AU712013B2 - Distributed adaptive traffic control system - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 0 *e pp P p S P

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ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "DISTRIBUTED ADAPTIVE TRAFFIC CONTROL SYSTEM" The following statement is a full description of this invention, including the best method of performing it known to us: 2 DISTRIBUTED ADAPTIVE TRAFFIC CONTROL SYSTEM This invention relates to a controller, for vehicle and pedestrian traffic light control, based on a system of distributed functional processing incorporated in multiple microprocessors.

BACKGROUND TO THE INVENTION A conventional traffic controller comprises a large control box, normally located on one corner of an intersection, that receives a mains power input and switches the mains power to the various traffic control lights. The entire system is based on mains power which leads to a heavy :10 switching and cabling requirement. Each traffic lantern requires a pair of cables as does each pedestrian lantern. All cable pairs are run back to the traffic controller. This system results in 60 or more cable pairs converging at the traffic controller.

a. ao The controller switches the traffic lanterns and pedestrian lanterns according to a programmed sequence. In some cases the sequence can a change in response to changed traffic volume conditions or in response to commands input at the controller or from a remote location. In prior art controllers the command sequence required to effect a change in operating conditions is complex. A typical controller has a limited number of available command sequences, each requiring a hexadecimal input code. The display of operating parameters is similarly restrictive, commonly being no more than a single line alphanumeric display.

Systems are known for linking individual controllers into a network 3 with a central command station. Such systems generally provide a more 'user friendly' interface for control of traffic lights at individual intersections and as part of the network. Typically, a linked system controller uses a high level programming language running on a multi-user multi-tasking platform, such as UNIX, to collect data from a range of sources and to transmit commands to the traffic controllers in the network. Although such sophisticated systems overcome a number of the disadvantages of prior art traffic control techniques they are impractical for single intersection controllers.

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:10 Improvements in single intersection controllers have been made in .o* recent years. Reference may be had to United States Patent number 5309155 in the name of Hsein et al. This patent discloses a control apparatus for traffic lights comprising a main control device and a plurality So of lamp control devices each connected to one or more lamps. A power 15 transmission ring line connects the main control device and the lamp i control devices. The Hsein apparatus utilises power line carrier communication technology to transmit control signals between the main control device and the lamp control devices which in turn control the operation of the lamps.

Power line carrier communication is prone to errors due to noise inherent in the power line and is therefore a less than satisfactory communication medium for traffic control. Furthermore, Hsein does not appear to have made provision for flashing amber lights.

In general, prior art technology takes a system approach to traffic light control and does not monitor individual lanterns. This approach can result in chaos at an intersection if one lamp is giving erroneous signals.

Most prior art traffic conditions do not detect and correct this condition.

OBJECT OF THE INVENTION It is an object of the present invention to provide a traffic control system that utilises distributed processing to minimise cabling requirements.

It is a further object to provide a traffic control system that is able to utilise a graphical user interface.

DISCLOSURE OF THE INVENTION In one form, although it need not be the only form, the invention resides in a traffic control system comprising: a main control module incorporating one or more processor means for coordinating the operation of the traffic control system; at least one traffic light assembly in signal connection with the main a a° control module, said traffic light assembly incorporating one or more ao.

processor means for local control of traffic lanterns; a power control module for supplying power to the traffic control system on a power loop, said power control module incorporating one or more processor means for controlling supply of power; and *a command cable loop providing signal connection between the main control module and the traffic light assembly for carrying command a. signals and a confirm cable loop providing signal connection between the main control module and the traffic light assembly for carrying confirm signals.

The main control module preferably incorporates a user interface card for providing a graphical user interface between a user and the traffic control system. The graphical user interface suitable incorporates a liquid crystal touch screen display.

The main control module preferably incorporates a computing (PC) backplane and a traffic control (TC) backplane. The PC backplane provides computational, storage and user interface functions. The TC backplane provides monitoring and command/confirm loop functions.

The traffic light assembly preferably comprises processor means for receiving signals from one or more detectors and sending signals to traffic lanterns. The traffic lanterns suitably comprise red, green and amber vehicle control lanterns as well as red and green pedestrian control lanterns. The traffic light assembly provides local traffic lantern S"control but communicates with the main control module for timing 9 :coordination.

*o °•The power control module preferably converts mains power input 20 to power for the operation of the traffic control system including DC voltages for logic elements and extra low AC voltages (ELV) for powering the traffic lanterns.

In preference the power loop is in electrical connection with the 6o main control module, traffic light assembly and power control module.

BRIEF DETAILS OF THE DRAWINGS To assist in understanding the invention preferred embodiments will now be described with reference to the following figures in which: FIG 1 is a schematic block diagram of a traffic light control system in accordance with a first embodiment of the present invention; FIG 2 is a block diagram of the components of the main control module of the first embodiment; FIG. 3 is a block diagram of the power control module; FIG 4 is a block diagram of the traffic light assembly; FIG 5 is a screen showing an aspect of the graphical user interface of the first embodiment; FIG 6 is a screen display showing a second aspect of the graphical user interface; FIG 7 is a screen display showing a third aspect of the graphical user interface; FIG 8 is a screen display showing a fourth aspect of the graphical user interface.

DETAILED DESCRIPTION OF THE DRAWINGS 20 The vehicle and pedestrian traffic control system is based on distributed functional processing incorporated in multiple microprocessors. The system incorporates the ubiquitous and highly developed PC based chipset technology to facilitate an accessible and user friendly interface *r 9

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a -a 7 for the operator, provide multiple coterminous timing functions and monitoring activities. The core traffic control function is provided by a system of distributed microprocessors located in a main control module and a number of lantern control modules. Data is pre-processed in the distributed microprocessors and passed to a central processor in a packaged form.

In the drawings, like reference numerals refer to like parts.

Referring to FIG 1, the traffic light control system comprises a main control module 1, power control module 2, traffic light assemblies 3 and detectors 4. The main control module 1 provides signals to control the power control module 2 on line 5. Control signals to the traffic light assemblies are transmitted on command loop 6 and confirmation signals from the traffic light assemblies 3 are transmitted to the main control module 1 on confirm loop 7. Power for the traffic light assemblies 3 is 15 supplied from the power control module 2 on the power loop 8. The main a. a control module 1 and power control module 2 are contained in a cabinet normally located at one corner of an intersection.

During normal operation each end of the command loop is separately 'driven' and each end of the confirm loop has its own receiver.

A simple open in either the command loop or confirm loop would not change the performance of the system. The integrity of the system is verified at 'power on' or when requested. The control module verifies the continuity of the two communication loops by connecting a transmitter to 8 one end and a receiver to the other end of each ring and sending a test message for the duration of the test.

Signals from the detectors 4 are provided directly to respective traffic light assemblies 3. The detector signals are also provided to the main control module 1 on confirm loop 7 via the respective traffic light assembly 3.

A safety flash loop 9 provides a fail safe signal to put the traffic light assemblies 3 into a 'flash amber' mode when required. The safety flash *o a facility isolates the traffic lights and replaces programmed operation with a 10 flashing amber signal generated from a pulsing (at flash rate 60/40) loll voltage supply feed.

The main control module 1 is shown in detail in FIG 2. The module 1 is based on two independent elements, 10 and 11, interconnected by dual port common memory such as a high speed 8K x 16 bit Sequential :i 15 Access Random Memory (SARAM) 12. Each element comprises a ale. a backplane and associated specialised circuitry. The sequential access port of the SARAM is connected to the PC backplane 10 and the random access port is connected to the specialised traffic controller backplane 11.

The SARAM module acts as a dual port common buffer memory between microprocessors.

The PC AT style backplane 10 utilises standard PC type circuit cards. The circuit cards include an industrial PC card 13 which provides all traffic control functions according to the program stored in on-board 9 memory. The program includes traffic movement and occupancy algorithms as well as user interface control, provision for constructing the graphical displays, error logging and analysis, historical data collection and other functions.

Also included is a user interface card 14 which provides a touch screen/liquid crystal display interface. The touch screen 15 is connectable to the PC backplane as required, but is not continuously resident in the main control module 1. A mass storage card 16 is provided to facilitate storage of data and programs on a mass storage device.

The traffic controller backplane 11 incorporates special cards designed specifically for the control, monitoring and operation of traffic S-lights. The lantern control card 17 provides signals on the command loop 6 for the control of the traffic light assemblies 3. The lantern control card 17 also receives signals from the traffic light assemblies 3 on the confirm loop 7. The cabinet monitor card 18 provides local control functions on a .i cabinet serial data bus 19. The cabinet monitor card 18 accepts inputs from a switch panel 21 and provides output to a light emitting diode display 22. There may be other inputs and outputs, as indicated by and other functions such as door open monitor, facility switch status (auto mode or flash mode), lantern status indication, detector status indication and manual detector input.

The cabinet monitor card 18 also provides a link between the main control module 1 and the power control module 2. The power control module 2 is shown in more detail in FIG 2.

The various cards 12, 13, 14, 16, 17 and 18 are interconnected by standard 16 bit PC data buses 23 and 24.

Extra functions can be added to the controller with minimal disturbance to existing programs and hardware as all CPUs read and write to the SARAM 12 at their own speed. This enables CPUs from different manufacturers and varying CPU types to be easily and effectively interconnected, thus multiple function driven CPUs facilitate the operation .9 9.

e 9 of the system.

The power control module 2 controls and monitors the electrical .O.o supply voltage used to operate the traffic control system. The system ~operates from 240VAC mains power which is converted to other required 9o t voltages by the power control module 2. Referring to FIG 3, the S. transformer 25 converts the 240VAC input to 12VDC and 5VDC required 15 for logic elements and local component power. A 24VDC switching regulator 26 generates 24VDC for activating the flash relay 27, described below with respect to FIG 4. Activation of the flash relay 27 is controlled by the CPU 28 through an opto-relay 29. A current monitor 30 monitors the flash relay activation.

The 240VAC main supply is also transformed by ELV transformer 31 to 48VAC an extra low voltage, such as 32VAC, for providing power to the traffic light assemblies 3 via the power loop 8. Using ELV offers a cabling advantage since communication cables and power cables can use 11 the conduit around the intersection. The inventors have found 32VAC to be preferably although voltages in the range 24VAC to 60VAC could be suitable.

A facility switch 32 switches operation of the power control module between AUTO, FLASH and OFF positions. The AUTO position is for normal operation controlled by the main control module 1. The FLASH position disables normally operation and activates the flash relay 27 to isolate the red 33 and green 34 lanterns (see FIG The CPU 28 4 *:.controls the opto-triac 35 to flash the ELV supply. The purpose of the 10 relays 36, 37 is to control high current switching to minimise arcing.

Steady state current goes through the relays 36, 37 but switching current °,°°ogoes through the triac 38. Timing of these operations is determined by the opto-coupler pair 39. The ELV is monitored by voltage monitor 40 and current monitor 41 15 A 100Hz phase locked loop 42 locked to the mains zero cross over generates an interrupt at the peak of each cycle whereupon the CPU performs all current and voltage checks. This is important to insure that during flashing amber the power triac is not 'half waving' (only positive OR negative cycle). Over an extended time this causes generation of heat and insulation breakdown in transformers. Current monitoring is employed to turn power to the lanterns off if it exceeds out of tolerance values (both above and below) based on the stored original value calibrated at commissioning. The integrity of the safety flash condition is 12 guaranteed by the current sensing circuit which monitors the safety-flash operation.

An RS485 interface 43 facilitates communication with the main control module 1. A serial EEPROM 44 provides local programme storage.

The traffic light assembly 3 is shown in detail in FIG 4 and comprises a lantern control module 45 that provides local control of the red 33, green 34 and amber 46 lanterns. The lantern control module receives signals from the main control module 1 on the command loop 6, 10 the detectors 4 (including vehicle identification detectors and vehicle detectors) on the vehicle detector bus 47, and pedestrian detectors 48.

The lantern control module 45 transmits signals to the main control module 1 on the confirm loop 7 and to the lanterns 33, 34 and 46. The traffic light assembly may incorporate a different lantern arrangement to that described above. The traffic control system may be applied to low usage control in which case the lanterns would normally be a red cross 0 and a green tick, or similar.

A CPU 49 performs local control in response to the signals from the main control module 1. Each traffic light assembly 3 has a unique address set by the dip switches 50. Signals from the main control module 1 have two parts, the first part is an address and the second part is a command.

The interfaces 51 and 52 facilitate communication between the main control module 1 and the CPU 49.

13 A decoder 53 receives signals from the CPU 49 and switches the opto-triacs 54, 55 and 56 which switch the triacs 57, 58 and 59 to switch power to the lanterns 33, 34 and 46. The purpose and operation of the flash relay 27 has been described previously.

The triac currents and lamp integrity are monitored by monitor The monitor is multiplexed according to the address decoded by decoder 61. The function of the monitor includes measuring the impedance of the lamp circuit during 'off time. The monitor output is supplied to the CPU 49 from which local decisions are made regarding fault reporting to the main control module 1.

The lantern control module 45 may also transfer data to and control the operation of driver information signs(not shown) located in the proximity of the intersection.

Synchronisation of the distributed processors including CPU 49, CPU 28 and the processors in cards 13, 17, 18 is conveniently effected by an ASCII break character transmitted by PC card 13. Synchronisation of the processors is important for maintaining correct operation. The break character can be sent at any time in the programme cycle and is completely software controllable.

The PC chipset drives a familiar screen display based on the personal computer presentation style. An active matrix 640x480 LCD touch screen user interface provides a suite of functions associated with a PC based VGA screen incorporating 16K colours, enhanced real time 14 graphic display, informative text, and standard icons for control of function access. An access control facility restricts user operation according to predetermined guidelines.

The graphical user interface provides 'user friendly' access to the displays and functions of the main control module. The functions and displays include: Real Time Geometric Display of Traffic Signal operational and fault states with vehicle, pedestrian and vehicle identification inputs.

Sixteen simultaneous Timing Rings Each vehicle, pedestrian or special function group is attached to a timing ring. All timing functions of all rings and their attached groups are displayed in real time selected by user.

"Statistical Data Display At the local intersection level Volume, Occupancy and vehicle identification data are stored on a mass oSS storage device for the development of a) adaptive traffic control, b) statistical data display and c) historical record.

55.5 Message Logging generic language screen based interactive display which facilitates sorting display according to user set parameters ie, message type, fault location and type, and date and time.

Vehicle counting system which identifies, collects and displays all traffic movements including timing and historical related data.

Intersection timing through user nomination may be based on traffic density calculations derived from the real time traffic counting module.

Conflict monitor which identifies correct lamp display, correct lamp switching status and correct orientation of the traffic signal lantern.

It will be appreciated that the traffic control system described herein has a number of advantages over prior art systems. The main differences between the traffic control system and prior art technology relate to a) the distributed control mechanism, b) the ability to capture and store traffic related data at the intersection and c) the user friendly operation of the system facilitated by the graphical user interface.

Fig's 5 to 8 exemplify the graphical user interface (GUI). Fig shows the main screen 100 of the GUI which is displayed when the liquid o.

~crystal touch screen is turned on. The left side of the main screen displays the activity log 101. The activity log 101 can be configured to log every oO°SS activity of the traffic control system, every error (such as temporary communication loss) or every fault (such as a blown bulb or a current out of range). The activity log maintains historical data for analysis by the main control module 1.

On the right side of the main screen 100 are four separate facilities.

At the top is a software facility switch 102. This allows a user to switch the operation of the traffic light control system between on line, off line and flashing amber.

Below the software facility switch 102 is a detector control 103 16 which sets whether the traffic lights should change in a timed sequence or respond to detected vehicles.

The master link 104 switches the system into a network mode in which it communicates with a central controller. It is also possible to configure a number of traffic light control systems into a small network with one main control module acting as the master controller for all the traffic light control systems in the network.

The step mode touch switch 105 puts the controller into a step mode in which the lights change each time the switch is touched. This is a useful facility if a traffic control officer considers it necessary to control an intersection manually.

A graphical display of tools and other screens is always at the right side of the liquid crystal touch screen 15. The top symbol is a wheel 106 which brings up the main screen described above.

The next symbol 107 brings up a group recall and detector control screen, shown in FIG 6.

ooiP This screen allows the user to arrange the recall priority of traffic light assembly groups using the group recall touch screen 108. A group would normally be formed of all the individual traffic light assemblies facing a particular direction. Another group would be the pedestrian control lights for a crossing direction. The groups can be configured to cycle around all the groups or to rest with one group at green unless a vehicle is detected. After the vehicle is cleared the priority group would return to green.

The screen also facilitates the control of individual detectors using the detector input touch screen 109. Each detector can be turned off, turned on, or forced to be always on (shorted). The status is indicated according to the legend 110.

The next symbol 111 brings up a graphical display of the intersection as shown in FIG 7. The display shows each group of traffic light assemblies, such as 112, and associated detectors 113. In the particular example, there are three traffic light groups (numbered 1, 2 and 10 3 in the figure) and two pedestrian groups. The display is coloured so that the status of all groups can be seen at a glance.

The next symbol 114, brings up a timing display as shown in FIG 8.

~This screen displays the timing settings for each group. Groups 1,2 and 3 are traffic control lanterns and the display indicates various timing periods for each lantern. Groups 4 and 5 are pedestrian control lanterns and the display indicates the periods for walk, don't walk and flashing.

aaaa a Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features.

Claims (11)

1. A traffic control system comprising: a main control module incorporating one or more processor means for coordinating the operation of the traffic control system; at least one traffic light assembly in signal connection with the main control module, said traffic light assembly incorporating one or more processor means for local control of traffic lanterns; a power control module for supplying power to the traffic control system on a power loop, said power control module incorporating one or more processor means for controlling supply of power; a command cable loop providing signal connection between the main control module and the traffic light assembly for carrying command signals; and a confirm cable loop providing signal connection between the main control module and the traffic light assembly for carrying confirm S-signals.

2. The traffic control system of claim 1 wherein the main control module incorporates a user interface card for providing a graphical user i• 0o interface between a user and the traffic control system.

3. The traffic control system of claim 2 wherein the graphical user S: interface suitable incorporates a liquid crystal touch screen display.

4. The traffic control system of any one of claims 1 to 3 wherein the main control module further comprises a computing backplane and a traffic control backplane. 19 The traffic control system of claim 4 wherein the computing backplane provides computational, storage and user interface functions.

6. The traffic control system of either claim 4 or claim 5 wherein the traffic control backplane provides monitoring and control functions.

7. The traffic control system of any one of claims 4 to 6 wherein the computing backplane and the traffic control backplane are interconnected by dual port common memory.

8. The traffic control system of any one of claims 1 to 7 further comprising one or more detectors providing signals to at least one of the processor means of the traffic light assembly.

9. The traffic control system of claim 8 wherein the detectors perform one or more functions selected from a list including vehicle detection, vehicle identification and pedestrian identification. The traffic control system of either claim 8 or claim 9 wherein the traffic lanterns comprise red, green and amber vehicle control lanterns as well as red and green pedestrian control lanterns.

11. The traffic control system of any one of claims 1 to 10 wherein 9 9.. ~the traffic light assembly provides local traffic lantern control but 9 communicates with the main control module for timing coordination. 20 12. The traffic control system of any one of claims 1 to 11 wherein the power control module converts mains power input to power for the operation of the traffic control system including DC voltages for logic elements and extra low AC voltages (ELV) for powering the traffic Slanterns. lanterns.

13. The traffic control system of any one of claims 1 to 12 wherein the power loop is in electrical connection with the main control module, traffic light assembly and power control module.

14. The traffic control system of any one of claims 1 to 13 further comprising a safety flash loop for providing a fail safe signal to cause an orange lantern of the traffic light assembly to flash. A traffic control system as hereinbefore described with reference to the accompanying drawings. DATED this Second day of September 1999 EXCEL TECHNOLOGY GROUP PTY LTD By their Patent Attorneys FISHER ADAMS KELLY S9 9 9 9 9