UPLINK: ULTRASONIC POSITION LOCATOR FOR INDOOR ENVIRONMENTS Aunim Mashrur Hossain, Giridhar...
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Transcript of UPLINK: ULTRASONIC POSITION LOCATOR FOR INDOOR ENVIRONMENTS Aunim Mashrur Hossain, Giridhar...
UPLINK: ULTRASONIC POSITION LOCATOR FOR INDOOR ENVIRONMENTS
Aunim Mashrur Hossain, Giridhar Nandipati
Advised By: Dr. Daniel Lee
Thursday, April 22nd1:30pm – 4:30pmRCA Laboratory
Demonstration
Applications
System Overview
Motivation and PurposeEstablish standard method of
determiningposition in indoor environments
Display accurate position in real time• Measure the time of arrival of
ultrasonic waves from various ultrasonic transmitters to the ultrasonic receiver
• Compute position relative to these transmitters within an accuracy of a few inches
Create simple, cost effective, and easy to use system• Install in any size rooms without
hassle• Use with same power needs as simple
appliances• Require around $35.00 (excluding
handheld device)
Stationary Clock Synchronizer• Notify Stationary Beacons when to
transmit ultrasonic signals• Ensure no two Beacons transmit
simultaneously• Send infrared synchronization signal to
Mobile Unit
Stationary Beacons• Send ultrasonic waves while signaled
by the Stationary Clock Synchronizer
Mobile Unit• Receive, filter, and amplify Infrared
Synchronization Signal and ultrasonic signals
• Find time difference between arrival of infrared signal and arrival of ultrasonic signal
• Send time differences to Handheld Device
• Display position in a real-time Graphical User Interface
Basic Premise• Infrared signals travel at the speed of
light• Ultrasonic signals travel at the speed of
sound (which is approximately one million times slower)
• Infrared signals can be thought of as immediately arriving at the receiver
Thus, can measure distance using time difference between arrival of infrared and ultrasonic pulses• Each millisecond in time difference
corresponds to approximately 1 foot of distance
• Time differences are accurate to within 100 microseconds ~ one tenth of a foot
Once four beacons send pulses, sequence is restarted• The new signal sequence is denoted by
a longer delay than that between the four transmitter signals
• In order to ensure accuracy, delay is set to ~100 ms
Location Determination Method
Results
Block Diagram
Front End of UPLINK System
• Transmitters denoted by red squares
• Position of user displayed on screen, shown by the blue dot
• Graphical interface updates in real time
Figure 1 – Sequence of Transmitted (above)
and Received Pulses (below)
Figure 2 – Single Transmitted (above) and Received Pulse (below)
Figure 3 – UPLINK Graphical Interface on IPAQ
UPLINK can be extended to many applications• Inventory control in warehouses• Indoor directions in office
buildings/shopping malls• Location-aware devices such as
computer terminals• Virtual rooms and Immersive Audio• Security systems that monitor object
position• Interface with existing outdoor
applications such as GPS to provide pervasive location awareness
Back End of UPLINK System
• Sequence of transmitted pulses is repeated with sufficient delay between them
• Time delay of each of four pulses determines relative position from beacons
• Delays are transmitted to IPAQ for computation of position