RFID Tag Positioning Using AHR Cone Intersection
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Solution Overview
Problem
Existing RFID-based systems for locating objects within a space face challenges due to limited directional precision and the potential for distance inversion in signal strength, which complicates accurate positioning, especially with passive RFID tags and requires extensive infrastructure like arrays of antennas.
Innovation Solution
The method involves using an Attitude and Heading Reference (AHR) device to generate inertial reference measurement data for an RFID reader, processing this data to estimate the reader's position, and defining cones based on signal strength and orientation to map and intersect these cones to determine the position of RFID inventory tags, allowing for accurate location without extensive infrastructure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If arrays of antennas with RFID readers are used, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The system segments the location determination task into multiple cone measurements taken at different times and positions, rather than requiring all measurements to be taken simultaneously by a large antenna array. Each cone represents a simplified measurement unit that can be processed independently and combined to achieve precise location determination.
Solution Approach 2:
The system adds the time dimension to the measurement process by taking multiple measurements at different times and positions. Instead of requiring spatial complexity (multiple antennas at one location), the system uses temporal complexity (single antenna at multiple locations and times) to achieve the same measurement precision.
2Measurement precision
If beam-steered antennas are used to provide relative angle information, then measurement precision is improved, but device complexity and deployment difficulty increase
Solution Approach 1:
The system uses the natural movement and repositioning of the RFID reader itself to gather the necessary angular and positional information, rather than requiring complex beam-steering mechanisms. The reader's own motion through space provides the varying observation angles needed for precise location determination.
Solution Approach 2:
The system changes the operational parameters by allowing the RFID reader to move to different positions and orientations over time, rather than maintaining a fixed position with complex beam-steering capabilities. This transforms a static, complex system into a dynamic, simpler system.
3Device complexity
If passive RFID tags are used, then device complexity is reduced, but measurement precision deteriorates due to signal strength corruption
Solution Approach 1:
The system introduces cones as an intermediary geometric construct that mediates between the corrupted signal strength measurements and the final position calculation. The cones transform the unreliable RSSI data into a visual and computational framework where position is determined by geometric intersection rather than direct signal strength interpretation.
Solution Approach 2:
The system replaces the direct reliance on electromagnetic signal strength (which is corrupted by multi-path effects) with a geometric construction method. Instead of using RSSI directly to calculate position, the system constructs cones in space and finds their intersection, substituting a geometric-mathematical approach for a direct electromagnetic measurement approach.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables timely and accurate determination of RFID tag positions within a facility, reducing the need for new equipment and installation costs, and improving location precision without requiring strict paths or additional wireless devices.
Implementation Method 1
generating inertial reference measurement data by an Attitude and Heading Reference (AHR) device that is useful for determining a position of an RFID reader within the space
Implementation Method 2
performing operations by the RFID reader to read a plurality of RFID inventory tags one or more times
Implementation Method 3
an angle which is in inverse proportion to a signal strength of a signal received from a respective RFID inventory tag
Data Source
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AI summary
Systems (100) and methods (600) for determining a location of an object within space. The methods comprise: generating Inertial Reference Measurement Data ("IRMD"); reading RFID inventory tags by an RF ID reader; processing IRMD to determine an RFID reader orientation and position estimates at a time of each RFID inventory tag read; defining cones associated with each RFID inventory tag, mapping the cones to a model; analyzing the model to identify a set of cones which overlap each other and are associated with reads for a respective RFID inventory tag; and deriving a position estimate for the respective inventory tag based on intersecting portions of the cones in the set of cones. Each cone has: a vertex which is the RFID reader position estimate at a respective time; and an angle which is in inverse proportion to a signal strength of a signal received from a respective RFID inventory tag.