Patent Publication Number: US-2007096887-A1

Title: Vehicle collision warning system

Description:
FIELD OF THE INVENTION  
      This invention relates to vehicle proximity warning systems. It is disclosed in the context of a system for warning vehicles approaching railroad crossings of the proximity of trains. However, it is believed to be useful in other applications as well.  
     DISCLOSURE OF THE INVENTION  
      According to the invention, a first vehicle includes a first device for receiving global positioning system (GPS) signals, generating at least one of a first time, position and velocity signal based on the received GPS signals, generating at least one of a second time, position and velocity signal based upon the motion of the first vehicle, comparing the first and second signals, generating at least one of a corrected first vehicle time, position and velocity signal, and transmitting the corrected first signal. A second vehicle includes a second device for receiving GPS signals, generating at least one of a third time, position and velocity based on the received GPS signals, generating at least one of a fourth time, position and velocity based on the motion of the second vehicle, comparing the third and fourth signals, generating a corrected second vehicle signal, receiving the corrected first signal, and calculating the likelihood that the positions of the first and second vehicles will coincide at some time.  
      According to an illustrative embodiment of the invention, the system further includes a third device for receiving differential GPS (DGPS) correction signals and retransmitting the DGPS correction signals. The first device receives the DGPS correction signals and combines the DGPS correction signals with the GPS signals to generate the first signal.  
      Further according to an illustrative embodiment of the invention, the second device receives the DGPS correction signals and combines the DGPS correction signals with the GPS signals to generate the third signal.  
      Additionally illustratively according to the invention, the first vehicle includes a device for recording the corrected first vehicle signal.  
      Illustratively according to the invention, the second vehicle includes a device for recording the corrected second vehicle signal.  
      Further illustratively according to the invention, the second device produces an indication to an occupant in the second vehicle that the it is likely that the positions of the first and second vehicles will coincide at some time.  
      Illustratively according to the invention, the indication is a visual indication.  
      Illustratively according to the invention, the indication is an audible indication.  
      Further illustratively according to the invention, the second vehicle includes a display coupled to the second device for indicating at least one of: the location of the first vehicle; the velocity of the first vehicle; the direction of travel of the first vehicle; the location of the second vehicle; the velocity of the second vehicle; and the direction of travel of the second vehicle.  
      Illustratively according to the invention, the display indicates the current positions of the first and second vehicles. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention may best be understood by referring to the following detailed description and accompanying drawings which illustrate the invention. In the drawings:  
       FIG. 1  illustrates a partly block and partly flow diagram for a component constructed according to the invention;  
       FIG. 2  illustrates a partly block and partly flow diagram for a component constructed according to the invention; and,  FIG. 3  illustrates a partly block and partly flow diagram for a component constructed according to the invention. 
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS  
      Referring now to  FIG. 1 , a system  10  provides a warning to vehicles traveling toward a railroad crossing of impending danger from a train either blocking the crossing or close enough to the crossing that there is a danger of collision. The positions, speeds and directions of travel of both the vehicle and train are determined using Global Positioning System (GPS) signals  12  and corrections from Differential Global Positioning Satellite (DGPS) signals  14  are used to calculate the distance between the two vehicles as well as project their arrival at the crossing. This information is further compared and corrected  16  by calculated position and velocity, using data  18  from accelerometer sensors on the vehicle and train.  
      The vehicle/train state can be one of the following: no known train within receiving distance of a receiver in the vehicle; a train has been detected within range of the receiver; the train and vehicle are both approaching the crossing at such a rate that, from their current positions, if they continue there is danger of collision; the train and vehicle are both approaching the crossing at such a rate that, from their current positions, if they continue a collision is practically certain; and, interference is such that no reliable signal can be received from the satellite or train on a timely basis.  
      Audible  20  or visual  22  indication, or both, of the above states can be provided.  
      The system  10  is not intended to replace the existing light and crossing gates in place at some crossings.  
      There are three major communicating components to the system  10 . Referring to  FIG. 1 , the first is a Train Sensor/Receiver/Transmitter (TSRT)  24 . One of these will be placed on a car or engine at each end of the train. Referring to  FIG. 2 , the second component is a Vehicle Sensor/Receiver (VSR)  26 . One of these will be placed on each road vehicle. Referring to  FIG. 3 , the optional third component is a Ground-Based Differential Correction Receiver/Transmitter (GBDCR)  28 . These will be positioned so that at any time each train and vehicle will be close enough to at least one, so that the train and vehicle can receive the correction signal.  
      Referring back to  FIG. 1 , the TSRT  24  receives GPS satellite signals  12 , receives differential GPS correction  14  when the GPS signal is scrambled, and calculates  16  at least one of, and illustratively all of, time, position and velocity based on this input. The TSRT  24  maintains a separate time and/or position and/or velocity based on a processor time and an onboard signal  18  from an accelerometer, compares and computes  16  a corrected time and/or position and/or velocity based on both. The TSRT  24  further records  30  the current state, time and/or position and/or velocity to a black box for a permanent log on the train and vehicle. The TSRT  24  also broadcasts  32  a transmission, for example, a digital transmission, of this state to be received and processed by any vehicle equipped with a VSR  26 .  
      Referring back to  FIG. 2 , the VSR  26  receives GPS satellite signals  12 , receives differential GPS correction  14  when the GPS signal is scrambled, and calculates  16  time and/or position and/or velocity based on this input. The VSR  26  maintains a separate time and/or position and/or velocity based on a processor time and an onboard signal from an accelerometer  18 . The VSR  26  compares and computes  16  a corrected time and/or position and/or velocity based on both the GPS-calculated time and the onboard accelerometer  18 -based time. The VSR  26  records  30  the current state, time and/or position and/or velocity to a black box for a permanent log. The VSR  26  determines the current status, vehicle time and/or position and/or velocity, and the train time and/or position and/or velocity. The VSR  26  maintains this vehicle/train state on its system bus  34  in order to provide to warning devices the information needed to provide the appropriate warning. The VSR  26  maintains the current train state and vehicle state on the system bus  34  to be used by a display  36  processor. The display  36  processor presents a map with the surrounding roadway, train track and intersection, marking the current position(s) of train(s) and/or vehicle(s). It should be understood that many road vehicles are already equipped with GPS receivers. In such cases, all that would need to be provided is an output from the existing GPS receiver to the VSR  26 .  
      Referring again to  FIG. 3 , if the GPS signal is scrambled, the GBDCR  28  receives differential correction signals  40  from the satellite, and relays corrections  14  to all trains and vehicles equipped with a TSRT  24  or VSR  26  by broadcast.  
      It is contemplated that part of the vehicle state that is transmitted will be the vehicle&#39;s identity, for example, the VIN number or some other unique identification.  
      Although the invention has been presented in the context of a system for avoiding collisions between trains and road vehicles, it is clear that the same components can be used on any two or more trains or other vehicles to avoid collisions between them. Each participating vehicle needs both components, the TSRT  24  and the VSR  26 . Since the two components  24 ,  26  share some functionality, integrating them into a single component is a reasonable approach to satisfying their requirements.  
      Examples of such uses in vehicle-to-vehicle collision avoidance systems include, but are not limited to: use on emergency vehicles, such as ambulances and fire trucks, and other vehicles to warn the other vehicles of the proximity of emergency vehicles; use on two vehicle traveling the same route in the same direction in low visibility conditions, such as fog, rain or snow, to warn of proximity; and for identification of congestion caused by road construction, accidents or the like.