Wireless control systems, controllers, terminals, and programs

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] Embodiments of the present invention relate to a wireless control system, a controller, a terminal, and a program.

Background Art

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

[0003] The controller transmits a control signal to the terminal. The terminal rotates the motor according to the control signal to control the arm. The terminal transmits a state signal representing the state of the arm (for example, the rotation angle), which is the control result, to the controller. The controller updates the control signal according to the state signal and transmits the updated control signal to the terminal. That is, the controller performs feedback control.

[0004] In a feedback control system, from the perspective of control quality, it is preferable for the controller to generate control signals in accordance with the most recent status signals. If AoI (Age of Information) is defined as the elapsed time from the observation point of a certain piece of information, then in a feedback control system, generating control signals based on short AoI status signals results in higher control quality than generating control signals based on long AoI status signals. For example, if the control signal is updated at a fixed period for ease of control, it is preferable for the terminal to transmit the latest status signal within one cycle after receiving the control signal. This allows the controller to generate control signals in accordance with the AoI status signals within one cycle, thereby maintaining a certain level of control quality for the arm. On the other hand, if the terminal is unable to transmit the latest status signal within one cycle after receiving the control signal and transmits it in the next cycle, the controller will generate control signals in accordance with AoI status signals between one and two cycles, resulting in a deterioration of the arm's control quality. Furthermore, the direct wireless connection between the controller and the terminal may be interrupted depending on the circumstances. For example, depending on the arm's position, an obstacle may exist between the controller and the arm, preventing the terminal from receiving control signals from the controller or preventing the controller from receiving status signals from the terminal. In this case, the controller transmits and receives signals to and from terminals whose direct wireless connection to the controller has been severed, via other terminals that are wirelessly connected to the controller. However, when transmitting and receiving signals via other terminals, the controller may not receive a status signal within one cycle after transmitting a control signal. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2015-192165 [Overview of the project] [Problems that the invention aims to solve]

[0006] The objective of this invention is to provide a wireless control system that achieves high-speed response. [Means for solving the problem]

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

[0008] [Figure 1] A diagram illustrating an example of a wireless control system according to the first embodiment. [Figure 2] A block diagram illustrating an example of a controller according to the first embodiment. [Figure 3] A block diagram illustrating an example of a terminal according to the first embodiment. [Figure 4] A diagram illustrating an example of the format of a wireless frame according to the first embodiment. [Figure 5] A diagram illustrating an example of processing performed by a terminal operating as a DL relay terminal according to the first embodiment. [Figure 6] A diagram illustrating an example of processing performed by a terminal operating as a relay terminal according to the first embodiment. [Figure 7] A diagram illustrating an example of processing performed by a terminal operating as a UL relay terminal according to the first embodiment. [Figure 8] A diagram illustrating an example of experimental results in a wireless control system related to a reference example. [Figure 9]A diagram illustrating an example of experimental results in a wireless control system according to the first embodiment. [Figure 10] A block diagram illustrating an example of a controller according to the second embodiment. [Figure 11] A diagram illustrating an example of the operation of the state signal prediction unit according to the second embodiment. [Figure 12] A block diagram illustrating an example of a controller according to the third embodiment. [Figure 13] A block diagram illustrating an example of a controller according to the fourth embodiment. [Figure 14] A block diagram illustrating an example of a controller according to the fifth embodiment. [Figure 15] A block diagram illustrating an example of a terminal according to the sixth embodiment. [Modes for carrying out the invention]

[0009] The embodiments will be described below with reference to the drawings. The following description exemplifies devices and methods for realizing the technical concept of the embodiments, and the technical concept of the embodiments 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 of are naturally included within the scope of disclosure. In order to make the explanation clearer, the shapes, etc. may be schematically represented in the drawings with modifications from the actual embodiments. In some cases, the same reference numeral may be used for corresponding elements in multiple drawings to omit redundant explanations. Some elements may be given multiple names, but these examples of names are merely illustrative and do not preclude the use of other names for these elements. Similarly, elements that do not have multiple names may also be given other names. In the following description, "connection" may include not only direct connections but also connections via other elements.

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

[0011] The controller 10 includes a wireless unit having a function capable of wireless communication with an external device such as a modulation / demodulation function, 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 a load flowing 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 table, a stand, etc. The arm 24a is attached to the base 22. The angle / position of the arm 24a with respect to the base 22 is variable as shown by the broken line. Similarly, the arms 24b, 24c, 24d are attached to the arms 24a, 24b, 24c. The angle / position of the arms 24b, 24c, 24d with respect to the arms 24a, 24b, 24c is variable as shown by the broken line. An openable / closable gripper 26 is attached to the tip arm 24d. The angle / position of the gripper 26 with respect 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 in which the arm rotates with respect to the base may be parallel to the floor, the table, the stand, etc. If there is an arm that is perpendicular to an arm whose plane of rotation of the arm with respect to the base is parallel to the floor, the table, the stand, etc., the position of the tip arm 24d can be moved three-dimensionally.

[0013] The base 22 includes a terminal 28a. Each of the arms 24a-24d includes terminals 28b, 28c, 28d, 28e. Each of the terminals 28a-28e is wirelessly connected to the controller 10. Each of the terminals 28a-28d includes a motor for changing the angle / position of each of the arms 24a-24d. The terminal 28e includes a motor for opening and closing the gripper 26.

[0014] When the motor included in the terminal 28e rotates, the gripper 26 opens and closes, and can grip by sandwiching an item or release the item. When the motors included in each of the terminals 28a - 28d rotate, 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 angles of the motors included in each of the terminals 28a - 28d, the gripper 26 can be moved to an arbitrary position. By controlling the angles of the motors included in each of the terminals 28a - 28e, operations such as transferring an item flowing on the belt conveyor to a tray can be performed.

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

[0016] FIG. 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 wired-connected to the wireless unit 40, the attribute selection unit 44, the control signal generation unit 46, and the memory 50.

[0017] The wireless unit 40 receives wireless frames transmitted from the terminal 28 using the antenna 48, demodulates the wireless frames, and generates a received signal. The wireless unit 40 measures the wireless characteristics of the wireless link between the terminal 28 and the controller 10. Wireless characteristics are information that represents the communication quality of the wireless link. An example of 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 source (terminal ID) and status signal from the received signal. The wireless unit 40 outputs the wireless characteristics, source, and status signal to the processing unit 42. The processing unit 42 outputs the control signal and attributes to the wireless unit 40. The wireless unit 40 modulates the control signal and attributes and transmits them as a wireless frame from the antenna 48. Each terminal 28 can operate as a terminal of any of the attributes. The terminal changes the order of processing according to the attribute.

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

[0020] Examples of attributes include downlink (DL) relay terminal, relayed terminal, uplink (UL) relay terminal, and normal terminal. A DL relay terminal is a terminal that receives control signals transmitted by the controller 10 to the relayed terminal and transmits control signals to the relayed terminal, i.e., a terminal that relays control signals. A UL relay terminal is a terminal that receives status signals transmitted by the relayed terminal to the controller 10 and transmits status signals to the controller 10, i.e., a terminal that relays status signals. A relayed terminal is a terminal whose wireless connection to the controller 10 is broken, receives control signals via a DL relay terminal, and transmits status signals via a UL relay terminal. A normal terminal is a terminal that receives control signals directly from the controller 10 and transmits status signals directly to the controller 10, and is not involved in relaying.

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

[0022] The processing unit 42 stores the information during the calculation in the memory 50. The processing unit 42 receives external control information. The processing unit 42 calculates a target value (for example, a target value for rotational speed) based on the external control information. The processing unit 42 outputs the target value and the status signal output from the wireless unit 40 to the control signal generation unit 46.

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

[0024] External control information may be target rotational speed information stored in an external memory unit (not shown). External control information may be target rotational speed information created from a pre-created program (not shown). External control information may be a human command transmitted via a computer (not shown), or it may be information about pressing an emergency stop button (not shown).

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

[0026] The controller 10 can select the attributes of the terminal 28 based on the wireless frame transmitted from the terminal 28, generate control signals for the terminal 28, and transmit the control signals to each terminal 28 at regular intervals.

[0027] The processing unit 42, attribute selection unit 44, and control signal generation unit 46 in Figure 2 may be implemented using dedicated hardware or in software. When implemented in software, the processing unit 42, attribute selection unit 44, and control signal generation unit 46 include a memory for storing the program and a CPU for executing the program. The processing unit 42, attribute selection unit 44, and control signal generation unit 46 are not limited to having one CPU, but may include multiple CPUs, each executing one of the multiple functions.

[0028] An example of a communication standard for sending 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 also send and receive control signals and status signals using other wireless communication standards or proprietary standards such as ZigBee® or local 5G.

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

[0030] Figure 3 is a block diagram illustrating an example of a terminal 28 according to the first embodiment. The terminal 28 comprises 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 wired to the wireless unit 60, the motor driver 64, and the memory. The motor driver 64 is wired to the motor 66.

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

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

[0033] If the attribute is DL relay terminal and the destination is the local terminal, the processing unit 62 outputs a status signal request signal to the motor driver 64 to request a status signal. The processing unit 62 receives the status signal output from the motor driver 64 and outputs the status signal (including the source) and the control signal of the relayed terminal (including the destination and attribute) (Figure 4(c)) to the wireless unit 60. The processing unit 62 outputs the control signal (the control signal included in Figure 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 as described above.

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

[0035] If the attribute is a relayed terminal and the destination is the local terminal, the processing unit 62 outputs a status signal request signal to the motor driver 64, receives the status signal output from the motor driver 64, outputs the status signal (including the source) to the wireless unit 60 (Figure 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 the reverse of the above.

[0036] If the attribute is a relay terminal and the destination is not the local terminal, the processing unit 62 discards information (such as control signals) related to that destination.

[0037] If the attribute is UL relay terminal and the destination is the local 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 receives the status signal output from the motor driver 64 and outputs the status signal (including the source) and the status signal (including the source) of the relayed terminal to the wireless unit 60 (Figure 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 UL relay terminal and the source is the relayed terminal, the processing unit 62 writes the status signal of the relayed terminal (including the source) to the memory 70. If the attribute is UL relay terminal and the destination is anything other than the above, the processing unit 62 discards information about that destination (such as status signals).

[0039] If the attribute is a normal terminal and the destination is the local 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 (Figure 4(b)). If the attribute is a normal terminal and the destination is not the local terminal, the processing unit 62 discards the information (such as the status signal) related to that destination.

[0040] The motor driver 64 receives a control signal or a status signal request signal from the processing unit 62. If the motor driver 64 receives a control signal, it controls the motor 66 according to the control signal. If the motor driver 64 receives a status signal request signal, it receives an encoder value representing the rotational speed from an encoder (not shown) attached to the motor 66 as a status signal. The motor driver 64 outputs the received status signal to the processing unit 62.

[0041] The motor 66 rotates its shaft according to the control signal output from the motor driver 64. The encoder attached to the motor 66 outputs an encoder value (also called a sensor value, Hall sensor value, or setting parameter value) representing the rotational speed of the motor 66 to the motor driver 64.

[0042] Motor 66 converts electrical power into rotational motion, etc. The position of arm 24 is determined by the encoder value of motor 66, such as the rotational speed. Motor 66 may also function as a sensor to determine the position of arm 24, gripper 26, or end 28. The encoder value of motor 66 corresponds to the sensor value. The center of rotation of motor 66 is sometimes referred to as the axis.

[0043] Terminal 28 writes the attributes of its own terminal contained in the wireless frame it received immediately before to memory 70. Terminal 28 operates as the terminal with the attributes stored in memory 70 and executes multiple processes in the order corresponding to the attributes. If the attributes contained in the received wireless frame differ from the stored attributes, the attributes stored in memory 70 are updated.

[0044] The processing unit 62 in Figure 3 may be implemented using dedicated hardware or in software. If implemented in software, the processing unit 62 includes memory for storing the program and a CPU for executing the program. The processing unit 62 is not limited to having one CPU, but may include multiple CPUs, each performing a different function.

[0045] Although an example has been shown where each terminal 28 has one motor 66, each terminal 28 may have multiple motors instead of just one. In that case, the controller 10 may include the 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 was shown in which terminal 28 has one wireless unit 60, terminal 28 may have multiple wireless units 60.

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

[0048] Figure 4 is a diagram illustrating an example of the wireless frame format according to the first embodiment.

[0049] Figure 4(a) shows an example of a wireless frame transmitted by the controller 10. The wireless frame includes a MAC header, destination, attributes, and control signals. The MAC header includes the MAC address of the destination terminal 28, the MAC address of the source (controller 10), etc. The destination represents the ID of the terminal 28 to which the wireless frame is sent. The attributes represent the attributes of the destination terminal 28. The control signals represent the control target value of the destination terminal 28. An example of a control target value is the target angular velocity of the motor.

[0050] Figure 4(a) shows an example where the controller 10 transmits to each terminal via unicast. When the controller transmits to each terminal via broadcast, a single wireless frame contains attributes and control signals addressed to each terminal (not shown).

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

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

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

[0054] Figure 5 is a diagram illustrating an example of processing by a terminal 28 operating as a DL relay terminal according to the first embodiment. Figure 5(a) shows an example of processing by a DL relay terminal according to a reference example. Figure 5(b) shows an example of processing by a DL relay terminal according to the first embodiment.

[0055] In the DL relay terminal (Figure 5(a)) shown in the reference example, when the wireless unit 60 receives a wireless frame (Figure 4(a)) transmitted from the controller 10, it outputs the destination, attributes, and control signals to the processing unit 62. The processing unit 62 outputs its own control signals to the motor driver 64. The processing unit 62 writes the control signals of the relayed terminal, along with the destination and attributes, to the memory 70 as relay signals.

[0056] When the motor driver 64 receives a control signal, it outputs an acknowledgment (ACK) to the processing unit 62. When the processing unit 62 receives an ACK, it outputs a control signal reflection signal to the motor driver 64. If the processing unit 62 does not receive an ACK within a certain period, it outputs its own control signal to the motor driver 64 again.

[0057] When the motor driver 64 receives a control signal reflection signal, it drives the motor 66 at the target rotational speed indicated by the control signal and outputs an ACK (acknowledgment) to the processing unit 62 as a response acknowledgment. When the processing unit 62 receives an ACK, it outputs a status signal request signal to the motor driver 64. If the processing unit 62 does not receive an ACK within a certain period, it outputs a control signal reflection signal to the motor driver 64 again. When the motor driver 64 receives a status signal request signal, it outputs a status signal to the processing unit 62.

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

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

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

[0061] The processing unit 62 outputs a status signal request signal to the motor driver 64. When the motor driver 64 receives the status signal request signal, it outputs a status signal to the processing unit 62.

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

[0063] The processing unit 62 outputs its own terminal control signal to the motor driver 64. When the motor driver 64 receives the control signal, it outputs an acknowledgment (ACK) to the processing unit 62. Upon receiving the ACK, the processing unit 62 outputs a control signal reflection signal to the motor driver 64. If the processing unit 62 does not receive an ACK within a certain period, it outputs its own terminal control signal to the motor driver 64 again.

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

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

[0066] The wireless frame transmitted by terminal 28, which operates as a DL relay terminal according to the first embodiment (Figure 4(c)), includes a relay signal, and the relay signal includes a control signal from the relayed terminal. Comparing the processing in Figure 5(a) and Figure 5(b), in the processing in Figure 5(b), the control signal from the relayed terminal is transmitted from the DL relay terminal at an earlier stage than in the processing in Figure 5(a). Therefore, in the first embodiment, terminal 28, which operates as a relayed terminal, receives the control signal at an earlier stage than the relayed terminal in the reference example, thus speeding up the control of terminal 28, which operates as a relayed terminal.

[0067] Figure 6 is a diagram illustrating an example of processing by a terminal 28 operating as a relayed terminal according to the first embodiment. Figure 6(a) shows an example of processing by a relayed terminal according to a reference example. Figure 6(b) shows an example of processing by a relayed terminal according to the first embodiment.

[0068] In the relay terminal shown in the reference example (Figure 6(a)), when the wireless unit 60 receives a wireless frame transmitted from the controller 10 (Figure 4(a)) or a wireless frame transmitted from another DL relay terminal (Figure 4(c)), it outputs the destination, attributes, and control signals to the processing unit 62. The processing unit 62 outputs its own control signals to the motor driver 64. The processing unit 62 discards information about other terminals (such as control signals).

[0069] When the motor driver 64 receives a control signal, it outputs an acknowledgment (ACK) to the processing unit 62. When the processing unit 62 receives an ACK, it outputs a control signal reflection signal to the motor driver 64. If the processing unit 62 does not receive an ACK within a certain period, it outputs the control signal to the motor driver 64 again.

[0070] When the motor driver 64 receives a control signal reflection signal, it drives the motor 66 at the target rotational speed indicated by the control signal and outputs an ACK (acknowledgment) to the processing unit 62 as a response acknowledgment. When the processing unit 62 receives an ACK, it outputs a status signal request signal to the motor driver 64. If the processing unit 62 does not receive an ACK within a certain period, it outputs a control signal reflection signal to the motor driver 64 again. When the motor driver 64 receives a status signal request signal, it outputs a status signal to the processing unit 62.

[0071] When the processing unit 62 receives a status signal, it outputs the source (its own terminal) and the status signal to the wireless unit 60. The wireless unit 60 transmits the wireless frame shown in Figure 4(b).

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

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

[0074] The processing unit 62 outputs a status signal request signal to the motor driver 64. When the motor driver 64 receives the status signal request signal, it outputs a status signal to the processing unit 62.

[0075] When the processing unit 62 receives a status signal, it outputs the source (its own terminal) and the status signal to the wireless unit 60. The wireless unit 60 transmits the wireless frame shown in Figure 4(b).

[0076] The processing unit 62 reads 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 (acknowledgment) to the processing unit 62 as an acknowledgment. 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 does not receive the 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 a control signal reflection signal, it drives the motor 66 at the target rotational speed indicated by the control signal and outputs an ACK (acknowledgment) to the processing unit 62 as a response acknowledgment. If the processing unit 62 does not receive an ACK within a certain period of time, it outputs the control signal reflection signal to the motor driver 64 again.

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

[0079] Comparing the process in Figure 6(a) with the process in Figure 6(b), in the process in Figure 6(b), the status signal is transmitted from the relay terminal earlier than in the process in Figure 6(a). Therefore, in the first embodiment, the controller 10 receives the status signal earlier than in the reference example, resulting in a faster response time for the control system.

[0080] In addition, if the relayed terminal 28 according to the first embodiment receives both a wireless frame directly transmitted from the controller 10 (Figure 4(a)) and a wireless frame relayed from the DL relay terminal (Figure 4(c)), the processing shown in Figure 6(b) may be performed on the wireless frame received first, and the above processing may be skipped for the wireless frame received afterward. Whether or not two or more received frames are duplicates may be determined by the content of the control signal, or by the sequence number if a sequence number is assigned to the wireless frame.

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

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

[0083] When the motor driver 64 receives a control signal, it outputs an acknowledgment (ACK) to the processing unit 62. When the processing unit 62 receives an ACK, it outputs a control signal reflection signal to the motor driver 64. If the processing unit 62 does not receive an ACK within a certain period, it outputs its own control signal to the motor driver 64 again.

[0084] When the motor driver 64 receives a control signal reflection signal, it drives the motor 66 at the target rotational speed indicated by the control signal and outputs an ACK (acknowledgment) to the processing unit 62 as a response acknowledgment. When the processing unit 62 receives an ACK, it outputs a status signal request signal to the motor driver 64. If the processing unit 62 does not receive an ACK within a certain period, it outputs a control signal reflection signal to the motor driver 64 again. When the motor driver 64 receives a status signal request signal, it outputs a status signal to the processing unit 62.

[0085] When the processing unit 62 receives a status signal, it reads the relay signal (source, status signal) from the memory 70 and outputs the source (local terminal), status signal, and relay signal to the wireless unit 60. The wireless unit 60 transmits the wireless frame shown in Figure 4(d). If the relay signal (source, status signal) has not been written to the memory 70 when 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 the status signal for the previous control signal addressed to the relayed terminal, to the wireless unit as a relay signal.

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

[0087] The UL relay terminal according to the first embodiment (Figure 7(b)) operates in substantially the same manner as the UL relay terminal according to the reference example (Figure 7(a)). The difference between the first embodiment and the reference example is that, when the processing unit 62 receives a status signal, if the relay signal (source, status signal) has not been written to the memory 70, or if the memory 70 has not been updated because a status signal has not been received from the relayed terminal, the processing unit 62 does not output any signal to the wireless unit and continues to wait until it receives a status signal from the relayed terminal.

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

[0089] Figure 8 illustrates an example of experimental results in a wireless control system related to a reference example. Here, the number of terminals 28 is assumed to be three. In this reference example, the DL relay terminal performs the process shown in Figure 5(a), the relayed terminal performs the process shown in Figure 6(a), and the UL relay terminal performs the process shown in Figure 7(b). The controller 10 controls the motors 66 of each of the three terminals 28 with a control period of 10ms. Figure 8 shows the waveforms of the wireless signals and the internal signals of the three terminals monitored with a digital oscilloscope while controlling the three motors, with some customization.

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

[0091] Figure 8(b) shows the 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, six blocks of high-level signals are communicated. Each block 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 group of frames (a) consisting of the control signal, ACK for the control signal, control signal reflection signal, and ACK for the control signal reflection signal, and a group of frames (b) consisting of a status signal request signal and a status signal. Approximately 0.5 ms after the status signal request signal and status signal frames (b), the DL relay terminal transmits a status signal (A2 in Figure 8(a)).

[0092] Figure 8(c) shows the signals between the processing unit 62 and the motor driver 64 at the relayed terminal. Approximately 1 ms after the DL relay terminal transmits the status signal, a block of six frames is communicated. These six frames are the same as those of the DL relay terminal. Approximately 3 ms after the status signal frame, the relayed terminal transmits the status signal.

[0093] Figure 8(d) shows the signals between the processing unit 62 and the motor driver 64 in the UL relay terminal. Six high-level signal blocks are communicated approximately 1 ms after the controller 10 transmits the control signal. 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 its status signal.

[0094] Controller 10 can receive status signals from DL relay terminals between the time it transmits a control signal and the time it transmits the next control signal. Therefore, it can generate and transmit control signals that reflect these status signals, thereby maintaining high control quality. Controller 10 may not be able to receive status information from the relayed terminal and UL relay terminal by the time it transmits the next control signal. Therefore, Controller 10 may not be able to perform the desired control.

[0095] Furthermore, when the UL relay terminal performs the process shown in Figure 7(a), the controller 10 can receive the status signal of the UL relay terminal by the time the next control signal is sent. 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 time the next control signal is sent. Therefore, in this case as well, the controller 10 cannot perform the desired control.

[0096] Figure 9 illustrates an example of experimental results in the wireless control system according to the first embodiment. Here, we assume there are three terminals 28. The DL relay terminal performs the process shown in Figure 5(a), the relayed terminal performs the process shown in Figure 6(a), and the UL relay terminal performs the process shown in Figure 7(b). The explanation of the same operation as in Figure 8 is omitted.

[0097] The DL relay terminal prioritizes receiving a status signal from the motor 66 and transmitting the status signal as a wireless frame over reflecting the control signal in the drive of the motor 66. As a result, the DL relay terminal transmits the status signal request signal and the status signal frame group (b) earlier than the frame group (a) consisting of the control signal, ACK for the control signal, control signal reflection signal, and ACK for the control signal reflection signal.

[0098] Similar to DL relay terminals, the relayed terminal prioritizes receiving a status signal from motor 66 and transmitting the status signal as a wireless frame, rather than reflecting the control signal in the drive of motor 66. As a result, the relayed terminal transmits the status signal request signal and the status signal frame group (b) earlier than the frame group (a) consisting of the control signal, ACK for the control signal, control signal reflection signal, and ACK for the control signal reflection signal.

[0099] The UL relay terminal performs the same processing as in Figure 8, but receives the status signal transmitted by the relayed terminal at an earlier timing than in Figure 8. Therefore, the UL relay terminal also transmits its own status signal at an earlier timing than in Figure 8.

[0100] In the first embodiment, the controller 10 receives status signals from DL relay terminals, relayed terminals, and UL relay terminals between one transmission timing of a control signal and the next transmission timing. The controller 10 generates and transmits a control signal reflecting these status signals. As a result, in a wireless control system consisting of the controller 10 and a plurality of terminals 28 that are feedback-controlled by the controller 10, the response time is shortened and the deterioration of the control quality of the motors 66 of the terminals 28 is suppressed.

[0101] Although the relayed terminal was described as a terminal whose wireless connection to the controller 10 is interrupted, it is not necessarily required that the wireless connection be interrupted. Among multiple terminals, the terminal with poor quality wireless connection to the controller may be designated as the relayed terminal. Alternatively, the quality of the wireless connection between the controller and each terminal may be predicted based on the status signals or control signals of each terminal, and the terminal with the predicted poor wireless connection quality may be designated as the relayed terminal.

[0102] It was explained that each terminal extracts attributes from the received signal and processes accordingly, but each terminal may either extract attributes from the received signal and process accordingly, or process as a relayed terminal. For example, if the attribute is DL relay terminal and the destination is other than the local terminal, the processing unit 62 does not discard the information about that destination (such as control information), and if a relay signal addressed to the local terminal is included, it processes it as a relayed terminal. On the other hand, if a relay signal addressed to the local terminal is not included, the attribute is not updated, and the processing unit 62 discards the information about that destination (such as control information). In this way, even if a terminal's wireless connection is suddenly interrupted and the controller cannot change its attributes in time, that terminal can still be controlled as a relayed terminal.

[0103] Second Embodiment Figure 10 is a block diagram illustrating an example of a 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 are omitted.

[0104] The controller 10 comprises a wireless 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 status signal for the past one instance for each terminal 28. The processing unit 42 outputs the target value, current status signal, and past status signal for the DL relay terminal to the status signal prediction unit 102, and outputs the target value and status signal for terminals other than the DL relay terminal to the control signal generation unit 46. The processing unit 42 receives the control signal for the DL relay terminal from the second control signal generation unit 104 and outputs that control signal to the wireless unit 40. The processing unit 42 receives the control signal for terminals other than the DL relay terminal from the control signal generation unit 46 and outputs that control signal to the wireless unit 40.

[0105] The function of terminal 28 changes according to the attribute selected by the attribute selection unit 44 of controller 10. The attributes of a certain terminal 28 may be those of a normal terminal up to a certain point in time, and then change to a DL relay terminal thereafter. As shown in Figure 5(b), in a 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. Normally, the terminal outputs a control signal to the motor driver 64 and then transmits a status signal. When the processing unit 42 receives the current status signal of the DL relay terminal as input, it reads the last status signal of the DL relay terminal from the memory 50 and outputs the target value of the DL relay terminal, the current status signal, and the last status signal 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 generation unit 104 receives the target value and the predicted state signal value from the state signal prediction unit 102. Based on the target value and the predicted state signal value, the second control signal generation unit 104 generates a control signal for the DL relay terminal and outputs the control signal to the processing unit 42.

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

[0109] Figure 11 is a diagram illustrating an example of the operation of the status signal prediction unit 102 according to the second embodiment. Let f(t) be the signal received by the controller 10 at timing t of a status signal (for example, the rotational speed of the motor 66) transmitted from terminal 28. t1 and t2 represent the timing at which the controller 10 receives the status signal transmitted from terminal 28 operating as a normal terminal. Assume that the attributes of terminal 28 operating as a normal terminal are changed to a DL relay terminal after timing t2. Timings t3, t5, and t7 represent the timing at which the controller 10 receives the status signal transmitted from terminal 28 operating as a DL relay terminal. Compared to a normal terminal, a DL relay terminal transmits the status signal earlier, and as a result, the AoI of the status signal is longer.

[0110] The status signal prediction unit 102 predicts the status signal that would be transmitted from a terminal if it were operating as a normal terminal instead of a DL relay terminal, based on the status signal transmitted from the terminal operating as a DL relay terminal and the timing of reception of that status signal, and uses that value as the predicted status signal value. If the control period is T, then t4 in Figure 11 is t4 = t2 + T. The status signal prediction unit 102 calculates the predicted value f(t4) of the status signal received at timing t4 using the following formula. f(t2) is the status signal for the past one instance stored in 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 can be 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 determines the status signal prediction value for the status signal received from the DL relay terminal at subsequent timings.

[0114] This formula is merely one example; you may use other formulas to predict the state signal.

[0115] The above explanation concerns an example where the terminal's attributes switch from a normal terminal to a DL relay terminal, but the same applies when the terminal's attributes switch from a relayed terminal to a DL relay terminal, or when the terminal's attributes switch from an UL relay terminal to a DL relay terminal.

[0116] The input to the control signal generation unit 46 is a status signal. The input to the second control signal generation unit 104 is a predicted value of the status signal. The second control signal generation unit 104 differs from the control signal generation unit 46 in that its input signal is changed from a status signal to a predicted value of the status signal; otherwise, it may be the same as the control signal generation unit 46. The second control signal generation unit 104 generates a control signal for the DL relay terminal based on the predicted value of the status signal. The control signal generation unit 46 generates control signals for the relayed terminal and the UL relay terminal based on the status signal. The second control signal generation unit 104 may generate a control signal based on the status signal and the predicted value of the status signal. For example, the second control signal generation unit 104 may generate a control signal based on the average value of the status signal and the predicted value of the status signal.

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

[0118] Third Embodiment Figure 12 is a block diagram illustrating 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 explanations are 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 control signals for each terminal to the wireless unit 40 and the timing at which the wireless unit 40 inputs status signals 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 designates terminals with attributes that are likely to disconnect from the wireless connection with the controller 10 as relay terminals. The attribute selection unit 44 designates the terminal with the shortest response time among all terminals 28, excluding terminals with the attribute of relay terminals, as the DL relay terminal.

[0121] If the processing unit 62 of terminal 28 is composed of a CPU, due to factors such as interrupt cycles, some terminals may have consistently short response times, while others may have consistently long response times. Furthermore, if the CPU performance of the terminals differs, some terminals may have consistently short response times, while others may have consistently long response times. Additionally, due to communication characteristics, some terminals may have consistently short response times for a certain period, while others may have consistently long response times for a certain period. By operating terminals with short response times as DL relay terminals, control signals can be transmitted to the relayed terminals at an earlier stage, thereby shortening the response time of the wireless control system.

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

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

[0124] Fourth Embodiment Figure 13 is a block diagram illustrating 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 explanations are omitted.

[0125] The processing unit 42 includes a communication quality measurement unit 122. The communication quality measurement unit 122 calculates the communication quality from the wireless characteristics of each terminal and obtains a communication quality measurement value. Wireless characteristics include, for example, the received power of a wireless frame. Communication quality may also be the average received power of wireless frames received n times in the past (where n is a natural number). In this case, a higher communication quality measurement value indicates better communication quality. Another example of wireless characteristics is whether or not a received wireless frame is a retransmitted frame. In this case, communication quality may also be the retransmission rate of wireless frames received n times in the past. In this case, a lower communication quality measurement value indicates better 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 designates terminals with attributes that are likely to disconnect from the wireless connection with the controller 10 as relayed terminals. The attribute selection unit 44 designates the terminal with the best communication quality among all terminals 28 excluding terminals with the attribute of relayed terminal as the UL relay terminal. The attribute selection unit 44 designates the terminal with the shortest response time among all terminals 28 excluding terminals with the attribute of relayed terminal or UL relay terminal as the DL relay terminal.

[0127] By operating terminals with good communication quality as UL relay terminals, the possibility of delays caused by retransmission of status signals can be reduced, and the likelihood of relaying status signals within the control cycle can be increased. Alternatively, 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 DL relay terminals.

[0128] The communication quality measurement unit 122 may not be installed in the processing unit 42, but rather in the wireless unit 40. The functions of the communication quality measurement unit 122 may be divided, and each function of the communication quality measurement unit 122 may be installed 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 shorten the response time between the controller 10 and the relayed terminal.

[0130] Fifth Embodiment Figure 14 is a block diagram illustrating 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 are omitted.

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

[0132] Based on the information output from the processing unit 42, the attribute selection unit 44 designates terminals with attributes that are likely to disconnect from the wireless connection with the controller 10 as relayed terminals. The attribute selection unit 44 designates the terminal with the largest absolute value of speed or acceleration among all terminals excluding those with the attribute of relayed terminal as a UL relay terminal. The attribute selection unit 44 designates the terminal with the shortest response time among all terminals excluding those with the attribute of relayed terminal or UL relay terminal as a DL relay terminal.

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

[0134] Normally, the attribute selection unit 44 selects the attribute of the terminal with the worst communication quality as the relayed terminal. However, if the communication quality of all terminals is reasonably good, as in the fifth embodiment, the attribute selection unit 44 may select the attribute of the terminal with the largest absolute value of speed or acceleration as the relayed terminal. Alternatively, the attribute selection unit 44 may select the attribute of the terminal with the largest absolute value of speed or acceleration as the relayed terminal, and then select the attribute of the terminal with the largest absolute value of speed or acceleration among all terminals excluding those with the attribute of a relayed terminal as the UL relay terminal.

[0135] According to the controller 10 of the fifth embodiment, the redundancy of control signals can be increased for terminals where AoI (information freshness) is more important, or a short AoI (high information freshness) status signal can be received from a terminal where AoI (information freshness) is more important, thereby suppressing deterioration of the quality of motor control.

[0136] Sixth Embodiment Figure 15 is a block diagram illustrating 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 are omitted.

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

[0138] The processing unit 62 receives information from the wireless frame received by the wireless unit 60 and performs processing according to its attributes. If the attribute is UL relay terminal and the destination is the local terminal, the processing unit 62 outputs a start trigger to the timer 142 and outputs a control signal to the motor driver 64. Subsequently, 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 source) to the processing unit 62.

[0139] When the processing unit 62 receives a control signal addressed to the relayed terminal, it outputs a termination trigger to the timer 142 and outputs its own terminal status signal and the relayed terminal status signal (including the source) to the wireless unit 60. If the elapsed trigger from the timer 142 is input to the processing unit 62 before the relayed terminal's control signal 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 signals of the relayed terminal (including the source) stored in the memory 70 to the wireless unit 60.

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

[0141] Variation The terminal 28 according to the above embodiment receives wireless frames destined for other terminals and uses that information to generate relay signals. A typical wireless LAN terminal can switch between management mode and monitor mode. A wireless LAN terminal operating in management mode discards wireless frames destined for other terminals and therefore cannot perform the relay described above. A wireless LAN terminal operating in monitor mode can receive wireless frames destined for other terminals and transfer the demodulated information to memory for storage without discarding it. However, a wireless LAN terminal operating in monitor mode cannot transmit. Therefore, if terminal 28 has two wireless units, with one operating in management mode and the other in monitor mode, a relay terminal can be realized using a typical wireless LAN terminal without the need for a special dedicated relay terminal.

[0142] It should be noted that the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments. Moreover, 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. Each of them includes multiple terminals containing the target of control, A controller that receives status signals transmitted from each of the plurality of terminals, generates control signals for each of the plurality of terminals according to the status signals, and transmits the control signals, Each of the aforementioned multiple terminals is capable of operating as a relay terminal or a downlink relay terminal. The downlink relay terminal transmits a first status signal representing the state of its controlled object and a first control signal for controlling the controlled object of the relayed terminal. The relayed terminal is a wireless control system that, after receiving the first control signal, acquires a second status signal representing the state of its controlled object, then transmits the second status signal, and controls its controlled object based on the first control signal.

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

3. The wireless control system according to claim 1, wherein the controller transmits control signals to each of the plurality of terminals at regular intervals, obtains a predicted value of the first status signal at the regular interval timing based on the first status signal transmitted from the downlink relay terminal, and obtains a control signal for the downlink relay terminal based on the predicted value.

4. Each of the aforementioned multiple terminals can also operate as an uplink relay terminal. The wireless control system according to claim 1, wherein the uplink relay terminal receives a third control signal and a second status signal, controls its own controlled object according to the third control signal, acquires a third status signal representing the state of its own controlled 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 the response time of the plurality of terminals and operates the terminal with the shortest response time as the downlink relay terminal or the uplink relay terminal.

6. The wireless control system according to claim 4, wherein the controller measures the communication quality of the plurality of terminals and operates the terminal with good communication quality as the uplink relay terminal.

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

8. The controller transmits a wireless frame consisting of a header, destination, attributes, and control signals. The aforementioned attributes are information representing the relayed terminal, the downlink relay terminal, the uplink relay terminal, or a normal terminal. The aforementioned standard terminal does not participate in relaying, The wireless control system according to any one of claims 4 to 7, wherein each of the plurality of terminals operates as the relayed terminal, the downlink relay terminal, the uplink relay terminal, or the normal terminal according to the attribute.

9. Each of the aforementioned multiple terminals can also function as an uplink relay terminal. The wireless control system according to claim 1, wherein the uplink relay terminal receives a third control signal, measures the elapsed time since receiving the third control signal, controls its own controlled object according to the third control signal, obtains a third status signal representing the state of its own controlled object, transmits the third status signal and the second status signal if it receives the second status signal before the elapsed time exceeds a certain period of time, and does not transmit the second status signal and transmits the third status signal if it does not receive the second status signal before the elapsed time exceeds a certain period of time.

10. Each can connect to multiple terminals, including the target of control. The system receives status signals transmitted from each of the multiple terminals, generates control signals for each of the multiple terminals according to the status signals, and transmits the control signals. 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 the state of its controlled object and a first control signal for controlling the controlled object of the relayed terminal. The second instruction is a controller that causes a terminal to acquire a second status signal representing the state of its controlled object after receiving the first control signal, then transmit the second status signal, and control its controlled object based on the first control signal.

11. A terminal that includes a controlled object, transmits a status signal representing the state of the controlled object to a controller, receives a control signal transmitted from the controller, and controls the controlled object according to the control signal, Depending on the attributes transmitted from the controller, it operates as a relayed terminal or a downlink relay terminal. When operating as the downlink relay terminal, it transmits a first status signal representing the state of its controlled object and a first control signal for controlling the controlled object of the relayed terminal. When operating as a relay terminal, the terminal receives the first control signal, then acquires a second status signal representing the state of its controlled object, and subsequently transmits the second status signal and controls its controlled object based on the first control signal.

12. A program that includes a controlled object, transmits a status signal representing the state of the controlled object to a controller, receives a control signal transmitted from the controller, and controls a terminal that controls the controlled object according to the control signal, Depending on the attributes transmitted from the controller, the terminal is operated as a relayed terminal or a downlink relay terminal. When the aforementioned terminal is operated as the downlink relay terminal, the terminal is instructed to transmit a first status signal representing the state of its controlled object and a first control signal for controlling the controlled object of the relayed terminal. A program that, when the terminal is operated as a relay terminal, causes the terminal to acquire a second status signal representing the state of its controlled object after receiving the first control signal, then transmit the second status signal, and control its controlled object based on the first control signal.

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