Transcript Ultrasonic Tracking System - Rensselaer Polytechnic Institute

Ultrasonic Tracking System
Group # 4
Bill Harris
Sabie Pettengill
Enrico Telemaque
Eric Zweighaft
Introduction
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What is our project?
 Pan and tilt implemented system tracking an ultrasonic beacon which
sends a signal to 3 ultrasonic receivers, is carried around the room by a
team member
How does it work?
 The signal coming from an ultrasonic transmitters is measured at three
different locations
 The difference in the time the signal is received at each sensor is used to
calculate a distance relationship
Why is this project practical?
 Mitsubishi Motor company uses a similar design in their automobiles for
a collision avoidence system
 Various pest and animal repellent systems use ultrasonic waves for
tracking and repelling.
Objective

Simulation of pan & tilt system used as a cost efficient
method to determine:
 Motor required to drive system
 Gear, belt and pulley combination needed
 Response of system to motor, gear, belt and pulley
 Maximum performance variables for system
 Rough estimate of system response to sample
payload
 Chance to show that we were paying attention in all
those math classes
Specifications
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The system will track objects between 2 and 10 meters from the
array
The system will track objects between 0 and 2 meters off the
ground
The system will track items within .5 degree of accuracy (within
10 cms of the object with beacon)
The system must be able to track the beacon at the speed of a
human walking (.64 rad/sec)
Major Change in Design
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With our previous sensor structure, there was
not a large enough motor that could handle the
torque
We decided make a more compact sensor
structure which allowed us to go with a much
smaller motor in the Pittman 8000 series.
The sensor structure was made L shaped instead
of T shaped to allow for a simpler timer circuit
Motor

Pittman GM8724S017
19.5:1 internal gearing ratio
 Encoder mounted directly to rotor increases
accuracy of encoder (encoder is not geared down)
 External transmission gives additional reduction
ratio of 3:1
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Motor
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Pittman GM8724S017
Larger gearing ratio does not allow us to meet our
speed requirements
 Smaller gearing ratio does not allow us to meet our
torque requirements
 Gains must be chosen carefully to remain inside the
feasible range for both speed and torque

Motor
Desired Input and Actual Output for Theta1
1
input
theta1
0.8
•Simulation
•Sinusoidal input
•Frequency of
0.63 rad/s
0.6
0.4
radians
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
0
2
4
6
8
10
time
12
14
16
18
20
Motor
Pittman GM8724S010
1200
1000
1000
800
motor 2 velocity (rad/s)
•Speed vs. Torque plot
•Shows that
motor is well
within limits, as
long as gains are
kept at reasonable
levels
motor 1 velocity (rad/s)
Pittman GM8724S010
1200
not feasible
600
400
200
0
0.05
0.1
0.15
motor 1 torque (Nm)
not feasible
600
400
200
feasible
0
800
0.2
0
feasible
0
0.05
0.1
0.15
motor 2 torque (Nm)
0.2
Controller
Theta1 from 1 radian to zero

0.9
0.8
0.7
0.6
Radians
By intuitive adjustment
of gains, a reasonable
response was obtained
0.5
0.4
0.3
But “guessing” is not a
valid design approach
0.2
0.1
0
0
0.5
1
1.5
Time (in Sec)
2
2.5
3
Desired Input and Actual Output for Theta1
1
input
theta1
0.8
0.6
0.4
0.2
radians
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1
0
-0.2
-0.4
-0.6
-0.8
-1
0
2
4
6
8
10
time
12
14
16
18
20
Controller
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SISO Design tool was used
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Linearized model was obtained using the linearlization
routines provided
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Alternatively, the “linmod” command could be called to create a
linear State Space model from the Simulink Diagram
This allows the designer to view pole/zero locations, bode
plots, AND response plots all at the same time, and adjust
poles, zeros, and gains in any of these formats
Controller
SISO Window
Step Response
Step Response
1.4
1.2
Amplitude
1
0.8
0.6
0.4
0.2
0
0
0.05
0.1
0.15
Time (sec)
Overshoot is very undesirable
0.2
0.25
0.3
0.35
Controller
SISO Window
Step Response
Step Response
1.4
1.2
Amplitude
1
0.8
0.6
0.4
0.2
0
0
0.05
0.1
Time (sec)
PM = 98.2° GM = Inf.
Zero overshoot, 1% ess
0.15
Notes on Controller
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Because of assumptions made in order to
linearize the system, this controller does not
perform perfectly on the non-linearized model,
so some adjustments will have to be made
during assembly and testing
We may wish to add an Integral term later to
cancel the 1% overshoot

Does not seem necessary now- it would only hurt
our transient response, and require more torque and
speed from the motor
Justification for Sensor Parts
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Given the cost of larger motors, needed to have
a design with a small moment of inertia
The higher the clock frequency of timer circuit,
the smaller our sensor structure has to be
The cheapest TTL components had a maximum
functional frequency of 5 MHz
Chose an oscillator accordingly
Cost
Pan and Tilt Parts
Part
Part #
Quanity
Price
Total $$
Motor
GM8724S017
2
192.86
385.72
Gear (large)
A 6A 675NF01812
2
15.15
30.30
Gear (small)
A 6A 625DF01806
2
7.76
15.52
Carbon Fiber
T155-5
1
43.40
43.40
Timing Belt
A6Z16-C018
2
1.86
3.70
Total
$478.64
Additional Costs
Total Amount for Timing Circuit and Sensors:
$46.52
Total Cost for project: $533.84
February
Week 2
Hardware
Software
Reports
Week 3
Week 4
Placing parts and
payload on CAD
drawings to
calculate P,I,M
values for Matlab
simulation (Bill,
Sabie)
Hardware - CAD
designed payload
added to Ben’s CAD
drawings system and
edited P,I,M values
are calculated
(Eric, Sabie)
Final design
specifications are
met
(All members)
Simulation of pan
and tilt system to
obtain feasibility and
performance of test
motor with a test
payload
(Bill)
Final Motor feasibility
simulation with
payload on pan and
tilt system
(Bill, Enrico)
Testing of control
system’s ability to
track a signal using
amplitude, or
distance and time
measurements
(All members)
Presentation writeup
(Enrico Eric)
Proposal writeup
(Sabie, Enrico)
TBD
Parts are ordered
(Eric, Sabie)
March
Weeks 1-2
Hardware
Sensor development
with focus on
time\distance
relationship
(Eric, Sabie)
Week 3
Design model
assembled
(Enrico, Sabie)
Week 4
Further tolerance
testing of physical
equipment
Sensor assembly
(Bill, Eric)
Encoder and
amplifier properties
researched
(Bill, Enrico)
Software
Current Feedback
control analyzing
and testing to find
proper gains for
accurate tracking
(Bill, Enrico)
Encoder and
amplifier properties
simulated
(Eric, Sabie)
Reports
Progress Report
(All members)
Testing and fine
tuning of control
feedback system
(Bill, Sabie)
Test mechanics of
system in terms of
motion
(Bill, Enrico)
Sensor testing with
system
(Enrico, Eric)
Test mechanics of
system in terms of
tracking
(Eric, Sabie)
TBD
TBD