Wireless control system, controller, terminal and program

Abstract

To provide a wireless control system that realizes high-speed response.SOLUTION: A wireless control system comprises a plurality of terminals, and a controller. Each terminal includes a control object. The controller receives a state signal transmitted from each terminal, generates a control signal for each terminal according to the state signal, and transmits the control signal for each terminal. Each of the plurality of terminals can operate as a relayed terminal or a downlink relay terminal. The downlink relay terminal transmits a first state signal representing a state of a control object of itself and a first control signal for controlling a control object of the relayed terminal. The relayed terminal acquires a second state signal representing a state of a control object of itself after receiving the first control signal, and thereafter, transmits the second state signal, and controls the control object of itself on the basis of the first control signal.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] An embodiment of the present invention relates to a wireless control system, a controller, a terminal, and a program. [Background technology]

[0002] There is a wireless control system including a controller and a plurality of terminals that are wirelessly connected. One example of the wireless control system is a control system for an industrial robot. The industrial robot includes a plurality of arms. A terminal is disposed on the arm. The terminal includes a wireless device and a motor.

[0003] The controller transmits a control signal to the terminal. The terminal rotates the motor and controls the arm according to the control signal. The terminal transmits a status signal indicating the state of the arm (e.g., the rotation angle) that is the result of the control to the controller. The controller updates the control signal according to the status signal, and transmits the updated control signal to the terminal. In other words, the controller performs feedback control.

[0004] In a feedback control system, it is preferable that the controller generates a control signal according to the latest state signal from the viewpoint of the quality of control. If AoI (Age of Information) is the time elapsed from the observation point of certain information, in a feedback control system, the quality of control can be improved by generating a control signal based on a state signal with a short AoI rather than generating a control signal based on a state signal with a long AoI. For example, when updating a control signal at a constant cycle from the viewpoint of controllability, it is preferable that the terminal transmits the latest state signal within one cycle after receiving the control signal. This enables the controller to generate a control signal according to the AoI state signal within one cycle, and the quality of control of the arm can be at a certain level or higher. On the other hand, if the terminal is unable to transmit the latest state signal within one cycle after receiving the control signal and transmits it within the next cycle, the controller will generate a control signal according to the AoI state signal within one cycle or more and within two cycles, and the quality of control of the arm will deteriorate. In addition, the direct wireless line between the controller and the terminal may be disconnected depending on the situation. For example, depending on the position of the arm, there may be an obstacle between the controller and the arm, and the terminal may not be able to receive a control signal from the controller or the controller may not be able to receive a state signal from the terminal. In this case, the controller transmits and receives signals to and from the terminal whose direct wireless link with the controller has been cut off via another terminal that is wirelessly connected to the controller. However, when transmitting and receiving signals via another terminal, the controller may not be able to receive a status signal within one cycle after transmitting a control signal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-192165 A Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a wireless control system that achieves high speed response. [Means for solving the problem]

[0007] A wireless control system according to an embodiment includes a plurality of terminals and a controller. Each terminal includes a control target. The controller receives a status signal transmitted from each terminal, generates a control signal for each terminal according to each status signal, and transmits the control signal for each terminal. Each terminal can operate as a relayed terminal or a downlink relay terminal. The downlink relay terminal transmits a first status signal representing a status of its own control target and a first control signal for controlling the control target of the relayed terminal. After receiving the first control signal, the relayed terminal acquires a second status signal representing a status of its own control target, and then transmits the second status signal and controls its own control target based on the first control signal. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram for explaining an example of a wireless control system according to a first embodiment. [Diagram 2] FIG. 2 is a block diagram illustrating an example of a controller according to the first embodiment. [Diagram 3] FIG. 2 is a block diagram illustrating an example of a terminal according to the first embodiment. [Figure 4] FIG. 2 is a diagram for explaining an example of a format of a radio frame according to the first embodiment. [Diagram 5] 5 is a diagram for explaining an example of processing of a terminal operating as a DL relay terminal according to the first embodiment. [Figure 6] 5 is a diagram for explaining an example of processing of a terminal operating as a relayed terminal according to the first embodiment. [Figure 7] 4 is a diagram for explaining an example of processing of a terminal operating as a UL relay terminal according to the first embodiment. [Figure 8] 11A and 11B are diagrams for explaining an example of an experimental result in a wireless control system according to a reference example. [Figure 9]5A to 5C are diagrams for explaining an example of an experimental result in the wireless control system according to the first embodiment. [Figure 10] FIG. 11 is a block diagram illustrating an example of a controller according to a second embodiment. [Figure 11] 13 is a diagram for explaining an example of the operation of a status signal prediction unit according to the second embodiment. FIG. [Figure 12] FIG. 13 is a block diagram illustrating an example of a controller according to a third embodiment. [Figure 13] FIG. 13 is a block diagram illustrating an example of a controller according to a fourth embodiment. [Figure 14] FIG. 13 is a block diagram illustrating an example of a controller according to a fifth embodiment. [Figure 15] FIG. 23 is a block diagram illustrating an example of a terminal according to the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described with reference to the drawings. The following description is an example of an apparatus and a method for embodying the technical idea of ​​the embodiment, and the technical idea of ​​the embodiment is not limited to the structure, shape, arrangement, material, etc. of the components described below. Modifications that a person skilled in the art can easily conceive are naturally included in the scope of the disclosure. In order to make the description clearer, the shape, etc. may be changed from the actual embodiment and shown diagrammatically. In multiple drawings, the same reference numerals may be given to corresponding elements, and duplicated descriptions may be omitted. Some elements may be given multiple names, but these examples of names are merely examples, and do not deny the use of other names for these elements. In addition, it is not denied that other names may be given to elements that do not have multiple names. In the following description, "connection" may include not only direct connection, but also connection via other elements.

[0010] First embodiment 1 is a diagram for explaining an example of a wireless control system according to a first embodiment. The wireless control system includes a controller 10 and a robot 20. The robot 20 is an example of an object to be controlled. The object to be controlled is not limited to the robot 20.

[0011] The controller 10 includes a wireless unit having a function such as a modulation / demodulation function that enables wireless communication with an external device, and a processing unit for processing data transmitted and received by wireless communication.

[0012] An example of the robot 20 is an industrial robot that performs work such as picking up parcels moving on a belt conveyor. The robot 20 includes a base 22, arms 24a, 24b, 24c, 24d, and a gripper 26. The base 22 is installed on a floor, a desk, a table, or the like. The arm 24a is attached to the base 22. The angle / position of the arm 24a relative to the base 22 is variable as shown by the dashed lines. Similarly, the arms 24b, 24c, 24d are attached to the arms 24a, 24b, 24c. The angle / position of the arms 24b, 24c, 24d relative to the arms 24a, 24b, 24c is variable as shown by the dashed lines. A gripper 26 that can be opened and closed is attached to the arm 24d at the tip. The angle / position of the gripper 26 relative to the arm 24d is variable. The total number of the arms 24a-24d is not limited to four and may be any number. The plane of rotation of the arm relative to the base may be parallel to a floor, desk, table, etc. If there is an arm whose plane of rotation of the arm relative to the base is perpendicular to an arm whose plane of rotation is parallel to a floor, desk, table, etc., the position of the tip arm 24d can be moved three-dimensionally.

[0013] The base 22 includes a terminal 28a. The arms 24a-24d include terminals 28b, 28c, 28d, and 28e, respectively. The terminals 28a-28e are wirelessly connected to the controller 10. The terminals 28a-28d include motors that change the angle / position of the arms 24a-24d, respectively. The terminal 28e includes a motor that opens and closes the gripper 26.

[0014] By rotating the motor included in the terminal 28e, the gripper 26 can open and close to pinch and grip an item or release the item. By rotating the motor included in each of the terminals 28a-28d, the angle / position between the arm 24a and the base 22, the angle / position between the arm 24b and the arm 24a, the angle / position between the arm 24c and the arm 24b, the angle / position between the arm 24d and the arm 24c, or the rotation speed of each arm 24 can be controlled. By controlling the angle of the motor included in each of the terminals 28a-28d, the gripper 26 can be moved to an arbitrary position. By controlling the angle of the motor included in each of the terminals 28a-28e, a work such as transferring an item flowing on a belt conveyor to a tray can be performed.

[0015] The controller 10 transmits motor control signals to the terminals 28a-28e. Each of the terminals 28a-28e transmits a motor status signal to the controller 10. The controller 10 receives the status signal, updates the motor control signal in response to the status signal, and transmits the updated control signal to the terminals 28a-28e. When the wireless line between the controller 10 and a certain terminal 28 is disconnected, the controller 10 and the certain terminal 28 are connected to each other via another terminal, and the control signal and the status signal are relayed by the other terminal and transmitted and received between the controller 10 and the certain terminal 28. When the controller 10 operates the other terminal as a relay terminal, the controller 10 shortens the response time of the wireless control system or improves the quality of control by controlling the order of multiple processes performed by the relay terminal.

[0016] 2 is a block diagram for explaining an example of the controller 10 according to the first embodiment. The controller 10 includes a wireless unit 40, a processing unit 42, an attribute selection unit 44, a control signal generation unit 46, an antenna 48, and a memory 50. The processing unit 42 is connected to the wireless unit 40, the attribute selection unit 44, the control signal generation unit 46, and the memory 50 by wires.

[0017] The wireless unit 40 receives the wireless frame transmitted from the terminal 28 by the antenna 48 and demodulates the wireless frame to generate a received signal. The wireless unit 40 measures the wireless characteristics of the wireless link between the terminal 28 and the controller 10. The wireless characteristics are information that indicates the communication quality of the wireless link. An example of the wireless characteristics is the received power of the wireless frame. The wireless unit 40 outputs the measurement results of the wireless characteristics to the processing unit 42.

[0018] The wireless unit 40 extracts the sender (terminal ID) and status signal from the received signal. The wireless unit 40 outputs the wireless characteristics, sender, and status signal to the processing unit 42. The processing unit 42 outputs a control signal and an attribute to the wireless unit 40. The wireless unit 40 modulates the control signal and the attribute, and transmits them as a wireless frame from the antenna 48. Each terminal 28 can operate as a terminal with any attribute. The terminal changes the order of processing depending on the attribute.

[0019] The processing unit 42 outputs the measurement results of the wireless characteristics output from the wireless unit 40 or the results of calculations using the measurement results to the attribute selection unit 44. The attribute selection unit 44 selects an attribute of the terminal 28 based on the information output from the processing unit 42. The attribute selection unit 44 outputs the attribute to the processing unit 42.

[0020] Examples of attributes are a downlink (DL) relay terminal, a relayed terminal, an uplink (UL) relay terminal, and a normal terminal. A DL relay terminal is a terminal that receives a control signal transmitted from the controller 10 to a relayed terminal and transmits the control signal to the relayed terminal, i.e., a terminal that relays the control signal. A UL relay terminal is a terminal that receives a status signal transmitted from the relayed terminal to the controller 10 and transmits the status signal to the controller 10, i.e., a terminal that relays the status signal. A relayed terminal is a terminal that has a wireless link with the controller 10 cut off, receives a control signal via a DL relay terminal, and transmits a status signal via a UL relay terminal. A normal terminal is a terminal that receives a control signal directly from the controller 10 and transmits a status signal directly to the controller 10, and is not involved in relaying.

[0021] For example, it can be determined that a terminal with poor communication quality is likely to have a disconnected wireless link with the controller 10 and is a terminal that requires a relay terminal. For example, it can be determined that a terminal with good communication quality can be used as a relay terminal. When the position of the arm 24 of the robot 20 changes, the state of the wireless link changes. When the state of the wireless link changes, the attribute selection unit 44 changes the attribute to be selected.

[0022] The processing unit 42 stores information during calculation in the memory 50. The processing unit 42 inputs external control information. The processing unit 42 calculates a target value (e.g., a target value of the rotation speed) based on the external control information. The processing unit 42 outputs the target value and the state signal output from the wireless unit 40 to the control signal generating unit 46.

[0023] The attribute selection unit 44 outputs the attribute of each terminal to the processing unit 42. The control signal generation unit 46 outputs a control signal of each terminal to the processing unit 42. The processing unit 42 outputs the attribute of each terminal and the control signal to the wireless unit 40. An example of the timing for outputting the attribute of each terminal and the control signal to the wireless unit 40 is the timing of a period T measured by a timer (not shown).

[0024] The external control information may be target value information of the rotation speed stored in an external storage unit (not shown). The external control information may be target value information of the rotation speed created from a program (not shown) created in advance. The external control information may be a human command via a computer (not shown) or may be information on pressing an emergency stop button (not shown).

[0025] The control signal generating unit 46 generates a control signal based on the target value and the state signal output from the processing unit 42. The control signal generating unit 46 outputs the control signal to the processing unit 42.

[0026] The controller 10 can select an attribute of the terminal 28 based on a wireless frame transmitted from the terminal 28, generate a control signal for the terminal 28, and transmit the control signal to each terminal 28 at a constant period.

[0027] 2 may be implemented by dedicated hardware or software. When implemented by software, the processing unit 42, the attribute selection unit 44, and the control signal generation unit 46 each include a memory that stores a program and a CPU that executes the program. The processing unit 42, the attribute selection unit 44, and the control signal generation unit 46 are not limited to including one CPU, and may each include multiple CPUs that execute multiple functions.

[0028] An example of a communication standard for transmitting and receiving control signals and status signals between the wireless unit 40 and the terminal 28 is wireless LAN (IEEE802.11). The wireless unit 40 may transmit and receive control signals and status signals according to other wireless communication standards such as ZigBee (registered trademark) and local 5G, or a proprietary standard.

[0029] The control signal transmitted by the controller 10 may be a unicast signal addressed to any one of the terminals 28, or a broadcast signal addressed to all of the terminals 28.

[0030] 3 is a block diagram for explaining an example of the terminal 28 according to the first embodiment. The terminal 28 includes a wireless unit 60, a processing unit 62, a motor driver 64, a motor 66, an antenna 68, and a memory 70. The processing unit 62 is connected to the wireless unit 60, the motor driver 64, and the memory by wires. The motor driver 64 is connected to the motor 66 by wires.

[0031] The wireless unit 60 receives wireless frames transmitted from the controller 10 or other terminals 28 via the antenna 68, and demodulates the wireless frames to generate a received signal. The wireless unit 60 extracts the transmission source, control signal, and attributes from the received signal. The wireless unit 60 outputs the extracted transmission source, control signal, and attributes to the processing unit 62. The wireless unit 60 inputs the destination (terminal ID), attributes, and status signal output from the processing unit 62, modulates the input information, and transmits it from the antenna 68 as a wireless frame.

[0032] The processing unit 62 writes the information output from the wireless unit 60 into the memory 70. The processing unit 62 determines the attributes and destination of the information output from the wireless unit 60, and performs processing accordingly.

[0033] When the attribute is DL relay terminal and the destination is the own terminal, the processing unit 62 outputs a status signal request signal for requesting a status signal to the motor driver 64. The processing unit 62 inputs the status signal output from the motor driver 64, and outputs the status signal (including the source) and a control signal (including the destination and attributes) (FIG. 4(c)) of the relayed terminal to the wireless unit 60. The processing unit 62 outputs a control signal (the control signal included in FIG. 4(a)) to the motor driver 64. The order of outputting the status signal and control signal to the wireless unit 60 and the control signal to the motor driver 64 may be reversed from that described above.

[0034] If the attribute is a DL relay terminal and the destination is a relayed terminal, the processing unit 62 writes the control signal (including the destination and the attribute) of the relayed terminal to the memory 70. If the attribute is a DL relay terminal and the destination is other than the above, the processing unit 62 discards the information (such as the control signal) about the destination.

[0035] When the attribute is a relayed terminal and the destination is the own terminal, the processing unit 62 outputs a status signal request signal to the motor driver 64, inputs the status signal output from the motor driver 64, outputs the status signal (including the sender) to the wireless unit 60 (FIG. 4(b)), and outputs a control signal to the motor driver 64. The order of outputting the status signal to the wireless unit 60 and the control signal to the motor driver 64 may be reversed as described above.

[0036] If the attribute is a relayed terminal and the destination is a terminal other than the own terminal, the processing unit 62 discards information about the destination (control signal, etc.).

[0037] When the attribute is a UL relay terminal and the destination is the own terminal, the processing unit 62 outputs a control signal to the motor driver 64 and outputs a status information request signal to the motor driver 64. The processing unit 62 inputs the status signal output from the motor driver 64, and outputs the status signal (including the transmission source) and the status signal (including the transmission source) of the relayed terminal to the wireless unit 60 (FIG. 4(d)). The processing unit 62 does not output the two status signals to the wireless unit 60 until the control signal from the relayed terminal arrives.

[0038] If the attribute is a UL relay terminal and the source is a relayed terminal, the processing unit 62 writes the status signal (including the source) of the relayed terminal to the memory 70. If the attribute is a UL relay terminal and the destination is other than the above, the processing unit 62 discards information about the destination (such as the status signal).

[0039] If the attribute is a normal terminal and the destination is the own terminal, the processing unit 62 outputs a control signal to the motor driver 64 and outputs a status information request signal to the motor driver 64. The processing unit 62 outputs the status signal output from the motor driver 64 to the wireless unit 60 (FIG. 4(b)). If the attribute is a normal terminal and the destination is a terminal other than the own terminal, the processing unit 62 discards information about the destination (such as the status signal).

[0040] The motor driver 64 inputs a control signal or a status signal request signal from the processing unit 62. When the motor driver 64 inputs a control signal, it controls the motor 66 in accordance with the control signal. When the motor driver 64 inputs a status signal request signal, it inputs an encoder value indicating the number of rotations from an encoder (not shown) associated with the motor 66 as a status signal. The motor driver 64 outputs the input status signal to the processing unit 62.

[0041] The motor 66 rotates its shaft in accordance with a control signal output from the motor driver 64. An encoder associated with the motor 66 outputs an encoder value (also referred to as a sensor value, a Hall sensor value, or a setting parameter value) indicating the number of rotations of the motor 66 to the motor driver 64.

[0042] The motor 66 converts electric power into rotary motion or the like. The position of the arm 24 is determined by an encoder value such as the number of rotations of the motor 66. The motor 66 may serve as a sensor for grasping the position of the arm 24, the gripper 26, or the terminal 28. The encoder value of the motor 66 corresponds to the sensor value. The center of rotation of the motor 66 is sometimes referred to as an axis.

[0043] Terminal 28 writes its own terminal attribute contained in the wireless frame it received immediately before to memory 70. Terminal 28 operates as a terminal with the attribute stored in memory 70 and executes a plurality of processes in an order according to the attribute. If the attribute contained in the received wireless frame differs from the stored attribute, the attribute stored in memory 70 is updated.

[0044] The processing unit 62 in Fig. 3 may be implemented by dedicated hardware or software. When implemented by software, the processing unit 62 includes a memory for storing a program and a CPU for executing the program. The processing unit 62 is not limited to including one CPU, and may include multiple CPUs each for executing multiple functions.

[0045] Although an example has been shown in which each terminal 28 includes one motor 66, each terminal 28 may include multiple motors instead of one motor 66. In that case, the controller 10 may include a motor ID in the destination of the control signal. The terminal 28 may select and control one of the multiple motors based on the motor ID specified in the destination of the control signal.

[0046] Although an example in which the terminal 28 includes one radio unit 60 has been shown, the terminal 28 may include multiple radio units 60.

[0047] 1 shows a wireless control system including one robot 20, the embodiment is not limited to one robot 20, but may be a wireless control system including a plurality of robots. The controller 10 is not limited to controlling one robot 20, but may control a plurality of robots 20. The wireless control system may include a plurality of controllers 10.

[0048] FIG. 4 is a diagram for explaining an example of a format of a radio frame according to the first embodiment.

[0049] Fig. 4(a) shows an example of a wireless frame transmitted by the controller 10. The wireless frame includes a MAC header, a destination, an attribute, and a control signal. The MAC header includes the MAC address of the destination terminal 28, the MAC address of the sender (controller 10), etc. The destination indicates the ID of the terminal 28 to which the wireless frame is to be transmitted. The attribute indicates the attribute of the destination terminal 28. The control signal indicates a control target value of the destination terminal 28. An example of the control target value is the target angular velocity of a motor.

[0050] 4(a) is an example in which the controller 10 transmits to each terminal by unicast. In the case in which the controller transmits to each terminal by broadcast, an attribute and a control signal addressed to each terminal are included in one wireless frame (not shown).

[0051] Fig. 4(b) shows an example of a wireless frame transmitted by a terminal 28 whose attribute is a relayed terminal or a normal terminal. The wireless frame includes a MAC header, a sender, and a status signal. The MAC header is the same as the MAC header in Fig. 4(a). The sender and the status signal respectively indicate the ID and status signal (encoder value, sensor value, etc.) of the terminal 28 itself.

[0052] Fig. 4(c) shows an example of a wireless frame transmitted by terminal 28 whose attribute is DL relay terminal. The wireless frame includes a MAC header, a source, a status signal, a destination, an attribute, and a control signal. The MAC header is the same as the MAC header in Fig. 4(a). The source and the status signal respectively represent the ID and status signal (encoder value, sensor value, etc.) of terminal 28 itself. The destination, the attribute, and the control signal respectively represent the ID, the attribute, and the control signal of terminal 28 whose attribute is relayed terminal. The destination, the attribute, and the control signal are the same as the destination, the attribute, and the control signal included in the wireless frame shown in Fig. 4(a), and are relay signals transmitted to the relayed terminal.

[0053] Fig. 4(d) shows an example of a wireless frame transmitted by terminal 28 whose attribute is a UL relay terminal. The wireless frame includes a MAC header, source 1, status signal 1, source 2, and status signal 2. The MAC header is the same as the MAC header in Fig. 4(a). Source 1 and status signal respectively represent the ID and status signal (encoder value, sensor value, etc.) of terminal 28 itself. Source 2 and status signal 2 are the same as the source and status signal respectively included in the wireless frame transmitted by the relayed terminal or normal terminal shown in Fig. 4(b), and are relay signals transmitted to controller 10.

[0054] Fig. 5 is a diagram for explaining an example of a process of a terminal 28 operating as a DL relay terminal according to the first embodiment. Fig. 5(a) shows an example of a process of a DL relay terminal according to a reference example. Fig. 5(b) shows an example of a process of a DL relay terminal according to the first embodiment.

[0055] In a DL relay terminal according to a reference example (FIG. 5(a)), when a wireless unit 60 receives a wireless frame (FIG. 4(a)) transmitted from the controller 10, it outputs a destination, an attribute, and a control signal to a processing unit 62. The processing unit 62 outputs a control signal of the own terminal to a motor driver 64. The processing unit 62 writes the control signal of the relayed terminal together with the destination and attribute into a memory 70 as a relay signal.

[0056] When the motor driver 64 receives the control signal, it outputs an ACK, which is a response confirmation, to the processing unit 62. When the processing unit 62 receives the ACK, it outputs a control signal reflection signal to the motor driver 64. If the processing unit 62 is unable to receive an ACK within a certain period of time, it outputs the control signal of its own terminal to the motor driver 64 again.

[0057] When the motor driver 64 receives the control signal reflecting signal, it drives the motor 66 at the target rotation speed indicated by the control signal and outputs an ACK as a response confirmation to the processing unit 62. When the processing unit 62 receives the ACK, it outputs a status signal request signal to the motor driver 64. If the processing unit 62 is unable to receive an ACK within a certain period of time, it outputs the control signal reflecting signal to the motor driver 64 again. When the motor driver 64 receives the status signal request signal, it outputs a status signal to the processing unit 62.

[0058] When the processing unit 62 receives the status signal, it reads the relay signal (the destination, attribute, and control signal of the relayed terminal) from the memory 70, and outputs the source (the ID of the own terminal), the status signal, and the relay signal to the wireless unit 60. The wireless unit 60 transmits the wireless frame shown in FIG. 4(c).

[0059] The processing unit 62 repeatedly executes the above series of processes.

[0060] In the terminal 28 (FIG. 5(b)) operating as a DL relay terminal according to the first embodiment, when a wireless unit 60 receives a wireless frame (FIG. 4(a)) transmitted from the controller 10, it outputs a destination, an attribute, and a control signal to a processing unit 62. The processing unit 62 writes the control signal of the own terminal together with the destination and attribute into the memory 70, and writes the control signal of the relayed terminal together with the destination and attribute into the memory 70 as a relay signal.

[0061] The processing unit 62 outputs a status signal request signal to the motor driver 64. The motor driver 64 outputs a status signal to the processing unit 62 upon receiving the status signal request signal.

[0062] When the processing unit 62 receives the status signal, it reads out the destination, attribute, and control signal of the relayed terminal from the memory 70. The destination, attribute, and control signal of the relayed terminal are referred to as a relay signal here. The processing unit 62 outputs the source (the ID of its own terminal), the status signal, and the relay signal to the wireless unit 60. The wireless unit 60 transmits the wireless frame shown in FIG. 4(c).

[0063] The processing unit 62 outputs the control signal of the terminal to the motor driver 64. When the motor driver 64 receives the control signal, it outputs an ACK, which is a response confirmation, to the processing unit 62. When the processing unit 62 receives the ACK, it outputs a control signal reflection signal to the motor driver 64. When the processing unit 62 is unable to receive an ACK within a certain period of time, it outputs the control signal of the terminal to the motor driver 64 again.

[0064] When the motor driver 64 receives the control signal reflecting signal, it drives the motor 66 at the target rotation speed indicated by the control signal and outputs an ACK as a response confirmation to the processing unit 62. If the processing unit 62 does not receive an ACK within a certain period of time, it outputs the control signal reflecting signal to the motor driver 64 again.

[0065] The processing unit 62 repeatedly executes the above series of processes.

[0066] The wireless frame (FIG. 4(c)) transmitted by terminal 28 operating as a DL relay terminal according to the first embodiment includes a relay signal, which includes a control signal for the relayed terminal. Comparing the process of FIG. 5(a) with the process of FIG. 5(b), the control signal for the relayed terminal is transmitted from the DL relay terminal earlier in the process of FIG. 5(b) than in the process of FIG. 5(a). For this reason, in the first embodiment, terminal 28 operating as a relayed terminal receives a control signal earlier than the relayed terminal in the reference example, and therefore the control of terminal 28 operating as a relayed terminal is accelerated.

[0067] Fig. 6 is a diagram for explaining an example of a process of a terminal 28 operating as a relayed terminal according to the first embodiment. Fig. 6(a) shows an example of a process of a relayed terminal according to a reference example. Fig. 6(b) shows an example of a process of a relayed terminal according to the first embodiment.

[0068] In the relayed terminal according to the reference example (FIG. 6(a)), when the wireless unit 60 receives a wireless frame transmitted from the controller 10 (FIG. 4(a)) or a wireless frame transmitted from another DL relay terminal (FIG. 4(c)), it outputs a destination, an attribute, and a control signal to a processing unit 62. The processing unit 62 outputs a control signal of the own terminal to a motor driver 64. The processing unit 62 discards information (such as a control signal) related to other terminals.

[0069] When the motor driver 64 receives the control signal, it outputs an ACK, which is a response confirmation, to the processing unit 62. When the processing unit 62 receives the ACK, it outputs a control signal reflection signal to the motor driver 64. If the processing unit 62 is unable to receive the ACK within a certain period of time, it outputs the control signal to the motor driver 64 again.

[0070] When the motor driver 64 receives the control signal reflecting signal, it drives the motor 66 at the target rotation speed indicated by the control signal and outputs an ACK as a response confirmation to the processing unit 62. When the processing unit 62 receives the ACK, it outputs a status signal request signal to the motor driver 64. If the processing unit 62 is unable to receive an ACK within a certain period of time, it outputs the control signal reflecting signal to the motor driver 64 again. When the motor driver 64 receives the status signal request signal, it outputs a status signal to the processing unit 62.

[0071] When the processing unit 62 receives the status signal, it outputs the source (its own terminal) and the status signal to the wireless unit 60. The wireless unit 60 transmits a wireless frame shown in FIG.

[0072] The processing unit 62 repeatedly executes the above series of processes.

[0073] In the terminal 28 (FIG. 6(b)) operating as the relayed terminal according to the first embodiment, when the wireless unit 60 receives a wireless frame transmitted from the controller 10 (FIG. 4(a)) or a wireless frame transmitted from another DL relay terminal (FIG. 4(c)), the wireless unit 60 outputs a destination, an attribute, and a control signal to a processing unit 62. The processing unit 62 writes the control signal of the terminal itself into a memory 70.

[0074] The processing unit 62 outputs a status signal request signal to the motor driver 64. The motor driver 64 outputs a status signal to the processing unit 62 upon receiving the status signal request signal.

[0075] When the processing unit 62 receives the status signal, it outputs the source (its own terminal) and the status signal to the wireless unit 60. The wireless unit 60 transmits a wireless frame shown in FIG.

[0076] The processing unit 62 reads out the control signal from the memory 70. The processing unit 62 outputs the control signal to the motor driver 64. When the motor driver 64 receives the control signal, it outputs an ACK, which is a response confirmation, to the processing unit 62. When the processing unit 62 receives the ACK, it outputs a control signal reflection signal to the motor driver 64. If the processing unit 62 is unable to receive an ACK within a certain period of time, it outputs the control signal to the motor driver 64 again.

[0077] When the motor driver 64 receives the control signal reflecting signal, it drives the motor 66 at the target rotation speed indicated by the control signal and outputs an ACK as a response confirmation to the processing unit 62. If the processing unit 62 does not receive an ACK within a certain period of time, it outputs the control signal reflecting signal to the motor driver 64 again.

[0078] The processing unit 62 repeatedly executes the above series of processes.

[0079] Comparing the process of Fig. 6(a) with the process of Fig. 6(b), the status signal is transmitted from the relayed terminal earlier in the process of Fig. 6(b) than in the process of Fig. 6(a). Therefore, in the first embodiment, the controller 10 receives the status signal earlier than in the reference example, and the response of the control system is accelerated.

[0080] When the relayed terminal 28 according to the first embodiment receives an overlapping wireless frame (FIG. 4(a)) directly transmitted from the controller 10 and an overlapping wireless frame (FIG. 4(c)) relayed from a DL relay terminal, the terminal may perform the process of FIG. 6(b) on the wireless frame received first and skip the above process on the wireless frame received thereafter. The determination of whether two or more received frames are overlapping may be made based on the contents of the control signal, or, if sequence numbers are assigned to the wireless frames, based on the sequence numbers.

[0081] Fig. 7 is a diagram for explaining an example of processing of a terminal 28 operating as a UL relay terminal according to the first embodiment. Fig. 7(a) shows an example of processing of a UL relay terminal according to a reference example. Fig. 7(b) shows an example of processing of a UL relay terminal according to the first embodiment.

[0082] In a UL relay terminal according to a reference example (FIG. 7(a)), when a wireless unit 60 receives a wireless frame (FIG. 4(a)) transmitted from a controller 10, a processing unit 62 outputs a control signal of the own terminal to a motor driver 64. When the processing unit 62 receives a wireless frame (FIG. 4(b)) transmitted from a relayed terminal, it writes a status signal of the relayed terminal together with the transmission source into a memory 70 as a relay signal.

[0083] When the motor driver 64 receives the control signal, it outputs an ACK, which is a response confirmation, to the processing unit 62. When the processing unit 62 receives the ACK, it outputs a control signal reflection signal to the motor driver 64. If the processing unit 62 is unable to receive an ACK within a certain period of time, it outputs the control signal of its own terminal to the motor driver 64 again.

[0084] When the motor driver 64 receives the control signal reflecting signal, it drives the motor 66 at the target rotation speed indicated by the control signal and outputs an ACK as a response confirmation to the processing unit 62. When the processing unit 62 receives the ACK, it outputs a status signal request signal to the motor driver 64. If the processing unit 62 is unable to receive an ACK within a certain period of time, it outputs the control signal reflecting signal to the motor driver 64 again. When the motor driver 64 receives the status signal request signal, it outputs a status signal to the processing unit 62.

[0085] When the processing unit 62 receives the status signal, it reads the relay signal (sender, status signal) from the memory 70 and outputs the sender (own terminal), the status signal, and the relay signal to the wireless unit 60. The wireless unit 60 transmits the wireless frame shown in Fig. 4(d). If the relay signal (sender, status signal) has not been written to the memory 70 at the time the processing unit 62 receives the status signal, the processing unit 62 outputs only the status signal from the motor driver 64, or the status signal from the motor driver 64 and a status signal for the previous control signal addressed to the relayed terminal, as a relay signal to the wireless unit.

[0086] The processing unit 62 repeatedly executes the above series of processes.

[0087] The UL relay terminal according to the first embodiment (FIG. 7(b)) operates in a manner similar to that of the UL relay terminal according to the reference example (FIG. 7(a)). The first embodiment differs from the reference example in that when the processing unit 62 inputs a status signal, if the relay signal (source, status signal) has not been written to the memory 70, or if the status signal has not been received from the relayed terminal and the memory 70 has not been updated, the processing unit 62 does not output any signal to the radio unit and continues to wait until it receives a status signal from the relayed terminal.

[0088] Comparing the process in Fig. 7(a) with the process in Fig. 7(b), in the process in Fig. 7(a), depending on the timing of receiving the status signal transmitted by the relayed terminal, the signal may not be relayed or an old status signal may be relayed. However, in the process in Fig. 7(b), the latest status signal transmitted by the relayed terminal is always relayed.

[0089] Fig. 8 is a diagram for explaining an example of an experimental result in a wireless control system according to a reference example. Here, it is assumed that the number of terminals 28 is three. In the reference example, the DL relay terminal executes the process shown in Fig. 5(a), the relayed terminal executes the process shown in Fig. 6(a), and the UL relay terminal executes the process shown in Fig. 7(b). The controller 10 controls the motors 66 of the three terminals 28 at a control period of 10 ms. Fig. 8 is a diagram partially customized by monitoring the waveforms of wireless signals and internal signals of the three terminals when the three motors are being controlled using a digital oscilloscope.

[0090] 8(a) shows a waveform of a wireless signal transmitted and received by the controller 10. The wireless signal includes a cluster of peaks A1 at a period of 10 ms. The cluster of peaks A1 represents a control signal transmitted by the controller 10 to three terminals. The wireless signal includes a peak A2 approximately 4 ms after the cluster of peaks A1. The peak A2 represents a status signal transmitted by a DL relay terminal. The wireless signal includes a peak A3 approximately 9 ms after the cluster of peaks A1. The peak A3 represents a status signal transmitted by a relayed terminal. The wireless signal includes a peak A4 approximately 10.2 ms after the cluster of peaks A1. The peak A4 overlaps with the cluster of peaks A1. The peak A4 represents a status signal transmitted by a UL relay terminal.

[0091] Fig. 8(b) shows a signal waveform between the processing unit 62 and the motor driver 64 in the DL relay terminal. Approximately 1 ms after the controller 10 transmits the control signal, a group of six high-level signals is communicated. One group of high-level signals represents one frame exchanged in the communication between the processing unit 62 and the motor driver 64. The six frames are, in order, a frame group (a) of a control signal, an ACK for the control signal, a control signal reflecting signal, an ACK for the control signal reflecting signal, and a frame group (b) of a status signal request signal and a status signal. Approximately 0.5 ms after the frames (b) of the status signal request signal and the status signal, the DL relay terminal transmits a status signal (A2 in Fig. 8(a)).

[0092] 8(c) shows signals between the processing unit 62 and the motor driver 64 in the relayed terminal. A chunk of six frames is communicated about 1 ms after the DL relay terminal transmits the status signal. The six frames are the same as those of the DL relay terminal. About 3 ms after the frame of the status signal, the relayed terminal transmits the status signal.

[0093] 8(d) shows signals between the processing unit 62 and the motor driver 64 in the UL relay terminal. Approximately 1 ms after the controller 10 transmits the control signal, a block of six high-level signals is communicated. The six frames are the same as those of the DL relay terminal. Approximately 1.2 ms after the wireless frame of the status signal of the relayed terminal is transmitted, the UL relay terminal transmits a status signal.

[0094] The controller 10 can receive the status signal of the DL relay terminal from the time of transmitting the control signal until the time of transmitting the next control signal. Therefore, the controller 10 can generate and transmit a control signal reflecting the status signal, and can maintain high quality of control. The controller 10 may not be able to receive the status information of the relayed terminal and the UL relay terminal before the time of transmitting the next control signal. Therefore, the controller 10 cannot perform the desired control.

[0095] When the UL relay terminal executes the process shown in Fig. 7(a), the controller 10 can receive the status signal of the UL relay terminal by the transmission timing of the next control signal. However, since the status signal of the relayed terminal is not relayed, the controller 10 cannot receive the status signal of the relayed terminal by the transmission timing of the next control signal. Therefore, in this case, the controller 10 cannot perform the desired control.

[0096] Fig. 9 is a diagram for explaining an example of an experimental result in the wireless control system according to the first embodiment. Here, it is assumed that the number of terminals 28 is three. The DL relay terminal executes the process shown in Fig. 5(a), the relayed terminal executes the process shown in Fig. 6(a), and the UL relay terminal executes the process shown in Fig. 7(b). The description of the same operations as those in Fig. 8 will be omitted.

[0097] The DL relay terminal gives priority to inputting a status signal from the motor 66 and transmitting the status signal as a wireless frame, rather than reflecting the control signal in the drive of the motor 66. As a result, the DL relay terminal transmits a status signal request signal and a group of frames (b) of the status signal earlier than a group of frames (a) of the control signal, an ACK for the control signal, a control signal reflecting signal, and an ACK for the control signal reflecting signal.

[0098] Like the DL relay terminal, the relayed terminal gives priority to inputting a status signal from the motor 66 and transmitting the status signal as a wireless frame, rather than reflecting the control signal in the drive of the motor 66. As a result, the relayed terminal transmits a status signal request signal and a status signal frame group (b) earlier than a control signal, an ACK for the control signal, a control signal reflecting signal, and an ACK for the control signal reflecting signal frame group (a).

[0099] The UL relay terminal executes the same process as in Fig. 8, but receives the status signal transmitted by the relayed terminal at an earlier timing than in Fig. 8. Therefore, the UL relay terminal also transmits the status signal of the UL relay terminal at an earlier timing than in Fig. 8.

[0100] The controller 10 according to the first embodiment receives a status signal of the DL relay terminal, a status signal of the relayed terminal, and a status signal of the UL relay terminal between a certain transmission timing of a control signal and the next transmission timing. The controller 10 generates and transmits a control signal reflecting these status signals. This shortens the response time in a wireless control system composed of the controller 10 and a plurality of terminals 28 feedback-controlled by the controller 10, and suppresses deterioration in the quality of control of the motor 66 of the terminal 28.

[0101] Although the relayed terminal has been described as a terminal whose wireless link with the controller 10 is disconnected, the wireless link does not necessarily have to be disconnected. A terminal whose wireless link with the controller is of poor quality among a plurality of terminals may be the relayed terminal. Also, the quality of the wireless link between the controller and each terminal may be predicted based on the status signal or control signal of each terminal, and the terminal whose predicted wireless link quality is poor may be the relayed terminal.

[0102] Although it has been described that each terminal extracts an attribute from a received signal and performs processing according to the attribute, each terminal may extract an attribute from a received signal and perform processing according to the attribute, or may perform processing as a relayed terminal. For example, if the attribute is a DL relay terminal and the destination is other than the terminal itself, the processing unit 62 does not discard information about the destination (such as control information), and performs processing as a relayed terminal if a relay signal addressed to the terminal itself is included. On the other hand, if a relay signal addressed to the terminal itself is not included, the attribute is not updated and the processing unit 62 discards information about the destination (such as control information). In this way, even if the wireless line of a certain terminal is suddenly cut off and the controller is unable to change the attribute in time, the terminal can be controlled as a relayed terminal.

[0103] Second embodiment 10 is a block diagram for explaining an example of the controller 10 according to the second embodiment. Parts corresponding to those according to the first embodiment are given the same reference numerals, and detailed explanations will be omitted.

[0104] The controller 10 includes a radio unit 40, a processing unit 42, an attribute selection unit 44, a control signal generation unit 46, an antenna 48, a memory 50, a status signal prediction unit 102, and a second control signal generation unit 104. The memory 50 stores the past status signal of each terminal 28. The processing unit 42 outputs the target value, the current status signal, and the past status signal of the DL relay terminal to the status signal prediction unit 102, and outputs the target value and the status signal of the terminal other than the DL relay terminal to the control signal generation unit 46. The processing unit 42 inputs the control signal of the DL relay terminal from the second control signal generation unit 104, and outputs the control signal to the radio unit 40. The processing unit 42 inputs the control signal of the terminal other than the DL relay terminal from the control signal generation unit 46, and outputs the control signal to the radio unit 40.

[0105] The function of the terminal 28 changes according to the attribute selected by the attribute selection unit 44 of the controller 10. The attribute of a certain terminal 28 may be a normal terminal until a certain timing, and may change to a DL relay terminal after a certain timing. As shown in FIG. 5(b), in the DL relay terminal, the timing at which the wireless unit 60 transmits a status signal is earlier than the timing at which the processing unit 62 outputs a control signal to the motor driver 64. The status signal transmitted by the DL relay terminal is old information that does not accurately reflect the state after control by the current control signal.

[0106] To improve this point, the controller 10 according to the second embodiment includes a status signal prediction unit 102 and a second control signal generation unit 104. The normal terminal transmits a status signal after outputting a control signal to the motor driver 64. When the processing unit 42 receives the current status signal of the DL relay terminal, it reads out the past status signal of the DL relay terminal from the memory 50, and outputs the target value, the current status signal, and the past status signal of the DL relay terminal to the status signal prediction unit 102. The status signal prediction unit 102 generates a status signal prediction value based on the status signal, and outputs the target value and the status signal prediction value to the second control signal generation unit 104.

[0107] The second control signal generating unit 104 receives the target value and the status signal predicted value from the status signal predicting unit 102. The second control signal generating unit 104 generates a control signal for the DL relay terminal based on the target value and the status signal predicted value, and outputs the control signal to the processing unit 42.

[0108] The processing unit 42 transmits the output of the control signal generating unit 46 or the output of the second control signal generating unit 104 to the radio unit 40 .

[0109] FIG. 11 is a diagram for explaining an example of the operation of the status signal prediction unit 102 according to the second embodiment. A status signal (e.g., the number of rotations of the motor 66) transmitted from the terminal 28 and received by the controller 10 at timing t is denoted as f(t). t1 and t2 represent the timings at which the controller 10 receives a status signal transmitted from the terminal 28 operating as a normal terminal. It is assumed that the attribute of the terminal 28 operating as a normal terminal is changed to a DL relay terminal after timing t2. Timings t3, t5, and t7 represent the timings at which the controller 10 receives a status signal transmitted from the terminal 28 operating as a DL relay terminal. Compared to a normal terminal, a DL relay terminal transmits a status signal earlier, and the AoI of the status signal is longer accordingly.

[0110] The status signal prediction unit 102 predicts a status signal to be transmitted from a terminal operating as a DL relay terminal when the terminal operates as a normal terminal rather than a DL relay terminal, based on the status signal transmitted from the terminal operating as a DL relay terminal and the timing of receiving the status signal, and sets the value as a status signal prediction value. If the control period is T, then t4 in FIG. 11 is t4=t2+T. The status signal prediction unit 102 calculates a prediction value f(t4) of the status signal received at timing t4 using the following equation. f(t2) is the past status signal stored in the memory 50.

[0111] f(t4) =(t4−t2)×(f(t3)−f(t2)) / (t3−t2)+f(t2) Equation 1 Similarly, the predicted value of the status signal for the status signal received at timing t5 is calculated using the following formula.

[0112] f(t6) =(t6−t3)×(f(t5)−f(t3)) / (t5−t3)+f(t3) Equation 2 Note that t6=t4+T.

[0113] The status signal prediction unit 102 similarly obtains status signal prediction values ​​for status signals received from DL relay terminals at subsequent timings.

[0114] This formula is merely an example, and the predicted value of the status signal may be calculated using another formula.

[0115] The above explanation is for an example in which the terminal attribute is changed from a normal terminal to a DL relay terminal, but the same applies to the case in which the terminal attribute is changed from a relayed terminal to a DL relay terminal, or the case in which the terminal attribute is changed from a UL relay terminal to a DL relay terminal.

[0116] The input of the control signal generating unit 46 is a state signal. The input of the second control signal generating unit 104 is a state signal prediction value. The second control signal generating unit 104 differs from the control signal generating unit 46 in that the input signal is changed from the state signal to the state signal prediction value, and may be the same as the control signal generating unit 46 in other respects. The second control signal generating unit 104 generates a control signal for the DL relay terminal based on the state signal prediction value. The control signal generating unit 46 generates control signals for the relayed terminal and the UL relay terminal based on the state signal. The second control signal generating unit 104 may generate a control signal based on the state signal and the state signal prediction value. For example, the second control signal generating unit 104 may generate a control signal based on an average value of the state signal and the state signal prediction value.

[0117] According to the controller 10 of the second embodiment, when the AoI of a status signal transmitted from a DL relay terminal is long, it is possible to predict a status signal with a short AoI, thereby making it possible to reduce the deterioration of the quality of control while shortening the response time of the wireless control system.

[0118] Third embodiment 12 is a block diagram for explaining an example of the controller 10 according to the third embodiment. Parts corresponding to those according to the second embodiment are given the same reference numerals, and detailed description thereof will be omitted.

[0119] The processing unit 42 includes a response time measurement unit 112. The response time measurement unit 112 measures the response time of each terminal based on the difference between the timing at which the processing unit 42 outputs a control signal for each terminal to the wireless unit 40 and the timing at which the wireless unit 40 inputs a status signal for each terminal.

[0120] The processing unit 42 outputs the response time of each terminal to the attribute selection unit 44. Based on the information output from the processing unit 42, the attribute selection unit 44 sets the attribute of a terminal that is likely to have its wireless link with the controller 10 disconnected as a relayed terminal. The attribute selection unit 44 sets the attribute of a terminal with the shortest response time among all terminals 28, excluding terminals whose attribute is relayed terminal, as a DL relay terminal.

[0121] When the processing unit 62 of the terminal 28 is configured with a CPU, there may be terminals whose response times are constantly short and terminals whose response times are constantly long due to the influence of the interrupt cycle, etc. Furthermore, when the performance of the CPU of the terminals is different, there may be terminals whose response times are constantly short and terminals whose response times are constantly long. Furthermore, there may be terminals whose response times are constantly short and terminals whose response times are constantly long due to the influence of communication characteristics. By operating a terminal whose response time is short as a DL relay terminal, it is possible to transmit a control signal to the relayed terminal at an early stage, and the response time of the wireless control system can be shortened.

[0122] The attribute selection unit 44 may select at least one terminal having a short response time as a terminal to be operated as a DL relay terminal. Alternatively, the attribute selection unit 44 may select one or more terminals having a short response time as terminals to be operated as UL relay terminals.

[0123] According to the controller 10 according to the third embodiment, the relay time can be shortened, and the response time between relayed terminals can be shortened.

[0124] Fourth embodiment 13 is a block diagram for explaining an example of the controller 10 according to the fourth embodiment. Parts corresponding to those according to the third embodiment are given the same reference numerals, and detailed description thereof will be omitted.

[0125] The processing unit 42 includes a communication quality measurement unit 122. The communication quality measurement unit 122 calculates communication quality from the wireless characteristics of each terminal to obtain a communication quality measurement value. The wireless characteristics are, for example, the received power of a wireless frame. The communication quality may be the average received power of wireless frames received the past n times (n is a natural number). In this case, the higher the communication quality measurement value, the better the communication quality. Another example of the wireless characteristics is whether or not the received wireless frame is a retransmission frame. In this case, the communication quality may be the retransmission ratio of wireless frames received the past n times. In this case, the lower the communication quality measurement value, the better the communication quality.

[0126] The processing unit 42 outputs the communication quality measurement value to the attribute selection unit 44. Based on the information output from the processing unit 42, the attribute selection unit 44 determines the attribute of a terminal that is likely to have its wireless link with the controller 10 disconnected as a relayed terminal. The attribute selection unit 44 determines the attribute of a terminal with the best communication quality among all terminals 28, excluding terminals whose attribute is a relayed terminal, as a UL relay terminal. The attribute selection unit 44 determines the attribute of a terminal with the shortest response time among all terminals 28, excluding terminals whose attribute is a relayed terminal or a UL relay terminal, as a DL relay terminal.

[0127] By operating a terminal with good communication quality as a UL relay terminal, the possibility of delays due to retransmission of the status signal can be reduced, and the possibility of relaying the status signal within the control period can be increased. Note that multiple terminals with good communication quality may be assigned to multiple UL relay terminals, or one or more terminals with good communication quality may be assigned to a DL relay terminal.

[0128] The communication quality measuring unit 122 may be provided in the wireless unit 40 instead of in the processing unit 42. The functions of the communication quality measuring unit 122 may be divided, and each function of the communication quality measuring unit 122 may be provided separately in the wireless unit 40 and the processing unit 42.

[0129] The controller 10 according to the fourth embodiment can shorten the relay time, and can shorten the response time between the controller 10 and the relayed terminal.

[0130] Fifth embodiment 14 is a block diagram for explaining an example of the controller 10 according to the fifth embodiment. Parts corresponding to those according to the fourth embodiment are given the same reference numerals, and detailed explanations will be omitted.

[0131] The processing unit 42 includes a control signal comparison unit 132. The control signal comparison unit 132 outputs the absolute value of the speed of the motor 66 or the absolute value of the acceleration of the motor 66 of each terminal, represented by the control signal of each terminal output from the control signal generation unit 46 or the second control signal generation unit 104, to the attribute selection unit 44. The acceleration of each terminal can be calculated from the difference between the speed of the control signal of each terminal received in the past and the speed of the control signal of each terminal received most recently, and the difference between the timing of reception in the past and the timing of reception most recently.

[0132] The attribute selection unit 44 determines the attribute of a terminal that is likely to have its wireless connection with the controller 10 cut off as a relayed terminal based on the information output from the processing unit 42. The attribute selection unit 44 determines the attribute of a terminal with the largest absolute value of speed or acceleration among all terminals excluding terminals whose attribute is a relayed terminal as a UL relay terminal. The attribute selection unit 44 determines the attribute of a terminal with the shortest response time among all terminals excluding terminals whose attribute is a relayed terminal or a UL relay terminal as a DL relay terminal.

[0133] Alternatively, the attribute selection unit 44 sets the attribute of the terminal with the largest absolute value of speed or acceleration as a relayed terminal.The attribute selection unit 44 sets the attribute of the terminal with the best communication quality among all terminals, excluding terminals whose attribute is a relayed terminal, as a UL relay terminal.The attribute selection unit 44 sets the attribute of the terminal with the shortest response time among all terminals, excluding terminals whose attribute is a relayed terminal or a UL relay terminal, as a DL relay terminal.

[0134] Usually, the attribute selection unit 44 sets the attribute of the terminal with the worst communication quality as the relayed terminal, but if the communication quality of all terminals is relatively good, the attribute selection unit 44 may set the attribute of the terminal with the largest absolute value of speed or acceleration as the relayed terminal as in the fifth embodiment. Alternatively, the attribute selection unit 44 may set the attribute of the terminal with the largest absolute value of speed or acceleration as the relayed terminal, and set the attribute of the terminal with the largest absolute value of speed or acceleration among all terminals excluding terminals whose attribute is the relayed terminal as the UL relay terminal.

[0135] According to the controller 10 of the fifth embodiment, it is possible to increase the redundancy of control signals for a terminal for which AoI (freshness of information) is more important, or to receive a status signal with a short AoI (freshness of information) from a terminal for which AoI (freshness of information) is more important, thereby suppressing deterioration in the quality of motor control.

[0136] Sixth embodiment 15 is a block diagram for explaining an example of a terminal 28 according to the sixth embodiment. Parts corresponding to those according to the first embodiment are given the same reference numerals, and detailed explanations will be omitted.

[0137] The terminal 28 includes a timer 142. The timer 142 is connected to the processing unit 62. The processing unit 62 outputs a start trigger or an end trigger to the timer 142. When a predetermined fixed time has elapsed since the timing of receiving the start trigger, the timer 142 outputs an elapsed trigger to the processing unit 62 at that timing and keeps the elapsed time at 0. However, if the timer 142 receives an end trigger before the predetermined fixed time has elapsed, the timer 142 keeps the elapsed time at 0. The predetermined fixed time is a time shorter than the control period. The fixed time is determined in consideration of an actual delay, etc. For example, if the control period is 10 ms, the actual delay (the sum of the time from when the controller 10 transmits a control signal until the timer 142 receives a start trigger and the time from when the timer 142 generates an elapsed trigger until the controller 10 receives a status signal of this terminal) may be assumed to be 3 ms, and the fixed time may be set to 7 ms, which is the control period of 10 ms minus the assumed delay of 3 ms.

[0138] The processing unit 62 inputs information about the wireless frame received by the wireless unit 60 and performs processing according to the attribute. If the attribute is a UL relay terminal and the destination is the own terminal, the processing unit 62 outputs a start trigger to the timer 142 and outputs a control signal to the motor driver 64. Thereafter, the processing unit 62 outputs a status information request signal to the motor driver 64. In response to the status information request signal, the motor driver 64 outputs a status signal (including the sender) to the processing unit 62.

[0139] When the processing unit 62 receives a control signal addressed to the relayed terminal, it outputs an end trigger to the timer 142 and outputs a status signal of its own terminal and a status signal of the relayed terminal (including the transmission source) to the wireless unit 60. If an elapsed trigger from the timer 142 is input to the processing unit 62 before the control signal of the relayed terminal is input to the processing unit 62, the processing unit 62 outputs the received status signal to the wireless unit 60. Alternatively, the processing unit 62 outputs the status signal output from the motor driver 64 and the past status signal of the relayed terminal (including the transmission source) stored in the memory 70 to the wireless unit 60.

[0140] According to terminal 28 whose attribute is a UL relay terminal in the sixth embodiment, even if the relay signal of the relayed terminal is not received by the next control period, feedback control of the UL relay terminal is possible, and deterioration of the quality of motor control can be suppressed.

[0141] Variations The terminal 28 according to the embodiment described above receives a wireless frame addressed to another terminal, and generates a relay signal using the information. The operation mode of a general wireless LAN terminal can be switched between a management mode and a monitor mode. A wireless LAN terminal operating in the management mode discards wireless frames addressed to other terminals, and is therefore unable to relay as described above. A wireless LAN terminal operating in the monitor mode can receive wireless frames addressed to other terminals, and transfer and store the demodulated information in memory without discarding it. However, a wireless LAN terminal operating in the monitor mode cannot transmit. Therefore, if the terminal 28 has two wireless units, and one wireless unit is operated in the management mode and the other wireless unit is operated in the monitor mode, a relay terminal can be realized by a general wireless LAN terminal without providing a special terminal dedicated to relaying.

[0142] The present invention is not limited to the above-described embodiment, and the components can be modified and embodied in the implementation stage without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0143] 10... controller, 24... arm, 26... gripper, 28... terminal, 40... wireless unit, 42... processing unit, 44... attribute selection unit, 46... control signal generation unit, 48... antenna, 50... memory, 60... wireless unit, 62... processing unit, 66... ​​motor, 68... antenna, 70... memory

Claims

1. Multiple terminals, each of which includes a control target, a controller that receives a status signal transmitted from each of the plurality of terminals, generates a control signal for each of the plurality of terminals in response to the status signal, and transmits the control signal; Each of the plurality of terminals is operable as a relayed terminal or a downlink relay terminal; The downlink relay terminal transmits a first state signal indicating a state of a control object of the downlink relay terminal and a first control signal for controlling the control object of the relayed terminal; a relayed terminal that receives the first control signal, acquires a second status signal representing a status of the controlled object, and then transmits the second status signal and controls the controlled object based on the first control signal.

2. 2. The wireless control system according to claim 1, wherein the downlink relay terminal acquires the first status signal after receiving a second control signal, and then transmits the first status signal and the first control signal and controls its own controlled object according to the second control signal.

3. 2. The wireless control system according to claim 1, wherein the controller transmits a control signal for each of the plurality of terminals at a constant cycle, calculates a predicted value of the first state signal at the timing of the constant cycle based on the first state signal transmitted from the downlink relay terminal, and calculates a control signal for the downlink relay terminal based on the predicted value.

4. Each of the plurality of terminals is also operable as an uplink relay terminal; 2. The wireless control system of claim 1, wherein the uplink relay terminal receives a third control signal and the second status signal, controls its own control object according to the third control signal, obtains a third status signal representing a state of the control object, and transmits the second status signal and the third status signal.

5. The wireless control system according to claim 4 , wherein the controller measures response times of the plurality of terminals and causes a terminal with a short response time to operate as the downlink relay terminal or the uplink relay terminal.

6. The wireless control system according to claim 4 , wherein the controller measures communication qualities of the plurality of terminals and causes a terminal having good communication quality to operate as the uplink relay terminal.

7. the controlled object includes a motor, 5. The wireless control system according to claim 4, wherein the controller causes a terminal related to a control signal that rotates the motor at the highest speed or a control signal that rotates the motor at the highest acceleration to operate as the uplink relay terminal or the relayed terminal.

8. The controller transmits a wireless frame including a header, a destination, an attribute, and a control signal; The attribute is information representing the relayed terminal, the downlink relay terminal, the uplink relay terminal, or a normal terminal, The normal terminal is not involved in relaying, 8. The wireless control system according to claim 4, wherein each of the plurality of terminals operates as the relayed terminal, the downlink relay terminal, the uplink relay terminal, or the normal terminal depending on the attribute.

9. Each of the plurality of terminals is also capable of operating as an uplink relay terminal; 2. The wireless control system according to claim 1, wherein the uplink relay terminal receives a third control signal, measures an elapsed time since receiving the third control signal, controls its own controlled object according to the third control signal, acquires a third status signal representing a state of the own controlled object, and if the uplink relay terminal receives the second status signal before the elapsed time exceeds a certain time, transmits the third status signal and the second status signal, and if the uplink relay terminal does not receive the second status signal before the elapsed time exceeds the certain time, does not transmit the second status signal and transmits the third status signal.

10. Each can be connected to multiple devices, including the ones to be controlled. Receive a status signal transmitted from each of the plurality of terminals, generate a control signal for each of the plurality of terminals in response to the status signal, and transmit the control signal; A controller that transmits a first instruction to operate each of the plurality of terminals as a downlink relay terminal or a second instruction to operate each of the plurality of terminals as a relayed terminal, The first instruction causes the terminal to transmit a first status signal representing a status of a control target of the terminal and a first control signal for controlling the control target of the relayed terminal; The second instruction causes the terminal to obtain a second status signal representing a status of the controlled object after receiving the first control signal, and then to transmit the second status signal and control the controlled object based on the first control signal.

11. A terminal including a control object, transmitting a status signal representing a status of the control object to a controller, receiving a control signal transmitted from the controller, and controlling the control object in response to the control signal, Operate as a relayed terminal or a downlink relay terminal according to the attributes transmitted from the controller; When operating as the downlink relay terminal, transmit a first state signal representing a state of a control object of the relay terminal and a first control signal for controlling the control object of the relayed terminal; A terminal, when operating as the relayed terminal, obtains a second status signal representing a status of its own controlled object after receiving the first control signal, and then transmits the second status signal and controls the own controlled object based on the first control signal.

12. A program for controlling a terminal that includes a control target, transmits a status signal representing a status of the control target to a controller, receives a control signal transmitted from the controller, and controls the control target in response to the control signal, Operate the terminal as a relayed terminal or a downlink relay terminal according to the attributes transmitted from the controller; When the terminal is operated as the downlink relay terminal, the terminal is caused to transmit a first state signal representing a state of a control target of the terminal and a first control signal for controlling the control target of the relayed terminal; A program for causing the terminal to acquire a second status signal representing a status of an object to be controlled by the terminal after receiving the first control signal, and then causing the terminal to transmit the second status signal and control the object to be controlled by the terminal based on the first control signal, when the terminal is operated as a relayed terminal.

Images