is determined. This makes it easy to synchronize the driving of the wheel motors  6 A,  6 B regardless of the wireless propagation delay. The wireless propagation delay can be estimated by measuring a round trip time between the external computer  40  and the wireless communication circuit  44 A by a publicly known technique. 
     The transmission interval of the control command transmitted from the external computer  40  to the first motor unit  42 A may be the same as the target achievement time for driving the wheel motors  6 A,  6 B. However, arrival time of a signal may vary depending on the propagation path in wireless communication. In view of this, the transmission interval of the control command is preferably shorter than the target achievement time. This can be applied whether the target achievement time is constant or variable. For example, the target achievement time can be set to 100 ms, and the transmission interval of the control command can be set to 80 ms. Even when the current rotational speed of each motor has not reached the target speed specified in the immediately preceding control command when anew control command is received, the moving body  1  can determine the instantaneous target speeds for the wheel motors  6 A,  6 B based on the current rotational speed and the target speed specified in the new control command. This makes it easy to synchronize the driving of the wheel motors  6 A,  6 B regardless of the wireless propagation delay. 
     In the present embodiment, the main control unit  46 A of the first motor unit  42 A receives a control command for the wheel motors  6 A,  6 B by wireless communication from the external computer  40 , and transmits control instruction information on the wheel motor  6 B to the main control unit  46 B of the second motor unit  42 B by wired communication, thereby facilitating synchronization of operation of the wheel motors  6 A,  6 B. Further, due to the solidity of wired communication, the control instruction information on the wheel motor  6 B can be reliably and promptly transmitted to the main control unit  46 B. In addition, the wired communication inside the moving body  1  leads to reduction in traffic of wireless communication with the external computer  40 . 
     With reference to  FIG. 9 , the description will be given of an example of operation of measuring and reporting the condition of the motor units  42 A,  42 B performed by the motor units  42 A,  42 B. This operation is individually performed for each moving body  1  in the moving device  30  including a plurality of moving bodies  1  (see  FIGS. 3 and 4 ). 
     As shown in  FIG. 9 , the external computer  40  transmits a measurement command for all the motor units  42 A,  42 B to the first motor unit  42 A by wireless communication. The measurement command for all the motor units  42 A,  42 B is a command instructing to measure the current rotational speed and the current torque of the first wheel motor  6 A of the first motor unit  42 A, the current rotational speed and the current torque of the second wheel motor  6 B of the second motor unit  42 B, and the current rotation angle of the rotating base  20  and to report the measured results. 
     As shown in  FIG. 10 , a format of the measurement command includes, for example, a field indicating a command type, a field indicating a condition-measurement start timing, a field indicating a reporting operation continuation period, and a field indicating a reporting cycle (measurement cycle). The field indicating a command type includes a bit string indicating that the transmitted command is a measurement command. 
     In the first motor unit  42 A, when the wireless communication circuit  44 A receives the measurement command from the external computer  40 , the main control unit  46 A stores the measurement command in the memory  48 A. Further, the main control unit  46 A transmits measurement instruction information for the second motor unit  42 B to the second motor unit  42 B by wired communication. The measurement instruction information has the same format as the measurement command, and indicates the condition-measurement start timing, the reporting operation continuation period, and the reporting cycle specified in the measurement command. In the second motor unit  42 B, when the main control unit  46 B receives the measurement instruction information from the first motor unit  42 A by wired communication, the main control unit  46 B stores the measurement instruction information in the memory  48 B. 
     The main control unit  46 A performs a condition measurement operation at the condition-measurement start timing specified in the measurement command. Specifically, the main control unit  46 A causes the motor drive control unit  50 A to measure the rotational speed and the torque of the first wheel motor  6 A, and receives the measured values of the rotational speed and the torque from the motor drive control unit  50 A. Further, the main control unit  46 A measures the rotation angle of the rotating base  20 . 
     Further, the main control unit  46 B performs the condition measurement operation at the condition-measurement start timing indicated by the measurement instruction information. Specifically, the main control unit  46 B causes the motor drive control unit  50 B to measure the rotational speed and the torque of the second wheel motor  6 B, and receives the measured values of the rotational speed and the torque from the motor drive control unit  50 B. After completion of the measurement operation, the main control unit  46 B transmits a report indicating the measurement result to the first motor unit  42 A by wired communication as a condition report of the second motor unit  42 B.  FIG. 11  shows an example of a format of the condition report of the second motor unit  42 B. A field for a report type shown in  FIG. 11  includes a bit string indicating that this report is a condition report of the second motor unit  42 B. 
     Upon receiving the condition report of the second motor unit  42 B, the main control unit  46 A of the first motor unit  42 A collectively transmits the condition report on all the motor units  42 A,  42 B indicating the measurement result by the main control unit  46 A and the measurement result by the main control unit  46 B to the external computer  40  by wireless communication. That is, the main control unit  46 A connects the measurement result by the main control unit  46 A with the measurement result by the main control unit  46 B to generate one condition report, and transmits the information report to the external computer  40 .  FIG. 12  shows an example of a format of the condition report of all the motor units  42 A,  42 B. A field for a report type shown in  FIG. 12  includes a bit string indicating that this report is a condition report of all the motor units. 
     Thereafter, in the reporting cycle (measurement cycle) specified in the measurement command, the main control unit  46 A of the first motor unit  42 A performs the condition measurement operation, and the main control unit  46 B of the second motor unit  42 B performs the condition measurement operation. Then, the second motor unit  42 B transmits the condition report of the second motor unit  42 B to the first motor unit  42 A by wired communication, and the first motor unit  42 A collectively transmits the condition report of all the motor units  42 A,  42 B to the external computer  40  by wireless communication. Since one condition report transmitted by wireless communication includes the measurement result by the main control unit  46 A and the measurement result by the main control unit  46 B, traffic of wireless communication can be reduced as compared with the case where the measurement results are individually transmitted by wireless communication, thereby reducing the load for reception processing on the external computer  40 . 
     Since the external computer  40  causes the measurement command to include the reporting cycle, a single transmission of the measurement command causes the moving body  1  to periodically perform the measurement and reporting operation. Therefore, traffic of wireless communication can be reduced as compared with the case where the command is transmitted periodically, thereby reducing the transmission processing load on the external computer  40 . 
     The above described condition reporting operation is repeated until the reporting operation continuation period specified in the measurement command has elapsed. When the reporting operation continuation period has elapsed, the motor units  42 A,  42 B end the condition measurement operation and the transmission of the condition report. Since the external computer  40  causes the measurement command to include the reporting operation continuation period, the moving body  1  can end the measurement and reporting operation without transmission of a command to end the measurement. Therefore, traffic of wireless communication can be reduced as compared with the case where a command to end the measurement is transmitted, thereby reducing the transmission processing load on the external computer  40 . 
     In the present operation example, the main control unit  46 A of the first motor unit  42 A receives the measurement command for the wheel motors  6 A,  6 B by wireless communication from the external computer  40 , and transmits the measurement instruction information on the wheel motor  6 B to the main control unit  46 B of the second motor unit  42 B by wired communication, thereby facilitating synchronization of the measurement on the wheel motors  6 A,  6 B. Further, due to the solidity of wired communication, the measurement instruction information on the wheel motor  6 B can be reliably and promptly transmitted to the main control unit  46 B. In addition, the wired communication inside the moving body  1  leads to reduction in traffic of wireless communication with the external computer  40 . Furthermore, due to a reporting operation using wired communication inside the moving body  1  and a collective reporting operation from the main control unit  46 A of the first motor unit  42 A using wireless communication, traffic of wireless communication with the external computer  40  can be reduced, thereby reducing the reception processing load on the external computer  40 . 
     In the present operation example, a plurality of items, that is, the rotational speed and the torque of the motors and the rotation angle of the rotating base  20 , are measured and reported in response to one measurement command. Therefore, traffic of wireless communication can be reduced as compared with the case where the measurement command is transmitted for each item by wireless communication, thereby reducing the transmission processing load on the external computer  40 . 
       FIG. 13  is a sequence diagram showing another example of operation of measuring and reporting the condition of the motor units  42 A,  42 B performed by the motor units  42 A,  42 B in the control system according to the embodiment. The external computer  40 , the first motor unit  42 A, and the second motor unit  42 B may operate according to the sequence diagram shown in  FIG. 13 . 
     In the operation example of  FIG. 13 , the wireless communication circuit  44 B of the second motor unit  42 B is used. The wireless communication circuit  44 A of the first motor unit  42 A is used for reception from the external computer  40 , and the wireless communication circuit  44 B of the second motor unit  42 B is used for transmission to the external computer  40 . 
     In the present operation example, the main control unit  46 B of the second motor unit  42 B does not transmit a condition report to the first motor unit  42 A, but the main control unit  46 A of the first motor unit  42 A transmits a condition report to the second motor unit  42 B. Further, instead of the main control unit  46 A of the first motor unit  42 A, the main control unit  46 B of the second motor unit  42 B transmits a condition report of all the motor units to the external computer  40 . The other features are the same as the operation example of  FIG. 9 . 
     That is, the external computer  40  transmits the measurement command for all the motor units  42 A,  42 B to the first motor unit  42 A by wireless communication, and the main control unit  46 A transmits the measurement instruction information for the second motor unit  42 B to the second motor unit  42 B by wired communication. 
     The main control unit  46 A performs the condition measurement operation at the condition-measurement start timing specified in the measurement command transmitted from the external computer  40  by wireless communication. Specifically, the main control unit  46 A causes the motor drive control unit  50 A to measure the rotational speed and the torque of the first wheel motor  6 A, and receives the measured values of the rotational speed and the torque from the motor drive control unit  50 A. Further, the main control unit  46 A measures the rotation angle of the rotating base  20 . 
     After completion of the measurement, the main control unit  46 A transmits a report indicating the measurement result to the second motor unit  42 B by wired communication as a condition report of the first motor unit  42 A. An example of a format of the condition report of the second motor unit  42 B is similar to the one shown in  FIG. 11 . However, a field for a report type includes a bit string indicating that this report is a condition report of the first motor unit  42 A. The condition report of the first motor unit  42 A indicates the rotational speed and the torque of the first wheel motor  6 A and the rotation angle of the rotating base  20 . 
     Further, the main control unit  46 B performs the condition measurement operation at the condition-measurement start timing indicated by the measurement instruction information. Specifically, the main control unit  46 B causes the motor drive control unit  50 B to measure the rotational speed and the torque of the second wheel motor  6 B, and receives the measured values of the rotational speed and the torque from the motor drive control unit  50 B. 
     Upon receiving the condition report of the first motor unit  42 A, the main control unit  46 B of the second motor unit  42 B collectively transmits the condition report on all the motor units  42 A,  42 B indicating the measurement result by the main control unit  46 A and the measurement result by the main control unit  46 B to the external computer  40  by wireless communication. That is, the main control unit  46 B connects the measurement result by the main control unit  46 A with the measurement result by the main control unit  46 B to generate one condition report, and transmits the information report to the external computer  40 . 
     Thereafter, in the reporting cycle (measurement cycle) specified in the measurement command, the main control unit  46 A of the first motor unit  42 A performs the condition measurement operation, and the main control unit  46 B of the second motor unit  42 B performs the condition measurement operation. Then, the first motor unit  42 A transmits the condition report of the first motor unit  42 A to the second motor unit  42 B by wired communication, and the second motor unit  42 B collectively transmits the condition report of all the motor units  42 A,  42 B to the external computer  40  by wireless communication. Since one condition report transmitted by wireless communication includes the measurement result by the main control unit  46 A and the measurement result by the main control unit  46 B, traffic of wireless communication can be reduced as compared with the case where the measurement results are individually transmitted by wireless communication, thereby reducing the load for reception processing on the external computer  40 . 
     Since the external computer  40  causes the measurement command to include the reporting cycle, a single transmission of the measurement command causes the moving body  1  to periodically perform the measurement and reporting operation. Therefore, traffic of wireless communication can be reduced as compared with the case where the command is transmitted periodically, thereby reducing the transmission processing load on the external computer  40 . 
     The above described condition reporting operation is repeated until the reporting operation continuation period specified in the measurement command has elapsed. When the reporting operation continuation period has elapsed, the motor units  42 A,  42 B end the condition measurement operation and the transmission of the condition report. Since the external computer  40  causes the measurement command to include the reporting operation continuation period, the moving body  1  can end the measurement and reporting operation without transmission of a command to end the measurement. Therefore, traffic of wireless communication can be reduced as compared with the case where a command to end the measurement is transmitted, thereby reducing the transmission processing load on the external computer  40 . 
     In the present operation example, the main control unit  46 A of the first motor unit  42 A receives the measurement command for the wheel motors  6 A,  6 B by wireless communication from the external computer  40 , and transmits the measurement instruction information on the wheel motor  6 B to the main control unit  46 B of the second motor unit  42 B by wired communication, thereby facilitating synchronization of the measurement on the wheel motors  6 A,  6 B. Further, due to the solidity of wired communication, the measurement instruction information on the wheel motor  6 B can be reliably and promptly transmitted to the main control unit  46 B. In addition, the wired communication inside the moving body  1  leads to reduction in traffic of wireless communication with the external computer  40 . Furthermore, due to a reporting operation using wired communication inside the moving body  1  and a collective reporting operation from the main control unit  46 B of the second motor unit  42 B using wireless communication, traffic of wireless communication with the external computer  40  can be reduced, thereby reducing the reception processing load on the external computer  40 . 
     In the present operation example, a plurality of items, that is, the rotational speed and the torque of the motors and the rotation angle of the rotating base  20 , are measured and reported in response to one measurement command. Therefore, traffic of wireless communication can be reduced as compared with the case where the measurement command is transmitted for each item by wireless communication, thereby reducing the transmission processing load on the external computer  40 . 
     Although the embodiments of the present disclosure have been described above, the above description should not limit the present disclosure, and various modifications including deletion, addition, and replacement of components can be considered to fall within the technical scope of the present disclosure. 
     For example, each moving body  1  includes two wheels  4 A,  4 B, and two wheel motors  6 A,  6 B according to the above embodiments. However, each moving body  1  may include three or more wheels, and three or more motor units for driving the three or more wheels. In this case, the main control unit of one of the motor units (first motor unit  42 A) can receive a control command and a measurement command from the external computer  40  by wireless communication, and transmit control instruction information and measurement instruction information to the other motor units (a plurality of second motor units) by wired communication. Further, the plurality of second motor units can transmit their respective condition reports to one of the motor units (first motor unit  42 A) that has received the measurement command from the external computer  40 , and the first motor unit  42 A can collectively transmit the condition report of all the motor units to the external computer  40  by wireless communication. Alternatively, the plurality of motor units including the first motor unit  42 A can transmit their respective condition reports to one of the motor units other than the first motor unit  42 A (second motor unit  42 B), and the second motor unit  42 B can collectively transmit the condition reports of all the motor units to the external computer  40  by wireless communication. 
     The rotation angle of the rotating base  20  is measured by the main control unit  46 A of the first motor unit  42 A according to the above embodiments, but may be measured by the main control unit  46 B of the second motor unit  42 B. 
     The speed and the torque of the motors and the rotation angle of the rotating base  20  are measured and reported according to the above embodiments. However, other conditions may be measured and reported. For example, the moving body  1  may measure its own position or the position of each wheel, and report the measured result to the external computer  40 . For example, the moving body  1  can measure its own position or the position of each wheel by a navigation satellite system, a Wi-Fi positioning system, a base station positioning system, a camera image positioning system, or a combination thereof. 
     An example of the automatic device is the moving body  1  according to the above embodiments, but the automatic device may be a robot, such as a manufacturing robot or a service robot, or may be a transfer apparatus, such as a belt conveyor or a roller conveyor. 
     According to the above embodiments, information transmission by wired communication is performed inside the moving body  1  in response to a control command or a measurement command transmitted from the external computer  40  by wireless communication. However, information transmission by wired communication may be performed inside the moving body  1  regardless of the command from the external computer  40 . 
     Features of the above-described preferred embodiments and the modifications thereof may be combined appropriately as long as no conflict arises. 
     While preferred embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.