U.S. patent application number 11/652398 was filed with the patent office on 2007-07-12 for visual mapping of field device message routes in a wireless mesh network.
This patent application is currently assigned to Fisher-Rosemount Systems, Inc.. Invention is credited to Patrick M. Dobrowski, Eric R. Lovegren, Kelly M. Orth, Kyle L. Stotz.
Application Number | 20070161371 11/652398 |
Document ID | / |
Family ID | 38257020 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070161371 |
Kind Code |
A1 |
Dobrowski; Patrick M. ; et
al. |
July 12, 2007 |
Visual mapping of field device message routes in a wireless mesh
network
Abstract
A control system uses a wireless mesh network to provide
communication between a host computer and field devices.
Performance of the wireless mesh network is monitored by collecting
network performance data from each node, such as the nodes with
which it is communicating, received signal strengths over links to
different nodes, the number of errors occurring on each link, and
how frequently communication is occurring with each of the other
nodes. A visual network map is generated using performance
statistics based on the data gathered from the nodes of the
wireless mesh network. The visual network map allows a user to
determine the routes that messages take through the wireless mesh
network, diagnose potential problems, and make adjustments to
improve network performance.
Inventors: |
Dobrowski; Patrick M.;
(Burnsville, MN) ; Lovegren; Eric R.; (Big Lake,
MN) ; Orth; Kelly M.; (Apple Valley, MN) ;
Stotz; Kyle L.; (Plymouth, MN) |
Correspondence
Address: |
KINNEY & LANGE, P.A.
THE KINNEY & LANGE BUILDING
312 SOUTH THIRD STREET
MINNEAPOLIS
MN
55415-1002
US
|
Assignee: |
Fisher-Rosemount Systems,
Inc.
Austin
TX
|
Family ID: |
38257020 |
Appl. No.: |
11/652398 |
Filed: |
January 11, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60758167 |
Jan 11, 2006 |
|
|
|
Current U.S.
Class: |
455/423 ;
455/456.3 |
Current CPC
Class: |
H04W 40/08 20130101;
H04L 45/22 20130101; H04W 52/02 20130101; H04W 92/00 20130101; H04W
8/26 20130101; H04L 47/10 20130101; H04W 56/00 20130101; H04L 47/28
20130101; H04W 40/00 20130101; H04W 40/10 20130101; H04L 41/22
20130101; H04L 45/24 20130101; H04L 41/12 20130101; H04W 40/22
20130101; Y02D 30/70 20200801; G05B 2219/31162 20130101; H04L 47/34
20130101; H04W 52/0229 20130101; H04W 80/00 20130101; H04W 16/18
20130101; H04W 52/0225 20130101; H04L 45/28 20130101; H04W 24/08
20130101; H04L 47/14 20130101; H04W 40/24 20130101; H04W 16/22
20130101; H04W 28/02 20130101; H04L 43/045 20130101; H04W 4/18
20130101; H04W 84/18 20130101; H04L 41/00 20130101; H04W 88/16
20130101; H04W 76/20 20180201 |
Class at
Publication: |
455/423 ;
455/456.3 |
International
Class: |
H04Q 7/20 20060101
H04Q007/20 |
Claims
1. A method of assessing performance of a wireless mesh network
having a plurality of nodes, the method comprising: collecting
positional information relating to the nodes; collecting network
performance data from the nodes; and generating a visual
representation of the network based upon the positional information
and the network performance data.
2. The method of claim 1, wherein the visual representation
includes an icon representing each node, and wherein each icon is
positioned in the visual representation based upon the positioned
information.
3. The method of claim 2, wherein the visual representation
includes lines connecting icons that represent communication links
between the nodes.
4. The method of claim 3, wherein the communication links are based
upon the network performance data.
5. The method of claim 2 wherein the visual representation includes
a representation of received radio signal strengths from
neighboring nodes.
6. The method of claim 1 wherein the network performance data
includes at least one of the received radio signal strength over a
link, lost messages over a link, and number of messages over a
link.
7. The method of claim 1 wherein the visual representation is
mapped on to a physical layout of an area where the nodes are
located.
8. A system comprising: a wireless mesh network having a plurality
of nodes; a gateway for collecting network performance data from
the nodes; data storage for storing the network performance data
and node positional data; a host computer including an application
program for generating a visual network map based upon the network
performance data and the node positional data; and a display for
displaying the visual network map.
9. The system of claim 8 and further comprising: a plurality of
field devices, each field device associated with one of the
plurality of nodes.
10. The system of claim 9 wherein the host computer sends messages
to and receives messages from the field devices through the gateway
and the wireless mesh network.
11. The system of claim 8 wherein the application program
dynamically updates the visual network map.
12. The system of claim 8 wherein the visual network map depicts
locations of nodes based upon the node positional data and depicts
wireless links between the nodes based upon the network performance
data.
13. The system of claim 12 wherein the visual network map includes
a layout of a physical plant in which at least some of the nodes
are received.
14. The system of claim 12 wherein the visual network map depicts
received radio signal strength over wireless links to nodes.
15. The system of claim 8 wherein the network performance data
includes at least one of received signal strength, lost messages,
and number of messages over links between nodes.
16. A method of assessing performance of a wireless mesh network
having a plurality of nodes, the method comprising: collecting
network performance data from the nodes; and displaying a visual
network map showing routes of messages through the wireless mesh
network, based upon the network performance data.
17. The method of claim 16 wherein the visual network map shows
positions of nodes of the wireless mesh network based upon node
positional data.
18. The method of claim 17 wherein the visual network map includes
lines between nodes representing wireless communication links, the
lines being derived from the network performance data.
19. The method of claim 16 wherein the wireless mesh network
includes a gateway, and wherein the gateway collects the network
performance data from the nodes.
20. The method of claim 16 wherein the visual network map includes
a depiction of a physical plant in which at least some of the nodes
are located.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from a co-pending
application entitled LOW POWER WIRELESS NETWORKS OF FIELD DEVICES,
Ser. No. 60/758,167, filed on Jan. 11, 2006, which is incorporated
by reference.
[0002] Reference is also made to co-pending applications filed on
even date with this application: CONTROL OF FIELD DEVICE ON LOW
POWER WIRELESS NETWORKS, Ser. No. ______; CONTROL SYSTEM WITH
WIRELESS ADDRESS DOMAIN TO FIELD DEVICE ADDRESS DOMAIN TRANSLATION,
Ser. No. ______; CONTROL SYSTEM WITH PREDICTIVE FIELD DEVICE
RESPONSE TIME OVER A WIRELESS NETWORK, Ser. No. ______; SELECTIVE
ACTIVATION OF FIELD DEVICES IN LOW POWER WIRELESS MESH NETWORKS,
Ser. No. ______; CONTROL OF LOW POWER WIRELESS NETWORKS FOR POWER
CONSERVATION, Ser. No. ______; and CONTROL SYSTEM WITH WIRELESS
MESSAGES CONTAINING MESSAGE SEQUENCE INFORMATION. Ser. No. ______,
which are incorporated by reference.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to wireless networks. In
particular, the invention relates to a wireless mesh network in
which process control messages are communicated between a host and
field devices at nodes of the wireless mesh network.
[0004] In many industrial settings, control systems are used to
monitor and control inventories, processes, and the like. Often,
such control systems have a centralized control room with a host
computer that communicates with field devices that are separated or
geographically removed from the control room.
[0005] Generally, each field device includes a transducer, which
may generate an output signal based on a physical input or generate
a physical output based on an input signal. Types of transducers
used in field devices include various analytical equipment,
pressure sensors, thermistors, thermocouples, strain gauges, flow
sensors, positioners, actuators, solenoids, indicators, and the
like.
[0006] Traditionally, analog field devices have been connected to
the process subsystem and the control room by two-wire twisted-pair
current loops, with each device connected to the control room by a
single two-wire twisted pair loop. Typically, a voltage
differential is maintained between the two wires of approximately
20 to 25 volts, and a current between 4 and 20 milliamps (mA) runs
through the loop. An analog field device transmits a signal to the
control room by modulating the current running through the current
loop to a current proportional to the sensed process variable. An
analog field device that performs an action under the control of
the control room is controlled by the magnitude of the current
through the loop, which is modulated by the ports of the process
subsystem under the control of the controller.
[0007] While historically field devices were capable of performing
only one function, more recently hybrid systems that superimpose
digital data on the current loop have been used in distributed
control systems. The Highway Addressable Remote Transducer (HART)
superimposes a digital carrier signal on the current loop signal.
The digital carrier signal can be used to send secondary and
diagnostic information. Examples of information provided over the
carrier signal include secondary process variables, diagnostic
information (such as sensor diagnostics, device diagnostics, wiring
diagnostics, process diagnostics, and the like), operating
temperatures, sensor temperature, calibration data, device ID
numbers, configuration information, and so on. Accordingly, a
single field device may have a variety of input and output
variables and may implement a variety of functions.
[0008] Another approach uses a digital communication bus to connect
multiple field devices to the host in the control room. Examples of
digital communication protocols used with field devices connected
to a digital bus include Foundation Fieldbus, Profibus, Modbus, and
DeviceNet. Two way digital communication of messages between a host
computer and multiple field devices can be provided over the same
two-wire path that supplies power to the field devices.
[0009] Typically, remote applications have been added to a control
system by running very long homerun cables from the control room to
the remote application. If the remote application is, for example,
a half of a mile away, the costs involved in running such a long
cable can be high. If multiple homerun cables have to be run to the
remote application, the costs become even higher. Wireless
communication offers a desirable alternative, and wireless mesh
networks have been proposed for use in industrial process control
systems. However, to minimize costs, it is also desirable to
maintain existing control systems and communication protocols, to
reduce the costs associated with changing existing systems to
accommodate the wireless communication.
[0010] In wireless mesh network systems designed for low power
sensor/actuator-based applications, many devices in the network
must be powered by long-life batteries or by low power
energy-scavenging power sources. Power outlets, such as 120 VAC
utilities, are typically not located nearby or may not be allowed
into the hazardous areas where the instrumentation (sensors) and
actuators must be located without incurring great installation
expense. The need for low installation cost drives the need for
battery-powered devices communicating as part of a wireless mesh
network. Effective utilization of a limited power source, such as a
primary cell battery which cannot be recharged, is vital for a well
functioning wireless device. Batteries are expected to last more
than 5 years and preferably as long as the life of the product.
[0011] In a true wireless mesh network, each node must be capable
of routing messages for itself as well as other nodes in the mesh
network. The concept of messages hopping from node to node through
the network is beneficial because lower power RF radios can be
used, and yet the mesh network can span a significant physical area
delivering messages from one end to the other. High power radios
are not needed in a mesh network, in contrast a point-to-point
system which employs remote nodes talking directly to a centralized
base-station.
[0012] A mesh network protocol allows for the formation of
alternate paths for messaging between nodes and between nodes and a
data collector, or a bridge or gateway to some higher level
higher-speed data bus. Having alternate, redundant paths for
wireless messages enhances data reliability by ensuring there is at
least one alternate path for messages to flow even if another path
gets blocked or degrades due to environmental influences or due to
interference.
[0013] Some mesh network protocols are deterministically routed
such that every node has an assigned parent and at least one
alternate parent. In the hierarchy of the mesh network, much as in
a human family, parents have children, children have grandchildren,
and so on. Each node relays the messages for their descendants
through the network to some final destination such as a gateway.
The parenting nodes may be battery-powered or limited-energy
powered devices. The more descendants a node has, the more traffic
it must route, which in turn directly increases its own power
consumption and diminishes its battery life.
BRIEF SUMMARY OF THE INVENTION
[0014] Performance of a wireless mesh network having a plurality of
nodes can be assessed using a visual representation of the network
that shows graphically the positions of the nodes and links between
nodes used to route messages through the mesh network. The visual
representation is based upon positional information relating to the
nodes and network performance parameters that are collected from
the nodes.
[0015] Network performance parameters can include, for example,
identification of other nodes with which a particular node has
established communication links, radio signal strength on each of
the links, number of lost messages or other errors on each link,
and how often communication occurs on each of the links. The visual
representation allows the user to inspect the communication paths
within the mesh network to identify potential problems and to make
adjustments to the network to improve communication
performance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a diagram illustrating a control system in which a
wireless mesh network routes wireless messages between a host and
field devices.
[0017] FIG. 2 is a flow chart of a method of providing a graphical
visualization of message routing and network performance of a
wireless mesh network.
[0018] FIGS. 3A and 3B are a visual network map of the wireless
mesh network of FIG. 1, formed using positional information and
performance statistics obtained from nodes of the wireless network
at different times.
[0019] FIGS. 4-6 show alternative visual network maps.
DETAILED DESCRIPTION
[0020] This invention provides a method for graphically visualizing
the route a message takes as it passes between nodes in a wireless
mesh network. In a typical control system, a host computer at a
control center interacts with field devices located within a
physical plant and displays information they have to offer. The
communication of messages between the host computer and the field
devices can be over wired connections or over a wireless mesh
network. In a low power wireless mesh network, a device message
does not pass from the host to the target field device directly; it
can take a multitude of routes within the wireless mesh network
before reaching its destination. In practice, it is desirable to
understand the routes messages take through the wireless mesh
network so that the topology of the physical network can be
adjusted if needed to enable the network to communicate in a more
desirable way. Presently there is no way for a qualified person to
inspect the dynamic nature of the wireless mesh network and see
this type of information so that adjustments could be made or
potential problems identified. This invention is a graphical method
to display the routes field device messages take as they travel
through a wireless mesh network on their way to their destinations.
The user can be provided a visual representation of the wireless
network (i.e. a visual network map) in which each node of the
network is represented by an icon. Lines are drawn interconnecting
the icons that represent the communication links between wireless
nodes. The graphical display can be dynamic in nature, in that the
paths through the network will be updated in real time based upon
network performance data collected from the nodes.
[0021] FIG. 1 shows control system 10, which is an example of a
system in which the visual mapping of signal routing in a wireless
network can be used. Control system 10 includes host computer 12,
highspeed network 14, and wireless mesh network 16, which includes
gateway 18 and wireless nodes 20, 22, 24, 26, 28, and 30. Gateway
18 interfaces mesh network 16 with host computer 12 over highspeed
network 14. Messages may be transmitted from host computer 12 to
gateway 18 over network 14, and are then transmitted to a selected
node of mesh network 16 over one of several different paths.
Similarly, messages from individual nodes of mesh network 16 are
routed through mesh network 16 from node-to-node over one of
several paths until they arrive at gateway 18 and are then
transmitted to host 12 over highspeed network 14.
[0022] Control system 10 can make use of field devices that have
been designed for and used in wired distributed control systems, as
well as field devices that are specially designed as wireless
transmitters for use in wireless mesh networks. Nodes 20, 22, 24,
26, 28, and 30 show examples of wireless nodes that include
conventional field devices.
[0023] Wireless node 20 includes radio 32, wireless device router
(WDR) 34, and field devices FD1 and FD2. Node 20 is an example of a
node having one unique wireless address and two unique field device
addresses.
[0024] Nodes 22, 24, 26, and 28 are each examples showing nodes
having one unique wireless address and one unique field device
address. Node 22 includes radio 36, WDR 38, and field device FD3.
Similarly, field device 24 includes radio 40, WDR 42, and field
device FD4; node 26 includes radio 44, WDR 46, and field device
FD5, and node 28 includes radio 48, WDR 50, and field device
FD6.
[0025] Node 30 has one unique wireless address and three unique
field device addresses. It includes radio 52, WDR 54, and field
devices FD7, FD8, and FD9.
[0026] Wireless network 16 is preferably a low power network in
which many of the nodes are powered by long life batteries or low
power energy scavenging power sources. Communication over wireless
network 16 may be provided according to a mesh network
configuration, in which messages are transmitted from node-to-node
through network 16. This allows the use of lower power RF radios,
while allowing the network 16 to span a significant physical area
to deliver messages from one end of the network to the other.
[0027] In control system 10, host computer 12 interacts with field
devices FD1-FD9, and displays information contained in messages
received from field devices FD1-FD9. In wireless mesh network 16,
messages from host computer 12 to field devices FD1-FD9, and
messages from field devices FD1-FD9 back to host computer 12 can
take multiple routes through network 16 before reaching a final
destination. FIG. 1 shows a simplified system, with only six
wireless nodes 20-30; it is possible, however, for wireless mesh
network 16 to have many more nodes, and therefore many more
potential routes for messages to travel.
[0028] In practice, it is desirable to understand the routes that
messages take through a wireless mesh network, so that that the
topology of the physical network can be adjusted if needed to
enable to the wireless mesh network to communicate effectively. In
the past, users have not been provided with an ability to inspect
the dynamic nature of a wireless mesh network in order to identify
strengths and weaknesses of the network, to diagnose and
troubleshoot problems within the network, to detect changes in
network performance that may be caused by damage to one or more
nodes, or to detect changes in performance due to changes in the
physical plant in which the network operates that can introduce new
sources of interference to wireless links between nodes.
[0029] Method 40, illustrated in FIG. 2, provides a tool by which
the user can assess performance of a wireless mesh network in order
to identify potential problems and to take corrective action. Using
positional information indicating the location of each node (step
42) and performance information gathered from each node (step 44),
a visual representation of the wireless network is generated (step
46). This visual representation can be a visual network map in
which each node of the network is represented by an icon. Lines can
be drawn between icons to represent communication activity between
the nodes. Other network performance parameters can also be
displayed as part of the map, such as received radio signal
strength on each link, error rate over particular links, and the
amount of activity occurring over each link.
[0030] The generation of a visual representation of the network
makes use of positional information relating to the nodes in order
to provide a physical layout of the topology of the wireless
network. The positional information can be gathered during
installation of the wireless network. The installer can provide
positional information of each node that is installed. The
positional information can be in the form of GPS coordinates, or
can be defined by relative position of the node to other structures
within an actual plant layout. Alternatively, some or all of the
nodes can include embedded GPS sensors, so that the GPS coordinates
of the node can be provided as part of messages sent over the
wireless mesh network. Still another alternative is to establish
positional information for certain nodes within the wireless mesh
network, and then use triangulation techniques in order to derive
the location of other nodes.
[0031] The position data is collected and stored in a database.
When new nodes are added to the network, or existing nodes are
moved, the position information must be updated in order for the
positions of the nodes to be accurately portrayed in a visual
network map.
[0032] The positional information allows a visual network map to
accurately show the relative positions of the nodes of the wireless
mesh network. In addition, the positional information can be used
to map the nodes of the network on to an image of the actual plant
layout. This can be used to show relative location of the nodes to
other physical objects in the plant, which may for example,
interfere with communication between particular nodes.
[0033] When control system 10 is first initialized, network
performance data is collected from each node. For a given node, the
performance data includes an identification of the nodes with which
the given node has established communication links. The performance
data may also include the number of transmissions occurring over
each established link, how many errors have occurred over each
link, and the signal strength of received signals over each
link.
[0034] This performance data is reported in messages sent to
gateway 18 and may be stored at gateway 18, or sent on to host
computer 12. In either case, as performance data is collected from
each node, the visual network map can be built up using that data.
Once data has been collected from all nodes, a complete map can be
displayed.
[0035] In the simplest form, the visual network map shows the
physical location of each node, and the links established by that
node with neighboring nodes. By viewing the nodes and the links,
the pathways over which messages are routed to a particular node
(and the field device located at that node) can be determined.
[0036] As the network continues to operate, performance data is
collected so that the visual network map can be updated
dynamically. The collection of performance data from the nodes can
occur at regularly scheduled times, or can be performed on demand
in response to a command sent to each of the nodes from gateway 18.
The on-demand collection of data may be initiated by a user
interacting with host computer 12.
[0037] The display of visual network maps occurs at host computer
12, although the display can occur at other locations as well. An
application program running on host computer 12 uses the stored
positional information and network performance data to create a
visual network map in one of several different formats, as
requested by a user. As new data is gathered from wireless network
16, the application dynamically redraws visual network maps by host
computer 12.
[0038] FIG. 3A shows visual network map 50, which represents
operation of wireless mesh network 16 at a first time. In this
example, visual network map 50 shows each node 20-30 as a square
block. Established communication links L1-L10 between the various
nodes 20-30 are represented by straight lines between nodes.
[0039] In this particular example, other performance data, such as
error rates, signal strengths, or frequency of use of a link are
not shown on map 50. However, other versions of the visual network
map can provide that information in various graphical forms. In
addition, visual network map 50 may include capability of a user
moving an arrow or cursor to select a particular link. When a
particular link is selected, a display of performance data specific
to that link can be provided. Similarly, selection of a particular
node can result in a display of network performance information
associated with that node. In addition to the data discussed above,
other parameters relating to operation of the nodes can be
displayed. For example, battery life at each node could be checked
as part of a visual inspection of the network using the
display.
[0040] FIG. 3B shows visual network map 50 at a later time, at
which communication between nodes 24 and 26 is no longer occurring.
Link L6 (shown in FIG. 3A) is not present in FIG. 3B. This may be
the result of damage or malfunction at one or the other of the
nodes, or by the introduction of a new source of interference, such
as a new piece of equipment, within the plant where network 16 is
installed. By monitoring changes in the links shown in visual
network map 50, a user can identify a potential problem, and
determine what corrective action, if any, is necessary. For
example, the addition of another node in the vicinity may provide
an alternative path to replace the link that no longer exists
directly between nodes 24 and 26. Alternatively, one of the nodes
may need to be repositioned in order to reestablish the link.
[0041] FIGS. 4-6 show other display formats and different numbers
of nodes. In FIG. 4, visual network map 60 includes a large number
of nodes N and links L are shown for a system much larger than
control system 10 of FIGS. 1, 3A and 3B. Multiple wireless networks
are shown in map 60. FIG. 5 illustrates visual network map 70,
which includes nodes N and links L superimposed on plant layout P.
In FIG. 6, signal strength charts S are shown as part of map 80. A
wide variety of display formats, using different network
performance data, is available to provide the user with information
needed to assess the performance of the wireless mesh network.
[0042] Although the present invention has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes may be made in form and detail without
departing from the spirit and scope of the invention.
* * * * *