JP7469142B2 - Communication control system and communication control method - Google Patents

Description

The present invention relates to a communication control system and a communication control method for performing I/O communication between a control device as a master and multiple external signal input/output devices (hereinafter referred to as "I/O units") connected to the control device as slaves.

A numerical control device that controls a machine tool and a robot control device that controls an industrial robot (hereinafter also referred to as a "control device"), for example, is connected to a plurality of external signal input/output devices (hereinafter referred to as "I/O units") as slaves via electric signal cables with the control device as a master, and the master communicates with each slave one-to-one. Specifically, the master performs cyclic communication, communicating with all slaves once at a preset fixed period.
For example, as described in Patent Document 1, a numerical control device transmits a DO signal (specifically, DO data) to an I/O unit, and when the I/O unit receives the DO signal, it returns a DI signal (specifically, DI data), thereby inputting and outputting a DI signal and a DO signal (hereinafter also referred to as an "I/O signal"). Here, the exchange of the DO signal and the DI signal is also referred to as "I/O communication" or "DI/DO communication". The DI data is transmitted, for example, as a collection of a start code, a header, DI data, a footer, a CRC, and a stop code (hereinafter also referred to as a "DI packet"). The DO data is transmitted, for example, as a collection of a start code, a header, DO data, a footer, a CRC, and a stop code (hereinafter also referred to as a "DO packet").

In the following, a description will be given of a daisy chain as an example of a communication connection configuration, with a numerical control device as a master and an I/O unit as a slave. Fig. 1 is a schematic diagram showing an example of a communication control system configured by connecting a numerical control device and a plurality of I/O units with electric communication cables.
As shown in Fig. 1, the numerical control device includes a CPU (hereinafter also referred to as a "controller"), an I/O memory, and a communication master, and the I/O unit includes a CPU (controller) and a communication slave. Note that, depending on the type of I/O unit, there are cases where the I/O unit does not include a CPU (controller).

Figure 2 shows an example of a communication schedule for DI/DO communication between a numerical control device (master) and multiple I/O units (slaves). Here, the preset fixed period is 2 ms. As shown in Figure 2, the numerical control device communicates with all I/O units once every 2 ms (i.e., cyclic communication in which the numerical control device transmits DO data, and the I/O units receive the DO data and then return DI data).

The numerical control device and the I/O unit may also include a communication function (hereinafter also referred to as "message communication") for exchanging messages, which are data other than I/O signals. Specifically, messages are transmitted in a form incorporated into cyclic communication of DO signals and DI signals in response to transmission requests from the CPU of the numerical control device and the CPU of the I/O unit. That is, messages from the numerical control device to the I/O unit are incorporated into DO packets and transmitted as DO packets, which are, for example, a collection of start codes, headers, DO data, messages, footers, CRCs, and stop codes. Messages from the I/O unit to the numerical control device are incorporated into DI packets and transmitted as DI packets, which are, for example, a collection of start codes, headers, DI data, messages, footers, CRCs, and stop codes.
As shown in FIG. 2, when the master transmits a DO packet to the slave and the slave responds by sending a DI packet, the slave is configured to transition to creating a DI packet header upon receiving the DO packet header from the master.

Here is an example of message communication. For example, a numerical control device (master) has a screen that displays various statuses of a specified I/O unit (slave). When an operator performs an operation to open the screen, the numerical control device (master) sends a message to the I/O unit (slave) requesting it to send various statuses. In response, the I/O unit (slave) replies with its various statuses as a reply message to the numerical control device (master). In this way, the numerical control device (master) can display on the screen various statuses of the I/O unit (slave) specified by the operator.

Another example of message communication will be described. For example, a numerical control device (master) has a screen for setting the filter of a specified I/O unit (slave). An operator can instruct a change to the filter setting of the I/O unit (slave) via this screen. In this case, the numerical control device (master) sends a change request message to the I/O unit (slave) specified by the operator, requesting that the filter setting be changed to the operator's desired value. In response, the I/O unit (slave) changes the filter value based on the received change request message. In this way, the numerical control device (master) can change the filter setting of the I/O unit (slave) specified by the operator.

Patent No. 5837146

During normal DI/DO cyclic communication, when message communication is performed between a numerical control device (master) and multiple I/O units (slaves), the amount of communication data increases significantly, and there is a possibility that all DI/DO communication cannot be completed within a preset fixed period (e.g., 2 ms).
3A and 3B are diagrams showing an example of a communication schedule when message communication is performed between a numerical control device (master) and multiple (N units: N≧3) I/O units (slaves). Here, the preset fixed period is 2 ms. Referring to FIG. 3A, a case is illustrated in which a message is incorporated in a DI packet transmitted from the second I/O unit to the numerical control device, but the DI/DO communication with the Nth I/O unit (slave) falls within the preset fixed period (e.g., 2 ms).
3B, a message is embedded in the DI packets sent from the first and second I/O units to the numerical control device, which illustrates a case in which the DI/DO communication with the Nth I/O unit (slave) does not fall within a preset fixed period (e.g., 2 ms).

As shown in FIG. 3B , for example, if the DI/DO communication between a numerical control device (master) and an Nth I/O unit (slave) does not fall within a preset constant period (e.g., 2 ms), the update period of the DI/DO between the numerical control device (communication master) and multiple I/O units (slaves) (DI/DO communication between the numerical control device and multiple I/O units is performed once every 2 ms) will not be guaranteed.
For this reason, even when message communication is performed between a numerical control device (master) and multiple I/O units (slaves) during normal cyclic communication, it is desirable to ensure the update period of the I/O signals by completing the exchange of at least DI and DO signals (DI/DO communication) between all I/O units (slaves) within a predetermined fixed period.

(1) One aspect of the present disclosure is a communication control system in which a control device having a communication master and a plurality of I/O units each having a communication slave communicatively connected to the control device by a daisy chain are connected to the control device at a predetermined fixed period to transmit and receive I/O signals to and from all of the I/O units,
The communication master includes:
Each communication slave is assigned a communication cycle in advance.
a margin data amount calculation unit that measures a communication time required for communication of only DI data and DO data excluding transmission messages for each cycle of I/O signal transmission and reception with each communication slave, and calculates a communication band margin data amount of each communication slave;
a DO packet creation unit that creates a DO packet incorporating the communication bandwidth margin data amount when transmitting DO data to the communication slave, and when a message amount to be transmitted to the communication slave exceeds the communication bandwidth margin data amount, divides the transmission message into a plurality of communications, and incorporates a divided partial message of the transmission message, which does not exceed the communication bandwidth margin data amount, into the DO packet for each communication period;
a DO transmission unit that transmits the DO packet to the communication slave;
The communication slave is
The communication slave is
a DO receiving unit for receiving a DO packet transmitted from the communication master;
a DI packet creation unit that acquires the communication bandwidth margin data amount included in the received DO packet, creates a DI packet when transmitting DI data to the communication master, and when a message amount to be transmitted to the communication master exceeds the communication bandwidth margin data amount, divides the transmission message into a plurality of communications, and incorporates a divided partial message of the transmission message that does not exceed the communication bandwidth margin data amount into the DI packet for each communication period;
a DI transmission unit that transmits the DI packet to the communication master,
Regarding communication control systems.

(2) One aspect of the present disclosure is a communication control method in which a control device including a communication master and a plurality of I/O units each including a communication slave communicatively connected to the control device by a daisy chain are used, the control device transmitting and receiving I/O signals to and from all of the I/O units at a constant period set in advance,
The communication master includes:
Each communication slave is assigned a communication cycle in advance.
a margin data amount calculation step of measuring a communication time required for communication of only DI data and DO data excluding a transmission message for each cycle of I/O signal transmission and reception with each communication slave, and calculating a communication band margin data amount of each communication slave;
a DO packet creation step of creating a DO packet incorporating the communication bandwidth margin data amount when transmitting DO data to the communication slave, and if the amount of a message to be transmitted to the communication slave exceeds the communication bandwidth margin data amount, dividing the transmission message into a plurality of communications and incorporating a partial message of the transmission message, which does not exceed the communication bandwidth margin data amount, into the DO packet for each communication period;
a DO transmission step of transmitting the DO packet to the communication slave;
The communication slave is
a DO receiving step of receiving a DO packet transmitted from the communication master;
a DI packet creation step of acquiring the communication bandwidth margin data amount included in the received DO packet, creating a DI packet when transmitting DI data to the communication master, and, if a message amount to be transmitted to the communication master exceeds the communication bandwidth margin data amount, dividing the transmission message into a plurality of communications and incorporating a divided partial message of the transmission message, which does not exceed the communication bandwidth margin data amount, into the DI packet for each communication period;
A DI transmission step of transmitting the DI packet to the communication master.
The present invention relates to a communication control method.

According to one aspect of the present disclosure, even when message communication is performed between a numerical control device (master) and multiple I/O units (slaves) during normal cyclic communication, it is possible to ensure the update period of the I/O signals by completing at least the exchange of DI and DO signals (DI/DO communication) between all I/O units (slaves) within a preset fixed period.

1 is a schematic diagram illustrating an example of a communication control system according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of a communication schedule relating to DI/DO communication between a numerical control device (master) and a plurality of I/O units (slaves). FIG. 13 is a diagram showing an example of a communication schedule when message communication is performed between a numerical control device (master) and a plurality of I/O units (slaves). FIG. 13 is a diagram showing an example of a communication schedule when message communication is performed between a numerical control device (master) and a plurality of I/O units (slaves). 2 is a schematic diagram showing functional blocks of a numerical control device 1 as a master and an I/O unit 3 as a slave. FIG. FIG. 13 is a diagram illustrating an example of calculation of a communication band margin data amount_k by a communication master. FIG. 13 is a diagram illustrating an example of dividing a message as necessary so that the message fits within a communication band margin data amount_k. 4 is an example of a flowchart showing an operation of the numerical control device 1 serving as a master. 10 is an example of a flowchart showing an operation of the I/O unit 3 as a slave. FIG. 2 is a schematic diagram showing functional blocks of the numerical control device 1 serving as a master. FIG. 13 is a diagram illustrating an example of optimizing a per-slave communication period based on per-slave division number_k. 4 is an example of a flowchart showing an operation of the numerical control device 1 serving as a master. 4 is an example of a flowchart showing an operation of the numerical control device 1 serving as a master.

First Embodiment
An embodiment of the present invention will be described. As an embodiment, a numerical control device and an I/O unit are connected by an electric signal cable to perform data communication (high-speed serial communication). Note that the device performing high-speed serial communication is not limited to a numerical control device. For example, it may be a control device for industrial machinery including an industrial robot.
As described above, Fig. 1 is a schematic diagram showing an example of a communication control system 1000 according to the embodiment, which is configured by daisy-chaining a numerical control device 1 as a master and a plurality of I/O units 3 as slaves with an electric signal cable 6. As shown in Fig. 1, the numerical control device 1 as a master includes a control unit 10, an I/O memory 12, and a communication master 15. The I/O unit 3 as a slave includes a communication slave 35. The I/O unit may include a control unit 30.

The multiple (N units: N≧2) I/O units 3 can be identified by the order k (1≦k≦N) in which they are connected to the control device 1. Specifically, the I/O unit 3 directly connected to the control device 1 can be identified as I/O unit 3_1, the I/O unit 3 directly connected to I/O unit 3_1 can be identified as I/O unit 3_2, and similarly, the I/O unit 3 directly connected to I/O unit 3_k can be identified as I/O unit 3_(k+1), etc. Unless otherwise specified below, it is assumed that N (N≧2) I/O units 3_k (1≦k≦N) are daisy-chained. Furthermore, unless otherwise specified, the control unit 30 included in I/O unit 3_k is referred to as control unit 30_k, and the communication slave 35 is referred to as communication slave 35_k.

In the daisy chain connection, when a communication slave 35_k receives a signal from the communication master 15 (when k=1) or communication slave 35_(k-1) (when k≧2) connected in the previous stage, it transmits the received signal as is to the communication slave 35_(k+1) in the subsequent stage. Also, when a communication slave 35_k receives a signal from the communication master 15 (when k=1) or communication slave 35_(k-1) (when k≧2) connected in the subsequent stage, it transmits the received signal as is to the communication master 15 (when k=1) or communication slave 35_(k-1) (when k≧2) connected in the previous stage. This allows the communication master 15 to communicate with a plurality of communication slaves 35_k.
In this way, each I/O unit 3_k can input and output input signals (DI signals)/output signals (DO signals) to and from the numerical control device 1.
Next, each component of the communication control system 1000 will be described in detail.

[Numerical control device 1]
4 is a schematic diagram showing functional blocks of the numerical control device 1 as a master and the I/O unit 3 as a slave. As shown in FIG. 4, the numerical control device 1 includes, for example, a control unit 10, an I/O memory 12, and a communication master 15.

The control unit 10 has a numerical control function unit (not shown) that is known to those skilled in the art, and an I/O interface unit 101. The numerical control function unit is known to those skilled in the art, and a description thereof will be omitted.

The I/O interface unit 101 sets DO data and messages to be transmitted from the communication master 15 to the I/O unit 3_k (1≦k≦N) via the I/O memory 12 in response to an instruction from the control unit 10. The I/O interface unit 101 also acquires DI data and messages received by the communication master 15 from the I/O unit 3_k (1≦k≦N) via the I/O memory 12. Here, the I/O memory 12 may include an I/O memory unit_k (1≦k≦N) corresponding to each I/O unit 3_k (1≦k≦N).
The I/O interface unit 101 sets the DO data and messages to be sent from the communication master 15 to the I/O unit 3_k (1≦k≦N) in, for example, the I/O memory unit _k (1≦k≦N), and also acquires the DI data and messages received by the communication master 15 from the I/O unit 3_k (1≦k≦N) from, for example, the I/O memory unit _k (1≦k≦N).
The communication master 15 inputs, for example, DO data and a transmission message to be transmitted from an I/O memory unit_k (1≦k≦N) to each I/O unit 3_k (1≦k≦N) and transmits them to a communication slave 35_k (1≦k≦N). As will be described later, when the transmission of a transmission message_k transmitted to each I/O unit 3_k (1≦k≦N) is completed, the communication master 15 notifies the control unit 10 (I/O interface unit 101) of the completion of transmission of the transmission message_k via, for example, the I/O memory unit_k (1≦k≦N).
As will be described later, the communication master 15 receives DI data and a message_k from each communication slave 35_k (1≦k≦N), and when reception of a transmission message_k from an I/O unit 3_k is completed, the communication master 15 can notify the control unit 10 (I/O interface unit 101) of the completion of reception of the transmission message_k and by recording the transmission message_k in, for example, an I/O memory unit_k (1≦k≦N). In this way, DI/DO communication and transmission/reception of messages may be performed between the control device 1 and the I/O unit 3_k (1≦k≦N).

[Communication Master 15]
As shown in FIG. 4, the communication master 15 includes a per-slave communication period allocation unit 151, a DI/DO communication time measurement unit 152A, a DI/DO communication time calculation unit 152B, a margin data amount calculation unit 153, a master transmission message determination unit 154, a DO packet creation unit 155, a DO transmission unit 158A, a DI reception unit 158B, and a buffer memory 159.

Before describing each functional unit of the communication master 15, a description will be given of the buffer memory 159. The buffer memory 159 includes, for example, a buffer memory unit_k (1≦k≦N) corresponding to the communication slave 35_k (1≦k≦N) of each I/O unit 3_k (1≦k≦N).
The buffer memory unit _k (1≦k≦N) may store various data related to communication between the communication master 15 and the communication slave 35_k (1≦k≦N) for each period. Specifically, the buffer memory unit _k may store the slave-specific communication period _k, the DI/DO basic communication measurement time _k, the DI/DO basic communication time _k, the communication band margin data amount _k, the message length _k to be carried over to the next communication, and the message _k to be carried over to the next communication, which will be described later. In this way, it is possible to control the transmission message exchanged between the communication master 15 and each communication slave 35_k (1≦k≦N) to be communicated in multiple parts, and even when message communication is performed between the numerical control device (master) and multiple I/O units (slaves), it is possible to complete the exchange of at least DI and DO signals (DI/DO communication) between all the I/O units (slaves) within a preset fixed period, thereby ensuring the update period of the I/O signals.

<Slave-by-Slave Communication Cycle Allocation Unit 151>
The per-slave communication cycle allocation unit 151 allocates a per-slave communication cycle_k to each communication slave 35_k (1≦k≦N) to enable I/O communication with all I/O units 3_k (1≦k≦N) at a predetermined fixed cycle.
Specifically, the slave-specific communication cycle allocation unit 151 may allocate a slave-specific communication cycle that is a preset fixed cycle divided equally by the number N of I/O units to each communication slave 35_k (1≦k≦N).
Furthermore, the slave communication cycle allocation unit 151 may allocate the slave communication cycles to each communication slave 35_k (1≦k≦N) in a graded manner based on the connection order of the I/O units 3_k (1≦k≦N). Specifically, the value of the slave communication cycle_k (1≦k≦N) of the communication slave 35_k (1≦k≦N) may be set as follows:
If j≦k, then slave communication cycle_j≦slave communication cycle_k
In a daisy chain connection, as described above, the subsequent communication slave 35_(k+1) transmits and receives data to and from the communication master 15 via the previous communication slave 35_k, so the slave-by-slave communication period of the subsequent communication slave 35 may be set to be equal to or greater than the slave-by-slave communication period of the previous communication slave 35. Note that the specific calculation formula may be set arbitrarily, for example, proportional to the cable length.
Furthermore, the slave-specific communication cycle allocation unit 151 may allocate a slave-specific communication cycle to each communication slave 35_k (1≦k≦N) based on the DI/DO points of each I/O unit 3_k (1≦k≦N). Specifically, the value of the slave-specific communication cycle 3_k (1≦k≦N) of the communication slave 35_k (1≦k≦N) may be allocated in a gradient such that the value increases as the DI/DO points increase. Specifically, when the DI/DO points of I/O unit 3_j≦the DI/DO points of I/O unit 3_k,
Slave-by-slave communication cycle_j≦slave-by-slave communication cycle_k
The allocation may be made in a gradual manner so that the following formula is satisfied: The specific calculation formula may be set arbitrarily, for example, to be proportional to the DI/DO points.
The slave communication cycle allocation unit 151 may also perform setting based on a value input by an administrator.

<DI/DO communication time measurement unit 152A>
The DI/DO communication time measurement unit 152A measures the communication time required for communication (I/O communication) of only DI data and DO data excluding transmission messages with each communication slave 35_k (1≦k≦N) at a preset fixed period. In other words, when the time during which a message is transmitted is included in addition to the DI/DO communication between the communication master 15 and the communication slave 35_k (1≦k≦N), the DI/DO communication time measurement unit 152A measures the communication time required for communication (I/O communication) of only DI data and DO data excluding the measurement time during which the message is transmitted. Hereinafter, this measured time is also referred to as "DI/DO basic communication measurement time_k".

<DI/DO communication time calculation unit 152B>
The DI/DO communication time calculation unit 152B calculates a statistical value related to the communication time required for communication (I/O communication) of only DI data and DO data for each communication slave 35_k (1≦k≦N) using a predetermined formula based on a set of DI/DO basic communication measurement times_k measured by the DI/DO communication time measurement unit 152A at a preset fixed cycle up to the present time. Hereinafter, the calculated statistical value related to the communication time is also referred to as "DI/DO basic communication time_k." Specifically, the DI/DO communication time calculation unit 152B calculates the DI/DO basic communication time_k for each communication slave 35_k (1≦k≦N) at a preset fixed cycle.
Here, the above calculation formula may calculate the maximum value included in the set of measurement times of each communication slave 35_k (1≦k≦N) and use this as the DI/DO basic communication time_k of the communication slave 35_k (1≦k≦N). Also, the average time of the measurement values included in the measurement set may be used as the DI/DO basic communication time_k of the communication slave 35_k (1≦k≦N).

<Margin Data Amount Calculation Unit 153>
The margin data amount calculation unit 153 calculates, for each communication slave 35_k (1≦k≦N), a communication bandwidth margin data amount _k for each communication slave 35_k (1≦k≦N) based on the per-slave communication cycle _k assigned to the communication slave 35_k (1≦k≦N) by the per-slave communication cycle allocation unit 151, the DI/DO basic communication time _k of the communication slave 35_k (1≦k≦N) calculated by the DI/DO communication time calculation unit 152B, and the data transfer rate from the start of communication to the present time.
Specifically, if the data transfer rate is RATE, it may be calculated using the following formula 1.

Communication bandwidth margin data volume_k =
(Slave-by-slave communication cycle_k - DI/DO basic communication time_k) / RATE (Formula 1)

Specifically, this value is the amount of data available for message transmission, for example, between the communication master 15 and each communication slave 35_k (1≦k≦N), excluding the DI/DO basic communication time_k.
Specifically, the margin data amount calculation unit 153 calculates the communication band margin data amount_k for each communication slave 35_k (1≦k≦N) at a preset fixed period. Therefore, the communication band margin data amount_k is not a fixed value but a variable value that varies at each communication period.
Fig. 5A is a diagram showing an example of calculation of communication band margin data amount_k. As shown in Fig. 5A, communication band margin data amount_k is calculated for each communication cycle.

<Master transmission message determination unit 154>
When a DO packet is transmitted from the communication master 15 to each communication slave 35_k (1≦k≦N) in the current DI/DO communication cycle, the master transmission message determination unit 154 determines whether or not a message_k to be carried over to the next communication occurred in the previous DI/DO communication cycle, and if a message_k to be carried over to the next communication occurs, it further determines the magnitude relationship between the message length_k to be carried over to the next communication and the value of the communication bandwidth margin data amount_k.
When the master transmission message determination unit 154 determines that there is no carried-over transmission message _k that has not been transmitted, it refers to the I/O memory 12 (I/O memory unit _k) as described above to determine whether or not there is a transmission message _k to be newly transmitted this time, and if there is a transmission message _k to be newly transmitted this time, it further determines whether the length of the new transmission message _k is larger than the value of the communication bandwidth margin data amount _k.

<DO Packet Creation Unit 155>
Next, the DO packet creation unit 155 will be described in detail. The DO packet creation unit 155 creates a DO packet, which is a collection of a start code, a header, DO data, a message, a footer, a CRC, and a stop code, as described above. Here, the DO data is a DO signal transmitted to the I/O unit 3_k (1≦k≦N) at a preset fixed period. The message is set when there is a message to be transmitted to the I/O unit 3_k (1≦k≦N). In addition to data set in normal packet communication, the header may be set with the presence or absence of a transmission message, the transmission message length, the message length carried over to the next communication, and the value of the communication band margin data amount_k calculated by the margin data amount calculation unit 153.
The DO packet creating unit 155 creates a DO packet in response to the following five cases.

<Normal DO Packet - Case 1>
When creating a DO packet to be transmitted to each communication slave 35_k (1≦k≦N) in the current cycle, if the master transmission message determination unit 154 determines that there is no message _k to be carried over to the next communication in the previous cycle and no transmission message _k to be newly transmitted this time, the DO packet creation unit 155 creates a DO packet (referred to as a "DO packet of case 1") in which the value of the communication bandwidth margin data amount _k calculated by the margin data amount calculation unit 153 is set, for example, in the header portion.

<Last Carry-Over Sent Message - Case 2>
If the master transmission message determination unit 154 determines that there is a message _k to be carried over to the next communication in the previous cycle and further determines that the message length _k to be carried over to the next communication does not exceed the value of the communication bandwidth margin data amount _k, the DO packet creation unit 155 sets the value of the communication bandwidth margin data amount _k, for example, in the header section, and creates a DO packet (referred to as a "DO packet of case 2") that incorporates the message _k to be carried over to the next communication as the current transmission message _k.
The DO transmitting unit 158A, which will be described later, transmits the DO packet ("DO packet of case 2"), thereby completing the transmission of the message requested for transmission by the control unit 10. In this case, as will be described later, the DO transmitting unit 158A may notify the control unit 10 (I/O interface unit 101) of the completion of transmission of the transmission message_k requested for transmission by the control unit 10 via, for example, an I/O memory unit_k (1≦k≦N).

<Further carryover transmission messages occur - Case 3>
When the master transmission message determination unit 154 determines that there is a message_k to be carried over to the next communication in the previous cycle for the communication slave 35_k (1≦k≦N) and further determines that the length of the message_k to be carried over to the next communication exceeds the value of the communication band margin data amount_k, the DO packet creation unit 155 sets a part of the message_k, which corresponds to the communication band margin data amount_k, among the messages_k to be carried over to the next communication, as the transmission message_k to be transmitted in the current cycle. The DO packet creation unit 155 stores the remaining part of the transmission message_k, excluding the transmission message_k to be transmitted in the current cycle, together with the message length_k to be carried over to the next communication, in, for example, the buffer memory unit_k. The DO packet creation unit 155 sets the value of the communication band margin data amount_k and the message length_k to be carried over to the next communication, for example, in the header part, and creates a DO packet (referred to as a "DO packet of case 3") incorporating the transmission message_k to be transmitted in the current cycle.
Since message_k remains to be carried over to the next communication, even if the DO packet is transmitted by a DO transmitting unit 158A (described later), the transmission of the message requested by the control unit 10 is not completed.

<New sent message - Case 4>
If the master transmission message determination unit 154 determines that there was no message _k to be carried over to the next communication with the communication slave 35_k (1≦k≦N) in the previous cycle and that there is a new transmission message _k in the current cycle, and further determines that the length of the new transmission message _k does not exceed the value of the communication bandwidth margin data amount _k, the DO packet creation unit 155 sets the value of the communication bandwidth margin data amount _k, for example, in the header section, and creates a DO packet (referred to as a “DO packet of case 4”) in which the new transmission message _k in the current cycle is incorporated as the current transmission message _k.
The DO transmitting unit 158A, which will be described later, transmits the DO packet ("DO packet of case 4"), thereby completing the transmission of the new transmission message requested by the control unit 10. In this case, as will be described later, the DO transmitting unit 158A notifies the control unit 10 (I/O interface unit 101) of the completion of transmission of the requested transmission message_k, for example, via an I/O memory unit_k (1≦k≦N).

<New sent message - Case 5>
When the master transmission message determination unit 154 determines that there is no message _k to be carried over to the next communication for the communication slave 35_k (1≦k≦N) in the previous cycle and that there is a new transmission message _k in the current cycle, and further determines that the length of the new transmission message _k exceeds the value of the communication band margin data amount _k, the DO packet creation unit 155 determines that a part of the new transmission message _k in the current cycle, which corresponds to the communication band margin data amount _k, is the transmission message _k to be transmitted in the current cycle. The DO packet creation unit 155 stores the remaining part of the message _k, excluding the transmission message _k to be transmitted in the current cycle, as the message _k to be carried over to the next communication, together with the message length _k to be carried over to the next communication, for example, in the buffer memory unit _k.
The DO packet creation unit 155 sets the value of the communication bandwidth margin data amount _k and the message length _k to be carried over to the next communication, for example, in the header section, and creates a DO packet ("DO packet for case 5") that incorporates the transmission message _k to be transmitted in the current cycle.
Since message_k remains to be carried over to the next communication, even if the DO packet is transmitted by the DO transmitting unit 158A described later, the new transmission message requested by the control unit 10 is not considered to have been completely transmitted.
5B is a diagram showing an example of dividing a message as necessary so that the message fits within the communication band margin data amount_k. As shown in FIG. 5B, if the message amount is equal to or less than the communication band margin data amount_k, the message is transmitted at once, and if the message amount exceeds the communication band margin data amount_k, the communication band margin data amount is transmitted first, and the remainder is transmitted in the next or subsequent communication.

<DO transmission unit 158A>
The DO transmission unit 158A periodically transmits the DO packet created by the DO packet creation unit 155 to the communication slave 35_k (1≦k≦N). As described above, when the DO transmission unit 158A completes transmission of the DO packet of case 2 and the DO packet of case 4, the DO transmission unit 158A may notify the control unit 10 (I/O interface unit 101) of the completion of transmission of the transmission message_k requested by the control unit 10, for example, by recording it in the I/O memory unit_k (1≦k≦N).

<DI receiving unit 158B>
The DI receiving unit 158B receives the DI data and the transmission message _k transmitted from each communication slave 35_k (1≦k≦N) via, for example, a buffer memory unit _k. The transmission message _k transmitted from each communication slave 35_k (1≦k≦N) may be divided and transmitted as described later.
When a transmission message _k sent from each communication slave 35_k (1≦k≦N) is divided and transmitted, the DI receiving unit 158B, upon receiving all the divided messages, restores the message _k and can notify the control unit 10 (I/O interface unit 101) of the completion of transmission of the message _k received from the I/O unit 3_k (1≦k≦N) and the restored message _k, for example, by recording it in the I/O memory unit _k (1≦k≦N).
The numerical control device 1 serving as the master has been described above.
Next, the I/O unit 3 as a slave will be described.

[I/O unit 3]
FIG. 4 shows a functional block diagram of the I/O unit 3 acting as a slave.
4, the I/O unit 3 includes, for example, a control unit 30, a memory 32, and a communication slave 35. Hereinafter, unless otherwise specified, when describing a configuration common to I/O units 3_k (1≦k≦N), it will be referred to as an I/O unit 3.
The control unit 30 has an I/O signal control function unit (not shown) known to those skilled in the art, and an I/O interface unit 301. The I/O signal control function unit is known to those skilled in the art, and a description thereof will be omitted.
The I/O interface unit 301 acquires DO signals and messages from the numerical control device 1 from the communication slave 35 via the memory 32. The I/O interface unit 301 may also be set, for example, via the memory 32, so as to transmit DI signals and transmission messages to the numerical control device 1 as the master to the communication slave 35.
Specifically, the I/O interface unit 301 may obtain DO signals and messages transmitted from the numerical control device 1 from the memory 32, and set DI signals and messages to be transmitted to the numerical control device 1 in the memory 32.
The communication slave 35 receives the DO signal and message from the communication master 15, and when the reception of the transmitted message from the numerical control device 1 is completed, it can notify the control unit 30 (I/O interface unit 101) of the completion of reception of the transmitted message and by recording the transmitted message, for example, in memory 32.
Furthermore, the communication slave 35 inputs DI data and a transmission message to the numerical control device 1 from, for example, the memory 32, and transmits a DI signal and a transmission message to the numerical control device 1. As will be described later, when the transmission of a transmission message requested to be transmitted is completed, the communication slave 35 notifies the control unit 30 (I/O interface unit 301) of the completion of transmission of the transmission message via, for example, the memory 32.

The communication slave 35 includes a slave transmission message determining unit 354 , a DI packet creating unit 355 , a DI transmitting unit 358 A, a DO receiving unit 358 B, and a buffer memory 359 .
Hereinafter, unless otherwise specified, in describing the functional unit of a communication slave 35_k (1≦k≦N), the communication slave will be referred to as a communication slave 35.

When creating a DI packet from the communication slave 35 to the communication master 15 in the current DI/DO communication cycle, the slave transmission message determination unit 354 determines whether or not a message to be carried over to the next communication occurred in the previous DI/DO communication cycle, and if a message to be carried over to the next communication occurred, it further determines the relative size of the message length to be carried over to the next communication and the value of the communication bandwidth margin data amount.
When the slave transmission message determination unit 354 determines that there is no unsent carried-over transmission message, it refers to the memory 32 as described above to determine whether there is a new transmission message to be transmitted this time, and if there is a new transmission message to be transmitted this time, it further determines whether the length of the new transmission message is larger than the value of the communication bandwidth margin data amount. Here, as the value of the communication bandwidth margin data amount, the value set in the header part of the DO packet received from the communication master 15 in the current DI/DO communication cycle is used.

Next, the DI packet creation unit 355 will be described in detail. As described above, when the communication slave 35 receives the header of the DO packet, the DI packet creation unit 355 can move on to creating the header of the DI packet. After that, the communication slave 35 can move on to creating the DI data and message.
<Normal DI packet_Case 1>
When creating a DI packet to be transmitted to the communication master 15 in the current cycle, if the slave transmission message determination unit 354 determines that there is no message to be carried over to the next communication in the previous cycle and no new transmission message to be transmitted this time, the DI packet creation unit 355 creates a DI packet (referred to as a "DI packet of case 1") in which, for example, the transmission message length to be carried over to the next communication cycle and the new transmission message length in the header section are both set to zero.

<Last Carry-Over Sent Message - Case 2>
If the slave transmission message determination unit 354 determines that there is a message in the previous cycle that will be carried over to the next communication, and further determines that the length of the message to be carried over to the next communication does not exceed the value of the communication bandwidth margin data amount, the DI packet creation unit 355 sets the transmission message length to be carried over to the next cycle, for example in the header section, to zero, and creates a DI packet (referred to as a "DI packet of case 2") that incorporates the carried over transmission message from the previous cycle as the current transmission message.
The DI transmission unit 358A, which will be described later, transmits the DI packet ("DI packet of case 2"), thereby completing the transmission of the message requested by the control unit 30. In this case, as will be described later, the DI transmission unit 358A may notify the control unit 30 (I/O interface unit 301) of the completion of the transmission of the requested transmission message via, for example, the memory 32.

<Further carryover transmission messages occur - Case 3>
When the slave transmission message determination unit 354 determines that there is a message to be carried over to the next communication in the previous cycle with the communication master 15, and further determines that the length of the message to be carried over to the next communication exceeds the value of the communication band margin data amount, the DI packet creation unit 355 sets a part of the message corresponding to the communication band margin data amount among the messages to be carried over to the next communication as a transmission message to be transmitted in the current cycle. The DI packet creation unit 355 may store the remaining part of the transmission message excluding the transmission message to be transmitted in the current cycle as a message to be carried over to the next communication together with the message length to be carried over to the next communication, for example, in the buffer memory 359. The DI packet creation unit 355 sets the value of the communication band margin data amount_k and the message length_k to be carried over to the next communication, for example, in the header part, sets the carryover transmission message length to be carried over to the next cycle in the header part, and creates a DI packet (referred to as a "DI packet of case 3") incorporating the transmission message to be transmitted in the current cycle.
Since there remains a message to be carried over to the next communication, even if the DI packet is transmitted by a DI transmitting unit 358A (described later), the message requested for transmission by the control unit 30 does not complete transmission.

<New sent message - Case 4>
If the slave transmission message determination unit 354 determines that there was no message carried over to the next communication with the communication master 15 in the previous cycle, and that there is a new transmission message in the current cycle, and further determines that the length of the new transmission message does not exceed the value of the communication bandwidth margin data amount, the DI packet creation unit 355 sets the carried over transmission message length (= zero) to be carried over to the next cycle, for example, in the header section, and creates a DI packet (referred to as a "DI packet of case 4") that incorporates the new transmission message in the current cycle as the current transmission message_k.
The DI transmitting unit 358A, which will be described later, transmits the DI packet ("DI packet of case 4"), thereby completing the transmission of the new transmission message requested by the control unit 30. In this case, as will be described later, the DI transmitting unit 358A notifies the control unit 30 (I/O interface unit 301) of the completion of the transmission of the transmission message requested by the control unit 30, for example, via the memory 32.

<New sent message - Case 5>
When the slave transmission message determination unit 354 determines that there is no message to be carried over to the next communication in the previous cycle with the communication master 15, but that there is a new transmission message in the current cycle, and further determines that the length of the new transmission message exceeds the value of the communication bandwidth margin data amount, the DI packet creation unit 355 sets a part of the new transmission message in the current cycle, which corresponds to the communication bandwidth margin data amount, as the transmission message to be transmitted in the current cycle. The DI packet creation unit 355 may store the remaining part of the message k, excluding the transmission message to be transmitted in the current cycle, as the message to be carried over to the next communication, together with the message length to be carried over to the next communication, for example, in the buffer memory 359.
The DI packet creating unit 355 sets the message length to be carried over to the next communication, for example, in the header, and creates a DI packet ("DI packet for case 5") incorporating the transmission message to be transmitted in the current cycle.
Since there remains a message to be carried over to the next communication, even if the DI packet is transmitted by a DI transmission unit 358A (described later), the new transmission message requested by the control unit 30 is not considered to have been completely transmitted.

<DI transmission unit 358A>
The DI transmission unit 358A periodically transmits the DI packet created by the DI packet creation unit 355 to the communication master 15. As described above, when the DI transmission unit 358A completes transmission of the DI packet of case 2 and the DI packet of case 4, the DI transmission unit 358A notifies the control unit 30 (I/O interface unit 301) of the completion of transmission of the transmission message requested by the control unit 30, for example, by recording it in the memory 32.

<DO receiving unit 358B>
The DO receiving unit 358B receives, via the buffer memory, DO data and a transmission message transmitted from the communication master 15. Upon receiving the header of a DO packet, the DI packet creating unit 355 is configured to transition to creating a header of a DI packet, as described above.
As described above, there are cases where the transmission message transmitted from the communication master 15 is divided before being transmitted. Therefore, when the DO receiving unit 358B receives all the divided messages in the case where the transmission message transmitted from the communication master 15 is divided before being transmitted, the DO receiving unit 358B can restore the message and notify the control unit 30 (I/O interface unit 301) of the completion of transmission of the message received from the control device 1 and the restored message by recording the message in the memory 32, for example.
The I/O unit 3 as a slave has been described above.

Next, the operation of this embodiment will be described with reference to the flowcharts of FIG. 6 and FIG. 7. FIG. 6 is an example of a flowchart showing the operation of the numerical control device 1 as a master cyclically communicating with all I/O units 3_k (1≦k≦N) as slaves once at a preset fixed period. FIG. 7 is an example of a flowchart showing the operation of the I/O unit 3_k (1≦k≦N) as a slave. The aforementioned fixed period is assumed to be preset. Note that the flowcharts shown in FIG. 6 and FIG. 7 are merely examples and are not limiting.

6, in step S10, before the numerical control device 1 as the master (hereinafter, for simplicity, also referred to as “master 1”) starts communication with the I/O unit 3_k (1≦k≦N) as the slave (hereinafter, for simplicity, also referred to as “slave 3_k”), the communication master 15 performs initial settings in the buffer memory unit _k, for example, of a per-slave communication cycle _k (1≦k≦N), a DI/DO basic communication time _k (1≦k≦N), a communication bandwidth margin data amount _k (1≦k≦N), and a length of a carried-over transmission message _k to be carried over to the next cycle (1≦k≦N) (hereinafter referred to as “control parameters”).
In step S11, the communication master 15 initializes i (sets i to 1) in order to control cyclic communication with all communication slaves 35_k (1≦k≦N) once at a predetermined fixed period.

In step S12, the communication master 15 detects the cycle start timing of each fixed cycle with the communication slave 35_i.
In step S13, the communications master 15 (DI/DO communication time measurement unit 152A) measures a DI/DO basic communication measurement time_i with the communications slave 35_i.
In step S14, the communications master 15 (DO packet generating unit 155) generates a DO packet_i to be transmitted to the communications slave 35_i.
In step S15, the communication master 15 (DO transmitting unit 158A) transmits a DO packet_i to the communication slave 35_i, and the communication master 15 (DI receiving unit 158B) receives the DI packet_i transmitted from the communication slave 35_i.
In step S16, if the created DO packet_i does not contain a DO message, the communications master 15 (DO transmitting unit 158A) proceeds to step S19.

In step S17, the communication master 15 (DO transmission unit 158A) detects whether or not there is a message_i to be carried over to the next time. If there is no message_i to be carried over to the next time, the process proceeds to step S18. If there is a message_i to be carried over to the next time, the process proceeds to step S19.
In step S18, the communication master 15 (DO transmitting unit 158A) determines that it has completed transmission of one message_i for which a transmission request was made by the control unit 10, and records the completion of transmission of the transmission message_i in the I/O memory 12 (I/O memory unit_i).
In step S19, if the received DI packet_i does not contain a DI message, the communications master 15 (DI receiving unit 158B) proceeds to step S22.
In step S20, if there is a message transmitted from the communication slave 35_i, the communication master 15 (DI receiving unit 158B) detects whether or not there is a message to be carried over to the next time. If there is no message_i to be carried over to the next time, the process proceeds to step S21. If there is a message_i to be carried over to the next time, the process proceeds to step S22.
In step S21, the communication master 15 (DI receiving unit 158B) determines that reception of one transmission message_i from the slave 3_i has been completed, and records the transmission message_i from the slave 3_i in the I/O memory 12 (I/O memory unit_i).
In step S22, the communication master 15 (DI/DO communication time calculation unit 152B) calculates and updates the DI/DO basic communication time_i. Also, the communication master 15 (margin data amount calculation unit 153) calculates and updates the communication band margin data amount_i.

In step S23, the communication master 15 judges whether or not it has cyclically communicated with all the slaves 3_i (communication slaves 35_i) (1≦i≦N) once each (whether or not i=N). If the answer is Yes (i.e., if i=N), the process proceeds to step S11. If the answer is No (i.e., if i<N), the process proceeds to step S24.
In step S24, i=i+1 is set, and the process proceeds to step S12.
The above has shown a process flow in which the numerical control device 1 as a master cyclically performs DI/DO communication with all I/O units 3_i (1≦i≦N) as slaves once each at a preset fixed period, and transmits a message (divided as necessary).

Next, with reference to Fig. 7, an operation of each I/O unit 3_k (1 <= k <= N) (hereinafter also referred to as "slave 3_k") as a slave when it receives a DO from the communication master 15 and returns a DI will be described. In Fig. 7, the process of step S33 and the process of step S34 and thereafter can be executed in parallel.
7, in step S30, the communication slave 35_k (DO receiving unit 358B) detects the DO communication from the communication master 15.
In step S31, the communications slave 35_k (DO receiving unit 358B) receives a DO packet transmitted from the communications master 15. (As described above, when the DO receiving unit 358B receives the header of the DO packet, the process can proceed to step S32).
In step S32, if the communication slave 35_k (DO receiving unit 358B) receives a DO packet_i containing no DO message, the communication slave 35_k (DO receiving unit 358B) proceeds to step S35.
In step S33, the communications slave 35_k (DO receiving unit 358B) detects whether or not there is a received message to be carried over to the next time. If there is no received message to be carried over to the next time, the process proceeds to step S34. If there is a message to be carried over to the next time, the process proceeds to step S35.
In step S<b>34 , the communication slave 35_k (DO receiving unit 358</b>B) determines that one transmission message has been received from the numerical control device 1 , and records the one transmission message from the communication master 15 in the memory 32 .
In step S35, the communication slave 35_k (DI packet creating unit 355) creates a DI packet.
In step S36, the communication slave 35_k (DI transmission unit 358A) transmits a DI packet to the communication master 15.
In step S37, if there is no DI message in the DI packet_i, the process proceeds to step S30.
In step S38, the communications slave 35_k (DI transmission unit 358A) detects whether or not there is a message to be carried over to the next time in the message to be transmitted to the communications master 15. If there is no message to be carried over to the next time, the process proceeds to step S39. If there is a message to be carried over to the next time, the process proceeds to step S30.
In step S39, the communications slave 35_k (DI transmission unit 358A) determines that one transmission message from the slave 3_i has been transmitted, and records the transmission completion of the transmission message in the memory 32. Then, the process proceeds to step S30.
The above has shown a process flow in which the I/O unit 3_k (1≦k≦N) as a slave cyclically performs DI/DO communication with the numerical control device 1 as a master once at a preset regular period, and transmits a message (divided as necessary).

In this way, even when the master 1 simultaneously communicates messages with multiple slaves 3_k (1≦k≦N), it can automatically adjust the communication bandwidth margin data amount_k for each slave 3_k (1≦k≦N) and complete the exchange of at least DI and DO signals (DI/DO communication) with all slaves 3_k within a preset fixed period. This concludes the description of the first embodiment.

In the first embodiment, the communication master 15 incorporates a communication bandwidth margin data amount _k into the header section of each communication slave 35_k (1≦k≦N) at each period for transmitting DO, thereby notifying each communication slave 35_k (1≦k≦N) of the maximum length of message _k that each communication slave 35_k (1≦k≦N) can transmit.
On the other hand, when the length of a message_k to be transmitted in the current cycle exceeds the communication bandwidth margin data amount_k, each communication slave 35_k (1≦k≦N) sets a part of the message equivalent to the communication bandwidth margin data amount_k as a transmission message_k to be transmitted in the current cycle, and sets the remaining part of the transmission message excluding the transmission message_k to be transmitted in the current cycle as a message_k to be carried over to the next communication, thereby performing message communication in multiple communications.
As a result, even when message communication is performed between the numerical control device 1 (master) and multiple I/O units 3_k (1≦k≦N) (slaves) during normal cyclic communication, it is possible to complete the exchange of at least DI and DO signals (DI/DO communication) between all I/O units 3_k (1≦k≦N) (slaves) within a predetermined fixed period, thereby ensuring the update period of the I/O signals.

However, there are various types of I/O units 3 that become slaves, and the amount and frequency of message communication are also diverse. Therefore, if the slave communication cycle_k (1≦k≦N) is left as a fixed value as the initial setting as in the first embodiment, there is a possibility that a certain I/O unit 3 (slave) will frequently perform message communication in multiple separate sessions. This may result in a large delay from a message transmission request in a certain I/O unit 3 (slave).
Therefore, in each I/O unit 3_k (1≦k≦N), it is desirable to prevent frequent occurrence of cases in which "message communication is performed in multiple parts" in a specific I/O unit 3 (slave).

Second Embodiment
In the second embodiment, the number of times that message communication is divided into multiple times is counted for each communication slave 35_k (1≦k≦N), and the communication cycle_k (1≦k≦N) for each slave is dynamically changed based on the count value, thereby preventing frequent cases in which "message communication is divided into multiple times" from occurring in a specific I/O unit 3 (slave).
For this reason, in the second embodiment, the communication master 15 includes, in addition to the functional units of the first embodiment, a per-slave division count unit 156 and a per-slave communication cycle optimization unit 157. Fig. 8 is a schematic diagram showing functional blocks of the numerical control device 1 as a master. As described above, the functional units other than the per-slave division count unit 156 and the per-slave communication cycle optimization unit 157 are the same as the functional units of the numerical control device 1 in the first embodiment described in Fig. 4, and therefore description thereof will be omitted.

[Communication Master 15]
As shown in FIG. 8, the communication master 15 has a per-slave communication cycle allocation unit 151, a DI/DO communication time measurement unit 152A, a DI/DO communication time calculation unit 152B, a margin data amount calculation unit 153, a master transmission message determination unit 154, a DO packet creation unit 155, a per-slave division number counting unit 156, a per-slave communication cycle optimization unit 157 (this is the second embodiment), a DO transmission unit 158A, a DI reception unit 158B, and a buffer memory 159.

<Slave division count unit 156>
The per-slave division counting unit 156 counts and updates the total number of times that one transmission message _k is divided and transmitted multiple times from the communication master 15 to each communication slave 35_k (1≦k≦N) and the number of times that one reply message _k in response to the transmission message _k is divided and transmitted multiple times from the communication slave 35_k (1≦k≦N) to the communication master 15 (referred to as the "per-slave division number _k") for each communication period.
Specifically, the per-slave division counting unit 156 initializes the per-slave division count_k to zero when, for example, DI/DO communication is started between the communication master 15 and the communication slave 35_k (1≦k≦N). After that, if a message to be carried over to the next communication occurs on the communication master 15 side in the current cycle, 1 is added to the per-slave division count_k, and if a message to be carried over to the next communication occurs on the communication slave 35_k side, 1 is added to the per-slave division count_k.

<Slave-by-Slave Communication Period Optimization Unit 157>
When the per-slave division number _i for at least one communication slave 35_i among the per-slave division number _k (1≦k≦N) for each communication slave 35_k (1≦k≦N) counted by the per-slave division number counting unit 156 is equal to or exceeds a preset threshold, the per-slave communication cycle optimization unit 157 adds a preset adjustment amount to the per-slave communication cycle _i assigned to the communication slave 35_i. Furthermore, at that time, even if the per-slave communication cycle optimization unit 157 subtracts the adjustment amount from the per-slave communication cycle_k assigned to the communication slave 35_k (1≦k≦N), it selects one communication slave 35_j having the smallest per-slave division count_k (1≦k≦N) from the set of communication slaves 35_k (1≦k≦N) that exceed the DI/DO basic communication time_k (i.e., the set of communication slaves 35 (1≦k≦N) whose communication bandwidth margin data amount_k has a positive value), and subtracts the adjustment amount from the per-slave communication cycle_j assigned to that communication slave 35_j.
The adjustment amount is, for all communication slaves 35 k (1≦k≦N),
DI/DO basic communication time_k > (per slave communication cycle_k - adjustment amount)
By doing so, one communication slave 35_j having the smallest value of per-slave division count_k (1≦k≦N) may be selected, and the adjustment amount may be subtracted from per-slave communication period_j assigned to the communication slave 35_j.
9 is a diagram showing an example of optimizing the per-slave communication period based on the per-slave division number_k. As shown in Fig. 9, when the per-slave division number in the Nth communication slave becomes equal to or greater than a threshold value (e.g., 100), X ms is added to the per-slave communication period of the Nth communication slave, and X ms is subtracted from the per-slave communication period of the first communication slave, which has the smallest per-slave division number.
In addition, when performing the above-mentioned optimization process, the slave-specific communication cycle optimization unit 157 may initialize the slave-specific division number_i in the I/O unit 3_i by adding a preset adjustment amount to the slave-specific communication cycle_i.
According to the configuration of the second embodiment, similarly to the first embodiment, it is possible to ensure that the periods of all DI/DO communications are performed within a preset fixed period, while minimizing delays in message communications from requests.
The configuration of the functional parts of the communication master 15 in the second embodiment has been described above. Next, the operation of the second embodiment will be described.

10A and 10B are examples of a flowchart showing the operation of the numerical control device 1 as a master in the second embodiment. In the flowchart shown in Fig. 10A, the processing in the steps having the same step numbers as those in the flowchart showing the operation of the numerical control device 1 in the first embodiment shown in Fig. 5 performs the same operation as the corresponding step numbers in the first embodiment.
In the second embodiment, the operation related to the added function is added in the step numbered with A. In the following explanation, only the steps where the function has been added will be explained, and the explanation of the steps with the same step numbers as those in the flowchart shown in FIG.
The operation of the I/O unit 3 as a slave is the same as that in the first embodiment (see FIG. 7), and a description thereof will be omitted.

Referring to FIG. 10A, in step S10A, the communication master 15 performs the initial setting (setting to zero) of the division count per slave_k (1≦k≦N) in addition to the initial setting in step 10.

In addition, in step S11A, a function of updating the slave-specific communication cycle_i is added. Therefore, step S11A includes steps S11_1 to S11_4. Fig. 10B shows a flowchart relating to step S11A.
10B, first, in step S11_1, master 1 (slave-based communication cycle optimization unit 157) selects k1 having the maximum value and k2 having the minimum value from among the slave-based division count_k (1≦k≦N).
In step S11_2, the master 1 (slave-by-slave communication cycle optimization unit 157) determines whether the slave-by-slave division count_k1 is equal to or greater than a preset threshold. If it is equal to or greater than the threshold (Yes), the process proceeds to step S11_3. If it is less than the threshold (No), the process proceeds to step S11_4.
In step S11_3, the master 1 (per-slave communication cycle optimization unit 157) adds a preset adjustment amount to the per-slave communication cycle_k1 and subtracts the adjustment amount from the per-slave communication cycle_k2. Note that the per-slave communication cycle_k1 may be initialized. Then, the process proceeds to step S12.
Step S11_4 performs the same process as step S11 in the flowchart showing the operation of the numerical control device 1 in the first embodiment. That is, in step S11_4, i is initialized (i is set to 1). Then, the process proceeds to step S12.

Furthermore, in step S22A, in addition to the process in step S22, the communications master 15 (slave-based division number counting unit 156) updates the slave-based division number_i between the communications master 15 and the communications slave 35_i in the current cycle.
The above has shown a process flow for updating the per-slave communication period _i when the per-slave division count _i becomes equal to or greater than a threshold value when the numerical control device 1 as the master cyclically communicates with all I/O units 3_i (1≦i≦N) as slaves once each at a preset constant period.
According to the second embodiment, the numerical control device 1 can prevent frequent occurrence of "message communication divided into multiple times" in a specific I/O unit 3 (slave) in each I/O unit 3_k (1≦k≦N). In other words, the numerical control device 1 can control message communication so that the delay from a request is small while ensuring the period of DI/DO communication that is performed at a constant period.
The second embodiment has been described above.

In the present invention, the various functional parts of the numerical control device 1 may be realized by cooperation between hardware and predetermined software stored in, for example, the ROM 11, or may be realized only by hardware (electronic circuits, LSIs, etc.). The same applies to the various functional parts of the I/O unit 3.
In addition, the programs, including the operating programs, used in the present invention can be stored in various types of non-transitory computer readable media and supplied to a computer. The non-transitory computer readable media includes various types of tangible recording media. Examples of non-transitory computer-readable media include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R/Ws, semiconductor memories (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, and RAMs (random access memories). The program may also be provided to the computer by various types of transient computer-readable media. Examples of transient computer-readable media include electrical signals, optical signals, and electromagnetic waves. The transient computer-readable medium can provide the program to the computer via a wired communication path such as an electric wire or optical fiber, or via a wireless communication path.

The above-described embodiment is one of the preferred embodiments of the present invention, but the scope of the present invention is not limited to the above-described embodiment, and the present invention can be implemented in various modified forms without departing from the spirit of the present invention.

<Modification 1>
In the above embodiment, the numerical control device 1 has been described as an example of a control device, but the present invention is not limited to this. As described above, the present invention may also be applied to high-speed serial communication in a control device for industrial machinery, such as a robot controller.

In other words, the communication control system and communication control method disclosed herein can take on a variety of different embodiments having the following configurations:

(1) A communication control system 1000 according to the present disclosure is a communication control system in which a control device 1 including a communication master 15 and a plurality of I/O units each including a communication slave 35 communicatively connected to the control device 1 by a daisy chain are arranged so that the control device 1 transmits and receives I/O signals to and from all of the I/O units at a constant period set in advance,
The communication master 15 is
A slave communication period is assigned to each communication slave 35 in advance.
a margin data amount calculation unit 153 that measures a communication time required for communication of only DI data and DO data excluding transmission messages for each period of I/O signal transmission and reception with each communication slave 35 and calculates a communication band margin data amount of each communication slave 35;
a DO packet creation unit 155 that creates a DO packet incorporating a communication bandwidth margin data amount when transmitting DO data to a communication slave 35, and when a message amount to be transmitted to the communication slave 35 exceeds the communication bandwidth margin data amount, divides the transmitted message into a plurality of communications, and incorporates a divided partial message of the transmitted message, which does not exceed the communication bandwidth margin data amount, into the DO packet for each communication period;
a DO transmission unit 158A that transmits a DO packet to the communication slave 35;
The communication slave 35 is
a DO receiving unit 358B that receives a DO packet transmitted from the communication master 15;
a DI packet creation unit 355 that acquires a communication bandwidth margin data amount included in a received DO packet, creates a DI packet when transmitting DI data to the communication master 15, and, if a message amount to be transmitted to the communication master 15 exceeds the communication bandwidth margin data amount, divides the transmission message into a plurality of communications, and incorporates a partial message obtained by dividing the transmission message and not exceeding the communication bandwidth margin data amount into a DI packet for each communication period;
and a DI transmission unit 358A that transmits a DI packet to the communication master 15.
As a result, even when message communication is performed between the numerical control device 1 (master) and multiple I/O units (slaves) during normal cyclic communication, the exchange of at least DI and DO signals (DI/DO communication) can be completed between all I/O units (slaves) within a predetermined fixed period, thereby ensuring the update period of the I/O signals.

(2) In the communication control system 1000 according to (1), the communication master 15 further comprises:
a slave division counting unit 156 for counting a transmission message division number, which is the number of times that one transmission message transmitted and received between each communication slave 35 is divided and transmitted multiple times;
a per-slave communication cycle optimization unit 157 which, when the number of divisions of the transmission message in at least one communication slave 35 is equal to or exceeds a preset threshold value, adds a preset adjustment amount to the per-slave communication cycle assigned to the communication slave 35, subtracts the adjustment amount from the per-slave communication cycle assigned to the communication slave 35 having the smallest number of divisions of the transmission message, and initializes the number of divisions of the transmission message in the communication slave 35 to which the adjustment amount has been added;
The above configuration may be adopted.
This allows the control device 1 to control message communication so as to reduce delays from requests while ensuring the period of DI/DO communication, which is performed at a constant cycle.

(3) In the communication control system 1000 described in (1) or (2), the margin data amount calculation unit 153 may calculate the communication bandwidth margin data amount based on the slave communication period assigned to each communication slave 35 and the current measurement time and the maximum value of the past measurement time calculated based on the communication time required for communicating only the DI data and DO data for each period of sending and receiving an I/O signal with each communication slave 35.
This allows the communication band margin data volume to be set to a safer value.

(4) In the communication control system 1000 described in any one of (1) to (3), the slave communication period may be a value obtained by equally dividing the predetermined fixed period by the number of the I/O units.
This allows the slave-specific communication cycle to be assigned to each communication slave 35 without bias toward a specific slave.

(5) In the communication control system 1000 described in any one of (1) to (3), the slave communication period may be a value that is calculated incrementally for each I/O unit based on the connection order of the I/O units.
This makes it possible to absorb communication delays caused by the cable length for I/O units with long cables.

(6) In the communication control system 1000 according to any one of (1) to (3), the slave-specific communication period may be a value calculated based on the number of DI/DO points of the I/O unit.
This makes it possible to absorb communication delays caused by the number of DI/DO points for I/O units with a large number of DI/DO points.

(7) The communication control method according to the present disclosure includes:
A communication control method in which a control device 1 having a communication master 15 and a plurality of I/O units each having a communication slave 35 communicably connected to the control device 1 by a daisy chain are used, and the control device 1 transmits and receives I/O signals to and from all of the I/O units at a preset fixed period,
The communication master 15 is
A slave communication period is assigned to each communication slave 35 in advance.
a margin data amount calculation step of measuring a communication time required for communication of only DI data and DO data excluding a transmission message for each period of I/O signal transmission and reception with each communication slave 35, and calculating a communication band margin data amount of each communication slave 35;
a DO packet creation step of creating a DO packet incorporating a communication bandwidth margin data amount when transmitting DO data to the communication slave 35, and if the amount of a message to be transmitted to the communication slave 35 exceeds the communication bandwidth margin data amount, dividing the message into a plurality of communications and incorporating a partial message of the transmitted message, which does not exceed the communication bandwidth margin data amount, into the DO packet for each communication period;
a DO transmission step of transmitting the DO packet to the communication slave 35;
The communication slave 35 is
a DO receiving step of receiving a DO packet transmitted from the communication master 15;
a DI packet creation step of acquiring a communication bandwidth margin data amount included in the received DO packet, creating a DI packet when transmitting DI data to the communication master 15, and, if the amount of a message to be transmitted to the communication master 15 exceeds the communication bandwidth margin data amount, dividing the message into a plurality of communications and incorporating a divided partial message of the transmitted message, which does not exceed the communication bandwidth margin data amount, into a DI packet for each communication period;
and a DI transmission step of transmitting the DI packet to the communication master 15.
This makes it possible to achieve the same effect as (1).

(8) In the communication control method according to (7),
The communication master further comprises:
a slave division counting step of counting a transmission message division number, which is the number of times that one transmission message transmitted and received between each communication slave is divided and transmitted;
a per-slave communication cycle optimization step of, when the number of divisions of the transmission message in at least one communication slave is equal to or exceeds a preset threshold value, adding a preset adjustment amount to the per-slave communication cycle assigned to the communication slave, and subtracting the adjustment amount from the per-slave communication cycle assigned to the communication slave having the smallest number of divisions of the transmission message, thereby initializing the number of divisions of the transmission message in the communication slave to which the adjustment amount has been added;
The above configuration may be adopted.
This can provide the same effect as (2).

1 Numerical control device 10 Control unit 101 I/O interface unit 12 I/O memory 15 Communication master 151 Slave-by-slave communication cycle allocation unit 152A DI/DO communication time measurement unit 152B DI/DO communication time calculation unit 153 Margin data amount calculation unit 154 Master transmission message determination unit 155 DO packet creation unit 156 Slave-by-slave division number count unit 157 Slave-by-slave communication cycle optimization unit 158A DO transmission unit 158B DI reception unit 159 Buffer memory 3 I/O unit 30 Control unit 301 I/O interface unit 32 Memory 35 Communication slave 354 Slave transmission message determination unit 355 DI packet creation unit 358A DI transmission unit 358B DO reception unit 359 Memory unit 6 Electric signal cable 1000 Communication control system

Claims (8)

A communication control system in which a control device having a communication master and a plurality of I/O units each having a communication slave communicatively connected to the control device by a daisy chain are arranged so that the control device transmits and receives I/O signals to and from all of the I/O units at a constant period set in advance,
The communication master includes:
Each communication slave is assigned a communication cycle in advance.
a margin data amount calculation unit that measures a communication time required for communication of only DI data and DO data excluding transmission messages for each cycle of I/O signal transmission and reception with each communication slave, and calculates a communication band margin data amount of each communication slave;
a DO packet creation unit that creates a DO packet incorporating the communication bandwidth margin data amount when transmitting DO data to the communication slave, and when a message amount to be transmitted to the communication slave exceeds the communication bandwidth margin data amount, divides the transmission message into a plurality of communications, and incorporates a divided partial message of the transmission message, which does not exceed the communication bandwidth margin data amount, into the DO packet for each communication period;
a DO transmission unit that transmits the DO packet to the communication slave;
The communication slave is
a DO receiving unit for receiving a DO packet transmitted from the communication master;
a DI packet creation unit that acquires the communication bandwidth margin data amount included in the received DO packet, creates a DI packet when transmitting DI data to the communication master, and when a message amount to be transmitted to the communication master exceeds the communication bandwidth margin data amount, divides the transmission message into a plurality of communications, and incorporates a divided partial message of the transmission message that does not exceed the communication bandwidth margin data amount into the DI packet for each communication period;
a DI transmission unit that transmits the DI packet to the communication master,
Communications control system. The communication master further comprises:
a slave division counting unit that counts a transmission message division count, which is the number of times that one transmission message transmitted and received between each communication slave is divided and transmitted;
a per-slave communication cycle optimization unit that, when the number of transmission message divisions in at least one communication slave is equal to or exceeds a preset threshold value, adds a preset adjustment amount to the per-slave communication cycle assigned to the communication slave, subtracts the adjustment amount from the per-slave communication cycle assigned to the communication slave having the smallest number of transmission message divisions, and initializes the number of transmission message divisions in the communication slave to which the adjustment amount has been added;
The communication control system according to claim 1 . The margin data amount calculation unit is
3. The communication control system according to claim 1, wherein the communication bandwidth margin data amount is calculated based on a slave-specific communication period assigned to each communication slave and a maximum value of a current measurement time and a past measurement time calculated based on the communication time required for communication of only the DI data and DO data for each period of I/O signal transmission and reception with each communication slave. The communication control system according to any one of claims 1 to 3, wherein the slave-specific communication period is a value obtained by equally dividing the preset fixed period by the number of the I/O units. The communication control system according to any one of claims 1 to 3, wherein the slave-specific communication period is a value calculated for each I/O unit in a progressive manner based on the connection order of the I/O units. The communication control system according to any one of claims 1 to 3, wherein the slave-specific communication period is a value calculated based on the number of DI/DO points of the I/O unit. A communication control method in which a control device having a communication master and a plurality of I/O units each having a communication slave communicatively connected to the control device by a daisy chain are used, the control device transmitting and receiving I/O signals to and from all of the I/O units at a constant period set in advance, the method comprising:
The communication master includes:
Each communication slave is assigned a communication cycle in advance.
a margin data amount calculation step of measuring a communication time required for communication of only DI data and DO data excluding a transmission message for each cycle of I/O signal transmission and reception with each communication slave, and calculating a communication band margin data amount of each communication slave;
a DO packet creation step of creating a DO packet incorporating the communication bandwidth margin data amount when transmitting DO data to the communication slave, and if the amount of a message to be transmitted to the communication slave exceeds the communication bandwidth margin data amount, dividing the transmission message into a plurality of communications and incorporating a partial message of the transmission message, which does not exceed the communication bandwidth margin data amount, into the DO packet for each communication period;
a DO transmission step of transmitting the DO packet to the communication slave;
The communication slave is
a DO receiving step of receiving a DO packet transmitted from the communication master;
a DI packet creation step of acquiring the communication bandwidth margin data amount included in the received DO packet, creating a DI packet when transmitting DI data to the communication master, and, if a message amount to be transmitted to the communication master exceeds the communication bandwidth margin data amount, dividing the transmission message into a plurality of communications and incorporating a divided partial message of the transmission message, which does not exceed the communication bandwidth margin data amount, into the DI packet for each communication period;
A DI transmission step of transmitting the DI packet to the communication master.
Communications control method. In the communication control method,
The communication master further comprises:
a slave division counting step of counting a transmission message division number, which is the number of times that one transmission message transmitted and received between each communication slave is divided and transmitted;
a per-slave communication cycle optimization step of, when the number of transmission message divisions in at least one communication slave is equal to or exceeds a preset threshold value, adding a preset adjustment amount to the per-slave communication cycle assigned to the communication slave, and subtracting the adjustment amount from the per-slave communication cycle assigned to the communication slave having the smallest number of transmission message divisions, thereby initializing the number of transmission message divisions in the communication slave to which the adjustment amount has been added;
The communication control method according to claim 7, comprising:

Images