CONVEYOR SYSTEM CONTROLLER, CONVEYOR SYSTEM AND METHOD OF DATA SYNCHRONIZATION

Abstract

The present disclosure provides a conveyor system controller (11, 12, 13, 14), comprising: a data storage unit (101) configured to store a plurality of data entries, each data entry comprising a data entry ID, a data entry version identifier, and a data payload representing operating information of the controller or another controller; a processing unit (102); a first interface (103) for communicating with another controller. The controller is configured to transmit a first data packet comprising data entry ID and data entry version identifier of a data entry in the data storage unit, to other controllers; and to receive a second data packet transmitted by said another controller, the second data packet comprising data entry ID and data entry version identifier of a data entry of said another controller; and compare the received data entry version identifier of the second data packet, with a data entry version identifier of a corresponding data entry in the data storage unit having a same data entry ID as the second data packet.

Claims

1. A conveyor system controller comprising: a data storage unit configured to store a plurality of data entries, each data entry comprising a data entry ID, a data entry version identifier, and a data payload representing operating information of the controller or another controller; a processing unit; and a first interface for communicating with said another controller; wherein the controller is configured to transmit a first heartbeat data packet comprising data entry ID and data entry version identifier of a data entry in the data storage unit, via the first interface, to other controllers; receive a second heartbeat data packet transmitted by said another controller, via the first interface, the second heartbeat data packet comprising data entry ID and data entry version identifier of a data entry of said another controller; and compare the received data entry version identifier of the second heartbeat data packet, with a data entry version identifier of a corresponding data entry in the data storage unit having a same data entry ID as the second heartbeat data packet; wherein, when the controller determines that the data entry stored in its storage unit is newer than the corresponding data entry in said another controller, the controller is configured to transmit to said another controller a first synchronizing data packet comprising the data entry ID, the data entry version identifier, and at least a portion of the data payload, of the corresponding data entry in the data storage unit; wherein a size of the first synchronizing data packet is greater than a size of the first heartbeat data packet; the controller is further configured to receive a second synchronizing data packet comprising a second data entry ID, a second data entry version identifier, and at least a portion of a second data payload, of a second data entry in said another controller's data storage unit, wherein a size of the second synchronizing data packet is greater than a size of the second heartbeat data packet, wherein, when the second data entry version identifier of the second synchronizing data packet is indicated as newer than a data entry version identifier of a corresponding data entry in the data storage unit, the controller is configured to update the data payload and the data entry version identifier of the corresponding data entry in the data storage unit, according to the portion of the second data payload and the second data entry version identifier of the second synchronizing data packet; wherein the controller further comprises a second interface for communicating with an external unit; wherein the controller is further configured to: receive a first signal from the external unit, via the second interface, for updating a data payload of a data entry in the data storage unit; update the data payload of the data entry in the data storage unit according to the first signal; and update the data entry version identifier of the updated data entry to indicate a newer version.

2. (canceled)

3. The conveyor system controller as claimed in claim 1, wherein the controller is configured to determine that the data entry stored in its storage unit is newer than the corresponding data entry in said another controller based on a change in its data payload and/or a change in its data version identifier.

4. The conveyor system controller as claimed in claim 1, wherein the controller is configured to determine that the data entry stored in its storage unit is newer than the corresponding data entry in said another controller based on that the data entry version identifier of the second heartbeat data packet is indicated as older than the data entry version identifier of the corresponding data entry in the data storage unit.

5. The conveyor system controller as claimed in claim 1, wherein the controller is configured such that the first synchronization data packet comprises a portion of the data payload, said portion being a subset of the data payload, wherein the first synchronization data packet further comprises an indication of total data payload size for the data entry and/or a data payload portion order indicator.

6. The conveyor system controller as claimed in claim 1, wherein the controller is configured to transmit the first heartbeat data packet only for data entries that meet a predetermined criterion, such as a data entry ID or a data entry ID range.

7. The conveyor system controller as claimed in claim 1, wherein the controller is configured to receive said heartbeat second data packet only if the data entry ID of the second heartbeat data packet meets a predetermined criterion, such as a data entry ID or data entry ID range.

8. (canceled)

9. The conveyor system controller as claimed in claim 1, wherein the controller is further configured to: provide a second signal to the external unit, via the second interface, for controlling the external unit.

10. (canceled)

11. The conveyor system controller as claimed in claim 1, wherein the data entry version identifier comprises a counter or a time stamp.

12. The conveyor system controller as claimed in claim 1, wherein the operating information comprises an operating mode, such as a controller configuration, and/or an operating status, such as a sensor state or an error state.

13. (canceled)

14. (canceled)

15. (canceled)

16. (canceled)

17. A method of data synchronization between a plurality of conveyor system controllers of a conveyor system, wherein each conveyor system controller comprises: a data storage unit configured to store a plurality of data entries, each data entry comprising a data entry ID, a data entry version identifier, and a data payload representing operating information of the controller or another controller; a processing unit; and a first interface for communicating with said another controller; the method comprising, in each controller: transmitting a first heartbeat data packet comprising data entry ID and data entry version identifier of a data entry in the data storage unit, via the first interface, to other controllers; receiving a second heartbeat data packet transmitted by said another controller, via the first interface, the second data packet comprising data entry ID and data entry version identifier of a data entry of said another controller; and comparing the received data entry version identifier of the second heartbeat data packet, with a data entry version identifier of a corresponding data entry in the data storage unit having a same data entry ID as the second heartbeat data packet; wherein, when the controller determines that the data entry stored in its storage unit is newer than the corresponding data entry in said another controller, the method comprises: transmitting to said another controller a first synchronizing data packet comprising the data entry ID, the data entry version identifier, and at least a portion of the data payload, of the corresponding data entry in the data storage unit; wherein a size of the first synchronizing data packet is greater than a size of the first heartbeat data packet; receiving a second synchronizing data packet comprising a second data entry ID, a second data entry version identifier, and at least a portion of a second data payload, of a second data entry in said another controller's data storage unit, wherein a size of the second synchronizing data packet is greater than a size of the second data packet, and when the second data entry version identifier of the second synchronizing data packet is indicated as newer than a data entry version identifier of a corresponding data entry in the data storage unit, the method further comprises updating the data payload and the data entry version identifier of the corresponding data entry in the data storage unit, according to the portion of the second data payload and the second data entry version identifier of the second synchronizing data packet; wherein each controller further comprises a second interface for communicating with an external unit; wherein the method comprises, in each controller: receiving a first signal from the external unit, via the second interface, for updating a data payload of a data entry in the data storage unit; updating the data payload of the data entry in the data storage unit according to the first signal; and updating the data entry version identifier of the updated data entry to indicate a newer version.

18. (canceled)

19. (canceled)

20. (canceled)

21. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] FIG. 1 is a schematic diagram of a conveyor system according to the present disclosure.

[0060] FIG. 2 is a schematic diagram of a conveyor system controller according to the present disclosure.

[0061] FIG. 3 is a first example of data entries stored in a data storage unit of a conveyor system controller according to the present disclosure.

[0062] FIGS. 4a-4c is a second example of data entries stored in a data storage unit of a conveyor system controller according to the present disclosure.

[0063] FIG. 5 is a method flowchart according to the present disclosure.

DESCRIPTION OF EMBODIMENTS

[0064] FIG. 1 illustrates a schematic diagram of a conveyor control system 1 according to the present disclosure. The system 1 may comprise a plurality of conveyor system controllers. For example, the system 1 in FIG. 1 comprises four conveyor system controllers 11, 12, 13, 14.

[0065] The system 1 may comprise devices other than the controllers (not shown), such as work stations for performing certain tasks, or HMI devices for receiving instructions from an operator and/or for providing feedback to the operator. The controllers may be associated with respective devices for performing certain tasks, such as conveyor flow control devices (turnout devices, stop devices), loading or unloading devices, tag readers and/or writers, or machines for performing work on the work pieces. The controller 11, 12, 13, 14 may be a device for controlling and/or monitoring one or more work stations of the system.

[0066] As shown in FIG. 2, each controller 11, 12, 13, 14 may comprise a data storage unit 101, a processing unit 102 and a first interface 103.

[0067] The data storage unit 101 can be any type of device or medium which is adapted for recording data or information in it. Data stored in the data storage unit can be read out. Any new data can be written in the data storage unit. Examples of such data storage units may be volatile or non-volatile memory devices, including but not limited to a CD-RW disk, a hard drive and a flash memory.

[0068] The processing unit 102 can be any type of device which is adapted for carrying out instructions by performing basic arithmetic, logical, control and input/output operations specified by the instructions. The processing unit may be a CPU, MCU, DSP, PLC or a single integrated circuit.

[0069] The first interface 103 may be used for communicating with one or more other controllers. The controller may transmit a first data packet to another controller or a plurality of other controllers in the system, via the first interface 103. The controller may receive a second data packet transmitted by one of the other controllers, via the first interface 103.

[0070] The first interface 103 may comprise a wireless interface. The second interface may comprise a wired interface. Consequently, the communication between one controller and the other controllers may be wired and/or wireless. The wired interface may be a serial interface comprising a protocol selected from CAN, Ethernet, PROF IBUS, I2C, SPI, or RS-485.

[0071] As shown in FIG. 2, each controller 11, 12, 13, 14 may comprise a second interface 104 for communicating with an external unit. In FIG. 2, the second interface 104 communicates with two external units 15 and 16.

[0072] The second interface may be a single interface, or two or more separate interfaces.

[0073] The external unit 15, 16 may be an actuator, a sensor, a tag writer, a tag reader, camera, photo eyes, push button, keyboard, cell phone, smart device, scanner, or the like.

[0074] The controller 11, 12, 13, 14 may thus receive a first signal from the external unit 15, 16, via the second interface 104. Receipt of such a signal may cause the processing unit to update a data payload of a data entry in the data storage unit 101.

[0075] For example, on receipt of a signal indicating arrival of a work piece carrier to a stop control device, the processor may update a corresponding data entry to indicate that a work piece carrier is present at the portion of the conveyor system that is associated with the controller.

[0076] The controller may provide a second signal, such as an instruction for controlling the external unit for performing a task, to the external unit, via the second interface 104.

[0077] For example, the controller may provide a signal to the external unit for causing the actuator to engage or disengage to stop or release a work piece carrier arriving to or being present at the portion of the conveyor system that is associated with the controller.

[0078] The second interface 104 may comprise a wireless interface. Alternatively, the second interface may comprise a wired interface, such as a serial interface. Consequently, the communication between the controller and the external unit via the second interface may be wired or wireless.

[0079] The present disclosure is particularly applicable to controllers 11, 12, 13, 14, which are configured to transmit information via a common communication network. The controllers 11, 12, 13, 14 may be configured to communicate in such a manner as to allow all controllers to receive all information that is communicated via the common communication network.

[0080] In the data storage unit 101, a plurality of data entries are stored. FIG. 3 is an example of data entries stored in a data storage unit 101 of a conveyor system controller 11, 12, 13, 14.

[0081] Each data entry may comprise a data entry ID, a data entry version identifier, and a data payload.

[0082] The data entry ID of each data entry may be unique, as shown in FIGS. 3 and 4a-4c. Thus, the unique data entry ID may be used to distinguish one data entry from other data entries.

[0083] The data payload may represent operating information of one controller. The operating information may comprise an operating mode and/or an operating status of the controller.

[0084] The operating mode may comprise operating configuration information, e.g., information of which function this or another conveyor system controller is to perform.

[0085] The operating status may comprise information of the actual status of the controller, such as, it is in full capacity or it is malfunctioning. The operating status may indicate, as non-limiting examples, information detected by a sensor, such as the presence of a work piece carrier near the sensor; data read from a tag on the work piece or work piece carrier; a position of a stop actuator or of a turnout device arm, etc.

[0086] The data entry version identifier may indicate a version of the data entry. Thus, it may be used for representing whether the data entry is a newer or older when comparing with a corresponding data entry of e.g. another controller.

[0087] The data entry version identifier may be a counter, as shown in FIGS. 3 and 4a-4c. When the data entry is updated, e.g. with an updated data payload, the counter may be updated by performing an arithmetic operation on a value of the counter. The value of the counter may be initially set as 0 for all data entries. For every update in one data entry, its data entry version identifier, i.e. the counter, may be increased by a predetermined value. The predetermined value may be 1. Alternatively, other arithmetic operation, such as subtraction may also be performed on the value of the counter.

[0088] The data entry version identifier may be a time stamp. The time stamp may be initially set as 0 for all data entries when the system starts. For each update in the data entry after the system starts, a time stamp may be accorded as its data entry version identifier. The accorded time stamp may be a time interval calculated from when the system started until when the update happened.

[0089] If a real time system is used, each controller in the system may be synchronized by, e.g. a global clock signal for the system, an external common time server, or an external GPS signal, which would inevitably increase the complexity of the whole system. Moreover, the system may comprise additionally a central controller for synchronizing all the controllers in real time. Thus, using the data entry version identifier may simplify the conveyor system.

[0090] Further, if a real time system is used, a minor miss-synchronization between two controllers may cause an error in the chronological order of the data entries such that the system is unable to function as desired. However, by using the time stamp instead of the real time, such a correct chronological order can be guaranteed by simply setting the time stamp to the initial value 0 when the system starts. Thus, using the data entry version identifier may improve the robustness of the conveyor system.

[0091] Each conveyor system controller may store an entire data set comprising all the data entries of all the conveyor system controllers in the system. Alternatively, each conveyor system controller may store only a portion of the entire data set. For example, each conveyor system controller may store only the data entries of some conveyor system controllers in the system which are relevant to itself. In particular, a certain group of conveyor system controllers may be configured such that each conveyor system controller stores complete information on the conveyor system controllers forming part of that group.

[0092] FIGS. 4a-4c is a second example of data entries stored in a data storage unit of a conveyor system controller.

[0093] In FIG. 4a, it has been illustrated how each data entry may be devised to represent one or more variables of operating information as described above. In this example, the first data entry, data entry ID 100, which has a length of 10 positions, may represent four different variables. Hence, the data structure is defined such that the first two positions of the data payload represents variable 1; the next three positions represent variable 2; the next two positions represent variable 3 and the final three positions represent variable 4. This data structure definition is known by all controllers that need to be able to handle this data entry.

[0094] In a similar manner, the second data entry 101 may have a length of 15 positions, and be defined to represent five different variables and the third data entry 102 may have a data payload of four positions and represent a single variable.

[0095] A heartbeat data package would then have the form:

TABLE-US-00001 100 1,

[0096] Where 100 represents the data entry ID and 1 represents the data entry version identifier.

[0097] A data synchronization packet may be defined such that the entire data payload of the data entry may be transmitted in one synchronisation data packet. Such a data synchronization packet only needs to contain the data entry ID, the data entry version identifier and the data payload.

[0098] Hence, a synchronization data packet based on FIG. 4a may take the following form:

TABLE-US-00002 100 1 1234567890.

[0099] In FIG. 4b, there is illustrated a data structure for the transmission of a data synchronisation packet in a situation where the data payload length that is being transmitted is limited to four positions. That is, the data payload length is smaller than the total data payload associated with the particular data entry. Hence, the data entry is divided into three messages. In such case, it is necessary to provide information that will allow the receiving controller to correctly patch together the entire data payload of the data entry based on two or more packets containing part of the data payload.

[0100] In FIG. 4b. an indication of data payload size and a flag, indicating which part of the data payload is being transmitted, have been provided. Hence, the receiving controller will, based on knowledge that a maximum data payload size is four, be able to determine in which order the data payloads from the packets should be patched together. Hence, the data synchronization packets may take on the following form:

TABLE-US-00003 100 1 15 1 1234, 100 1 15 2 5678, 100 1 15 3 90.

[0101] As one alternative, the payload size for each data entry may be known by all the controllers, in which case only the flag is needed.

[0102] It is noted that in the example above, the payload flag forms a separate data field or a predetermined position in the data entry.

[0103] As one alternative, the payload flag may be included in one of the other data fields, such as in the data entry ID field. For example, the synchronization data packets for the first data entry 100 as per the example above may be:

TABLE-US-00004 1001 1 15 1234, 1002 1 15 5678, 1003 1 15 90.

[0104] That is, the data field indicating the data entry ID may be expanded to indicate what part of this data entry is enclosed in the data packet.

[0105] Referring to FIG. 4c, as yet another alternative, the payload flag may be entirely dispensed with by determining that a certain range of data entry IDs together form one data entry, such that each synchronisation data package having an ID within that range can be identified as belonging to that data entry, whereby the receiving controller will merge the data payloads of synchronization data packets having a data entry ID in said range. In this case, the corresponding data packets for the first data entry 100 may be

TABLE-US-00005 100 1 15 1234, 101 1 15 5678, 102 1 15 90.

[0106] Also in this example, the data payload size may be omitted.

[0107] The description will now be directed to the operation of the system 1 with reference to FIG. 5.

[0108] The controller 11, 12, 13, 14 may be configured to transmit a first data packet comprising data entry ID and data entry version identifier of one or more, preferably all, data entries in the data storage unit, via the first interface 103, to other controllers, step s1. This transmission may be performed on a regular basis, as a heartbeat signal.

[0109] The controller 11, 12, 13, 14 may be configured to receive one or more second data packets transmitted by one, some or all of the other controllers, via the first interface 103, wherein the second data packet comprises data entry ID and data entry version identifier of a data entry of said one of the other controllers, step s2. Hence, each controller may transmit its own heartbeat signal as well as receive heartbeat signals from one or all of the other controllers.

[0110] The controller 11, 12, 13, 14 may be configured to compare the received data entry version identifier of the second data packet, with a data entry version identifier of a corresponding data entry in the data storage unit having a same data entry ID as the second data packet, step s3. Typically, such comparison may be performed for each received second data packet.

[0111] The controller may be configured to update the data payload of the data entry in the data storage unit, e.g., upon receipt of the first signal for updating a data payload and update the data entry version identifier of the updated data entry to indicate a newer version.

[0112] When the data entry version identifier of the second data packet is indicated as older than the data entry version identifier of the corresponding data entry in the data storage unit in step s3, the controller may be configured to transmit the first synchronizing data packet comprising the data entry ID, the data entry version identifier, and at least a portion, preferably all, of the data payload, of the corresponding data entry in the data storage unit, wherein a size of the first synchronizing data packet is greater than a size of the first data packet, step s4.

[0113] Hence, when the controller receives a data packet comprising an older data entry compared with the corresponding data entry in the controller's data storage unit, the controller sends out the most current corresponding data entry until all the controllers have updated in respect of the data entry.

[0114] When the data entry version identifier of the second data packet is indicated as newer than the data entry version identifier of the corresponding data entry in the data storage unit, and when the second data packet comprises a portion of a data payload associated to the same data entry ID as the corresponding data entry in the data storage unit, the controller may be configured to update the data payload and the data entry version identifier of the corresponding data entry in the data storage unit, according to the portion of the data payload and the data entry version identifier of the second data packet, step s5.

[0115] If, on the other hand, the data entry version identifier of the second data packet is the same as that of the corresponding data entry in the storage unit, no synchronization operation needs to be carried out.

[0116] The data synchronization between a plurality of conveyor system controllers 11, 12, 13, 14 of a conveyor system 1 will be described in the following example involving two controllers 11, 12.

[0117] The first controller 11 may have a data entry A-11 stored in its data storage unit. The data entry A-11 may have a data entry ID 100, a data entry version identifier 1, and a data payload comprising information of an operating status of the first controller 11.

[0118] The second controller 12 may have a data entry A-12 stored in its data storage unit. The data entry A-12 may be a copy of the data entry A-11. Consequently, the data entry A-12 may also have the data entry ID 100, the data entry version identifier 1, and the data payload comprising information of the operating status of the first controller 11, as the data entry A-11.

[0119] The first controller 11 may receive a signal from an external sensor indicating arrival of a work piece carrier to a portion of the conveyor system associated with the first controller 11.

[0120] On receipt of the signal, the processing unit 102 of the controller 11 may cause an update of the data payload of data entry A-11. Thus, in the updated data entry A-11, the updated data payload may indicate the arrival of the work piece carrier detected by the external sensor. In consequence, the controller 11 may update the data entry version identifier of the updated data entry A-11 to indicate a newer version. For example, the data entry version identifier of A-11 may be updated from 1 to 2.

[0121] That is, the change in data payload for a data entry may trigger the sending of the synchronization data packet.

[0122] Alternatively, it is possible to trigger sending of the data synchronization packet in response to a first controller discovering that received heartbeat data packets have an older data entry version identifier.

[0123] The second controller 12 may transmit a second data packet comprising data entry ID 100 and data entry version identifier 1 of the data entry A-12, to the first controller 11.

[0124] The first controller 11 may receive the second data packet transmitted by the second controller 12. Since the received data entry ID is 100, the first controller 11 may compare the received data entry version identifier 1 of the received second data packet, with the data entry version identifier 2 of the corresponding data entry A-11 in its data storage unit, which has the same data entry ID 100.

[0125] After comparing, it is concluded that the data entry version identifier 1 of the second data packet is indicated as older than the data entry version identifier 2 of the corresponding data entry A-11. That is, the data entry A-12 of the second controller 12, which corresponds to data entry A-11, is not as updated as the updated data entry A-11 of the first controller 11.

[0126] On detection of an older version of the data entry A-12 of the received second data packet, the first controller 11 may transmit a first synchronizing data packet comprising the data entry ID 100, the data entry version identifier 2, and at least a portion of the data payload indicating the arrival of the work piece carrier, of the updated data entry A-11.

[0127] As comprising the additional data payload for updating, the size of the first synchronizing data packet may be greater than a size of the data packet it sent previously.

[0128] The second controller 12 may receive the first synchronizing data packet transmitted by the first controller 11. The first synchronizing data packet may comprise data entry ID 100, data entry version identifier 2 and the part of the data payload indicating the arrival of the work piece carrier, of the updated data entry A-11 of the first controller 11.

[0129] Since the data entry ID of the received first synchronizing data packet is 100, the second controller 12 may compare the received data entry version identifier 2 of the first synchronizing data packet, with the data entry version identifier 1 of the corresponding data entry A-12 in its data storage unit, which has the same data entry ID 100.

[0130] After comparing, it is concluded that the data entry version identifier 2 of the first synchronizing data packet is indicated as newer than the data entry version identifier 1 of the corresponding data entry A-12. That is, the data entry A-12 stored in the second controller 12, being a copy of data entry A-11, is not as updated as the updated data entry A-11 stored in the first controller 11.

[0131] Upon detection of a newer version of the data entry A-11 of the controller 11, and that the first synchronizing data packet comprises a portion of a data payload belonging to the corresponding data entry A-11 in the data storage unit of the controller 11, the second controller 12 may update the data payload and the data entry version identifier 1 of the data entry A-12, according to the received first synchronizing data packet.

[0132] The updated data entry A-12 may have a data entry ID 100, an updated data entry version identifier 2, and the updated data payload indicating the arrival of the work piece carrier as that of the data entry A-11. That is, the updated data entry A-12 stored in the second controller 12 is updated as a copy of the updated data entry A-11 of the first controller 11.

[0133] The second controller 12 will continue to send out second data packets indicating the old data entry version until the data entry has been updated. After the data entry has been updated, the controller 12 will update also the data entry version identifier.

[0134] In the event more than one data synchronization packets need to be transmitted, then the second controller may defer updating its data entry version identifier until all data synchronization packets have been received and the corresponding data payload has been received in its entirety.

[0135] Optionally, the controller 12 may send a first notification to the controller 11 to inform the controller 11 that the first synchronizing data packet is received completely, stored completely, and/or the update is successfully. The first notification may be a data packet comprising the data entry ID 100 and the updated data entry version identifier 2 of the updated data entry A-12.

[0136] Optionally, the second controller 12 may send a second notification comprising the data entry version identifier 1 and the data entry ID 100 of the data entry A-12 to the first controller 11, until the first synchronizing data packet is received completely, stored completely, and/or the update is successfully. The second notification may be used to inform the first controller 11 that the first synchronizing data packet has not been completely received, not been completely stored, and/or the update is not completed yet.

[0137] Other controllers 13, 14 in the system 1 may each comprise a data entry A-13 and A-14, respectively, as a copy of the data entry A-11 of the controller 11. The other controllers 13, 14 may also perform the same synchronization as the controllers 11, 12, such that the updated data entry version identifier for the updated data entries A-13 and A-14 may also be updated to 2, as the updated data entry A-12. Afterwards, the first controller 11 may not receive data packet from the second controller 12 and the other controllers 13, 14 in which the data entry version identifier for the data entry having data entry ID 100 is indicated as older than the data entry version identifier 2.

[0138] The first controller 11 may transmit a second synchronizing data packet comprising the data entry ID 100, the data entry version identifier 2, of the data entry A-11 in its data storage unit. The size of the second synchronizing data packet may be less than the size of the first synchronizing data packet.

[0139] That is, after all the controllers 12, 13, 14 in the system are synchronized to the updated data entry A-11, it is not necessary for the controller 11 to continue transmitting the first synchronizing data packet comprising any data payload. The first controller 11 may start transmitting data packet with a smaller size comprising only the data entry ID 100 and the data entry version identifier 2 of the updated data entry A-11, or comprising the data entry ID 100, the data entry version identifier 2, and a small portion of the data payload, of the updated data entry A-11.

[0140] When a new controller needs to be installed in the system 1 comprising a plurality of the present conveyor system controllers 11, 12, 13, 14, the new controller may be configured to comprise data entries having an old data entry version identifier, e.g., 0. Thus, the new controller may be automatically synchronized to the other existing controllers 11, 12, 13, 14 by the synchronization triggered by those controllers having newer data entries. Thus, the installation of a new controller in the system may be facilitated.

[0141] When the controller 11 needs to be reconfigured, the controller may be automatically synchronized to the other controllers by the synchronization triggered by those controllers having newer data entries, without any human intervention. Thus, the reconfiguration of the existing controllers may be facilitated.

[0142] In the data entry structures disclosed in FIGS. 4a-4c, an additional field may be included, which may be used to indicate whether the controller needs this data entry or not. Based on such a field, it is possible for controllers to ignore all data packets relating to data entries that are not needed.

[0143] A plurality of controllers as disclosed herein may be connected to form a network. Such a network may further comprise a flow configurator, i.e. a device that is used to determine the functions of each controller. Such determination may be made based on input from a user interface or based on a configuration plan that has been received. The flow configurator may communicate in the same manner as described above with regard to the controllers, with the difference that its payload may be manipulated through the user interface or through the configuration plan.

[0144] Hence, configuring the controllers may be achieved by updating some or all of the flow configurator's data entries. Hence, the flow configurator will begin to send out updated data entries as soon as it starts receiving messages from other controllers indicating that they have older data entries.

[0145] Moreover, a controller may be introduced by assigning to it a certain function, such that it will know what data it needs to receive and store, and its data entries may be reset to a very low data entry version indicator value, such as 0 or 1, whereby, when it is introduced into an existing network, and begin to send out the first heartbeat data packets, other controllers will recognize that there is a controller with an older data version, and thus begin to send out synchronization data packets to allow the new controller to update its data entries.