Device for transmitting data and control commands via radio connections in a distributed control system for one or more machines and/or processes

• US 20040047473A1
• Filed: 01/13/2003
• Published: 03/11/2004
• Est. Priority Date: 03/31/2000
• Status: Active Grant

• Current Assignee: CommWorks Solutions, LLC (IP Investments Group LLC), Kvaser Consultant Aktiebolag
• Original Assignee: Kvaser Consultant Aktiebolag
• Inventors: Fredriksson, Lars-Berno, Lennartsson, Kent
• Granted Patent: US 6,985,724 B2
• Time in Patent Office: Days
• US Class Current: 380/278
• CPC Class Codes: G05B 15/02 electric
• CPC Class Codes: G05B 19/0423 Input/output
• CPC Class Codes: G05B 19/4185 characterised by the network communication
• CPC Class Codes: G05B 2219/25049 Master processor gives timing information to slaves
• CPC Class Codes: G05B 2219/25187 Transmission of signals, medium, ultrasonic, radio
• CPC Class Codes: G05B 2219/25215 Time triggered protocol for fault tolerant real time application
• CPC Class Codes: G05B 2219/31136 Name of bus, canbus, controller area network
• CPC Class Codes: G05B 2219/31189 Time multiplex
• CPC Class Codes: G05B 2219/31218 Scheduling communication on bus
• CPC Class Codes: G05B 2219/31375 LAS link active scheduler, distribute bandwidth between processing nodes
• CPC Class Codes: G05B 2219/33144 Module clock, synchronised by controller message, to send message in time slice
• CPC Class Codes: G05B 2219/33192 Radio link, wireless
• CPC Class Codes: G05B 2219/33273 DCS distributed, decentralised controlsystem, multiprocessor
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

In a distributed control system for one or more machines and/or one or more processes, data and control commands are transmitted via radio connections between nodes in the control system. The nodes operate with radio transmitters and radio receivers and comprise or are controlled by activation devices for activating their transmission and receiver functions. The nodes also operate with time-determination devices which comprise or control the abovementioned activation devices. The time-determination devices are arranged to determine the transmission or reception position of the nodes by means of the activation devices and allocated settings or controls. The abovementioned settings or controls can be determined by means of one or more schedules implemented in or for the control system, in which the nodes are given unique or co-ordinated transmission and reception times on the radio connections.

Claims

1. Device for transmitting data and control commands via radio connections between nodes in a distributed control system for one or more machines and/or one or more processes, characterized in that the nodes operate as or with radio transmitters and/or radio receivers, in that the nodes comprise or are controlled by activation devices for activating their transmission and receiver functions, in that the nodes also operate with the abovementioned activation devices comprising or controlling time-determination devices arranged to determine the transmission and reception positions of the nodes by means of the activation device and the allocated settings or controls, and in that the abovementioned settings and controls can be set by means of one or more schedules drawn up in or for the control system, in which the node or nodes are allocated unique or co-ordinated transmission and reception times on the radio connections.

2. Device according to claim 1, characterized in that the respective node comprises a connection device, incorporated for example in the above-mentioned activation device, which upon the commencement of the node'"'"'s transmission or reception time connects the node to a relevant radio connection and in that the node'"'"'s transmitter or receiver transmits or receives data or control command(s) concerning only that node and referring to the machine or process in question, and can thus omit identification or address data and any sorting data in order to reduce the transmission or reception time and thereby save bandwidth.

3. Device according to claim 1 or 2, characterized in that the nodes belonging to a particular geographical area operate with a common time base.

4. Device according to claim 1, 2 or 3, characterized in that the system operates with a time slot arrangement for the exchange of data and control commands between the nodes and in that each node is allocated its time slots in the system.

5. Device according to any of claims 1-4 characterized in that each node is allocated first time slots for the reception of data or control command(s) and second time slots for the transmission of data or control command(s).

6. Device according to any of the preceding claims, characterized in that the nodes operate with a number of types of message, for example a first message type which is intended for internal processing or forwarding to and/or receiving from equipment or information concerning the node, and a second type of message for transmission and/or reception via fixed connections.

7. Device according to any of the preceding claims, characterized in that one or more of the above-mentioned nodes are arranged to effect the control of the transmission power(s) in the respective nodes concerned as a function of a time selected or established in the system, called here common time.

8. Device according to any of the preceding claims, characterized in that one or more of the above-mentioned nodes comprise a device or devices arranged to control the propagation and/or the directions of their antenna lobe or lobes in accordance with a particular pattern or depending on the common time.

9. Device according to any of the preceding claims, characterized in that the system is arranged with one or more units, for example arranged in one or more nodes, which comprise and control, preferably completely automatically, the transmission and layout schedule for the nodes in the system.

10. Device according to any of the preceding claims, characterized in that the system is arranged in such a way that transmission and reception sequences which concern the node are distributed to the respective node.

11. Device according to any of the preceding claims, characterized in that for transmission to a second node located within the first node'"'"'s coverage area, a first node transmits with a signal strength which provides a reception signal at the second node which exceeds the interference level by a predetermined dB value, for example 10 dB.

12. Device according to claim 11, characterized in that additional nodes which are located within the coverage area of the first node and which can disregard the signalling between the first node and the second node are deactivated for transmission.

13. Device according to claim 12, characterized in that the additional nodes comprise devices which measure and record the signal strength from the first node and in that the recorded signal strength can be used in the time scheduling within the system.

14. Device according to any of the preceding claims, characterized in that nodes located outside the coverage area or areas of a first node for a particular period of time are able during the same period of time to form one or more other first nodes which establish coverage area or areas for one or more other second nodes.

15. Device according to claim 14, characterized in that second nodes which are outside the coverage areas of the first nodes during the relevant period or periods of time record that a reception signal has not been received or that a signal has been received with interference noise and in that this recording is incorporated in the scheduling for optimal bandwidth utilization.

16. Device according to any of the preceding claims, characterized in that in the case when a first node transmits to a second node and one or more additional nodes are located within the coverage area or areas of the first node, the additional node or nodes are arranged to establish control of the connection between the first node and the abovementioned second node(s).

17. Device according to claim 15, characterized in that in the event of interruption or interference, for example caused by temporarily reduced coverage area, in the transmission between the first node and the abovementioned second node, one or more of the additional nodes act as a relay station or stations and take over the connection which is interrupted or subject to interference.

18. Device according to claim 17, characterized in that the taking over of the connection between the first node and the second node by means of one or more relay station nodes is incorporated in the general scheduling of the system.

19. Device according to any of the preceding claims, characterized in that when there are two first nodes which are activated at the same time alongside each other in the system and their coverage areas each cover their own second nodes, one or both the nodes is arranged to change the direction of its coverage area temporarily in order to effect temporarily the exchange of data or control command (s) with a second node in the coverage area of the other first node.

20. Device according to claim 14, characterized in that different first nodes can be activated at successive times, in that for activation of a first node and transmission to a second node which is covered by the first first node'"'"'s coverage area(s) a first data or control command(s) can be transmitted and stored in the second node during one or more successive periods of time and in that the abovementioned second node during the periods of time allocated to it forms a first node which with its coverage area(s) covers the second node(s) belonging to the latter first node, and in that the abovementioned stored data or control command(s) can be forwarded to the latter second node or nodes and if necessary forwarded again.

21. Device according to any of claims 17-20, characterized in that relaying nodes forward data or control command(s) only with the knowledge that the data, control command(s) or message received during a certain period of time must be forwarded during a certain subsequent period of time in accordance with the scheduling of the behaviour of the node.

22. Device according to any of the preceding claims, characterized in that the communication by data and control command(s) in the system is based on a common time base and-time, called here global time.

23. Device according to claim 21, characterized in that the common time is based on a continuous time which is zeroed at regular intervals, so-called circular timing.

24. Device according to claim 22 or 23, characterized in that the nodes in the system operate with internal clocks and in that one of the system'"'"'s nodes is selected to determine the setting of the clocks in the other nodes by means of time-synchronization messages exchanged in the system in the form of digital signals, in that the respective nodes read off their respective clocks and actuate the time-synchronization messages at a predetermined offset, in that the selected node commences the time transmission in the system and attaches the time, in that other nodes'"'"' clocks synchronize themselves with the time of the selected node by deducting any deviations and in that the system thereafter relates to the common or global time thus established.

25. Device according to claim 22, 23 or 24, characterized in that in the determination of the common time from the selected node, other nodes take into account the delay of the data or control command(s) from the selected node, and/or in that the respective nodes compare subsequent time messages from the selected node and depending on the comparison corrects (adjusts) their clock with respect to deviations in the time.

26. Device according to any of the preceding claims, characterized in that the system is arranged for position determination of movable nodes.

27. Device according to claim 24, characterized in that the respective movable nodes are allocated a place in the schedule before their entry into the system, and in that the respective movable nodes signal to one or more schedule-monitoring or scheduling nodes either directly or via relaying nodes.

28. Device according to claim 25, characterized in that upon entry into the system the movable node synchronizes its clock with the common or global time, and in that the movable node thereafter, preferably while stationary, listens passively for a period of time to on-going traffic in the system and records reception times for the message(s) concerned and signal strength(s).

29. Device according to claim 27 or 28, characterized in that when convenient the movable node reports the time(s) and strength(s) of the signal or signals to the scheduling node and in that the scheduling node estimates the position of the respective movable node by comparing the signals and signal strengths obtained with other scheduled signalling in the time and propagation diagram.

30. Device according to claim 28 or 29, characterized in that the accuracy of the estimation of the geographical position of the respective movable node can be increased with an increased number of nodes which the movable node detects and/or with the length of the listening time.

31. Device according to any of claims 26-29, characterized in that the estimate of the geographical position is improved if the schedule is prepared for movable nodes and if a number of fixed nodes are instructed to listen for the movable node or nodes.

32. Device according to any of claims 27-31, characterized in that the respective movable node is provided with a movement-detecting unit, for example a gyro in combination with a calculation unit, which calculates the relative movement of the movable node, which calculated information together with any other information reduces the requirement for the movable node to be stationary while the measurements are carried out.

33. Device according to claim 32, characterized in that the other information comprises knowledge of the geography of the site, such as obstacles, walls, etc, in order to improve the determination of the geographical position.

34. Device according to any of claims 1-33, characterized in that a scheduling node can operate with a propagation diagram for a predetermined area in which the node in question is preferably centrally positioned, in that for scheduling the scheduling node commences transmission at a maximum power, for example 20 dBm, in accordance with a selected protocol, in that other fixed nodes located in the area adopt the listening position, in that the scheduling node transmits a number of time-stamped messages at the abovementioned maximum power so that other nodes can synchronize themselves with its clock in order to establish a common or global time, and in that the scheduling node thereafter transmits a transmission and/or reception schedule.

35. Device according to claim 34, characterized in that the respective receiving node listens for the time message, in that if the time message is received it records this together with the reception time, the signal strength for reception and whether a so-called CRC is correct, and in that if no message is received the signal strength of the background noise is recorded.

36. Device according to claim 33 or 34, characterized in that for the abovementioned transmission, reception and recording the scheduling node transmits a schedule in which the respective nodes, one by one, report their results, in that the scheduling node thereafter carries out the abovementioned transmission and the nodes concerned repeat the abovementioned reporting, but at a lower power, for example at 17 dBm, and so on until transmission and reporting have been carried out at the lowest output power, for example minus 10 dBm, after which the scheduling node compiles the results from the different transmissions and reports and uses these as the basis for later scheduling of the traffic in order to select a suitable output power and antenna for communication between interacting nodes.

37. Device according to any of claims 33-35, characterized in that for the scheduling of a movable node this can be given a measurement schedule which allows it to transmit continuously for a certain period of time, in that there is an exact position of the starting point and thereafter the position can be calculated using gyro data or similar data, and in that the movable node'"'"'s clock is synchronized at the starting point with the common time or global time.

38. Device according to any of claims 33-37, characterized in that one or more control points within the area are used for the measurement procedure or the scheduling of the movable node, in that the message in the movable node gives the output power, time and position, in that all fixed nodes in the system listen to and record messages which concern the specified position, and in that the signal strength of the movable node is estimated by compiling the results.

39. Device according to any of claims 33-38, characterized in that the movable node receives ongoing traffic, records the times and signal strengths of the received messages and its own position, and in that by compiling the results the movable node can estimate with what signal strength the different nodes can be received.

40. Device according to claim 38 or 39, characterized in that in addition to the scheduling of movable nodes, the abovementioned results can be used to calculate the positions of the movable nodes with the aid of the signal strengths of transmitted and received messages.

41. Device according to any of claims 33-40, characterized in that as the scheduling is based on a predetermined signal pattern, the known positions of the fixed nodes and the calculated positions of the movable nodes, the system can operate with messages which lack information about the identity of the sender and/or information about the content of the messages, which makes it possible for normal traffic to need to use only values, as all other information is known in advance.

42. Device according to claim 41, characterized in that the transmission time and the position of the information in the message are sufficient for the message to be able to be interpreted, which reduces the bandwidth required for a particular amount of information.

43. Device according to any of the preceding claims, characterized in that the system operates with cable connections or radio connections.