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A Pyroelectric Infrared Sensor-based Indoor Location-Aware System for the Smart Home
指導老師 : 張耀仁 學生 : 莊育嘉
Reference
S Lee, KN Ha, KC Lee - Consumer Electronics, IEEE Transactions on, 2006 - ieeexplore.ieee.org
Outline
Abstract Introduction Architecture of the PILAS ( PIR Sensor-
Based Indoor Location-Aware System) Performance evaluation of the PILAS Summary and conclusions
Abstract
Key issue of smart home how to detect the locations of resident
Two approaches of research effort Terminal-based
Resident must carry a type of device Non-terminal-based
Resident don’t carry such device
This paper use non-terminal-based approach Pyroelectric infrared sensors( PIR sensors)
Introduction
How to enhance a resident’s convenience and safety multimedia appliance Internet appliances were connected via a home network
system Controlled or monitored remotely using a TV or PDA Location-based service
Can anticipate the resident Offer appropriate intelligent service
Introduction (continued)
According to the measurement technology, indoor location-aware system have been classified into three types Triangulation Scene analysis Proximity methods
Triangulation
This method uses multiple distances from multiple known points.
Example Active Badges
Use infrared sensors Active Bats
Use ultrasonic sensors Easy Living
Use vision sensors
Scene analysis
The Scene analysis method examines a view from a particular vantage point.
Examples MotionStar
Use a DC magnetic tracker RADAR
Use IEEE 802.11 local area network (LAN)
Proximity methods
The proximity methods measures nearness to a known set of points.
Example Smart Floor
Uses pressure sensors
Introduction (continued)
According to the need for terminal should be carried by the resident, indoor location-aware system have been classified into two types. Terminal-based method Non-terminal method
Terminal-based methods
Active Bats Use RFID tag Use infrared transceiver It is impossible to recognize the resident’s location
when user didn’t carry such devices.
Non-terminal methods
This method can find resident’s location without such devices
Easy Living Be regarded to invade the resident’s privacy
Smart Floor This method has difficulty with extendibility and
maintenance
Introduction (continued)
This paper presents a non-terminal based location-aware system
Use pyroelectric infrared (PIR) sensors Detection areas of adjacent
sensors overlap Locate a resident
Combining the outputs of
multiple PIR sensors,
Architecture of the PILAS
Framework of the smart home Location-recognition algorithm
Framework of the smart home
An indoor location-aware system must satisfy the following requirements Location-aware system should be
implemented relatively low cost Sensor installation must be flexible Sensors have to be robust to noise Sensors should not be affected by their
surroundings It is desirable that the system’s accuracy is
adjustable according to room types
Advantage of PIR sensors Have been used to turn on a light when it detects
human movements Less expensive Robust to surroundings
Infrared detect wavelength between 9.4~10.4μm In terms of temperature, humidity, electromagnetic
noise Possible to control the accuracy Easily installed on the ceiling
Framework of the smart home( continue)
Device are connected via a home network PIR sensors Room terminals Smart home server Home appliances
Each room is a cell Each PIR sensor detect the resident at a constant period
Functions in smart home server
Generating a virtual map Writing the resident’s movement Provide intelligence services
Via the home network Save the current information
Movement trajectory of the resident Current action of home appliance Current home environment
May offer human-oriented intelligent services
Location-recognition algorithm
In Fig. 3, Resident in 1 a output ‘ON’, b and c outputs ‘OFF’
In Fig. 3, Resident in 2 a and b output ‘ON’, c outputs ‘OFF’
If three or more sensors signal ‘ON’, the resident is located at the centroid of the centers
Location-recognition algorithm( continue )
The accuracy of this system is adjustable. In Figure.3, the radius of the sensing area is1m, then
the maximum error is 1m. When resident is at point 2, the
maximum error is √3/2
m
More sensing areas will increase the accuracy of the system
Fig. 4. Location accuracy according to the sensor arrangement of PIR sensors. (a) 40 sensing areas. (b) 21 sensing areas. (c) 28 sensing areas with twelve sensors.
Sensors on the edges must to be located a little inwards
Fig. 5. The effect of compensating for the center point of the outer sensors. (a) Resident’s movement. (b) Before compensating for the outer sensors. (c) After compensating for the outer sensors.
Performance evaluation of the PILAS
Resident-detection method using PIR sensors The requirements of resident-detection method Implementation method for the resident-detection met
hod for PIR sensors Performance evaluation using an experimental te
st bed
Resident-detection method using PIR sensors
Recognize the resident’s location by combining outputs from all the sensors belonging to one cell Every sensor’s state will influence location accuracy the ‘ON’/’OF’ values can be determined by
comparing a predefined threshold and the digitized sensor output acquired by sampling the analog signal from a PIR sensor
It’s important to find appropriate threshold
Signal output of PIR sensor
Resident enters a sensing area
The variation in the
Infrared radiation increase
PIR sensor outputs an Increasing voltage
The requirements of resident-detection method
PIR sensors must not malfunction by other disturbance
It should be possible to precisely determine the point in time, include resident’s speed and height.
It is necessary to know if a resident stays within the sensing area
The resident -detection method for PIR sensors (continue)
Use Fresnel lens Allows human waveforms to pass through it while
reject other waveforms To eliminate malfunctioning due to pets or
temperature changes Resident has entered a sensing area
Output of a PIR sensor exceeds the positive threshold voltage
This state maintained for several intervals
The resident -detection method for PIR sensors (continue)
Threshold must be sufficient for the method The method can distinguish variation between the
resident’s infrared and other’s infrared The resident has left
Sensor’s output falls below a negative threshold voltage The status maintained for several sampling intervals
A resident stays within the sensing area Output voltage remains between two threshold voltage
Performance evaluation using an experimental test bed
Design the system have a location accuracy of 0.5 m
Room 4×4×2.5 m
(width× length× height) 12 PIR sensors fixed on
the ceiling The method is
shown in Fig. 4(c)
Performance evaluation using an experimental test bed (continue)
Signal processing and judging ‘ON/OFF’ Atmel AT89C51CC001 microcontroller A Nippon Ceramic RE431B PIR sensor NL-11 Fresnel lens A horn was installed on each PIR sensor to limit the sen
sing area to the circle with 2 m diameter
Performance evaluation using an experimental test bed (continue)
Fig. 8 shows the experimental results with the horn In a, walk straight
line In b, moves within
the circle In c, moves outside
the circle
Choose threshold
To judge the signal is ’ON’ or ‘OFF’ When the threshold of the RE431B was ‘ ‘
This value based on the the respect to the internal temperature change
External environmental temperature change didn’t affect its performance at detecting the resident
Pets didn’t affect the performance
Determine the resident’s location
PC-based location recognition algorithm Collected data every 10msec Use an NI 6025E data acquisition (DAQ) board
In Fig. 9 It was drawn using a mouse in left window On the right is the estimated movement trajectory of
resident
Determine the resident’s location
Fig. 9, moving along a T-shaped path Trajectory made by connecting the resident’s location
recognized by the PILAS Maximum location
error is about 30 cm
Summary and conclusions
The location accuracy in this paper is lower than 0.5 m
It is possible to enhance the location accuracy of the system
This system should be extended to deal with a room occupied by more than one resident