WO1997038408A1 - A method and apparatus for providing trailer status data to a tractor (tailtag) - Google Patents

A method and apparatus for providing trailer status data to a tractor (tailtag) Download PDF

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Publication number
WO1997038408A1
WO1997038408A1 PCT/DK1997/000152 DK9700152W WO9738408A1 WO 1997038408 A1 WO1997038408 A1 WO 1997038408A1 DK 9700152 W DK9700152 W DK 9700152W WO 9738408 A1 WO9738408 A1 WO 9738408A1
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WO
WIPO (PCT)
Prior art keywords
trailer
tractor
load
function
current
Prior art date
Application number
PCT/DK1997/000152
Other languages
French (fr)
Inventor
Søren TRÆHOLT
Original Assignee
Navigato A/S
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Navigato A/S filed Critical Navigato A/S
Priority to AU25681/97A priority Critical patent/AU2568197A/en
Publication of WO1997038408A1 publication Critical patent/WO1997038408A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/54—Systems for transmission via power distribution lines
    • H04B3/548—Systems for transmission via power distribution lines the power on the line being DC
    • G—PHYSICS
    • G08—SIGNALLING
    • G08G—TRAFFIC CONTROL SYSTEMS
    • G08G1/00—Traffic control systems for road vehicles
    • G08G1/123—Traffic control systems for road vehicles indicating the position of vehicles, e.g. scheduled vehicles; Managing passenger vehicles circulating according to a fixed timetable, e.g. buses, trains, trams
    • G08G1/127—Traffic control systems for road vehicles indicating the position of vehicles, e.g. scheduled vehicles; Managing passenger vehicles circulating according to a fixed timetable, e.g. buses, trains, trams to a central station ; Indicators in a central station
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R16/00—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for
    • B60R16/02—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements
    • B60R16/03—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for
    • B60R16/0315—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for using multiplexing techniques
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5429—Applications for powerline communications
    • H04B2203/5441—Wireless systems or telephone
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5429—Applications for powerline communications
    • H04B2203/5458—Monitor sensor; Alarm systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5462—Systems for power line communications
    • H04B2203/547—Systems for power line communications via DC power distribution
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5462—Systems for power line communications
    • H04B2203/5495—Systems for power line communications having measurements and testing channel

Definitions

  • the present invention relates to a fleet management system for managing and monitoring the status of a fleet of vehicles and particularly to a method and a system for provision of trailer status data to a tractor from one or more trailers connected to the tractor.
  • a fleet manager must keep track of the status and location of each tractor and trailer in the fleet. Thus, for each trailer in the fleet, the fleet manager must know whether it is in service (i.e. coupled to a tractor) or out of service (i.e. not coupled to any tractor) . The fleet manager must have similar information with respect to whether each tractor in the fleet is hauling a trailer or is available for service. The fleet manager should also be able to monitor the progress of each vehicle in the fleet for scheduling purposes.
  • Mobile communication systems are utilized by commercial trucking companies to locate, identify and ascertain status of their vehicles.
  • Methods of and systems for provision of trailer status data to a tractor from a trailer connected to the tractor are known in the art.
  • a trailer identification system which incorporates a tractor-trailer data link which is capable of providing trailer identification information and status data to the tractor.
  • the system comprises a transmitter located in the trailer for generating an identification signal of the trailer in which the transmitter is located.
  • the transmitter generates a carrier signal that is modulated by the identification signal and the modulated carrier signal is transmitted to the tractor via a power bus common to the tractor and the trailer.
  • the equipment in the tractor may be adapted to display the information to the driver of the tractor. Further, the equipment may be adapted to transmit the information to the trucking company home base via a mobile communications terminal in the tractor. It is another object of the present invention to provide a trailer status monitoring system and method that require minimum modifications to the existing tractor-trailer electrical wiring.
  • a method of providing trailer status data to a tractor from a trailer connected to the tractor comprising the steps of
  • a status monitoring system for providing trailer status data to a tractor from a trailer connected to the tractor, comprising
  • a data transmitter comprising
  • encoding means for controlling the load as a function of time in such a way that load current drawn by the load from the first and second circuits varies as a specific function of time, the function identifying a specific status value of the trailer, and
  • a current sensor for providing a sensor signal corresponding to the load current flowing in the second circuit as a function of time
  • a processor connected to the current sensor for receiving the sensor signal and identifying, based on the sensor signal, the status value of the trailer connected to the tractor corresponding to the load current as a function of time.
  • trailer status data is communicated to the truck hauling the trailer in an extremely simple manner by loading the power supply of the truck with a current as a function of time, the function identifying the corresponding status data of the trailer. The shape of the load current function is then sensed and may be decoded in the truck.
  • a trailer status monitoring system according to the invention to the existing trailer electrical wiring to facilitate the implementation of the system.
  • the first circuit of the trailer may comprise wires energizing the brake lamps of the trailer, i.e. the system is energized each time the truck driver activates the brakes of the vehicle enabling the system to transmit status data during these brake activation periods.
  • the system may comprise an energy reservoir, such as a capacitor, for storage of electrical energy during a period when the first circuit is energized.
  • the energy reservoir may then be used as a power supply of the system during periods when the first circuit is not energized.
  • the trailer status data may comprise any parameter, such as parameters affecting the cargo of the trailer and the operation of the trailer, such as parameters of the climate inside the trailer, such as temperature, pressure, humidity, etc, etc, radiation level, gas leakage, mechanical vibration, mechanical shock, etc.
  • the trailer status data comprise identification data that identifies the specific trailer from which the status data are transmitted.
  • the electronic load is a simple electronic device for drawing current from a circuit to which it is connected according to a load control signal supplied to a load control input of the electronic load.
  • the electronic load may attain a specific resistance value or conductance value or it may sink a specific amount of current in response to a specific control input voltage.
  • the first circuit of the trailer may comprise any wire utilized to energize a trailer device, such as a brake lamp, a winking light lamp, a rear light lamp, a side light lamp, a rear drive lamp, etc, or any wire being energized by the tractor power supply whenever the trailer is coupled to the tractor.
  • the first circuit of the trailer and the corresponding second circuit of the tractor are interconnected through a tractor/trailer connector when the trailer is coupled to the tractor.
  • the load current drawn from the second circuit by the electronic load is controlled to vary as a specific function of time by encoding means that control the load control input signal correspondingly.
  • the electronic load may be controlled to draw current from the first circuit according to any known encoding scheme suitable for transmission of data from a transmitter to a receiver.
  • each trailer of a fleet may be assigned a specific identification number that identifies the trailer in question.
  • the identification number of the trailer may then be transmitted to the tractor hauling the trailer as a binary number by controlling the electronic load to draw high and low amounts of current, respectively, during specific time periods corresponding to high and low values of the binary number identifying the trailer in question.
  • the electronic load may be controlled to draw current as a periodic function of time, such as a square wave function, a sine function, etc, the frequency of the periodic function identifying the trailer in question, or, the load current may be controlled to switch between two periodic functions of a high and a low frequency, respectively, during specific time periods corresponding to high and low values of the binary number identifying the trailer in question.
  • a periodic function of time such as a square wave function, a sine function, etc
  • the load current is drawn from the power supply through wires of the first and second circuits and, obviously, the current may be sensed anywhere in the closed circuit from the power supply to the electronic load by any suitable current sensor, such as a current sensing resistor, a Hall element, a current transformer, etc.
  • a current transformer enclosing the power supply wire connecting the second circuit to the power supply of the tractor is utilized for sensing of the load current.
  • Utilization of a current transformer is advantageous, as it provides a particularly simple way of connecting the current sensor of the system to the existing wires of the tractor, it provides a galvanic separation between the tractor power and signalling circuits and the current sensor of the system, and it inherently filters the DC current component from the current to be sensed.
  • the output of the current sensor e.g. the current transformer output, is connected to the processor which is adapted to determine load current values as a function of time and which may be further adapted to decode the load current function of time into trailer status data.
  • the current transformer output current is converted in a current to voltage converter of the processor into a voltage compatible with high and low voltages of the logic circuitry, such as TTL, CMOS, NMOS, ECL, etc, utilized in the processor. High and low values, respectively, of the load current may then be identified as a function of time whereby a binary number transmitted from the trailer is decoded by the processor.
  • the status monitoring system may further comprise means for interrogation of a physical parameter monitoring system in the trailer and in response thereto receive from the physical parameter monitoring system signals indicative of measured physical parameters.
  • the status monitoring system modulates the parameter data as described above and transmits the modulated data via the first and second circuits to the processor located in the tractor.
  • the status monitoring system may further comprise display means for displaying identification and status data of the trailer to the driver of the tractor.
  • More than one trailer may be coupled to a common tractor so that the tractor hauls a train of trailers.
  • a current sensor may be provided in the data transmitter of each trailer for sensing of whether the. first circuit of a trailer is already occupied by transmission of data by another transmitter of another trailer positioned after the trailer in question.
  • the current sensor may be connected to the encoding means and the encoding means may be adapted to initiate a data transmission only when the first circuit is not occupied by transmission of data from another transmitter.
  • the status monitoring system is connected to a mobile communications terminal located in the truck so that the identification and status data provided by the system can be transmitted to a control center via the mobile communications terminal.
  • the mobile terminal may communicate with the control center via any kind of communication system, such as via the NMT or GSM mobile phone systems, via satellite, such as Inmarsat-C, via radio, etc, or any combination of such communication systems.
  • Fig. 1 shows a blocked diagram of a status monitoring system according to the invention
  • Fig. 2 shows a plot of various signals in the status monitoring system as a function of time.
  • Fig. 1 shows a blocked diagram of a status monitoring system according to the invention for providing trailer status data to a tractor from a trailer connected to the tractor.
  • the status monitoring system shown comprises a data transmitter 1 located on the trailer and a data receiver 2 located on the truck.
  • Parts 3 , 4 of the brake light circuitry of the tractor, including the brake switch 5, and of the trailer, including the trailer brake lights 6, are also shown.
  • the electronic load 7 of the transmitter 1 is connected to a wire that energizes the brake lights of the trailer and the transmitter 1 whenever the driver of the truck to which the trailer is connected activates the brake switch 5.
  • the transmitter 1 further comprises a microcontroller 8 for reading the identification code of the trailer from an EEPROM 9 and for controlling the electronic load 7 in accordance with the identification code of the trailer in which the transmitter is located.
  • the electronic load comprises a transistor 16 and a resistor 17 and when the transistor 16 is controlled to be in the on-state, the load draws an additional current from the brake light circuitry and when the transistor 16 is controlled to be in the off- state, the load draws no additional current from the brake light circuitry.
  • the transmitter 1 draws a pulsating current from the brake light circuitry 3, 4 that adds to the current consumption of the brake lights 6. The added current is detected by the data receiver 2 located in the truck.
  • the identification code of the trailer may be entered into the EEPROM 9 of the data transmitter 1 through a RS 232 C interface 10 of the transmitter 1.
  • the data receiver 2 located in the truck is energized whenever the truck is active.
  • the data receiver 2 comprises a microcontroller 11, a RS 232 C interface 12, a brake activation sensor signal line 13, a current transformer 14, and a current detector circuit 15.
  • the current transformer 14 encloses the brake light wiring 3 and generates an output current that is proportional to the AC current in the brake light wiring 3.
  • the brake activation sensor signal 13 goes high whereby the microcontroller 11 is made ready to read the signal from the current transformer 14.
  • the transmitter 1 transmits the trailer identification code through the brake light circuitry 3, 4.
  • the AC current consumption is detected by the current transformer 14 and current detector circuit 15, and the identification code is decoded by the microcontroller 11 and compared with a corresponding code transmitted previously. If the present code is identical to the previous code, no further action is taken but if the code has changed or it is the first code transmitted after activation of the truck, the code is transmitted through the RS 232 C interface 12 to the truck computer.
  • Fig. 2 shows a plot of various signals in the status monitoring system as a function of time. Reference numerals of the signals plotted are also shown in Fig. 1 at positions in the circuitry where the signals are present.
  • the upper curve 20 of the plot shows the current flowing in the brake light circuitry 4 of the trailer upon activation of the brakes and the curve 21 shows the corresponding current drawn by the electronic load 7.
  • the amplitude of the current 21 is 200 mA and the carrier is a 2 kHz square wave with a 50 % duty cycle for a logic 1 and a 25 % duty cycle for a logic 0.
  • the encoded signal is decoded by clocking at the leading edge 22 and sampling the current value at a time 23 37.5 % into the time period of the square wave after the leading edge 22.
  • the curve 24 shows the output current of the current transformer 14 and the curve 25 shows the corresponding output signal from the current detector circuit 15.
  • the curve 26 shows the brake activation sensor signal 13.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Arrangements For Transmission Of Measured Signals (AREA)

Abstract

The present invention relates to a fleet management system for managing and monitoring the status of a fleet of vehicles. A status monitoring system for providing trailer status data to a tractor from a trailer connected to the tractor is provided. The system comprises a data transmitter positioned on-board the trailer. The data transmitter has an electronic load that is connected across a specific first circuit of the trailer that is connected to a corresponding second circuit of the tractor when the trailer is coupled to the tractor. Further, the transmitter has encoding means for controlling the load as a function of time in such a way that load current drawn by the load from the first and second circuits varies as a specific function of time. The function identifies a specific status value of the trailer. Further, the system comprises a data receiver positioned on-board the tractor. The data receiver has a current sensor for providing a sensor signal corresponding to the load current flowing in the second circuit as a function of time, and a processor connected to the current sensor for receiving the sensor signal and based on the sensor signal identifying the status value of the trailer connected to the tractor corresponding to the load current as a function of time. The system requires minimum modifications to the existing tractor-trailer electrical wiring and it may be connected to a type of signal lines that is provided in any tractor-trailer vehicle.

Description

A METHOD AND APPARATUS FOR PROVIDING TRAILER STATUS DATA TO A TRACTOR (TAILTAG)
FIELD OF THE INVENTION
The present invention relates to a fleet management system for managing and monitoring the status of a fleet of vehicles and particularly to a method and a system for provision of trailer status data to a tractor from one or more trailers connected to the tractor.
BACKGROUND OF THE INVENTION
Fleet management is a major concern in the trucking industry. A fleet manager must keep track of the status and location of each tractor and trailer in the fleet. Thus, for each trailer in the fleet, the fleet manager must know whether it is in service (i.e. coupled to a tractor) or out of service (i.e. not coupled to any tractor) . The fleet manager must have similar information with respect to whether each tractor in the fleet is hauling a trailer or is available for service. The fleet manager should also be able to monitor the progress of each vehicle in the fleet for scheduling purposes.
Hitherto, it has been difficult to keep track of the locations of various trailers of a fleet. Quite often a trailer is left at a location, either by design or accident, and later forgotten about.
Along with ascertaining the location of various trailers, it is also desirable to ascertain the status of equipment, environmental conditions, or payloads within these trailers. Typically, it is useful to be able to monitor various parameters affecting the cargo of the trailers.
Mobile communication systems are utilized by commercial trucking companies to locate, identify and ascertain status of their vehicles. Methods of and systems for provision of trailer status data to a tractor from a trailer connected to the tractor are known in the art.
In US 5.142.278, a trailer identification system is disclosed which incorporates a tractor-trailer data link which is capable of providing trailer identification information and status data to the tractor. The system comprises a transmitter located in the trailer for generating an identification signal of the trailer in which the transmitter is located. The transmitter generates a carrier signal that is modulated by the identification signal and the modulated carrier signal is transmitted to the tractor via a power bus common to the tractor and the trailer.
It is a disadvantage of known trailer status monitoring systems that they have to be connected to a permanently energized power bus that is common to a tractor and a trailer when the trailer is coupled to the tractor. A permanently energized common power bus is not provided in every tractor- trailer vehicle.
It is another disadvantage of known trailer status monitoring systems that they are complex and expensive and are complex to connect to the existing tractor and trailer wiring.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a novel and improved method and system for communicating trailer identification and status information to equipment located in the tractor hauling the trailer. The equipment in the tractor may be adapted to display the information to the driver of the tractor. Further, the equipment may be adapted to transmit the information to the trucking company home base via a mobile communications terminal in the tractor. It is another object of the present invention to provide a trailer status monitoring system and method that require minimum modifications to the existing tractor-trailer electrical wiring.
It is a further object of the invention to provide a trailer status monitoring system that is connected to a type of signal lines that is provided in any tractor-trailer vehicle.
According to the invention these and other objects are fulfilled by a method of providing trailer status data to a tractor from a trailer connected to the tractor, the method comprising the steps of
connecting an electronic load across a specific first circuit of the trailer that is connected to a corresponding second circuit of the tractor when the trailer is coupled to the tractor,
controlling the load as a function of time in such a way that the load current drawn by the load from the first and second circuits varies as a specific function of time, the function identifying a specific status value of the trailer, and
sensing the load current flowing in the second circuit as a function of time whereby the corresponding status value of the trailer connected to the tractor can be identified in the tractor.
Further, according to the invention the above-mentioned and other objects are fulfilled by a status monitoring system for providing trailer status data to a tractor from a trailer connected to the tractor, comprising
on-board the trailer a data transmitter comprising
an electronic load connected across a specific first circuit of the trailer that is connected to a corresponding second circuit of the tractor when the trailer is coupled to the tractor, and
encoding means for controlling the load as a function of time in such a way that load current drawn by the load from the first and second circuits varies as a specific function of time, the function identifying a specific status value of the trailer, and
on-board the tractor a data receiver comprising
a current sensor for providing a sensor signal corresponding to the load current flowing in the second circuit as a function of time, and
a processor connected to the current sensor for receiving the sensor signal and identifying, based on the sensor signal, the status value of the trailer connected to the tractor corresponding to the load current as a function of time.
It is an important advantage of the present invention that trailer status data is communicated to the truck hauling the trailer in an extremely simple manner by loading the power supply of the truck with a current as a function of time, the function identifying the corresponding status data of the trailer. The shape of the load current function is then sensed and may be decoded in the truck. Thus, it is extremely simple to connect a trailer status monitoring system according to the invention to the existing trailer electrical wiring to facilitate the implementation of the system.
As a permanently energized circuit is not provided in every tractor-trailer vehicle, it is a further advantage of the present invention that a permanently energized circuit is not required for the system to operate properly. For example, the first circuit of the trailer may comprise wires energizing the brake lamps of the trailer, i.e. the system is energized each time the truck driver activates the brakes of the vehicle enabling the system to transmit status data during these brake activation periods.
The system may comprise an energy reservoir, such as a capacitor, for storage of electrical energy during a period when the first circuit is energized. The energy reservoir may then be used as a power supply of the system during periods when the first circuit is not energized.
The trailer status data may comprise any parameter, such as parameters affecting the cargo of the trailer and the operation of the trailer, such as parameters of the climate inside the trailer, such as temperature, pressure, humidity, etc, etc, radiation level, gas leakage, mechanical vibration, mechanical shock, etc.
Preferably, the trailer status data comprise identification data that identifies the specific trailer from which the status data are transmitted.
The electronic load is a simple electronic device for drawing current from a circuit to which it is connected according to a load control signal supplied to a load control input of the electronic load. For example, the electronic load may attain a specific resistance value or conductance value or it may sink a specific amount of current in response to a specific control input voltage.
The first circuit of the trailer may comprise any wire utilized to energize a trailer device, such as a brake lamp, a winking light lamp, a rear light lamp, a side light lamp, a rear drive lamp, etc, or any wire being energized by the tractor power supply whenever the trailer is coupled to the tractor. The first circuit of the trailer and the corresponding second circuit of the tractor are interconnected through a tractor/trailer connector when the trailer is coupled to the tractor. The load current drawn from the second circuit by the electronic load is controlled to vary as a specific function of time by encoding means that control the load control input signal correspondingly.
The electronic load may be controlled to draw current from the first circuit according to any known encoding scheme suitable for transmission of data from a transmitter to a receiver.
For example, each trailer of a fleet may be assigned a specific identification number that identifies the trailer in question. The identification number of the trailer may then be transmitted to the tractor hauling the trailer as a binary number by controlling the electronic load to draw high and low amounts of current, respectively, during specific time periods corresponding to high and low values of the binary number identifying the trailer in question.
Alternatively, the electronic load may be controlled to draw current as a periodic function of time, such as a square wave function, a sine function, etc, the frequency of the periodic function identifying the trailer in question, or, the load current may be controlled to switch between two periodic functions of a high and a low frequency, respectively, during specific time periods corresponding to high and low values of the binary number identifying the trailer in question.
As the first circuit is energized from the power supply of the tractor, the load current is drawn from the power supply through wires of the first and second circuits and, obviously, the current may be sensed anywhere in the closed circuit from the power supply to the electronic load by any suitable current sensor, such as a current sensing resistor, a Hall element, a current transformer, etc. According to a preferred embodiment of the invention a current transformer enclosing the power supply wire connecting the second circuit to the power supply of the tractor is utilized for sensing of the load current.
Utilization of a current transformer is advantageous, as it provides a particularly simple way of connecting the current sensor of the system to the existing wires of the tractor, it provides a galvanic separation between the tractor power and signalling circuits and the current sensor of the system, and it inherently filters the DC current component from the current to be sensed.
The output of the current sensor, e.g. the current transformer output, is connected to the processor which is adapted to determine load current values as a function of time and which may be further adapted to decode the load current function of time into trailer status data.
According to a preferred embodiment of the invention, the current transformer output current is converted in a current to voltage converter of the processor into a voltage compatible with high and low voltages of the logic circuitry, such as TTL, CMOS, NMOS, ECL, etc, utilized in the processor. High and low values, respectively, of the load current may then be identified as a function of time whereby a binary number transmitted from the trailer is decoded by the processor.
The status monitoring system may further comprise means for interrogation of a physical parameter monitoring system in the trailer and in response thereto receive from the physical parameter monitoring system signals indicative of measured physical parameters. The status monitoring system modulates the parameter data as described above and transmits the modulated data via the first and second circuits to the processor located in the tractor. The status monitoring system may further comprise display means for displaying identification and status data of the trailer to the driver of the tractor.
More than one trailer may be coupled to a common tractor so that the tractor hauls a train of trailers. In order to avoid that data is transmitted from more trailers simultaneously, a current sensor may be provided in the data transmitter of each trailer for sensing of whether the. first circuit of a trailer is already occupied by transmission of data by another transmitter of another trailer positioned after the trailer in question. The current sensor may be connected to the encoding means and the encoding means may be adapted to initiate a data transmission only when the first circuit is not occupied by transmission of data from another transmitter.
Preferably, the status monitoring system is connected to a mobile communications terminal located in the truck so that the identification and status data provided by the system can be transmitted to a control center via the mobile communications terminal. The mobile terminal may communicate with the control center via any kind of communication system, such as via the NMT or GSM mobile phone systems, via satellite, such as Inmarsat-C, via radio, etc, or any combination of such communication systems.
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 shows a blocked diagram of a status monitoring system according to the invention, and
Fig. 2 shows a plot of various signals in the status monitoring system as a function of time. DETAILED DESCRIPTION OF THE DRAWING
Fig. 1 shows a blocked diagram of a status monitoring system according to the invention for providing trailer status data to a tractor from a trailer connected to the tractor. The status monitoring system shown comprises a data transmitter 1 located on the trailer and a data receiver 2 located on the truck. Parts 3 , 4 of the brake light circuitry of the tractor, including the brake switch 5, and of the trailer, including the trailer brake lights 6, are also shown.
The electronic load 7 of the transmitter 1 is connected to a wire that energizes the brake lights of the trailer and the transmitter 1 whenever the driver of the truck to which the trailer is connected activates the brake switch 5.
The transmitter 1 further comprises a microcontroller 8 for reading the identification code of the trailer from an EEPROM 9 and for controlling the electronic load 7 in accordance with the identification code of the trailer in which the transmitter is located. As shown in Fig. 1, the electronic load comprises a transistor 16 and a resistor 17 and when the transistor 16 is controlled to be in the on-state, the load draws an additional current from the brake light circuitry and when the transistor 16 is controlled to be in the off- state, the load draws no additional current from the brake light circuitry. In this way, the transmitter 1 draws a pulsating current from the brake light circuitry 3, 4 that adds to the current consumption of the brake lights 6. The added current is detected by the data receiver 2 located in the truck.
Whenever desirable the identification code of the trailer may be entered into the EEPROM 9 of the data transmitter 1 through a RS 232 C interface 10 of the transmitter 1.
The data receiver 2 located in the truck is energized whenever the truck is active. The data receiver 2 comprises a microcontroller 11, a RS 232 C interface 12, a brake activation sensor signal line 13, a current transformer 14, and a current detector circuit 15.
The current transformer 14 encloses the brake light wiring 3 and generates an output current that is proportional to the AC current in the brake light wiring 3.
Upon activation of the brakes, the brake activation sensor signal 13 goes high whereby the microcontroller 11 is made ready to read the signal from the current transformer 14. After a short start up delay, the transmitter 1 transmits the trailer identification code through the brake light circuitry 3, 4. In the data receiver 2, the AC current consumption is detected by the current transformer 14 and current detector circuit 15, and the identification code is decoded by the microcontroller 11 and compared with a corresponding code transmitted previously. If the present code is identical to the previous code, no further action is taken but if the code has changed or it is the first code transmitted after activation of the truck, the code is transmitted through the RS 232 C interface 12 to the truck computer.
Fig. 2 shows a plot of various signals in the status monitoring system as a function of time. Reference numerals of the signals plotted are also shown in Fig. 1 at positions in the circuitry where the signals are present.
The upper curve 20 of the plot shows the current flowing in the brake light circuitry 4 of the trailer upon activation of the brakes and the curve 21 shows the corresponding current drawn by the electronic load 7. The amplitude of the current 21 is 200 mA and the carrier is a 2 kHz square wave with a 50 % duty cycle for a logic 1 and a 25 % duty cycle for a logic 0. The encoded signal is decoded by clocking at the leading edge 22 and sampling the current value at a time 23 37.5 % into the time period of the square wave after the leading edge 22. The curve 24 shows the output current of the current transformer 14 and the curve 25 shows the corresponding output signal from the current detector circuit 15. The curve 26 shows the brake activation sensor signal 13.

Claims

1. A method of providing trailer status data to a tractor from a trailer connected to the tractor, the method comprising the steps of
connecting an electronic load across a specific first circuit of the trailer that is connected to a corresponding second circuit of the tractor when the trailer is coupled to the tractor,
controlling the load as a function of time in such a way that the load current drawn by the load from the first and second circuits varies as a specific function of time, the function identifying a specific status value of the trailer, and
sensing the load current flowing in the second circuit as a function of time whereby the corresponding status value of the trailer connected to the tractor can be identified in the tractor.
2. A method according to claim 1, wherein the load is controlled in such a way that the load current alternates between two specific values as a specific square-shaped function of time corresponding to a specific status value of the trailer.
3. A method according to claim 1 or 2, wherein the load current is sensed in the tractor by positioning a current transformer around a supply line connected between the power supply of the tractor and the second circuit and by determining the output current of the current transformer as a function of time.
4. A method according to any of the preceding claims, wherein the trailer status data comprises identification data of the trailer.
5. A status monitoring system for providing trailer status data to a tractor from a trailer connected to the tractor, comprising
on-board the trailer a data transmitter comprising
an electronic load connected across a specific first circuit of the trailer that is connected to a corresponding second circuit of the tractor when the trailer is coupled to the tractor, and
encoding means for controlling the load as a function of time in such a way that load current drawn by the load from the first and second circuits varies as a specific function of time, the function identifying a specific status value of the trailer, and
on-board the tractor a data receiver comprising
a current sensor for providing a sensor signal corresponding to the load current flowing in the second circuit as a function of time, and
a processor connected to the current sensor for receiving the sensor signal and based on the sensor signal identifying the status value of the trailer connected to the tractor corresponding to the load current as a function of time.
6. An apparatus according to claim 5, wherein the encoding means controls the load in such a way that the load current alternates between two specific values as a specific square- shaped function of time corresponding to a specific status value of the trailer.
7. An apparatus according to claim 5 or 6, wherein the current sensor comprises a current transformer positioned around a supply line that energizes the second circuit.
8. An apparatus according to any of claims 5-7, wherein the trailer status data comprises identification data of the trailer.
PCT/DK1997/000152 1996-04-10 1997-04-09 A method and apparatus for providing trailer status data to a tractor (tailtag) WO1997038408A1 (en)

Priority Applications (1)

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AU25681/97A AU2568197A (en) 1996-04-10 1997-04-09 A method and apparatus for providing trailer status data to a tractor (tailtag)

Applications Claiming Priority (2)

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DK40896 1996-04-10
DK0408/96 1996-04-10

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WO2005022480A1 (en) * 2003-08-27 2005-03-10 James Grant Hook On board vehicle detection & monitoring
WO2014086449A1 (en) * 2012-12-07 2014-06-12 Wabco Gmbh Method and apparatuses for transmitting telematics data from a lorry to a telematics portal
US11665016B2 (en) 2019-06-27 2023-05-30 Drivertech, Llc Tractor-trailer communication system

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