Personal protection system with RF time-of-flight ranging
A radio frequency time-of-flight ranging system for protecting pedestrians and vehicles on mine sites or similar environments with heavy duty equipment, the system particularly locates people around heavy duty equipment and warns both pedestrian and equipment operator.
1. A system for generating proximity warnings on a site on which a regular size object is at risk from a movement of an oversized movable object, the system comprising:
a point-to-point radio ranging system comprising
a set of anchors adapted and specifically foreseen to be mounted on the oversized object,
a tag adapted and specifically foreseen to be mounted on the regular size object, and
a distance determining unit configured for providing a set of distance determinations between each one of the set of anchors and the tag, based on a defined measuring protocol of a time-of-flight measurement by radio frequency signals, particularly ultra-wideband signals,
a warning unit configured for providing a proximity warning based on the set of distance determinations,
an anchor status dataset stored in a system storage, comprising information on local positions within an arrangement of the set of anchors, wherein a local position is assigned to each one of the set of anchors,
a position determining unit configured for determining position information of the tag relative to the arrangement of the set of anchors, based on an automated procedure comprising the steps of
identifying one of the set of anchors as a position determination anchor, wherein the position determination anchor is defined as the anchor with the closest measured distance to the tag determined by the distance determining unit, and
assigning a field of observation to the position determination anchor, based on the anchor status dataset,
wherein the warning unit comprises a position indicator configured for indicating the position of the tag relative to the arrangement of anchors, based on at least
a first indication associated with the field of observation assigned to the position determination anchor, and
a second indication associated with the distance between the position determination anchor and the tag.
2. The system according to claim 1 , wherein the automated procedure for determining position information of the tag further comprises the steps of
identifying another anchor as an auxiliary anchor to the position determination anchor, and
deriving the position of the tag relative to the arrangement of anchors, based on the anchor status dataset, the field of observation assigned to the position determination anchor, and a triangulation including the position determination anchor, the auxiliary anchor, and the tag.
3. The system according to claim 1 , wherein:
each one of the set of anchors comprises a first and a second transceiver, which are co-located and configured to be time synchronized, and
the measuring protocol comprises determining a time difference between receive timestamps of radio frequency signals receiving the first transceiver and the second transceiver of the positioning determination anchor,
in such a way that
an angle-of-arrival of radio-frequency signals is calculated for the position determination anchor, based on the time difference,
wherein assigning the field of observation to the position determination anchor is based on the calculated angle-of-arrival of the position determination anchor.
4. The system according to claim 1 , wherein:
each one of the set of anchors comprises its local position information with respect to the arrangement of anchors, and
the measuring protocol comprises transmission of anchor positions as payload within the point-to-point radio ranging system,
such that:
the position information of the tag is determined by the tag, particularly based on triangulation including the position determination anchor, the tag, and at least another one of the set of anchors, wherein
the position information of the tag is transmitted to the set of anchors as payload within the point-to-point radio ranging system.
5. The system according to claim 4 , wherein:
the system comprises a global positioning system configured for providing global position information of the arrangement of anchors,
each one of the set of anchors is configured to be provided with global positioning information from the global positioning system, and
the measuring protocol comprises transmission of absolute anchor positions as payload within the point-to-point radio ranging system, based on local position information of anchors and the global positioning information,
such that:
the position information determined by the tag is determined as an absolute position.
6. The system according to claim 1 , wherein:
the system comprises a global positioning system configured for providing global position information of the arrangement of anchors,
each one of the set of anchors comprises its local position information with respect to the arrangement of anchors,
each one of the set of anchors is configured to be provided with global positioning information from the global positioning system, and
the system comprises a central position determination unit,
wherein the system is configured that absolute anchor positions, based on local position information of anchors and the global positioning information, and the set of distance determinations are provided to the central position determination unit, in such a way that the position information of the tag is determined by the central position determination unit as an absolute position based on triangulation including the position determination anchor, the tag, and at least another one of the set of anchors.
7. The system according to claim 1 , wherein the arrangement of anchors comprises at least three anchors, which are arranged in such a way that the vertical projection points of the at least three anchors are arranged along the sides of a rectangular basic shape and that a combination of assigned fields of observation of the at least three anchors provides a horizontal all-round visibility around the basic rectangular shape, wherein
a first anchor projection is arranged at a first corner of the basic rectangular shape,
a second anchor projection is arranged at a second corner, adjacent to the first corner, of the basic rectangular shape, and
a third anchor projection is arranged at the side of the basic rectangular shape opposite to the side spanned by the first and second anchor.
8. The system according to claim 7 , wherein a fourth anchor is arranged in such a way that its vertical projection point lies within the basic rectangular shape.
9. The system according to claim 1 , wherein the position indicator is configured to provide the position indication of the tag by at least one of
a visual coding,
an acoustic coding, and
a tactile coding.
10. The system according to claim 1 , the position indication further comprises indication of a threat level.
11. The system according to claim 10 , wherein the threat level is determined based on at least one of:
a tag identification,
an anchor identification,
the position information of the tag,
heading information for the arrangement of anchors, and
the speed of the arrangement of anchors.
12. The system according to claim 10 , wherein different position determination modes or different position indication modes are triggered based on a defined set of threat levels.
13. The system according to claim 1 , wherein the system is configured that the position information or the threat level is transmitted as payload within the point-to-point radio ranging system.