Abstract:
When a cargo trailer is coupled to a truck, a trailer tracking device on the trailer acquires an identifier of a truck tracking device attached to the truck. The trailer tracking device then transmits a message to a central server indicating that the trailer is coupled to the truck, which message includes the identifiers of the two tracking devices. The central server associates the identifiers of the two tracking devices in a database. When the trailer is decoupled from the truck, the trailer tracking device transmits a message to the central server indicating that the trailer is decoupled. The trailer tracking device then goes into a sleep mode until the trailer is again coupled to a truck, a predetermined time interval expires, a motion sensor indicates trailer movement, location coordinates indicate a geofence violation, or a low battery voltage condition occurs. Upon any of these events, the trailer tracking device wakes up and transmits to the central server a message indicating which situation caused the transmission and including the location coordinates of the trailer.

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. provisional patent application Ser. No. 61/567,786, filed Dec. 7, 2011, titled “System for Communicating between a Trailer Tracking Device, a Truck Tracking Device, and a Central Monitoring Station.” 
     FIELD 
     This invention relates to the field of tracking the location of vehicles and cargo trailers in transit. More particularly, this invention relates to a system for coordinating communication of information between a tracking device on a truck, a tracking device on a trailer which may be pulled by the truck, and a central monitoring station. 
     BACKGROUND 
     Each day, thousands of trucks travel over the nation&#39;s highways towing thousands of cargo trailers carrying millions of dollars worth of cargo. At any given time, many thousands more cargo trailers are not connected to trucks, but are parked in storage lots after decoupling from the trucks that towed them to their current locations, awaiting connection to the trucks that will tow them to their next destinations. Keeping track of the status and location of each of these thousands of cargo trailers represents a significant record-keeping burden for shipping, trucking and logistics companies. 
     What is needed is a system for providing automatic, seamless and reliable communications between trucks and the trailers to which they are connected, between trailers and a central monitoring station of a monitoring service provider, and between trucks and the central monitoring station for the reporting of location and status information. 
     SUMMARY 
     The above and other needs are met by a system for communicating between a trailer tracking device, a truck tracking device, a central server of a monitoring service provider, and a customer device. In a preferred embodiment, when a trailer is initially coupled to a truck, the trailer tracking device acquires an identification number of the truck tracking device via a short-range communication interface and acquires location coordinates using a GPS module. The trailer tracking device then transmits a message via a long-range communication interface to the central server indicating that the trailer is coupled to the truck, which message includes the identification number of the trailer tracking device, the identification number of the truck tracking device, the location coordinates, and a time stamp. The central server then associates the identification number of the trailer tracking device with the identification number of the truck tracking device in a database maintained by the monitoring service provider. 
     When the trailer is decoupled from the truck, the trailer tracking device transmits a message to the central server indicating that the trailer is decoupled, which message includes the identification number of the trailer tracking device, the location coordinates, and a time stamp. The trailer tracking device then goes into a sleep or low-power mode until one or more of the following happen: (1) the trailer becomes coupled to a truck; (2) a predetermined reporting time interval expires; (3) a motion sensor indicates the trailer has moved; (4) location coordinates from the GPS module indicate the trailer has moved outside a geofence; or (5) battery voltage in the trailer tracking device drops below a threshold level. Upon occurrence of any of these events, the trailer tracking device wakes up and transmits a message to the central server, which message indicates the situation that caused the transmission and includes the location coordinates of the trailer and a time stamp. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages of the invention are apparent by reference to the detailed description in conjunction with the figures, wherein elements are not to scale so as to more clearly show the details, wherein like reference numbers indicate like elements throughout the several views, and wherein: 
         FIGS. 1 and 2  depict a system for communicating between a trailer tracking device, a truck tracking device, a central monitoring station of a monitoring service provider, and a customer device according to an embodiment of the invention; and 
         FIG. 3  depicts a flow chart of a method for communicating between a trailer tracking device, a truck tracking device, a central monitoring station of a monitoring service provider, and a customer device according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIG. 1 , a communication system  10  includes a trailer tracking device  12  attached to a cargo trailer  38  and a truck tracking device  14  attached to a truck  40  (also referred to as a tractor) configured to haul the trailer  38 . 
     As shown in  FIG. 2 , the trailer tracking device  12  and the truck tracking device  14  communicate with a service provider&#39;s central monitoring station  50  via a wireless communication network  54 , such as a cellular network or Wi-Fi network, and a wide area communication network  52 , such as the Internet. The central monitoring station  50  is also referred to herein as the central server. The central monitoring station  50  is also operable to communicate with a customer device  56  via the network  52  or the network  54 . The customer device  56  may be a computer, a tablet, or a smartphone through which a customer entity receives communications from the service provider. The customer entity may be a subscriber to asset tracking and monitoring services provided by the service provider. 
     A preferred embodiment of the trailer tracking device  12  includes a Global Positioning System (GPS) module  16 , a central processing unit (CPU)  18 , a long-range communication interface  20 , a short-range communication interface  22 , a power supply  24 , and a motion sensor  46 . Similarly, a preferred embodiment of the truck tracking device  14  includes a GPS module  26 , a CPU  28 , a long-range communication interface  30 , a short-range communication interface  32 , and a power supply  34 . 
     The GPS module  16  determines location coordinates of the trailer tracking device  12  based on timing signals received from GPS satellites. These location coordinates may be communicated to the CPU  18  for storage in associated memory or to the long-range communication interface  20  to be transmitted to the central monitoring station  50  of the monitoring service provider. In some embodiments, the location of the trailer tracking device  12  may be determined based on the presence of a given Wi-Fi network or a particular cellular tower detected by the long-range communication interface  20 . 
     The CPU  18  of the trailer tracking device  12  executes instructions to make decisions and direct communications between the trailer tracking device  12  and the truck tracking device  14  and the central monitoring station  50 . In preferred embodiments, memory associated with the CPU  18  stores a unique identification/serial number assigned to the trailer tracking device  12 . 
     The long-range communication interface  20  of the trailer tracking device  12  comprises a wireless RF transceiver, such as cellular modem, a satellite modem and/or a Wi-Fi modem, for providing two-way wireless communications between the trailer tracking device  12  and the central monitoring station  50 . In embodiments that include multiple modems for wireless communication with the central monitoring station  50 , the CPU  18  activates the appropriate wireless modem based on the current availability of wireless networks, with the order of preference determined based on the air-time cost of the available wireless networks. For example, Wi-Fi may be assigned highest priority based on lowest cost, while satellite may be assigned lowest priority based on highest cost. 
     The short-range communication interface  22  of the trailer tracking device  12  comprises a wired and/or wireless transceiver for providing two-way short-range communications between the trailer tracking device  12  and the truck tracking device  14 . In wireless embodiments, the short-range communication interface  22  comprises an RF transceiver, such as a Bluetooth or Wi-Fi or RFID transceiver. In wired embodiments, the short-range communication interface  22  may include an RS-232 link or Universal Serial Bus (USB) link or other well-known wired interface configuration. In some preferred embodiments of the trailer tracking device  12 , the short-range communication interface  22  includes both a wireless transceiver and a wired communication interface. 
     The trailer tracking device  12  includes a power supply  24  that receives and conditions power from the truck power supply when the trailer  38  is tethered to the truck  40 . The power supply  24  includes a backup battery for providing power to the trailer tracking device  12  when the trailer  38  is not tethered to the truck  40 . In some embodiments, the power supply  24  also includes a solar panel for providing a charging voltage to the backup battery. 
     With continued reference to  FIG. 2 , the GPS module  26  of the truck tracking device  14  determines location coordinates of the truck tracking device  14  based on timing signals received from GPS satellites. These location coordinates may be communicated to the CPU  28  for storage in associated memory or to the long-range communication interface  30  to be transmitted to the central monitoring station  50 . In some embodiments, the location of the truck tracking device  14  may be determined based on the presence of a given Wi-Fi network or a particular cellular tower detected by the long-range communication interface  30 . 
     The CPU  28  of the truck tracking device  14  executes instructions to make decisions and direct communications between the truck tracking device  14 , the trailer tracking device  12  and the central monitoring station  50 . In preferred embodiments, memory associated with the CPU  28  stores a unique identification/serial number assigned to the truck tracking device  14 . 
     The long-range communication interface  30  of the truck tracking device  14  comprises a wireless transceiver, such as cellular modem, satellite modem, or WiFi modem, for providing two-way long-range wireless communications between the truck tracking device  14  and the central monitoring station  50 . In embodiments that include multiple modems for wireless communication with the central monitoring station  50 , the CPU  28  activates the appropriate wireless modem based on the current availability of wireless networks, with the order of preference determined based on the air-time cost of the available wireless networks as discussed above. 
     The short-range communication interface  32  of the truck tracking device  14  comprises a wired and/or wireless transceiver for providing two-way short-range communications between the truck tracking device  14  and the trailer tracking device  12 . In wireless embodiments, the short-range communication interface  32  comprises an RF transceiver, such as a Bluetooth or Wi-Fi or RFID transceiver. In wired embodiments, the short-range communication interface  32  may include an RS-232 link or Universal Serial Bus (USB) link or other well-known wired interface configuration. In some preferred embodiments of the truck tracking device  14 , the short-range communication interface  32  includes both a wireless transceiver and a wired communication interface. 
     The truck tracking device  14  includes a power supply  34  that receives and conditions power from a truck power supply when the truck tracking device  14  is installed in the truck  40 . The power supply  34  may also include a backup battery for providing power to the truck tracking device  14  when the truck tracking device  14  is not installed in the truck  40 , or if power from the truck power supply fails. 
     Typically, when the cargo trailer  38  is coupled to the truck  40 , an electrical harness is connected from the truck&#39;s electrical system to the trailer&#39;s electrical system. As shown in  FIG. 2 , such an electrical harness  36  may provide a wired electrical connection  42 , such as an RS-232 link or USB link, between the short-range communication interface  22  in the trailer tracking device  12  and the short-range communication interface  32  in the truck tracking device  14 . In alternative embodiments, the short range communication link between the short-range communication interface  22  and the short-range communication interface  32  may be implemented by modulating a communication signal onto a power line in the electrical harness  36 . 
     The harness  36  preferably includes a power connection  44  between the power supply  24  in the trailer tracking device  12  and the power supply  34  in the truck tracking device  14 . In preferred embodiments, when the harness  36  is connected between the truck  40  and the trailer  38 , the power supply  24  of the trailer tracking device  12  receives power from the power supply  34  of the truck tracking device  14  or from the electrical system of the truck  40 . Thus, when the harness  36  is connected between the truck  40  and the trailer  38 , the battery of the power supply  24  can be recharged by the power supply  34  of the truck tracking device  14  or the electrical system of the truck  40 . The electrical harness  36  is an optional feature included in some embodiments of the invention, and is not required to provide the communication functions described herein. 
     In preferred embodiments, communications between the trailer tracking device  12  and the truck tracking device  14  take place via the short-range communication interfaces  22  and  32 . In alternative embodiments, communications between the trailer tracking device  12  and the truck tracking device  14  may be routed through the central monitoring station  50  via Wi-Fi, wireless cellular or satellite links. 
     In a preferred embodiment of a communication process depicted in  FIG. 3 , when a trailer  38  is coupled to a truck  40  and the harness  36  is initially connected (step  100 ), the trailer tracking device  12  accesses the unique identification/serial number of the truck tracking device  14  via the short range communication interfaces  32  and  22  (step  102 ). The trailer tracking device  12  then transmits a first data packet via the long-range communication interface  20  to the central monitoring station  50  indicating that the trailer  38  and truck  40  are coupled (step  104 ). This first data packet preferably includes the unique identification/serial number of the trailer tracking device  12 , the unique identification/serial number of the truck tracking device  14 , current location coordinates acquired from the GPS module  16 , and a time stamp. The association of these two unique identification/serial numbers and the location coordinates and time stamp are stored in a database of the central monitoring station  50  (step  106 ). The first data packet may also include information indicating that the transmission was initiated by the coupling of the trailer  38  to the truck  40 . 
     In embodiments having no wired harness connection between the trailer tracking device  12  and the truck tracking device  14 , communications between the two units may be via Bluetooth, Wi-Fi, RFID, or other wireless communication means when the units come into proximity of each other. In these embodiments, the presence of the wireless signal between the short-range communication interfaces  22  and  32  is used to indicate coupling of the trailer  38  to the truck  40 . 
     After transmission of the first data packet, the CPU  18  of the trailer tracking device  12  preferably enters a sleep mode wherein the various components of the device  12  are powered down or put into a low-power state. While in the sleep mode, one ongoing function provided by the CPU  18  is to sense whether the trailer  38  is coupled to the truck  40 , such as via the harness  36  or wireless means. 
     When the trailer  38  becomes decoupled from the truck  40  (step  108 ), the CPU  18  senses the disconnection and “wakes up” the GPS module  16  and the long-range communication interface  20 , and the GPS module  16  acquires location coordinates of the trailer  38 . The trailer tracking device  12  then transmits a second data packet via the long-range communication interface  20  to the central monitoring station  50  indicating that the trailer  38  and truck  40  have been disconnected (step  110 ). This second data packet preferably includes the unique identification/serial number of the trailer tracking device  12 , the unique identification/serial number of the truck tracking device  14 , the current location coordinates, a value indicating that the transmission was initiated based on disconnection from the truck, and a time stamp. After transmitting the second data packet, the trailer tracking device  12  reenters the sleep mode (step  112 ) and begins monitoring status (step  116 ). 
     Upon receipt of the second data packet, the central monitoring station  50  may send an alert message to the customer device  56 , such as via email or text message, indicating that the trailer to which the tracking device  12  identified in the second data packet is installed has been decoupled from the tractor (step  114 ). The alert message may also indicate the location of the tracking device  12 . Whether or not this or any other alert message is sent to the customer device  56  is determined by stored customer preferences. 
     Preferably, while in the sleep mode after decoupling from the truck  40 , one ongoing function provided by the CPU  18  of the trailer tracking device  12  is monitoring whether the trailer  38  becomes coupled to a truck  40  (step  118 ). If coupling to a truck is detected, the trailer tracking device  12  accesses the unique identification/serial number of the truck tracking device  14  via the short range communication interfaces  32  and  22  (step  102 ), and the process continues as depicted in  FIG. 3 . 
     While in the sleep mode after decoupling from the truck  40 , another ongoing function provided by the CPU  18  of the trailer tracking device  12  is a timer function (step  120 ) to determine time intervals at which the tracking device  12  wakes up and acquires its location coordinates (step  122 ), and transmits a third data packet to the central monitoring station  50  (step  128 ). In a preferred embodiment, the transmission interval of the third data packet is once per day. The third data packet preferably includes at least the location coordinates of the trailer  38 , the unique identification/serial number of the trailer tracking device  12 , a value indicating that the transmission was made at a regular transmission interval, and a time stamp. The third data packet may also include a battery voltage value indicating the voltage level of the backup battery of the power supply  24 . After transmitting the third data packet, the trailer tracking device  12  reenters the sleep mode (step  130 ) and continues monitoring status (step  116 ). 
     If the periodically-determined location coordinates indicate that the trailer  38  has moved outside a boundary of a predetermined area, also referred to as a “geofence” (step  124 ), then the third data packet also includes a value indicating a geofence violation (step  126 ). 
     In some embodiments, while in the sleep mode after decoupling from the truck  40 , an ongoing function provided by the CPU  18  is to monitor the output of the motion sensor  46  to determine if the trailer  38  is moved (step  130 ). Upon sensing that the trailer  38  has moved based on the output of the motion sensor  46 , the trailer tracking device  12  wakes up and acquires its location coordinates (step  122 ), and transmits a fourth data packet to the central monitoring station  50  (step  128 ). The fourth data packet preferably includes at least the location coordinates of the trailer  38 , the unique identification/serial number of the trailer tracking device  12 , a value indicating that motion was detected by the motion sensor  46 , and a time stamp. After transmitting the fourth data packet, the trailer tracking device  12  reenters the sleep mode (step  130 ) and continues monitoring status (step  116 ). 
     If the location coordinates indicate that the trailer  38  has moved outside the boundary of a geofence (step  124 ) then the fourth data packet also includes a value indicating a geofence violation (step  126 ). 
     Upon receipt of the fourth data packet, the central monitoring station  50  may send an alert message to the customer device  56 , such as via email or text message, indicating that the trailer to which the tracking device  12  identified in the second data packet has moved (step  132 ). The alert message may also indicate the location of the tracking device  12 . 
     In some embodiments, while in the sleep mode after decoupling from the truck  40 , an ongoing function provided by the CPU  18  is to monitor the backup battery voltage to determine whether the voltage has dropped below a predetermined minimum threshold (step  134 ). Upon sensing that the battery voltage has dropped below the threshold, the tracking device  12  wakes up and determines its location coordinates (step  122 ), and transmits a fifth data packet to the central monitoring station  50  (step  128 ). The fifth data packet preferably includes at least the location coordinates of the trailer  38 , the unique identification/serial number of the trailer tracking device  12 , a value indicating the battery voltage, and a time stamp. After transmitting the fifth data packet, the trailer tracking device  12  reenters the sleep mode (step  130 ) and continues monitoring status (step  116 ). 
     Upon receipt of the fifth data packet, the central monitoring station  50  may send a message to the customer device  56 , such as via email or text message, indicating that the backup battery should be replaced in the trailer tracking device  12  identified in the sixth data packet (step  132 ). The message may also indicate the location of the tracking device  12 . 
     As discussed above, one way to determine that the trailer  38  has been decoupled from the truck  40  (steps  108  or  118 ) is to sense the breaking of a wired connection, such as disconnection of the harness  36 . In other embodiments, where communication between the trailer tracking device  12  and the truck tracking device  14  is via Bluetooth, Wi-Fi, RFID, or other wireless communication means, loss of the wireless signal between the short-range communication interfaces  22  and  32  could be used to indicate decoupling and separation of the trailer  38  from the truck  40 . 
     In an alternative embodiment, when a trailer  38  is coupled to a truck  40  and the harness  36  is initially connected, the truck tracking device  14  accesses the unique identification/serial number of the trailer tracking device  12  via the short range communication interfaces  32  and  22 . The truck tracking device  14  then transmits a first data packet via the long-range communication interface  20  to the central monitoring station  50  indicating that the trailer  38  and truck  40  are connected. This first data packet preferably includes the unique identification/serial number of the trailer tracking device  12 , the unique identification/serial number of the truck tracking device  14 , current location coordinates acquired from the GPS module  36 , and a time stamp. 
     In yet another alternative embodiment, when a trailer  38  is coupled to a truck  40  and the harness  36  is initially connected, the truck tracking device  14  accesses the unique identification/serial number of the trailer tracking device  12 , and the trailer tracking device  12  accesses the unique identification/serial number of the truck tracking device  14 , both via the short range communication interfaces  32  and  22 . Both tracking devices  12  and  14  then transmit first data packets via their long-range communication interfaces  20  and  30  to the central monitoring station  50  indicating that the trailer  38  and truck  40  are coupled. 
     Thus, based on the automatic generation of the first data packets, second data packets, third data packets, fourth data packets, and fifth data packets, the central monitoring station  50  receives (1) event-based notifications when trailers are coupled; (2) event-based notifications when trailers are decoupled from trucks; (3) periodic notifications indicating the locations of trailers after the trailers are decoupled from trucks; (4) notifications when motion sensors indicate trailer movement; (5) notifications when GPS coordinates indicate trailer movement beyond a geofence boundary; and (6) notifications indicating low-battery conditions in the trailer tracking devices. 
     The foregoing description of preferred embodiments for this invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide the best illustrations of the principles of the invention and its practical application, and to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention.