Transcript Final Presentation

Technion – Israel Institute Of Technology
Electrical Engineering Department
ELECTRONIC GUIDING CANE
FINAL PRESENTATION
Students : David Eyal
Tayar Yosi
Instructor : Miki Itzkovitz
07/03/04
1
MOTIVATION
• The electronic guiding cane is designed to provide a more
accurate guiding tool for the blind, than the existing laser guiding
cane.
•The electronic guiding cane will alert its user of objects in front of
him, with estimation for the distance to it.
•The electronic guiding cane will identify objects above the
ground, that might be in the users way (should cover a little more
then the users entire height ).
• High accuracy ( the cane should identify even the smallest
objects that can interfere the user ).
• minimum false alarms.
• Low cost.
2
BLOCK DIAGRAM
US.R
US.R
US.T
Signal
detecting
circuits
PIC
40kHZ pulse
transmitting
circuit
US.T
IR
sensor
A/D
BUZZER
3
ELECTRONIC GUIDING CANE
• Uses Infra-Red & Ultra-Sound sensors.
• The microprocessor compares the measurements, and
calculates the distance to the object detected.
• Alerts its user by vibrations, according to the distance
from the object.
• DC consumption : 5v 120 mA.
4
The Infra-Red sensor
• Sends an Infra-Red beam.
• Receives the beam returned.
• Calculates the distance according to the angle
between the beams.
• Outputs a DC voltage accordingly.
5
The Ultra-Sound measurement
• The transmitters send a train of 40 kHz pulses.
• The sensors receive the returned pulses.
• The microprocessor checks the time delay between
the pulses.
receiver 1
transmitters
receiver 2
6
The Ultra-Sound measurements
• The Ultra-Sound transmitter send a 40 kHz pulse for
200 μsec.
• The microprocessor waits 1.5 msec before checking the
Ultra-Sound receivers input, to avoid false
identifications.
• The microprocessor measures the time until the pulse
is returned, and calculates the distance.
US transmitter
US receiver
7
The Ultra-Sound measurement
• In case the object identified is not in front of the
guiding cane, the microprocessor will identify it
according to the time difference between the received
pulses.
receiver 1
transmitters
receiver 2
The Ultra-Sound measurement
• the time between transmitting the pulse and receiving
it is used to measure the distance from the object ( X ).
receiver 1
transmitters
X
receiver 2
The Ultra-Sound measurement
• the time between the received pulses indicates how sided
the object is ( Y ).
• if Y is small, the measurement is taken into account.
• if Y is too big, the object will not be recognized, because
it is not in the users way.
receiver 1
Y
transmitters
X
receiver 2
8
ELECTRONIC GUIDING CANE
• The microprocessor measures the distance using the
Ultra-Sound circuit.
PIC
buzzer
ELECTRONIC GUIDING CANE
• The microprocessor measures the distance using the
Infra-Red circuit.
PIC
buzzer
ELECTRONIC GUIDING CANE
• If no objects detected the microprocessor takes no
action.
Ultra Sound
Infrared
Microprocessor
Φ
Φ
Φ
PIC
buzzer
ELECTRONIC GUIDING CANE
• If both measurements indicate an object, the minimal
distance measured is the effective distance.
Ultra Sound
Infrared
Microprocessor
95 Cm
100 Cm
95 Cm
PIC
buzzer
ELECTRONIC GUIDING CANE
• if the Ultra-Sound measurement indicates a close object
(less then 20 Cm), and the Infra-Red indicates nothing,
the microprocessor will ignore the measurement.
Ultra Sound
15 Cm
Infrared
Microprocessor
Φ
Φ
PIC
buzzer
ELECTRONIC GUIDING CANE
• If the object identified by the two sensors is in the
effective range, the microprocessor activates the buzzer
PIC
buzzer
9
ELECTRONIC GUIDING CANE
• the measurements from the sensors are normalized
and compared.
• If the measurements match, the microprocessor
generates a frequency according to the shortest
measurement, and activates the buzzer.
10
PROBLEMS & SOLUTIONS
• Problem :
the Ultra-Sound identifies very close ( less then 15cm )
objects that are not in front of the cane.
• Solution :
disregarding those measurements in the distance
calculation algorithm.
11
PROBLEMS & SOLUTIONS
• Problem :
the Infra-Red sensor identifies strong light ( pointed to
the sun ) as a close object.
• Solution :
the microprocessor identifies this case according to
the Ultra-Sound measurement. If the Ultra-Sound
doesn’t identify an object in the effective range, it
disregards the measurement. (not implemented)
components
Component
Amount
price
Total Price
Pic microprocessor
1
5$
5$
Infra Red sensor
1
20 $
20 $
Ultra Sound sensor
4
1$
4$
Operative amp ps974
3
0.94 $
2.82 $
Operative amp pl084
1
0.92 $
0.92 $
NPN transistor
3
0.64 $
1.92 $
Resistors & capacitors
~ 80
0.07 $
5.6 $
20 MHz crystal
1
1.47 $
1.47 $
Buzzer
1
2.39 $
2.39 $
Battery
1
14 $
14 $
Total
~ 58 $
12
DEVELOPMENTS & APPLICATIONS
•
An additional variable resistor can change the
maximal distance measured.
•
Additional switches for Disabling the IR
measurements for outdoors.
•
More accurate US sensors can improve the cane’s
accuracy significantly.
13
Device tests
Lab tests 1.
2.
3.
Object size ( identifies 5mm width objects ).
Loud noise ( the US sensors are not affected by loud or
hi frequency noise ).
Materials ( the cane has no problem identifying any kind
of materials ).
Outdoor tests –
1.
the IR sensor had false alarms when it was aimed towards the
sun.
14
ELECTRONIC GUIDING CANE
Electronic guiding cane
Laser guiding cane
• gives distance estimation to
close object by multilevel
vibrations.
• One vibration level no regards
to the distance.
• uses 2 kinds of sensors that
back each other.
• uses only laser distance
measurement.
• disrupted by direct sun rays.
• not affected by direct sun
rays.
• low cost ( components cost ~
58 $ ).
• expensive (costs ~ 1500 $ ).
15
ELECTRONIC GUIDING CANE
•
High accuracy - identifies 5mm cable 1 Meter far .
• Multilevel vibrations - the vibrations varies according to
the distance .
• Effective range - the cane identifies over 5 mm objects
in the distances between 10 Cm & 150 Cm.
• Low cost – components cost - 58 $.
• current consumption - 120 mA.