Vehicle location systems

• US 3,876,980 A
• Filed: 11/05/1973
• Issued: 04/08/1975
• Est. Priority Date: 11/05/1973
• Status: Expired due to Term

• Current Assignee: Adrian Haemmig, James A. Gibson
• Original Assignee: Adrian Haemmig, James A. Gibson
• Inventors: Haemmig, Adrian, Gibson, James A.
• Primary Examiner(s): Morrison, Malcolm A.
• Assistant Examiner(s): Krass, Errol A.
• Application Number:
  US05/413,040
• Time in Patent Office: 519 Days
• Field of Search: 340/146.1C,146.1BA,22,23,24 325/51,53,55,64
• US Class Current: 714/822
• CPC Class Codes: G08G 1/127 to a central station ; Indicators in a central station
• CPC Class Codes: G08G 1/20 Monitoring the location of vehicles belonging to a group, e.g. fleet of vehicles, countable or determined number of vehicles

Abstract

A vehicle location system having a plurality of stationary wayside stations positioned at predetermined geographical locations. The passage of a vehicle near a station references the location of the vehicle at that point in time and automatically supplies the remote headquarters with information as to the whereabouts of all vehicles operating in the system. Efficient utilization of the communication link between the vehicle and the remote headquarters is enabled by transmitting only updated location information to headquarters. The system enables low power radio frequency signals to automatically communicate error free location information between the wayside station and the vehicle by repetitively transmitting identical digitally coded messages and inhibiting utilization of the information contained in such message until receipt in succession of two location messages identical in code format.

Claims

1. In a vehicle locating system wherein stationary wayside stations are used to reference the location of said vehicle at a given point in time and wireless paths are used for transmitting digitally encoded messages between said stationary wayside stations and said vehicle, the improvement for efficiently utilizing the communication path between said vehicle and another site comprising:

means for temporarily storing said digitally encoded messages, comparator means for comparing a transmitted digitally encoded message with said temporarily stored message, means responsive to said comparator means for automatically initiating re-transmission of said digitally encoded message to said other site, said automatic re-transmission being initiated in response to an updated location message being received by said vehicle and independently of any control stimulus from said other site, and means for inhibiting additional re-transmissions of said digitally encoded message to said other site so long as the received digitally encoded messages correspond to said temporarily stored message so that only updated messages are re-transmitted thereto.

2. In a vehicle locating system wherein stationary wayside stations are used to reference the location of said vehicle at a given point in time and wireless paths subject to interference and substantial attenuation when any appreciable distance separates the vehicle from a wayside station are used for transmitting digitally encoded messages between said stationary wayside stations and said vehicle, the improvement for maintaining the integrity of said messages by detecting errors resulting from the interference and attenuation of said wireless path comprising:

repetitively transmitting identical digitally encoded messages between said stationary wayside station and said vehicle, means for temporarily storing one of said digitally encoded messages, means for comparing the next received digitally encoded message with the temporarily stored message and providing an output signal indicative of a compare or a non-compare therebetween, means responsive to a non-compare output signal for entering said next received digitally encoded message in place of the message in said temporary storage, said comparison being repeated as said digitally encoded messages are received until the received message and the temporarily stored messages are identical at which time a compare output signal is generated, each such message thereby being used twice in said comparison, once when it is compared with a message in said temporary store means and once when it is stored in said temporary store means, and means responsive to said non-compare output signal for inhibiting utilization of said digitally encoded message.

3. In a vehicle locating system wherein stationary wayside stations are used to reference the location of said vehicle at a given point in time and wireless paths are used for transmitting digitally encoded messages between said stationary wayside stations and said vehicle, the improvement for efficiently utilizing the communication path between said vehicle and another site comprising:

register means for registering each received encoded message, temporary store means for temporarily retaining an encoded message, comparator means responsive to said register means for comparing said registered message with a previously received message retained in said temporary store means, and means responsive to said comparator means for automatically initiating only a single transmission of said message over said communication path between said vehicle and another site when said registered message corresponds to said temporarily stored message, said automatic message transmission between said vehicle and another site being initiated in response to an updated location message being received by said vehicle and independently of any control stimulus from said other site.

4. Apparatus as in claim 3 further including:

transmit enable means triggered to a first state when said registered message corresponds to said temporarily stored message and to a second state when said registered message is different than said stored message, said means being retained in said first state during receipt of successive encoded messages so long as the registered message corresponds to said temporarily stored message, transmitter means for transmitting the message in said temporary storage means over said communication path, and means responsively connecting said transmitter means to said transmit enable means for automatically initiating a transmission of the message in said temporary storage only when said transmit enable means is triggered to said first state.

5. In a vehicle locating system wherein stationary wayside stations are used to reference the location of said vehicle at a given point in time and wireless paths subject to interference and substantial attenuation when any appreciable distance separates the vehicle from a wayside station are used for transmitting digitally encoded messages between said stationary wayside stations and said vehicle, the improvement comprising:

repetitively transmitting identical digitally encoded messages between said stationary wayside station and said vehicle, means for temporarily storing one of said digitally encoded messages, comparator means for comparing the next received digitally encoded message with the temporarily stored message, and providing an output signal indicative of a compare or a non-compare therebetween, means responsive to a non-compare output signal for entering said next received digitally encoded message in place of the message in said temporary storage, said comparison being repeated as said identical digitally encoded messages are received until the received message and the temporarily stored message are identical at which time a compare output signal is generated, means responsive to said non-compare output signal for inhibiting re-transmission of said digitally encoded message, means responsive to said compare output signal for automatically initiating re-transmission of said digitally encoded message, said automatic re-transmission being initiated in response to an updated location message being received by said vehicle and independently of any control stimulus from said other site, said means inhibiting re-transmission of said digitally encoded message so long as the received digitally encoded messages correspond to said temporarily stored message so that only updated messages are re-transmitted.

6. In a vehicle locating system wherein stationary wayside stations are used to reference the location of said vehicle at a given point in time and wireless radio frequency channel are used for transmitting digitally encoded location messages between said stationary wayside stations and said vehicle and between said vehicle and a remote headquarters, the improvement for efficiently utilizing the radio frequency channel between said vehicle and said remote headquarters comprising:

radio receiver means carried by said vehicle for receiving said digitally encoded location message when said vehicle is near a stationary wayside station, means coupled to said receiver means for temporarily storing said digitally encoded message, comparator means for comparing a subsequently received message with said temporarily stored message, radio transmitter means carried by said vehicle for transmitting digitally encoded messages from said vehicle to said remote headquarters, means coupling said temporary store means to said radio transmitter, means for transmitting a digital signal from said vehicle to said headquarters which encodes both the vehicle identification and said location message, and means responsive to said comparator means and operatively coupled to said radio transmitter means for automatically initiating transmission of an updated location message from said vehicle to said remote headquarters in response to an updated location message being received by said radio receiver means and independent of any control stimulus from said remote headquarters, said means also inhibiting additional transmissions of the same location signal so that only updated location messages are automatically transmitted from said vehicle to said remote headquarters.