RFID Shelf Occupancy Detection Using Reference Transponders
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Solution Overview
Problem
Current RFID systems face challenges in accurately and efficiently assigning RFID transponders to specific shelf compartments, particularly in intralogistics, due to high setup and maintenance costs and limited accuracy in tracking transport box movements.
Innovation Solution
An RFID device uses multiple reference transponders in known positions to indirectly locate RFID transponders by analyzing changes in communication properties, such as signal strength and phase, to determine when objects are added or removed from the shelf, allowing for unambiguous assignment and flexible shelf management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of RFID antennas with small reading fields are used to solve localization and assignment, then localization accuracy is improved, but wiring effort and device complexity increase enormously
Solution Approach 1:
The patent divides the shelf into multiple compartments, each equipped with its own RFID antenna. This segmentation allows each antenna to cover a specific compartment with a small reading field, enabling precise localization of transport boxes to specific compartments without requiring a complex centralized system with extensive wiring.
Solution Approach 2:
The patent introduces a vertical dimension by mounting RFID antennas on the shelf compartments themselves rather than using a horizontal array of antennas. This dimensional change allows each compartment to have its own reading field, achieving localization accuracy without the wiring complexity of a traditional extensive antenna network.
2Device complexity
If polling cycles for all antennas are increased to reduce complexity, then device complexity is reduced, but the ability to record all necessary movements of transport boxes deteriorates
Solution Approach 1:
By segmenting the monitoring system into independent compartment-level RFID antennas, each antenna can operate with its own polling cycle. This allows the system to maintain simple polling cycle management for each individual antenna while collectively achieving comprehensive movement detection across all compartments, as each compartment's changes are detected independently and continuously.
3Measurement precision
If additional sensors such as light barriers are used to detect container positions, then measurement precision is improved, but manufacturing costs and device complexity increase
Solution Approach 1:
The RFID antenna serves multiple functions: it not only reads the RFID transponders on transport boxes for identification but also detects the presence and position of containers by monitoring changes in the RFID signal. This multi-functionality eliminates the need for separate light barriers or other position detection sensors, reducing both manufacturing costs and device complexity while maintaining measurement precision.
Solution Approach 2:
The RFID system is self-sufficient in that the same RFID infrastructure used for identification also provides position detection capabilities. The RFID antenna and transponders work together to automatically detect container presence and position without requiring additional external sensors, making the system self-service and reducing overall complexity.
4Ease of operation
If manual material control via routing cards is used, then ease of operation is maintained, but productivity and automation level are low
Solution Approach 1:
The RFID system enables self-service material control where the automated reading and monitoring of transport boxes on shelves occurs without manual intervention. The system automatically detects when boxes are added or removed, tracks their positions, and provides real-time inventory information, significantly improving productivity while eliminating the need for manual routing cards and paper-based control methods.
5Ease of operation
If barcode reading with handheld scanners is used, then ease of operation is improved compared to manual control, but automation level and productivity are still limited
Solution Approach 1:
The RFID system automatically performs the tracking and recording functions that previously required handheld barcode scanners. The RFID antennas continuously and automatically read transponders on transport boxes, eliminating the need for manual scanning operations. This automation significantly improves tracking efficiency and productivity while maintaining ease of operation through centralized system management.
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 solution enables accurate and efficient assignment of transport boxes to shelf compartments with reduced setup and wiring effort, using inexpensive reference transponders that can be flexibly arranged, and provides real-time monitoring of shelf occupancy without the need for additional sensors or complex evaluation.
Implementation Method 1
The control and evaluation unit (22) is designed to determine the location of an RFID transponder (14) by means of changes in communication properties of the RFID communication with reference transponders (24) at known positions
Data Source
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AI summary
An RFID device (18) for detecting shelf occupancy in a shelf (10) is specified, comprising at least one antenna (16), an RF transceiver (20) connected to the antenna (16), and a control and evaluation unit (22) for communication with an RFID transponder (14) via the RF transceiver (22) and the antenna (16) by means of an RFID signal and for detecting and localizing changes in shelf occupancy. The RFID device (18) has a plurality of reference transponders (24) to be attached to the shelf (10) in a known position, and the control and evaluation unit (22) is designed to locate the removed or added RFID transponder (14) by means of the position of a reference transponder (24) in which communication properties of the RFID communication have changed with the change in the detectable RFID transponder population.