Proximity detection system with concurrent RF and magnetic fields

摘要

This disclosure provides a method and system for extending the capability of a proximity detection system that is based on use of low frequency magnetic fields, to avoid conflicts in crowded work sites. The improvement is attained by combining the advantages of these low frequency magnetic fields with the advantages of much higher frequency, radiated (RF) signals that are controlled to be produced at the same time, concurrent with each other, in a coordinated and/or synchronous manner.

主权项

1. A proximity detection system for complex work environments for detecting the presence of a worker or operator or vehicle carrying an alarm device in a potentially hazardous location at a work site, the proximity detection system comprising:
a plurality of vehicles; each of the vehicles having at least one magnetic field generator; each of the at least one magnetic field generators adapted to generate ping pulses of a magnetic field, the magnetic field oscillating at low frequency during each ping pulse, the ping pulses having predetermined pulse durations; each of the at least one magnetic field generators adapted to generate radio frequency electromagnetic signals during the predetermined pulse durations; each of the at least one magnetic field generators adapted to sense radio frequency electromagnetic signals during a listening time period, the listening time period having a predetermined initial time length, the initial time length starting at an initial listening start time and ending at an initial listening stop time; each of the at least one magnetic field generators adapted to, upon sensing a radio frequency electromagnetic signals during said listening time period, continue to sense radio frequency electromagnetic signals during an additional listening time length, to extend the listening time period; each of the at least one magnetic field generators adapted to, upon not sensing a radio frequency electromagnetic signal during said listening time period, start generating the magnetic field ping pulses and the radio frequency electromagnetic signals; a plurality of alarm devices located on the persons of a plurality of workers and/or operators and/or vehicles, each device being adapted to sense the strength of the ping pulse magnetic field in which the device is located and to generate an echo response signal after a predetermined echo time delay, wherein the length of the predetermined echo time delay is based on the sensed strength of the ping pulse magnetic field, wherein a first length of the predetermined echo time delay corresponds to a first zone of the magnetic field and a second length of the predetermined echo time delay corresponds to a second zone of the magnetic field; and each of the at least one magnetic field generators being adapted to receive the echo response signals, and to, in response to receiving the echo response signal during a window of time corresponding to the predetermined echo time delay, identify that the device is located in the first or second zone of the magnetic field, each zone being smaller than the magnetic field, wherein the window of time corresponding to the predetermined echo time delay is different than the listening time period.