Dual-Frequency Access Control for Disoriented Residents
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Solution Overview
Problem
Access control systems fail in care facilities with disoriented residents who cannot handle electronic ID cards, leading to unreliable access control due to limitations in mental and physical abilities.
Innovation Solution
The system employs dual-frequency communication using UHF (868 MHz) for high-data-rate transactions and LF (125 kHz) for precise location detection, with a PIR sensor to conserve energy and prevent unnecessary activations, allowing for reliable access control even with limited user capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional access control systems using electronic ID cards and RFID technology are used, then access control function is provided, but the system fails when users have limited mental and physical abilities to handle the cards
Solution Approach 1:
The system enables automatic access control where the electronic ID card automatically wakes up the UHF transceiver and establishes communication with the detection device without requiring manual card presentation or user interaction. The card holder simply needs to approach the door, and the system handles the authorization process autonomously, making it suitable for users with limited physical or mental abilities.
2Productivity
If UHF transceivers are continuously active for high data rate communication, then fast authorization dialog is achieved, but energy consumption increases significantly
Solution Approach 1:
The UHF transceiver in the electronic ID card is not continuously active but is periodically activated only when needed. The LF receiver detects wake-up signals from the detection device and triggers the UHF transceiver to establish communication temporarily for the authorization dialog, then returns to idle state. This periodic activation maintains fast authorization capability while dramatically reducing energy consumption during idle periods.
3Measurement precision
If LF transmitters are used for precise location detection, then accurate positioning is achieved, but data transmission rate is limited
Solution Approach 1:
The system segments the communication functions by using two different frequency ranges with specialized roles: LF (125 kHz) is dedicated to wake-up signaling and location identification, while UHF (868 MHz) handles high-speed authorization dialog and data exchange. This segmentation allows each frequency band to optimize its specific function without being constrained by the limitations of the other.
4Length of stationary object
If the range of UHF transceivers is increased for better coverage, then communication range is improved, but the predictability and reliability of the range decreases due to interference from people and objects
Solution Approach 1:
The LF transmitter and receiver act as an intermediary layer between the user and the UHF transceiver. The LF signal provides a stable, predictable wake-up mechanism that is less susceptible to interference from people and objects. This intermediary ensures reliable activation of the UHF transceiver only when the user is within the intended detection zone, compensating for the unpredictability of UHF range propagation.
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
Ensures reliable and efficient access control by enabling disoriented residents to access their rooms automatically while preventing unauthorized access, with adjustable detection ranges and energy-efficient design for prolonged battery life and reduced energy consumption.
Implementation Method 1
A PIR sensor ensures that the LF transmitter is only activated when the thermal image changes due to a person approaching the door
Implementation Method 2
a wake-up function in the LF range, namely 125 kHz. The LF receiver in the electronic ID card is permanently active
Implementation Method 3
uses data transmissions in both the UHF range, namely 868 MHz, and a wake-up function and location information in the LF range, namely 125 kHz
Data Source
Figure 1~4
Figure 5
AI summary
An access control system consisting of electronic identification cards carried by individuals and stationary scanning devices is described. When an electronic identification card approaches a stationary scanning device, an authorization dialog takes place, and upon authorization, a release device is activated.