Patent Publication Number: US-6342847-B1

Title: Virtual fence system and method

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of positioning systems and more particularly to a moving fence system and method. 
     BACKGROUND OF THE INVENTION 
     The ability to quickly locate high value assets for maintenance or routine servicing would greatly increase the efficiency of companies involved in using or maintaining the high value assets. The global positioning system and other satellite positioning systems have provided the promise of locating the high value assets. Unfortunately, a number of practical problems have limited the ability to track high value assets. For instance, one problem has been communicating the position information to a user. Construction equipment must communicate two or more times per day even when it has not moved from the site. This message load is costly. Another problem is the mobility of these assets. The assets may be easily moved from one site to another making the process of locating the assets difficult. Yet another problem is the determination of the proper maintenance schedule for the assets. Some equipment requires maintenance after a predetermined numbers of hours of operation. The equipment may be difficult to locate to determine the number of hours of operation that have elapsed. 
     Thus there exists a need for a system that can locate high value assets, that can determine the number of hours of operation for that equipment, and can transmit the position and maintenance information reliably anywhere. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram depicting a tracking and monitoring system in accordance with one embodiment of the invention; 
     FIG. 2 is a diagram depicting the flow of events performed by a tracking monitoring system in accordance with one embodiment of the invention; 
     FIG. 3A is a diagram depicting the flow of events performed by the tracking and monitoring system in accordance with one embodiment of the invention; 
     FIG. 3B is a diagram depicting the flow of events performed by the tracking and monitoring system in accordance with one embodiment of the invention; 
     FIG. 4 is a diagram of the monitoring areas of the tracking and monitoring system in accordance with one embodiment of the invention; 
     FIG. 5 is a flow chart of the steps used in a method of operating a moving fence system in accordance with one embodiment of the invention; 
     FIG. 6 is a flow chart of the steps used in a method of operating a site fence system in accordance with one embodiment of the invention; and 
     FIG. 7 is a flow chart of the steps used in a method of operating a moving fence system in accordance with one embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     A method of operating a moving fence system includes a global positioning system (GPS) receiver. The GPS receiver provides information on the device&#39;s position. The system records the device&#39;s reported position, and determines whether the time is within an operation or nonoperation period. When the time is within an operation period, the system determines whether the device has moved a predetermined number of moving fences since the last reported position. The device then determines whether the device has been within the current moving fence for a predetermined amount of time. The device transmits a position message when the device has both moved the predetermined number of moving fences and has been within a moving fence for a predetermined amount of time. 
     The benefits of such a system are that a device may be moved a finite distance without triggering a message, and that the movement will not result in an overwhelming number of position messages. Thus, the system is easier to use and interpret. 
     FIG. 1 is a block diagram of a tracking and monitoring system  10  in accordance with one embodiment of the invention. A GPS receiver  12  sends a position signal and a time signal to a processor  14 . The GPS receiver  12  determines both the position and time from the GPS satellite signals. The processor  14  is connected to at least two wireless communication systems  26 ,  28  through a communication interface  24 . The at least two communication systems  26 ,  28  transmit signals to a monitoring site  32 . A power management system  16  provides power to the processor  14 . The power management system  16  is designed to reduce the amount of power consumed by the tracking and sensing system  10 . A power source  18  is connected to a switch  20 . The switch  20  is controlled by an output  30  of a motion sensor  22 . As a result, the processor  14  and the rest of the tracking system  10  receive power when the motion sensor  22  indicates motion. This significantly reduces the power consumption of the tracking system  10 . In one embodiment the motion sensor is a vibration sensor. In another embodiment, the motion sensor is an accelerometer. 
     The at least two wireless communication systems  26 ,  28  allow the system  10  to select the second communication system  28  when the first communication system is unable to transmit a position message. This significantly increases the areas where the tracking system  10  may be used and significantly increases the usefulness of the invention. Note that more than two communication systems may be used. In one embodiment, one of the wireless communication systems  26 ,  28  is a satellite communication system. In another embodiment, the system  10  includes a sensor interface connected to the processor  14 . The sensor interface receives a sensor information from a sensor, such as revolutions per minute from a tachometer. The processor  14  transmits the sensor information using the satellite communication system. 
     In another embodiment, the processor  14  includes a moving fence routine. The moving fence routine is divided into operation and nonoperation periods. An operation period is a time of normal business operation, where the emphasis is on a larger, or nonexistent, moving fence boundary and less frequent (or no) position reporting intervals. A nonoperation period is a time of inactivity, or reduced activity, such as the time period after normal working hours. Note that, in one embodiment, the actual fence will be defined in terms of latitude and longitude and therefore will not be an exact square, rectangle, or other polygon. 
     FIG. 2 is a diagram depicting the flow of events performed by a tracking and monitoring system in accordance with one embodiment of the invention. A starting position  34  is the first reported position. A first moving fence boundary  36  is created around the starting position  34  based upon a predetermined set of parameters  54 ,  56 . As the device crosses the first moving fence boundary  36 , a second moving fence boundary  38  is created. The second moving fence boundary  38  is centered on point  46 , the point at which the device crosses the first moving fence boundary  36 . The size and orientation of the second moving fence boundary  38  and all subsequent moving fence boundaries  40 ,  42 ,  44  is based on the same predetermined parameters  54 ,  56  as the first moving fence  36 . The position may be reported based on predetermined parameters, for example, the number of moving fence boundaries that are crossed, when a device is within a moving fence for a minimum amount of time, when a device moves a predetermined distance, or any other helpful parameter. In FIG. 2, the device is programmed to report its position when it crosses four moving fence boundaries. In that instance position  52  is reported to the monitoring site  32 . 
     FIG. 3A is a diagram depicting the flow of events performed by the tracking and monitoring system in accordance with one embodiment of the invention. A starting position  58  is the first reported position. A first moving fence boundary  66  is created around the starting position  58  based upon a predetermined set of parameters  74 ,  76 . As the device crosses the first moving fence boundary  66 , a second moving fence boundary  68  is created. The second moving fence boundary  68  is centered on point  60 , the point at which the device crosses the first moving fence boundary  66 . The size and orientation of the second moving fence boundary  68  and all subsequent moving fence boundaries  70 ,  72  is based on the same predetermined parameters  74 ,  76  as the first moving fence  66 . The position may be reported based on predetermined parameters, for example, the number of moving fence boundaries that are crossed, or when a device is within a moving fence for a minimum amount of time, or any other helpful parameter. In FIG. 3A, the device is programmed to report its position when it moves a predetermined distance  74 . In this example, the device would report its position between points  62  and  64 . 
     FIG. 3B is a timeline, representing the same points and route as FIG. 3A, but the reporting position is based upon a predetermined amount of time  76  within a moving fence. The device is not within a single moving fence boundary for the predetermined amount of time until the fourth moving fence  72 . At time  78  the device has been within the fourth moving fence boundary  72  for the predetermined amount of time  76 . Thus, the position is reported at time  78 . 
     FIG. 4 is a diagram of the monitoring areas of the tracking and ant monitoring system in accordance with one embodiment of the invention. Monitoring areas  80  are selected to give the desired information. Here, the monitoring areas  80  are centered on the cities of Denver and Colorado Springs, in Colorado. The monitoring areas  80  may be centered on any desired area, for example, a construction job site. As monitored devices  82  report their positions, those positions are mapped on a display  84 . As a monitored device  82  enters the monitoring area  80 , the monitored device  82  is catalogued. When the monitored device  82  is catalogued, the device&#39;s hours of operation are compared to a maintenance standard. Other useful parameters and operating conditions are recorded as well. This system allows the user to monitor the traffic into and out of a selected area to oversee delivery schedules, equipment allocation, and the like. The system also gives the operator accurate data for bidding similar jobs. 
     FIG. 5 is a flow chart of the steps used in a method of operating a moving fence system in accordance with one embodiment of the invention. The process starts, step  90 , by recording a reported position of a device at step  92 . The device determines if a time is within an operation or nonoperation period at step  94 . When the time is within an operation period, it is determined if the device has moved a predetermined number of moving fences at step  96 . Next it is determined if the device has been within a moving fence for a predetermined amount of time at step  98 . When the device has moved the predetermined number of moving fences and has been within the moving fence for the predetermined amount of time, the device transmits a position message at step  100  which ends the process at step  102 . In one embodiment, while in a nonoperation period, a position message is sent when the distance the device has moved exceeds a nonoperation predetermined number of moving fences and the device has been within the moving fence for the nonoperation predetermined amount of time. In another embodiment, the reported position is retained until the position message is transmitted. In another embodiment, the step of recording a reported position of a device  92  includes establishing the operation period and nonoperation period. The predetermined number of moving fences and the predetermined amount of time for both the operation period and nonoperation period is established. When the time is within the operation period, the system uses the operation predetermined number of moving fences and operation amount of time. When the time is within the nonoperation period, the system uses the nonoperation predetermined number of moving fences and nonoperation predetermined amount of time. In another embodiment, the step of determining if a device has moved a predetermined number of fences for an operation period  96  includes creating a new moving fence when the device crosses a previous moving fence. The system creates subsequent moving fences when the device crosses the new moving fence. The system determines a new position, and establishes the new moving fence boundary. In another embodiment, when the device has moved the predetermined number of moving fences, but has not been within the moving fence for the predetermined amount of time, a position message is not transmitted. In another embodiment, the position message is transmitted when the predetermined amount of time has elapsed. In another embodiment, the position message is transmitted when the device has moved the predetermined number of moving fences. In another embodiment, the position message is not transmitted when the device has been within the moving fence for the predetermined amount of time, but has not moved the predetermined number of moving fences. In another embodiment, the step of determining if a time is within an operation period or a nonoperation period  94  includes breaking a previous moving fence. In another embodiment, the system determines if the device is within a defined area when the position message is received at a monitoring site. In another embodiment, the system catalogues a plurality of devices within the defined area. In another embodiment, the position message further comprises a time, a location, and an equipment identification information. 
     FIG. 6 is a flow chart of the steps used in a method of operating a site fence system in accordance with one embodiment of the invention. The process starts, step  110 , by defining a monitoring area at step  112 . The system determines when a device enters and departs the monitoring area at step  114 . If a device is within a monitoring area at step  116 , then the device is added to a catalog list at step  118 , which ends the process at step  120 . In one embodiment, the position message includes a device&#39;s engine hours. In another embodiment, the system compares the device&#39;s engine hours to a predetermined maintenance interval. When the device&#39;s engine hours meet or exceed the predetermined maintenance interval, the system alerts the monitoring site. In another embodiment, when a base station establishes the monitoring area, it catalogues and transmits the description of the monitoring area to the device. An entry message is transmitted when the device crosses into the monitoring area. A departure message is transmitted when the device crosses out of the monitoring area. The time and date may be included in the messages. The monitoring area may be displayed using accurate mapping software. 
     FIG. 7 is a flow chart of the steps used in a method of operating a moving fence system in accordance with one embodiment of the invention. The process starts, step  130 , by recording the position of a device at step  132 . The system transmits a position message when the device has satisfied a reporting criteria at step  134 . The device stores the position message at step  136 . The device discards the reported position at step  138 , which ends the process at step  140 . In one embodiment, the reporting criteria comprises the device breaking a moving fence and traveling a predetermined distance. In another embodiment, the reporting criteria includes the device breaking a predetermined number of moving fences. In another embodiment, the reporting criteria comprises the device breaking a predetermined number of moving fences and being within a moving fence for a predetermined amount of time. In another embodiment, the predetermined number of moving fences is one. In another embodiment, the reporting criteria comprises a predetermined period of time. In another embodiment, the step of transmitting a position message when the device has satisfied a reporting criteria  134  includes determining a received signal strength for a wireless communication system. When the received signal strength is less than a predetermined signal strength, the system switches to a second wireless communication system and sends the position message. 
     Thus, there has been described a method of operating a moving fence system which can monitor the position of assets, that can permit some movement of the asset without triggering a message, and that does not overwhelm the user with data and cost in tracking mode. 
     The methods described herein can be implemented as computer-readable instructions stored on a computer-readable storage medium that when executed by a computer will perform the methods described herein. 
     While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alterations, modifications, and variations in the appended claims.