METHOD AND A SYSTEM FOR MONITORING PLURALITY OF MOVABLE OBJECTS

• US 20020024448A1
• Filed: 01/20/1999
• Published: 02/28/2002
• Est. Priority Date: 05/23/1996
• Status: Active Grant

• Current Assignee: Unwire AB (CellPoint AB)
• Original Assignee: Unwire AB (CellPoint AB)
• Inventors: OLESEN, LYKKE
• Granted Patent: US 6,366,216 B1
• Time in Patent Office: Days
• US Class Current: 340/825.49
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 13/78 discriminating between different kinds of targets, e.g. IFF-radar, i.e. identification of friend or foe G01S13/75, G01S13/79 take precedence
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 19/16 Anti-theft; Abduction
• CPC Class Codes: G01S 19/51 Relative positioning
• CPC Class Codes: G01S 2205/007 for management of a communication system
• CPC Class Codes: G01S 5/0027 of actual mobile position, i.e. position determined on mobile
• CPC Class Codes: G08B 21/0227 System arrangements with a plurality of child units
• CPC Class Codes: G08B 21/023 Power management, e.g. system sleep and wake up provisions
• CPC Class Codes: G08B 21/0263 System arrangements wherein the object is to detect the direction in which child or item is located

Abstract

A method and a system for monitoring a plurality of movable objects, wherein each of the objects is equipped with a transponder with which a stationary node is arranged to communicate. Each transponder is caused to reply to a unique signal from the node and each transponder that sends a response signal gives to the response signal a transponder identification addition. A node is caused to detect the speed and direction at which each transponder moves towards and away from the node. Movement of the transponder relative to the node is evaluated by node associated means on the basis of the speed and direction of the transponder. A register over those transponders with which the node shall communicate is setup for each node. A plurality of separate nodes are provided and each node is provided with such a register. The nodes are arranged to communicate with one another, so as to enable a node to record in its monitoring register a transponder from another node.

Claims

1. A method of monitoring a plurality of movable objects, wherein each object is equipped with a transponder and a stationary node is arranged to communicate with said transponders, wherein each transponder is caused to respond to a unique signal from the node, wherein each transponder that sends a response signal gives the response signal a transponder identification addition, wherein the node is caused to detect the speed of movement and direction of each transponder towards and away from the node and with the aid of node associated means is caused to evaluate movement of the transponder in relation to the node on the basis of transponder speed and direction, characterized by setting-up for each node a register of the transponders with which the node shall communicate;

providing a plurality of separate nodes, each having such a register; and

enabling the nodes to communicate with one another and therewith enable a node to take over in its monitoring register a transponder from another node.

2. A method according to claim 1, characterized by causing said node associated means to deliver an alarm signal when the distance of the transponder from the node deviates from a permitted value.

3. A method according to claim 1 or 2, characterized by delivering an alarm signal when the speed of the transponder exceeds a predetermined value.

4. A method according to any one of claims 1-3, characterized by causing the node to effect detection by the Doppler effect.

5. A system for monitoring a plurality of movable objects, wherein each object is provided with a transponder, wherein a stationary node is arranged to communicate with the transponders, wherein each transponder is adapted to respond to a unique signal from the node, wherein each transponder that sends a response signal is adapted to give said signal a transponder identification addition, wherein the node includes means for detecting the speed at which each transponder moves towards or away from the node and is adapted to deliver, with the aid of node associated means, an alarm signal when movement of the transponder towards or away from the node exceeds a predetermined value, characterized in that the node has a register of those transponders with which the node shall communicate;

in that the system includes a plurality of nodes; and

in that the nodes are adapted to communicate such as to enable a node to record in its monitoring register a transponder from another node.

6. A system according to claim 5, characterized in that said means are adapted to deliver an alarm signal when the transponder moves at a speed greater than a predetermined value.

7. A system according to claim 5 or 6, characterized in that said means are adapted to determine changes in the position of the transponder on the basis of said detected speeds of movement.

8. A system according to any one of claims 5-7, characterized in that the detection means of said node are adapted to operate with Doppler effect.

9. A system according to any one of claims 5-8, characterized in that a monitoring node is adapted to contain criteria for which an alarm shall be triggered when a transponder leaves a node in which the transponder is registered.