Patent Grant
8487781
This invention relates to sensor nodes acting as inductive loops to detect the presence and/or movement of vehicles on at least one roadway. The invention further relates to processors using at least one sensor node to communicate vehicle detection to a traffic management system. The vehicle detection is statistically compatible with the inductive loop response to the vehicles. The invention also relates to the sensor nodes, and/or their installation, configuring at least one of the sensor nodes to implement the inductive loop compatibility. The invention also relates to clusters of sensor nodes, referred to herein as sensor clusters, installed in a roadway to act as inductive loops.
Inductive loops have been employed for years in traffic management systems to provide vehicle detection and are often used to monitor traffic flow. When properly installed and maintained, the inductive loops provide a high level of accuracy. However, they are prone to fail due to any of the following: cracks in the pavement, freeze and thaw cycles, roadway displacement, poor installation, construction on the roadside and/or the roadway. When any part of the inductive loop wiring is damaged or destroyed, detecting vehicles with the inductive loop becomes erratic or stops entirely.
Detection devices are needed to solve the reliability problems of inductive loops. These detection devices need to be reliable, long lasting and/or more immune to the problems of weather and aging of the roadways and the detection devices.
Before discussing the various embodiments of the invention, there is another problem to point out. Until recently, inductive loops were the only vehicle detection devices used in most, if not all, traffic management systems. As various adaptive control systems and programs evolved to handle traffic control, they exclusively relied on these inductive loops. In some situations more recent vehicle detection sensors have turned out to be more sensitive than the inductive loops. However, the owners and managers of pre-existing traffic management systems may require that the newer sensors be just as insensitive as the old inductive loops in order to minimize upgrade expenses and/or compatibility issues to the adaptive control software.
The apparatus embodiments of the invention may include a processor configured to use at least one sensor node positioned in a roadway to detect a vehicle passing near the sensor node. A vehicle detection is generated that is statistically compatible with the detection of the vehicle by an inductive loop. The vehicle detection may be used by a traffic management system to provide a traffic flow estimate of the roadway.
Other apparatus embodiments may include sensor clusters configured to act like an inductive loop in response to a vehicle passing near the apparatus. The sensor cluster may include a first and second sensor node, with the first sensor node configured to generate a start of the vehicle detection and the second sensor node configured to generate an end of the vehicle detection. Both sensor nodes may be installed so that the vehicle approaches the first sensor node before traveling away from the second sensor node.
The sensor node may include a wireless transceiver and/or a magnetic sensor. The wireless transceiver may be configured to deliver at least part of the vehicle detection. The magnetic sensor may be configured to respond to the presence of the vehicle to generate at least part of the vehicle detection. The magnetic sensor may employ the Hall effect and/or a magneto-resistive effect, to respond to the presence of the vehicle. The sensor node may also include a wireline transceiver, possibly compliant with a wireline communications protocol.
The processor may include at least one instance of a finite state machine and/or of a computer. The processor may further include a memory that may be configured for access by the finite state machine and/or by the computer. The memory may contain a program system and/or an installation package configured to instruct the computer to install the program system in the finite state machine and/or the computer.
Embodiments of the invention include a server, an installation device, and/or a computer readable memory, configured to deliver the program system and/or the installation package to the processor.
The program system may include at least one of the program steps of generating the vehicle detection by using the sensor node response to the presence of the vehicle and/or sending the vehicle detection to the traffic management system. Various embodiments may implement these program steps differently. For instance, generating the vehicle detection may include altering the vehicle detection to be compatible with the inductive loop for a specific traffic management system and/or the adaptive control system. The alteration may alter the ending time and/or the start time of the vehicle detection. The alteration may retard or extend one or both of these times. As used herein, retarding a time moves it earlier and extending a time moves it later.
The apparatus may include an access point and/or a router to communicate with the sensor node to support the processor using the sensor node. The access point and/or the router may include the processor.
In other embodiments, the processor may be included in a traffic controller, the traffic management system and/or the adaptive controller. Alternatively, the processor may be an independent component communicating with the traffic controller, the traffic management system and/or the adaptive controller.
This invention relates to sensor nodes acting as inductive loops to detect the presence and/or movement of vehicles on at least one roadway. The invention further relates to processors using at least one sensor node to communicate vehicle detection to a traffic management system that is statistically compatible with the inductive loop response to the vehicles. The invention also relates to the sensor nodes and/or their installation configuring at least one of the sensor nodes to implement the inductive loop compatibility. The invention also relates to the sensor clusters of sensor nodes installed in a roadway to act as inductive loops.
In various embodiments of the invention, the vehicle 6 may include at least one of a bicycle, an automobile, a truck, a tractor, a trailer, and/or an airplane. Traffic reports may be provided for bicycles separate from automobiles, etc. traveling through intersections such as the MIMO node 7.
The wireless communications 26 will be discussed in greater detail later. The traffic controller 32 may communicate 38 with the traffic management system 38 to deliver the first vehicle detection 300-1 based upon the response of the third sensor node 20-3 and/or the sensor cluster 22, as well as the second vehicle detection 300-2 resulting from 31 the first inductive loop 30-1 responding to the vehicle 6 passing near 4 the first inductive loop.
By way of example, three sensor nodes 20-1, 20-2 and 20-3 may be positioned in pavement in the first in Lane 8 and the first out lane 8 the roadway 9. These two lanes feed the left side of the MIMO node 7.
A sensor cluster 22 may include a first sensor node 20-1 and a second sensor node 20-2 that may contribute their responses to the vehicle 6 passing near 4 them to generate the first vehicle detection 300-1 by the processor 200. The sensor cluster 22 may be configured to act like an inductive loop 30 in response to the vehicle 6 passing near 4 to the sensor nodes. Both sensor nodes may be installed so that the vehicle 6 approaches the first sensor node 20-1 before traveling away from the second sensor node 20-2. The first sensor node 20-1 may contribute to indicating the start 302 of the first vehicle detection. The second sensor node 20-2 may contribute to indicating the end 304 of the first vehicle detection.
The traffic management system 50 may preferably find the response of the sensor cluster 22 and/or the third sensor node 20-3 to be statistically compatible with the second vehicle detection 300-2 generated based upon the response of the first inductive loop 30-1 to a vehicle 6 passing near 4 the first inductive loop. The traffic management system may use these two vehicle detections 300-1 and 300-2 in a compatible fashion to generate a traffic flow estimate 308 of the various lanes 8 in the roadway 9.
Because of the compatibility of the first vehicle detections 300-1 from the sensor nodes 20-3 and/or the sensor cluster 22 with the second vehicle detections 300-2 from the inductive loop, the traffic management system can generate the traffic flow estimate 308 from any combination of inductive loops 30-1 and/or 30-2, the third sensor nodes 20-3 and/or the sensor cluster 22.
Further, these traffic flow estimates 310 may be used by an adaptive control system 52 to control the traffic on the roadway 9 and/or at the MIMO node 7 through the generation of a signal plan update 320 that may be sent via 38 to the traffic controller 32 to potentially alter and/or generate the traffic signal plan 36. The traffic controller may direct the traffic signals 33 based upon the traffic signal plan to implement the traffic management system's control the traffic flow.
The processor 200 may generate the first vehicle detection 300-1 in response to the sensor nodes 20 positioned in the roadway 9, more specifically in a lane 8 to detect a vehicle 6 passing near 4 one or more of the sensor nodes 20-1, 20-2 and/or 20-3.
The traffic controller 32 may, for example, include of a Model 170, and/or a Model 2070, and/or a NEMA TS1 detector rack, and/or a NEMA TS2 detector rack. The following are considered fairly standard terms for traffic controllers, either as the result of a standardization group and/or through common use: NEMA, 170, 2070, and ATC. As of the time of filing this patent application, the following companies were considered to manufacture implementations of the traffic controller 32: Scae, Peek, Siemens, Econolite, and Naztec. Note that this list is not meant to be exhaustive, but rather to provide examples of the start of the art at the time of the filing of this application.
As another set of examples, the traffic management system 50 may include at least one of the following:
The traffic management system 50 may adaptively direct via communication 38 the traffic controller 302 in response to the traffic flow estimate 308. The traffic management system may further adaptively direct based upon an adaptive control system 52, for example, as at least one of the following:
The adaptive control system 52 may be implemented as a processor, like the processor 200, or as the processor 200. Alternatively, the adaptive control system 52 may be implemented as a program system, which will be described in greater detail starting with
At least one of the sensor nodes 20, such as 20-1, 20-2 and/or 20-3, may include a wireless transceiver 23 to at least partly deliver the vehicle detection 300 and/or the sensor node may include a magnetic sensor 24 configured to respond to the presence of the vehicle 6 to at least partly generate the vehicle detection 300, as further shown in
Sending the vehicle detection 300 may also vary between different implementations. In some embodiments, the sending may support triggering a switch or relay to ground to assert vehicle 6 presence and may trigger to a voltage, say 12, 24 and/or 48 volts to unassert the vehicle presence. In other embodiments assertion and its logical complement, unassertion may be reversed. In yet other embodiments, sending the vehicle detection may involve packets and/or messages sent compliant with a wireline and/or wireless communication protocol.
The wireless transceiver 23 may employ at least one wireless communications protocol that may employ at least one of the following: a time division multiple access protocol, a frequency division multiple access protocol, a code division multiple access protocol, a frequency hopping multiple access protocol, a time hopping multiple access protocol, a near-field wireless connection and/or a wavelet division multiple access protocol.
The magnetic sensor 24 may employ the Hall effect 25 and/or a magneto-resistive effect 26, to respond to the presence of the vehicle 6 passing near 4 the magnetic sensor 24 to at least partly generate the vehicle detection 310.
The sensor cluster 22 may have its effective width, referred to herein as the sensor cluster width W1 that may approximate the inductive loop width within a range of no more than 20 percent, in other words, from 80% of the W0 to 120% of the W0. In other situations, W1 may approximate W0 to within 10% and in certain situations, to within 5%.
The inductive loop 3 have an effective length of L0, which may be greater than three meters and may further be less than six meters. The effective length L0 may further be greater than three and a half meters and less than five meters. In some situations, the effective length L0 may be specified as four and a half meters to within a range of ten percent or less.
The sensor cluster 22 may have two or more length parameters associated with it. Some of these parameters (L1 and L2) may be associated with a front 21 of the sensor cluster where a vehicle 6 most probably enters the sensor cluster's ability to sense its presence, whereas other parameters such as L3 may not need to be directly associated with the front.
The magnetic sensor 24 may further generate a sensor reading, which will be referred to as the raw signal 10, in response to the presence of the vehicle 6 in at least two and possibly three dimensions, with the sensor reading being used to at least partly generate the vehicle detection 300.
While
Various embodiments may be implemented differently, the sensor node 20 response to the vehicle 6 may include extending the vehicle detection 300 to be compatible with the inductive loop 30 for a specific adaptive control system 52. By way of example, if the adaptive control system 52 employs SCATS, the extension may vary based upon the estimate speed of the vehicle. Another example, if the adaptive control system employs SCOOT, the extension may be a fixed amount, say about 200 milliseconds.
The vertical axis represents a Boolean value, which is asserted in the low state and unasserted in the high state. The horizontal axis represents time, which may be measured in time increments, such as seconds or fractions of seconds.
Generating the vehicle detection 300 may include altering the vehicle detection to be compatible with the inductive loop 30 for a specific traffic management system 50 and/or the adaptive control system 52. The alteration may alter the ending time 304 and/or the start time 302 of the vehicle detection 300. The alteration may retard or extend one or both of these times. As used herein, retarding a time moves it earlier and extending a time moves it later.
The start time 302 of the first vehicle detect 310-1 may be merged with the end time 304 of the second vehicle detect 310-2 to generate the vehicle detection 300, both of which may not be extended in some embodiments.
To summarize the examples of altering the start times 302 and the end times 304 in certain embodiments of the vehicle detection 300 supporting inductive loop 30 compatibility: The end time 304 may be extended by a DeltaT to insure the compatibility, which is seen in the third trace. The start time 302 may be retarded by DeltaT1, which is seen in the fifth trace.
The sensor node 20 may also include a wireline transceiver 28 possibly compliant with a wireline communications protocol. The wireline communications protocol may be Ethernet, possibly Power Over Ethernet, and/or RS-485. The wireline communication 122 may be arranged in a fault tolerant network that can lose a percentage of its wire lines and still function.
The memory 208 may include an installation package 240 that may be configured to instruct the computer to install the program system 250 to instruct the computer and/or to configure the FSM 202. In some embodiments, the processor may include more than one instance of the FSM 202 and/or more than one instance of the computer 204, and the installation package 250 may be used to install the program system 250 into some and/or all the instances.
As used herein, a FSM 202 may be configured to receive at least one input, maintain at least one state and generate at least one output in response to a value of at least one of the inputs and/or in response to the value of at least one of the states. The FSM configuration 242 may be used to configure the FSM 202 implemented by a programmable logic device, such as a Field Programmable Gate Array (FPGA) to at least partly implement the processor 200.
As used herein, the computer 204 may include at least one instruction processor and at least one data processor with at least one of the instruction processor instructed by at least one of the instruction processors in response to the program system 250, possibly through accesses of the memory 208 by the computer.
As used herein, the installation package 240 may be configured to instruct the computer 204 to install the program system 250 and/or may be configured to instruct the computer and/or the FSM 202 to install the FSM configuration 242. In some embodiments the installation package may include files or folders that may be nested one or more layers deep, which may or may not be compressed. The files may include text that may be compiled, or translated, or linked, or loaded by the computer to at least partly generate and/or install the program system and/or the FSM configuration.
As used herein, the memory 208 and/or the computer readable memory 214 may include at least one instance of a volatile and/or a non-volatile memory component. A volatile memory component tends to lose its memory contents without a regular supply of power, whereas a non-volatile memory component tends to retain its memory contents without needing such a regular supply of power.
The memory 208 and/or the computer readable memory 214 and/or the server 212 and/or the installation device 210 may include various communications interfaces to deliver the program system 250, the installation package and/or the FSM configuration 242:
These two program steps 270 and 280 may have different implementations in order to insure statistical compatibility with inductive loops 30 for differing embodiments of the traffic management system 50, the adaptive control system 52, the MIMO node 7 and/or the roadway 9.
A sensor node 20 and/or the processor 200 may respond to the passage 4 of a vehicle 6 near the sensor node, for instance, the first sensor node 20-1 and/or the second sensor node 20-2 by using a raw signal received as a magnetic sensor signal from the magnetic sensor to generate a start time and an ending time for the vehicle passing near the magnetic sensor, by performing the following steps:
Note that in various embodiments, the quantities and/or the Boolean values shown in
The preceding discussion serves to provide examples of the embodiments and is not meant to constrain the scope of the following claims.
This patent application claims priority to Provisional Patent Application No. 61/369,033, filed Jul. 29, 2010, entitled “Sensor Nodes Acting as Inductive Loops for Traffic Sensing” which is incorporated herein in its entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 6337640 | Lees | Jan 2002 | B2 |
| 6342845 | Hilliard et al. | Jan 2002 | B1 |
| 6345228 | Lees | Feb 2002 | B1 |
| 6483443 | Lees et al. | Nov 2002 | B1 |
| 20070050240 | Belani et al. | Mar 2007 | A1 |
| 20080238720 | Lee | Oct 2008 | A1 |
| 20080287144 | Sabata et al. | Nov 2008 | A1 |
| 20100017103 | Kwong et al. | Jan 2010 | A1 |
| 20100073154 | Kim et al. | Mar 2010 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20120026013 A1 | Feb 2012 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61369033 | Jul 2010 | US |
