JP2013115517A - Communication system, communication device, communication method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the utilization efficiency of communication resources for transmission and reception of slot information excellent and also to quickly restore a terminal station which does not normally hold the information to a network.SOLUTION: A communication system comprises multiple communication means comprising transmission means which transmits a signal in a slot allocated by time division communication, and reception means for receiving a signal, and first communication means and second communication means communicate with each other. The first communication means determines whether or not the second communication means holds information on a slot. If the second communication means does not hold the information, the second communication means stops transmitting a signal, and if the first communication means does not receive a signal from the second communication means in a slot allocated to the second communication means, the first communication means determines that the second communication means does not hold the information.

Description

  The present invention relates to a communication system, a communication apparatus, a communication method, and a program for performing communication by assigning slots in a time division manner.

  One of the control systems that require motion control is a robot system represented by an industrial robot. A robot system generally has an arithmetic processing unit (CPU) and a plurality of sensors and actuators. The sensor outputs the acquired information to the arithmetic processing unit. The arithmetic processing unit calculates a deviation from the target value from information input from the sensor, and outputs a correction value to the actuator. The actuator performs a predetermined operation based on the correction value input from the arithmetic processing unit. The robot system performs a desired operation in consideration of the actual environment by periodically repeating the feedback control as described above.

  In Patent Literature 1, mechanically and electrically independent joint modules are selected and connected to each other, and overall motion control is performed by transmitting and receiving information related to motion control using communication means provided in the joint module. The robot system to perform is described. As shown in FIG. 2 of Patent Document 1, the described robot system has a structure in which each joint module has communication means, and communication means of a plurality of joint modules are connected to each other to construct a network. ing. With this structure, even when a large number of joint modules are combined, it is possible to construct a flexible robot system that can be rearranged according to changes in work contents. Patent Document 2 describes a robot system that recognizes work contents, autonomously selects an appropriate end effector according to the work contents, and performs replacement. If the robot systems of Patent Document 1 and Patent Document 2 are used, it is not necessary to prepare a dedicated robot for each work content. Therefore, for example, these robot systems can be said to be suitable systems for automatic machines used for assembling products for high-mix low-volume production.

  A control system network used in a control system such as a robot system needs to ensure synchronization and real-time property and realize cyclic (cyclic) communication. For this reason, a time division multiple access (TDMA) system is widely adopted as a communication system. In the TDMA method, communication resources used for transmission are divided into units called time slots (hereinafter referred to as “slots”) having a fixed time length in the time domain and allocated to each terminal station, thereby sharing the communication resources. This is one of the multiplexing methods. The slot allocation method includes a fixed allocation method in advance and a dynamic allocation method as necessary. A slot is allocated to each terminal station by any allocation method.

  Here, in the robot systems described in Patent Literature 1 and Patent Literature 2, there is a possibility that an allocation method for dynamically allocating slots may be employed in order to ensure flexibility in network construction. This is because the addition / deletion of terminal stations and the change of sensors and actuators may be performed with recombination of modules and replacement of end effectors in the robot system, and the amount of information flowing on the network may change accordingly. .

  Conventional techniques for dynamically assigning slots are described in Patent Document 3, Patent Document 4, and Patent Document 5. In Patent Document 3, a master station allocates a slot to be transmitted by a slave station for each frame, transmits information about the allocation (hereinafter referred to as “slot information”) to the slave station, and the slave station receives it. A communication method for transmitting data according to slot information is described. Patent Document 4 describes a communication method in which a master station transmits slot information to a slave station every predetermined number of frames, and the slave station performs transmission / reception control according to the received slot information. Patent Document 5 describes a communication method in which a slave station that has not acquired slot information stops transmission until the next slot information is received. Note that Patent Literature 3, Patent Literature 4, and Patent Literature 5 adopt a method of immediately applying the received slot information without confirming or retransmitting the slot information. In this method, since slot assignment can be changed quickly, recombination of modules and replacement of end effectors can be performed smoothly, and a highly productive robot system can be realized.

JP 09-029671 A JP 2009-148845 A Japanese Patent Laid-Open No. 08-251096 Japanese Patent Application Laid-Open No. 07-107546 JP 2000-092019 A

  In many robot systems, an electric motor typified by a servomotor is used as an actuator. However, driving of the electric motor is accompanied by impulsive noise. If an impulsive noise occurs during communication of slot information, a transmission error may be caused. That is, there may occur a slave station that cannot normally acquire slot information, that is, does not hold accurate slot information.

  As described above, the technique of Patent Document 3 is effective as a technique for quickly changing slot allocation without disconnecting the data link. However, a coping method when there is a slave station that cannot normally acquire slot information is not described. If a slave station that has not successfully acquired slot information continues to operate based on previously acquired slot information, a data collision occurs with data transmitted by other slave stations based on the latest slot information. May occur. In addition, it is considered that the robot systems described in Patent Document 1 and Patent Document 2 often do not change slot assignment during the same period of work. On the other hand, Patent Document 3 transmits slot information for each frame. For this reason, when Patent Document 3 is applied to the robot systems described in Patent Document 1 and Patent Document 2, there is a problem that the use efficiency of communication resources is reduced by repeatedly transmitting slot information having the same content.

  The technique of Patent Document 4 can transmit slot information every predetermined number of frames. Therefore, this technique is effective when it is desired to improve the utilization efficiency of communication resources. However, as in the technique of Patent Document 3, there is no description of a method for dealing with a slave station that has not acquired slot information normally.

  In the technique of Patent Document 5, when there is a slave station that has not acquired slot information normally, the slave station controls to stop transmission. Therefore, data collision can be reliably prevented. However, even if there is a slave station that has not acquired slot information normally, the master station transmits slot information at predetermined intervals. In the case of a control system such as a robot system, if feedback control is stopped for a long period of time, the control becomes unstable. Therefore, when the technique of Patent Document 5 is applied to the robot systems described in Patent Document 1 and Patent Document 2, it is necessary to repeatedly transmit slot information at a period that does not become unstable even when feedback control is stopped. As a result, similar to the technique of Patent Document 3, slot information having the same content is repeatedly transmitted, resulting in a decrease in communication resource utilization efficiency.

  The present invention has been made in view of the above problems, and maintains a good use efficiency of communication resources related to transmission / reception of slot information, and a communication system, communication apparatus, and communication for quickly returning a slave station that does not hold the information to the network An object is to provide a method and a program.

  In order to achieve the above object, a communication system according to the present invention comprises a plurality of communication means including a transmission means for transmitting a signal and a reception means for receiving a signal in a slot allocated by time-division communication. And a second communication unit, wherein the first communication unit includes a determination unit that determines whether or not the second communication unit holds information on the slot. When the second communication means does not hold the information, the second communication means stops transmission of the signal, and the first communication means performs the second communication in the slot assigned to the second communication means. If no signal is received from the means, it is determined that the second communication means does not hold the information.

  According to the present invention, it is possible to provide a technique for quickly returning a slave station that does not normally hold the information to the network while maintaining good utilization efficiency of communication resources related to transmission / reception of slot information.

The block diagram which shows the structural example of a communication system. The block diagram which shows the internal structural example of a master station. The block diagram which shows the internal structural example of a sub_station | mobile_unit. The figure which shows the example of a frame structure at the time of normal operation | movement. The figure which shows the example of a frame structure at the time of abnormal operation | movement. Explanatory drawing of the slot table at the time of normal operation | movement. Explanatory drawing of the slot table of the master station at the time of abnormal operation | movement. Explanatory drawing of the slot table of the slave station at the time of abnormal operation. The operation | movement flowchart of the slot information setting part installed in a slave station. FIG. 3 is an operation flow diagram of a transmission stop station determination unit installed in a master station in the first embodiment. The figure which shows the example of a frame structure at the time of normal operation | movement in the case of transmitting slot information by two slots. The figure which shows the example of a frame structure at the time of abnormal operation | movement in the case of transmitting slot information by two slots. Explanatory drawing of the slot table at the time of normal operation | movement in the case of transmitting slot information by two slots. Explanatory drawing of the slot table of the master station at the time of abnormal operation | movement when transmitting slot information by two slots. FIG. 5 is a block diagram illustrating an internal configuration example of a slave station according to the second embodiment. FIG. 6 is a diagram illustrating an example of a frame configuration during abnormal operation according to the second embodiment. Explanatory drawing of the slot table of the master station at the time of abnormal operation | movement which concerns on Embodiment 2. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< Embodiment 1 >>
(Configuration of communication system)
FIG. 1 is a diagram showing a configuration of a communication system in a robot system to which the present invention is applied. In this embodiment, a master station 10 and a plurality of slave stations A20 to C40 are cascaded to constitute a communication system. In the following description, a slave station close to the master station 10 as viewed from any slave station A20 to C40 is called an upper station, and a slave station far from the master station is called a lower station. That is, in the slave station B30, the slave station A20 is an upper station, and the slave station C40 is a lower station.

  The master station 10 transmits motor control information to the slave stations A20 to C40. The master station 10 includes a slave station connection connector 11, and the slave station connection connector 11 is connected to an upper station connection connector 21 of a slave station A20 which is the highest slave station. The slave station A20 and the slave station B30 are joint modules that are components of the robot system, and the slave station C40 and the slave station D50 are end effectors for the robot system. In the robot system according to the present embodiment, end effectors are autonomously exchanged, for example, exchange between a slave station C40 and a slave station D50, without intervention of human hands, according to work contents. Note that this exchange naturally changes the configuration of the communication system. The slave stations A20 to D50 are provided with upper station connection connectors 21 to 51 and lower station connection connectors 22 to 32, which are connected to the upper station / lower station to form a network. The slave station C40 and the slave station D50 are end effectors, and since there are no slave stations lower than that, no slave station connection connector is provided, but this may be provided if necessary. . The slave stations A20 to D50 are connected to motors 23 to 53 and 55 for bending a joint and angle sensors 24 to 54 for detecting a bending angle of the joint.

  The motor control information transmitted by the master station 10 may include voltage values applied to the motors 23 to 53 and 55, for example. The slave stations A20 to D50 drive the motors 23 to 53 and 55 based on the motor control information. The slave stations A20 to D50 acquire joint bending angles from the angle sensors 24 to 54, and transmit the acquired angle information to the master station 10 as angle information. The master station 10 generates the next motor control information according to the received angle information. In this embodiment, feedback control of the entire system is performed by performing such communication and motor control at regular intervals.

(Configuration of master station)
FIG. 2 is a diagram showing an internal configuration of the master station 10 of the present embodiment. The master station 10 includes, for example, a motor control information generation unit 101, a slot information generation unit 102, a synchronization information generation unit 103, a maintenance information request generation unit 104, a slot information storage unit 110, a transmission stop station determination unit 111, and a slot information rewrite The unit 112 is provided. The master station 10 further includes, for example, a selector 105, a transmission unit 106, a slave station connection connector 107, a reception unit 108, a counter 109, a transmission / reception control unit 113, and a slave station maintenance unit 114.

  The motor control information generation unit 101 generates motor control information for controlling the motor of the slave station according to the system operation. The motor control information generation unit 101 generates the next motor control information according to the angle information received from the slave stations A20 to C40 during system operation. When the end effector is exchanged, the slot information generation unit 102 generates slot information used in time-division communication according to the exchanged end effector. The slot information may be generated when the robot system is started or when the robot system is reset. By assigning a unique identifier to the slot information, the slave station can acquire the slot information based on the identifier without knowing the position of the slot transmitting the slot information. The slot arrangement will be described later.

  The synchronization information generation unit 103 generates synchronization information including a current frame number and a synchronization signal used for synchronization between the master station and the slave station. The configuration of the frame will be described later. The synchronization information is transmitted from the master station to the slave stations A20 to C40 for each frame, and the slave station synchronizes with the master station 10 using the synchronization information and performs communication in a time division manner. The maintenance information request generation unit 104 generates a maintenance information request that is data for requesting maintenance information described later. The maintenance information request is non-isochronous information that does not require strict isochronism, unlike motor control information and angle information. The selector 105 selects and outputs any of the above-described motor control information, slot information, synchronization information, and maintenance information request based on the control of the transmission / reception control unit 113 described later.

  Based on the control of the transmission / reception control unit 113 described later, the transmission unit 106 performs error detection encoding processing and modulation processing on the motor control information, slot information, synchronization information, or maintenance information request data output from the selector 105 and performs communication. As a signal, it transmits to slave station A20-C40. The receiving unit 108 performs error detection decoding processing and demodulation processing on the communication signals received from the slave stations A20 to C40 based on the control of the transmission / reception control unit 113 described later, and acquires angle information and maintenance information. The master station 10 is connected to the slave station A20 via the slave station connection connector 107, and transmits and receives signals to and from the slave stations A20 to C40 via the slave station connection connector 107.

  The counter 109 counts the frame number and the slot number, and outputs a count signal including information on the current frame number and the slot number. The slot information storage unit 110 stores and holds the slot information generated by the slot information generation unit 102 as a built-in table (hereinafter referred to as slot table). The transmission stop station determination unit 111 detects a signal transmitted from the slave station based on the count signal of the counter 109, and compares the detection result with the slot table held in the slot information storage unit 110, thereby It is determined whether or not the transmission operation of the station is normally performed. For example, when detecting a slave station that does not transmit a signal in a slot allocated for transmission, the transmission stop station determining unit 111 determines that the slave station is a transmission stop station and outputs a transmission stop station detection signal. . The transmission stop station determining unit 111 can determine whether the slave station holds the slot information to be used by monitoring whether the communication is performed according to the slot information.

  When a transmission stop station detection signal is input, the slot information rewriting unit 112 receives a slot for transmitting information from the transmission stop station to the parent station, or a slot for transmitting information from the parent station to the transmission stop station. Search from the slot table stored in the storage unit 110. Of the slots found by the search, the slot corresponding to the nearest time after the current slot is determined as a slot information retransmission slot (hereinafter referred to as “slot information retransmission slot”). Then, the slot table of the slot information storage unit 110 is rewritten with the determined slot information retransmission slot. When there are a plurality of slots necessary for transmission of slot information, slot information retransmission slots corresponding to all of them are determined and the slot table is rewritten. That is, since the transmission stop station does not hold the correct slot information, the slot information rewriting unit 112 provides a slot information retransmission slot in the time slot as early as possible in order to transmit the correct slot information to the transmission stop station.

  The transmission / reception control unit 113 performs operation control on each of the selector 105, the transmission unit 106, and the reception unit 108 based on the slot information held in the slot information storage unit 110 and the count value from the counter 109. The slave station maintenance unit 114 diagnoses and maintains the life / abnormality of each slave station based on maintenance information described later transmitted from the slave station.

(Configuration of slave stations)
Then, the structure of slave station A20-D50 of this embodiment is demonstrated. FIG. 3 is a diagram showing an internal configuration of the slave station A20. The slave station A20 includes, for example, an angle information generation unit 201, a maintenance information generation unit 202, a slot information storage unit 209, and a slot information setting unit 210. The slave station A20 further includes, for example, a selector 203, a transmission unit 204, an upper station connection connector 205, a lower station connection connector 206, a reception unit 207, a counter 208, a transmission / reception control unit 211, and a motor drive unit 212.

  The angle information generation unit 201 acquires a bending angle from the angle sensor 24 connected to the outside, and generates angle information. When the maintenance information generation unit 202 receives the maintenance information request transmitted from the master station 10, the maintenance information generation unit 202 generates maintenance information indicating the operation time, the degree of wear, and the like of the local station. The maintenance information is non-isochronous information that does not require strict isochronism as in the maintenance information request. The selector 203 selects and outputs either the angle information or the maintenance information described above based on the control of the transmission / reception control unit 211 described later. The transmission unit 204 performs error detection encoding processing and modulation processing on the angle information or maintenance information output from the selector 203 based on the control of the transmission / reception control unit 211 described later, and transmits it to the master station 10 as a communication signal. The receiving unit 207 performs error detection decoding processing and demodulation processing on the communication signal received from the master station 10 based on the control of the transmission / reception control unit 211 described later, and requests motor control information, synchronization information, slot information, or maintenance information. get.

  The slave station A20 is connected to the master station 10 via the host station connection connector 205, and transmits and receives signals to and from the master station 10 via the host station connection connector 205. Similarly, the slave station A20 is connected to the slave station B30 via the lower station connection connector 206, and transmits and receives signals to and from the slave station B30 via the lower station connection connector 206.

  The counter 208 counts the frame number and the slot number and outputs a count signal. The slot information storage unit 209 stores and holds slot information output from a slot information setting unit 210, which will be described later, as a slot table. The slot table is rewritten every time the slot information setting unit 210 outputs slot information. The slot information setting unit 210 determines whether or not the slot information has been normally acquired. If the slot information has been normally acquired, the slot information setting unit 210 writes the acquired slot information to the slot information storage unit 209 as it is. However, if the operation is not performed normally, the abnormal slot information with all slots after the current slot as reception slots is written into the slot information storage unit 209. This operation is executed every time slot information is input.

  The transmission / reception control unit 211 performs operation control on each of the selector 203, the transmission unit 204, and the reception unit 207 based on the slot table held by the slot information storage unit 209 and the count signal from the counter 208. The motor driving unit 212 drives the motor 23 connected to the outside according to the motor control information transmitted from the master station 10. The internal configuration and operation of the slave station B30 are the same as those of the slave station A20. Further, the slave station C40 is the same as the slave station A20 except that it does not have a lower-level station connection connector, and therefore detailed description thereof is omitted.

(Slot assignment operation)
Next, the slot allocation operation for time division communication according to the present embodiment will be described in detail.

[Normal operation]
First, an operation when slot allocation is normally performed (hereinafter, normal operation) will be described. In the following description, it is assumed that the transmission delay is sufficiently small in signal transmission from the master station 10 to the slave stations A20 to C40 and from the slave stations A20 to C40 to the master station 10.

  FIG. 4A is a diagram showing a frame configuration during normal operation in the present embodiment. As shown in FIG. 4A, the super frame is composed of N frames having a fixed time width of 1 / N of the super frame, and M frames (10 in this embodiment) having a fixed time width in the frame. It is divided into slots. In the robot system of the present embodiment, the amount of information required varies depending on the type of end effector, so the slot allocation varies depending on the end effector. For this reason, when the end effector is exchanged, the slot assignment is changed according to the exchanged end effector. In the following description of the operation, it is assumed that the slave station C50 is replaced with the end effector of the slave station C40 in the previous superframe. In each slot in the figure, “T” indicates that a signal is transmitted, and “R” indicates that a signal is received.

  The master station 10 transmits, to the slave stations A20 to C40, FIG. 5A that is slot information when the slave station C40 that is the end effector is connected at time T1 (the last slot of the previous superframe). Looking at the slot information in FIG. 5A, slot number 0 is assigned to transmission of synchronization information from the master station 10 to the slave stations A20 to C40. Slot numbers 1 to 3 are assigned to transmission of angle information from the slave stations A20 to C40 to the master station 10. Slot numbers 4 to 6 are assigned to transmission of motor control information from the master station 10 to the slave stations A20 to C40. Further, slot numbers 7 to 9 of frame numbers 1 to N-1 and slot numbers 7 to 8 of frame number N are slots for random access. The non-isochronous information such as the above-described maintenance information request and maintenance information is transmitted using a random access slot. The terminal station in which the isochronous information to be transmitted is generated transmits the information by securing the transmission right by a known transmission control such as CSMA / CD, CSMA / CA system, and slotted aloha system in the random access slot. To do. The slot number 9 of the frame number N is assigned to transmission of slot information from the master station 10 to the slave stations A20 to C40. The slot assignment of the next superframe is transmitted using this slot.

  Note that the slot information in FIG. 5A is shown in a form in which the slot information of all frames is described for convenience of explanation, but naturally it may be transmitted after being compressed. For example, in FIG. 5A, if slot number 9 of frame number N is defined in advance as a slot for transmitting slot information, only slot allocation information per frame and information on the number of frames N are transmitted. The slot information of FIG. 5A can be notified. Further, the value of the number N of frames may be fixed or variable. For example, in a robot system using predictive control, if the end effector replacement is not performed for a while, the value of N should be set larger, and if the end effector replacement will be performed soon, the value of N should be set smaller. Can do. As described above, by compressing the slot information and dynamically setting the value of N, it is possible to minimize the communication resources necessary for transmitting the slot information, and to effectively use the transmission band. it can.

  Next, the operation of each terminal station at time T1 (the last slot of the previous superframe) in FIG. 4A will be described. At time T1, the transmission unit 106 of the master station 10 transmits a communication signal obtained by modulating slot information to the slave stations A20 to C40. At time T1, in the master station 10, the slot table stored in the slot information storage unit 110 is updated to the same slot information transmitted to the slave stations A20 to C40.

  The receiving unit 207 of the slave station A20 demodulates the received communication signal and outputs the slot information and the error detection result to the slot information setting unit 210. When slot information and an error detection result are input, the slot information setting unit 210 determines slot information to be output to the slot information storage unit 209 based on the slot information and the error detection result. The process for determining the slot information to be output will be described with reference to FIG. The slot information setting unit 210 executes this processing every time slot information and an error detection result are input to the slot information setting unit 210. Also, the slave station B30 and the slave station C40 execute the same processing.

  When the processing is started, the slot information setting unit 210 confirms the error detection result from the receiving unit 207, and determines whether or not the slot information has been normally acquired (S61). When the slot information is normally acquired (Yes in S61), the normally acquired slot information is directly written in the slot information storage unit 209 (S62). On the other hand, when the slot information is not normally acquired (No in S61), the abnormal slot information is written in the slot information storage unit 209 (S63). Here, as described above, the case where the slot information is normally acquired in the slave stations A20 to C40 (Yes in S61), that is, the case of normal operation is described. In this case, at time T1, the slot information storage unit 209 of the master station 10 and the slave stations A20 to C40 holds the slot information shown in FIG. 5A in the slot table.

  Next, operations of the master station 10 and the slave stations A20 to C40 at time T2 (frame number 1, slot number 0) will be described. The transmission stop station determination unit 111 of the master station 10 determines whether or not the transmission operations of the slave stations A20 to C40 are normally performed for each slot. The determination process will be described with reference to FIG.

  When the determination process is started, the transmission stop station determination unit 111 determines whether or not there is a slave station that performs transmission in the current slot (hereinafter, the current slot), and stores the count signal from the counter 109 and the slot information storage. The determination is made from the slot table held by the unit 110 (S71). For example, at time T2 (frame number 1, slot number 0), since the master station 10 performs transmission, it is determined that there is no slave station that performs transmission (No in S71). When there is no slave station that performs transmission (No in S71), the determination process ends. On the other hand, for example, at time T3 (frame number 1, slot number 1), since the slave station A20 performs transmission, it is determined that “there is a slave station that performs transmission in the current slot” (Yes in S71). When there is a slave station that performs transmission in the current slot (Yes in S71), it is determined whether or not the slave station is a transmission stop station that has stopped transmission (S72). That is, it is determined whether the slave station that performs transmission in the current slot holds correct slot information. Here, the determination as to whether or not the slave station that performs transmission in the current slot is a transmission stop station is performed, for example, by detecting the reception power of the signal in the current slot. If the received power of the current slot is equal to or greater than the threshold value, the slave station is performing a transmission operation and is determined not to be a transmission stop station (No in S72), and the process ends. On the other hand, if the received power of the current slot is smaller than the threshold, it is determined that the slave station is a transmission stop station that is not performing a transmission operation (Yes in S72). That is, it is determined that the slave station does not hold correct slot information. In this case, the transmission stop station determination unit 111 outputs a transmission stop station detection signal to the slot information rewriting unit 112 (S73), and ends the process.

  At time T2, since the master station 10 performs transmission, it is determined that there is no slave station that performs transmission (No in S71), and the determination process ends without outputting a transmission stop station detection signal.

  Then, the transmission / reception control unit 113 of the master station 10 controls the selector 105 and the transmission unit 106 based on the slot table held by the slot information storage unit 110 to transmit the synchronization information. Similarly to the master station 10, the transmission / reception control unit 211 of the slave station A20 also controls the reception unit 207 based on the slot table held by the slot information storage unit 209, and receives synchronization information. The transmission / reception control units of the slave station B30 and slave station C40 also perform the same operation as the slave station A20.

  Next, the operation of each terminal station at time T3 (frame number 1, slot number 1) will be described. The transmission stop station determination unit 111 of the master station 10 performs the determination process shown in FIG. In the processing, as described above, since the slave station A20 performs transmission at time T3, it is determined that “there is a slave station that performs transmission in the current slot” (Yes in S71). Here, in this description, the slave station A20 normally transmits a signal at time T3 and is not a transmission stop station (No in S72). For this reason, the master station 10 ends the determination process.

  Therefore, the master station 10 and the slave stations A20 to C40, like the time T2, perform the signal transmission / reception operation based on the slot tables held in the respective slot information storage units, so that the respective selectors and transmission units Or one of the receiving units is controlled.

  By repeating the above operation for each slot, a frame configuration (FIG. 4A) according to the slot information shown in FIG. 5A is formed, and information is transmitted and received.

[Operation when an error occurs]
Next, an operation (hereinafter referred to as an abnormal operation) when the slot information is not normally acquired will be described. FIG. 4B shows a frame configuration when slot information is not normally received in slave station A20 and an abnormal operation occurs.

  At time T4 (the last slot of the previous super frame), the master station 10 transmits a communication signal obtained by modulating the slot information shown in FIG. 5A to the slave stations A20 to C40, as in the normal operation described above. At time T4, in the master station 10, the slot table stored in the slot information storage unit 110 is updated to the same slot information transmitted to the slave stations A20 to C40.

  Here, it is assumed that at time T4, a transmission error occurs in the transmission path to the slave station A20, and slot information is not normally acquired. The receiving unit 207 of the slave station A20 demodulates the received communication signal and outputs the slot information and the error detection result to the slot information setting unit 210. As described above, when the slot information and the error detection result are input, the slot information setting unit 210 performs the process of determining the slot information to be output shown in FIG. Since the slot information is not normally acquired here (No in S61), the abnormal slot information for setting all the slots defined in advance as reception slots is written in the slot information storage unit 209 (S63).

  FIG. 5C shows an example of the abnormal slot information. MAX in the figure is the maximum number of frames that can be set. The maximum number of frames may be a fixed value when the number of frames included in the superframe is fixed. As shown in FIG. 5C, the abnormal slot information is slot information that stipulates that a transmitting station and information to be transmitted are indefinite, but a slave station that has failed to receive slot information is always in a receiving state. . That is, the slave station in which the slot information for abnormality is written in the slot information storage unit 209 does not transmit a signal during the period in which the slot information for abnormality is written, and thus becomes a transmission stop station. That is, in this example, the slave station A20 is a transmission stop station.

  On the other hand, it is assumed that the slot information is normally acquired in the slave station B30 and the slave station C40. In this case, the slot information storage unit 209 of the slave station B30 and the slave station C40 holds the slot information shown in FIG. 5A in the slot table. That is, at time T4, the slot information storage units of the master station 10, the slave station B30, and the slave station C40 hold the slot information shown in FIG. 5A and the slave station A20 holds the slot information for abnormality shown in FIG. 5C in the slot table. become.

  Next, the operation at time T5 (frame number 1, slot number 0) will be described. The transmission / reception control unit 211 of the slave station A 20 controls the selector 203, the transmission unit 204, and the reception unit 207 based on the slot table held by the slot information storage unit 209. Here, since FIG. 5C is written in the slot table, the transmission / reception control unit 211 determines that the current slot is a reception slot, and controls the reception unit 207 to perform reception. Since the operations of the master station 10, the slave station B30, and the slave station C40 are the same as those described at the time T2 during normal operation, the details are omitted.

  Next, the operation at time T6 (frame number 1, slot number 1) will be described. The transmission stop station determination unit 111 of the master station 10 performs the determination process shown in FIG. 7 as described above. In the determination process, since the slave station A20 performs transmission in the slot at time T6 (Yes in S71), the process proceeds to S72. Then, it is determined whether or not the slave station A20 that performs transmission in the current slot is a transmission stop station that stops the transmission operation (S72). Here, since the slave station A20 is a transmission stop station (Yes in S72), the transmission stop station determination unit 111 outputs a transmission stop station detection signal to the slot information rewriting unit 112 (S73).

  When a transmission stop station detection signal is input, the slot information rewriting unit 112 receives a slot from the transmission stop station (slave station A20) to the master station 10 from the slot table of the slot information storage unit 110, or the master station 10 extracts a slot for transmitting information to a transmission stop station. Then, the slot table is rewritten so that the slot transmitted / received earliest after the current slot is used as the slot information retransmission slot among the extracted slots. In FIG. 5A, first, slot numbers 1 and 4 of frame number 1, slot number 1 of frame number 2, and the like are extracted. Then, among the extracted slots, the slot with the slot number 4 with the frame number 1 is identified as the slot that is transmitted and received earliest after the slot number 1 with the frame number 1 as the current slot. For this reason, the slot information rewriting unit 112 rewrites the specified slot to a slot information retransmission slot. As described above, the slave station A20 that does not hold the correct slot information is detected, and a slot information retransmission slot is provided for retransmitting the slot information. The slot table after rewriting is shown in FIG. 5B.

  Next, the operation at time T7 (frame number 1, slot number 4) will be described. The transmission / reception control unit 113 of the master station 10 controls the selector 105, the transmission unit 106, and the reception unit 108 based on the slot table held in the slot information storage unit 110. At this time, since FIG. 5B is written in the slot table as described above, the slot information is transmitted to the slave station A20 at time T7. Note that the slot information transmitted here is the same as the slot information transmitted at time T4 (FIG. 5A).

  The slave station A20 operates based on slot information (FIG. 5C) that is in a reception state in all slots, and therefore can receive the slot information transmitted from the master station 10. As described above, by adding a unique identifier to the slot information, the receiving unit 207 of the slave station A20 can recognize that the received information is the slot information by confirming the identifier. As a result, the received slot information and error detection result are output to the slot information setting unit 210. Here, assuming that the slot information is normally acquired, the slot information of FIG. 5A is written in the slot table of the slot information storage unit 209. Therefore, the slave station A20 can perform normal transmission / reception control in the slot after the time T8.

  In the above embodiment, the slot information is described as being transmitted in one slot. However, transmission may be performed using one or more slots. FIG. 8 shows a frame configuration when slot information is transmitted in two slots. FIG. 8A shows a frame configuration at the time of normal operation, and FIG. 8B shows a frame configuration at the time of an abnormal operation in which the slave station A20 cannot normally acquire slot information. The slot information is transmitted from the master station 10 to the slave stations A20 to C40 at time T10, T11 or time T12, T13 (the last two slots of the previous superframe). The slot information transmitted at this time is shown in FIG. 9A. As shown in FIG. 9A, in this example, slot information is transmitted using two slots as slot information 1 and slot information 2. The normal operation is the same as the operation when the slot information is transmitted in one slot, and the detailed description is omitted.

  The abnormal operation will be described with reference to FIG. 8B. First, operations of the master station 10 and the slave stations A20 to C40 at times T12 and T13 (the last two slots of the previous superframe) will be described. The transmission unit 106 of the master station 10 divides the slot information shown in FIG. 9A into two, slot information 1 and slot information 2, and transmits each modulated communication signal to the slave stations A20 to C40 using two slots. To do.

  The receiving unit 207 of the slave station A20 demodulates the received communication signal, combines the slot information 1 and the slot information 2 divided into two slots, and outputs the slot information and the error detection result to the slot information setting unit 210. . Here, it is assumed that the slot information has not been acquired normally. In this case, the slot information setting unit 210 of the slave station A20 writes the abnormal slot information (FIG. 5C) to the slot information storage unit 209. As a result, the slave station A20 becomes a transmission stop station. On the other hand, the slot information is normally acquired in the slave station B30 and the slave station C40, and the slot information storage unit 209 of the slave station B30 and the slave station C40 holds the slot information shown in FIG. 9A in the slot table. As described above, at time T13, the master station 10, the slave station B30, and the slave station C40 store the slot information shown in FIG. 9A, and the slave station A20 stores the slot information for abnormality shown in FIG. Will be retained.

  Next, the operation of the master station 10 at time T14 (frame number 1, slot number 1) will be described. The transmission stop station determination unit 111 of the master station 10 performs the determination process shown in FIG. 7 for each slot as described above. Here, the slave station A20 is a transmission stop station as described above. Therefore, the transmission stop station determination unit 111 outputs a transmission stop station detection signal to the slot information rewriting unit 112. When the transmission stop station detection signal is input, the slot information rewriting unit 112 receives from the slot table of the slot information storage unit 110 a slot for transmitting information from the transmission stop station (slave station A20) to the master station, or the master station. A slot for transmitting information to the transmission stop station is extracted. Then, the slot table is rewritten so that the slot in which transmission / reception is first performed after the current slot and the slot in which about transmission / reception is performed next is used as the slot for retransmission of slot information. In FIG. 9A, first, slot numbers 1 and 4 of frame number 1, slot number 1 of frame number 2, and the like are extracted. Then, among the extracted slots, the slot with the slot number 4 with the frame number 1 is identified as the slot that is transmitted and received earliest after the slot number 1 with the frame number 1 as the current slot. Furthermore, the slot of slot number 1 of frame number 2 is specified as the slot that is transmitted and received second fastest after slot number 1 of frame number 1 that is the current slot. For this reason, the slot information rewriting unit 112 rewrites the specified slot to a slot information retransmission slot. The slot table after rewriting is shown in FIG. 9B.

  Next, operations of the master station 10 and the slave stations A20 to C40 at time T15 (frame number 1, slot number 4) and time T16 (frame number 2, slot number 1) will be described. The transmission / reception control unit 113 of the master station 10 controls the selector 105, the transmission unit 106, and the reception unit 108 based on the slot table held in the slot information storage unit 110. In this case, the slot information shown in FIG. 9B is written in the slot table as described above. Therefore, slot information 1 is transmitted to slave station A20 at time T15 (frame number 1, slot number 4) and slot information 2 is transmitted at time T16 (frame number 2, slot number 1). The slot information transmitted here is the same as the slot information (FIG. 9A) transmitted at times T12 and T13.

  The slave station A20 waits for signal reception according to the slot table in which the slot information shown in FIG. 5C is written. The receiving unit 207 determines whether the received information is slot information based on the above-described identifier, and confirms reception of slot information 1 and slot information 2. Receiving section 207 outputs slot information and error detection result obtained by combining slot information 1 and slot information 2 to slot information setting section 210. Here, assuming that the slot information is normally acquired, the slot information of FIG. 9A is written in the slot table of the slot information storage unit 209. Accordingly, the slave station A20 can perform normal transmission / reception control in the slot after time T17.

  The slot information 1 and the slot information 2 need not be combined by the receiving unit 207, and may be performed by the slot information setting unit 210, for example. Further, for example, when the slot information 1 includes information from the first frame to the N / 2 frame, and the slot information 2 includes other information, the slot information storage unit sequentially does not combine them. The slot table 209 may be updated. Also, when the slot information is transmitted using three or more slots, the same processing as described above may be performed.

  As described above, by the operation of each station, it is possible to quickly return a slave station that has transmitted slot information and has not successfully acquired slot information to the network without wasting communication resources. Thereby, the robot system of this embodiment can perform replacement | exchange of an end effector smoothly without delay. Moreover, even if there is a slave station that has not been able to acquire slot information normally in the robot system, the control does not become unstable, and high productivity and reliability can be ensured.

  In this embodiment, the slot information retransmission slot is a slot assigned for transmission to a transmission stop station or a slot assigned for transmission of motor control information to a transmission stop station by a master station. However, if there is a spare slot (hereinafter referred to as “reserve slot”) that can be used to transmit arbitrary information as a transmission slot of the master station, it is retransmitted as slot information. It may be used as a slot for use. This spare slot may be, for example, a slot for transmitting an emergency stop signal in an emergency or a reset signal for initialization. When these signals are not transmitted, the slot information is transmitted. May be.

  In this embodiment, a random access slot for transmitting non-isochronous information is provided. In addition, the transmission of the slot information in this embodiment is performed for each super frame, but the present invention is not limited to this, and the slot information may be transmitted only when the end effector is exchanged.

<< Embodiment 2 >>
The technique described in the first embodiment is particularly effective when the amount of slot information is not so large. For example, in the first embodiment, when the slot information is one slot, the transmission stop station can be returned to the network within one frame. The present embodiment proposes a method for returning a transmission stop station to a network flexibly and at high speed even when the amount of slot information increases. Specifically, in this embodiment, in addition to the slot allocated to the transmission stop station, a random access slot is used as a slot for retransmission of slot information. Note that the overall configuration of the robot system according to the present embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

(Configuration of master station)
The functional configuration of the master station 10 is substantially the same as that of FIG. However, in the master station 10 of this embodiment, the slot extracted when the transmission stop station detection signal is input to the slot information rewriting unit 112 is different. The slot information rewriting unit 112 according to the present embodiment extracts a random access slot in addition to a slot for transmitting a signal from the transmission stop station to the master station 10 or from the master station 10 to the transmission stop station. Then, a predetermined number of slots that can be transmitted / received to / from the transmission stop station earliest after the current slot are specified. Then, the slot information rewriting unit 112 rewrites the slot table so that the slot information is transmitted in the specified slot. Other functions of the master station 10 are the same as those in the first embodiment.

(Configuration of slave stations)
FIG. 10 is a diagram showing an internal configuration of the slave station A20 of the present embodiment. The blocks having the same functions as those of the slave station A20 of the first embodiment are denoted by the same reference numerals as those in FIG. 3, and the description thereof is omitted. In the present embodiment, the slave station A20 further includes a transmission stop station determination unit 213 and a slot information rewrite unit 214. These operations are the same as the transmission stop station determination unit 111 and the slot information rewrite unit 112 of the master station, respectively.

(Slot assignment operation)
Next, the slot allocation operation of this embodiment will be described in detail. FIG. 11 is a diagram showing a frame configuration at the time of abnormal operation in the present embodiment. Note that the frame configuration and operation during normal operation are the same as the configuration in FIG.

  FIG. 11 shows a frame configuration at the time of abnormal operation in which the slave station A20 cannot normally acquire slot information. The slot information is transmitted from the master station 10 to the slave stations A20 to C40 at times T20 and T21 (the last two slots of the previous super frame). The slot information transmitted at this time is the same as in FIG. 9A. Specifically, the transmission unit 106 of the master station 10 divides the slot information shown in FIG. 9A into two of slot information 1 and slot information 2, and each modulates a communication signal using two slots. Send to A20-C40. At time T21, slot information storage section 110 updates the slot table held in slot information storage section 110 to the same slot information transmitted to slave stations A20 to C40.

  The receiving unit 207 of the slave station A20 demodulates the received communication signal, combines the slot information 1 and slot information 2 divided into two slots, and sends the received slot information and error detection result to the slot information setting unit 210. Output. In this description of the operation, since slot information is not normally acquired, the slot information setting unit 210 writes the abnormal slot information (FIG. 5C) in the slot information storage unit 209. As a result, the slave station A20 becomes a transmission stop station. On the other hand, the slot information is normally acquired in the slave station B30 and the slave station C40, and the slot information storage unit 209 of the slave station B30 and the slave station C40 holds the slot information shown in FIG. 9A as a slot table. In this way, at time T23, the slot information storage units of the master station 10, the slave station B30, and the slave station C40 use the slot information shown in FIG. 9A and the slave station A20 uses the slot information for abnormality shown in FIG. Will hold.

  Next, operations of the master station 10 and the slave stations A20 to C40 at time T22 (frame number 1, slot number 0) will be described. The transmission stop station determination unit 111 of the master station 10 performs the determination process shown in FIG. At time T22, since the master station 10 performs transmission, there is no slave station that performs transmission. For this reason, the transmission stop station determination unit 111 ends the flow process without performing anything. In the present embodiment, the transmission stop station determination unit 213 of the slave station A20 similarly performs the determination process shown in FIG. The slot information storage unit 209 of the slave station A20 holds FIG. 5C in the slot table. Therefore, since the transmitting station is unknown and it cannot be determined that there is a slave station that performs transmission, the flow ends. In addition, the transmission stop station determination unit 213 of the slave stations B30 and C40 also performs the same operation as the master station 10. The slave station B30 and the slave station C40 know that the master station 10 transmits in the current slot. For this reason, it is determined that there is no slave station that performs transmission in the current slot, and nothing is performed and the flow process is terminated.

  Next, the operation of each terminal station at time T23 (frame number 1, slot number 1) will be described. The transmission stop station determination unit 111 of the master station 10 also performs the determination process shown in FIG. In this case, there is a slave station (slave station A20) that transmits in the current slot, but the slave station A20 is a transmission stop station as described above. Therefore, the transmission stop station determination unit 111 outputs a transmission stop station detection signal to the slot information rewriting unit 112.

  When a transmission stop station detection signal is input, the slot information rewriting unit 112 first transmits a slot from the transmission stop station to the master station or from the master station to the transmission stop station from the slot table of the slot information storage unit 110. Or a random access slot is extracted. Then, the slot table of the slot information storage unit 110 is rewritten so that two slots that can be transmitted / received earliest among the extracted slots that are transmitted / received after the current slot are used as slots for slot information transmission. In this embodiment, first, slots such as slot numbers 4 and 7 to 9 of frame number 1 and slot number 1 of frame number 2 are extracted. Then, 2 slots that can be transmitted / received earliest are selected from among them. In this case, slot number 4 of frame number 1 and slot number 7 of frame number 1 are selected. The selected slot is rewritten to a slot information transmission slot. FIG. 12 shows the slot table after rewriting.

  The transmission stop station determination unit 213 of the slave station A20 also performs the determination process shown in FIG. 7. However, since the transmission station is unknown as in the time T22, the determination process flow ends without doing anything. The transmission stop station determination unit 213 and the slot information rewrite unit 214 of the slave station B30 and the slave station C40 also perform the same operation as the master station 10, and rewrite the slot table held in the slot information storage unit 209 with the contents of FIG.

  Next, the operation of each terminal station at time T24 (frame number 1, slot number 4) and time T25 (frame number 1, slot number 7) will be described. The transmission / reception control unit 113 of the master station 10 controls the selector 105, the transmission unit 106, and the reception unit 108 based on the slot table held in the slot information storage unit 110. At this time, since the slot information of FIG. 12 is written in the slot table as described above, slot information 1 is transmitted at time T24 and slot information 2 is transmitted at time T25. The slot information transmitted here is the same as the slot information (FIG. 9A) transmitted at times T20 and T21.

  The slave station A20 is able to receive the slot information transmitted by the master station 10 because reception control is performed based on the slot information shown in FIG. 5C. Then, the receiving unit 207 confirms that the received signals are slot information 1 and slot information 2 based on the identifier described above. Upon confirming that the slot information has been received, the receiving unit 207 combines slot information 1 and slot information 2 and outputs the combined slot information and error detection result to the slot information setting unit 210. Here, when the slot information is normally acquired, the slot information of FIG. 9A is written in the slot table of the slot information storage unit 209. As a result, the slave station A20 can perform normal transmission / reception control in slots after time T26.

  As described above, in this embodiment, since the random access slot is also used as the slot information retransmission slot, even when the number of slots in the slot information is large, the slave stations that have not been able to acquire the slot information normally can be quickly found. It can be returned to the network. This embodiment is more effective as there are more random access slots.

  In the first embodiment and the second embodiment, communication between the master station and the slave station has been described. However, the present invention is not limited to this, and a slot for performing communication between slave stations may be included. Also, in this case, if a slave station that receives data in a certain slot does not receive a signal from the slave station that performs transmission, the slave station that performs reception uses the other party's slot information stored as a slot table. You may transmit to a slave station (slave station which performs transmission). In addition, the subordinate relationship between the master station and the slave station is not necessarily required. When the end effector is exchanged, the first communication means in any one of all the terminal stations generates slot information. Then, it may be transmitted to the second communication means in another terminal station. For example, using the example of FIG. 1, the first communication means described above is the communication means of the slave station B30 directly connected to the end effector, and the second communication means described above is the master station 10, the slave station. A20, the communication means of the slave station C40 may be used. By using the communication means of the terminal station closer to the end effector as the first communication means for transmitting the slot information, the time from the detection of the exchange of the end effector to the transmission of the slot information can be shortened as much as possible. Further, for example, in a cascade connection network, the communication means of the terminal station at the intermediate position of the cascade connection may be the first communication means. This makes it possible to reduce the time for transmitting slot information to the entire network, particularly when the network scale is large to some extent. Furthermore, a parallel connection network in which the first communication unit is directly connected to the plurality of second communication units may be used in the robot system.

  In the first embodiment and the second embodiment, the slot allocation indicated by the slot information is applied from the next slot from which the slot information is acquired. However, the present invention is not limited to this. For example, when there is time until slot allocation is applied, a method of applying slot allocation described in the slot information from M slots after the slot information may be used.

  In the first and second embodiments, the slot information storage unit that holds the slot information generated by the slot information generation unit and the slot information rewrite unit that rewrites the slot information according to the transmission stop station detection signal are provided. It is not limited to. For example, all slot information is stored in advance in the ROM, predetermined slot information is selected from a plurality of stored slot information according to the transmission stop station detection signal, and the transmission / reception control unit selects the selected slot Control may be performed based on the information.

  In the first and second embodiments, the description has been given using the robot system in which the slot assignment is changed by exchanging the end effector. However, the present invention is not limited to this. The present invention can be applied to an industrial automatic control device that changes slot assignments as needed, such as a robot system that has a plurality of functions such as a gripping / processing function and includes an end effector that switches according to the work content. .

<< Other Embodiments >>
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (10)

A communication system including a plurality of communication means including a transmission means for transmitting a signal and a reception means for receiving a signal in a slot allocated by time division communication, wherein the first communication means and the second communication means communicate with each other. There,
The first communication unit includes a determination unit that determines whether the second communication unit holds information on the slot;
The second communication means stops transmitting the signal when the information is not held,
When the first communication means does not receive a signal from the second communication means in the slot assigned to the second communication means, the second communication means does not hold the information. To determine,
A communication system characterized by the above. The first communication means transmits the information to the second communication means prior to communication.
The communication system according to claim 1, wherein: The second communication means includes detection means for receiving the information via the receiving means and detecting an error in the received information.
When the second communication means detects an error in the information, the second communication means does not hold the information.
The communication system according to claim 1 or 2. The first communication means, when it is determined that the second communication means does not hold the information, the slot for communicating with the second communication means in the slot allocation, the plurality of The information is transmitted to the second communication means in at least one of a slot that is not assigned to any communication performed by the communication means and a spare slot in which the first communication means is allowed to transmit a signal. ,
The communication system according to any one of claims 1 to 3, wherein the communication system is characterized. The first communication means performs the transmission using a slot that can transmit the earliest among the slots that can transmit the information to the second communication means.
The communication system according to claim 4, wherein: When the second communication means does not hold the slot allocation information, the second communication means receives signals in all slots.
The communication system according to any one of claims 1 to 5, wherein: The second communication unit performs communication according to the allocation of the slot included in the information when the first communication unit transmits the information and receives the information.
The communication system according to any one of claims 1 to 6, characterized in that: A communication device comprising a transmission means for transmitting a signal and a reception means for receiving a signal in a slot allocated by time division communication, and for communicating with another communication device,
In a slot allocated to the other communication device, when a signal is not received from the other communication device, the determination unit includes a determination unit that determines that the other communication device does not hold information on the slot.
A communication device. A communication method in a communication apparatus comprising a transmission means for transmitting a signal and a reception means for receiving a signal in a slot allocated by time-division communication, and communicating with another communication apparatus,
A determination step of determining that the other communication device does not hold information regarding the slot when the determination unit does not receive a signal from the other communication device in the slot assigned to the other communication device. Having
A communication method characterized by the above.   The program for functioning a computer as each means with which the communication apparatus of Claim 8 is provided.

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