Parking Garage Management and Parking Assistance Device

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Parking Garage Management and Parking Assistance
Device

• Daniel Parente and Kamran Mazhar
• ECE 445 Senior Design Laboratory
• University of Illinois at Urbana-Champaign

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Outline

• Project Overview
• Features
• Design review specifications
• Technical Implementation
• Testing Information
• Challenges and Triumphs
• Opportunities for learning
• Future Directions
• Acknowledgements

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Project Overview

• Motivation A high density of cars require
  parking in a small amount of space.
• This imposes two difficulties
• Drivers must execute precise maneuvers within a
  parking garage
• Garage managers must have information regarding
  the current state of their facilities.
• We have designed a system that solves both of
  these problems by providing a visual cue to
  drivers to assist in parking and providing
  occupancy information to a garage manager via a
  wireless link.

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Features

• Bright, visible signal to a driver that their car
  is in danger of hitting the wall
• Wireless transmission of parking data to parking
  manager
• Attractive, graphical interface for a parking
  garage manager
• Determine which parking spots are in use
• Operates off a standard wall power source
• Durable housing for use inhospitable conditions
• Circuit performs in the face of adverse
  conditions and at multiple temperature regimes
• Scalable design for use in facilities of varying
  size
• Shown to work in an actual parking structure

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Final Product
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Implementation (Overview)

• Two primary parts
• Sensor Module
• We have built an ultrasonic sensor using a PIC
  microprocessor and two ultrasonic transducers.
• Producers a short chirp pulse which travels
  through air until reflected by an object and
  received by our sensor.
• Uses this information to determine if a large
  object is nearby.
• Base Module
• Accepts information from sensors over a wireless
  link.
• Converts this information to RS-232 voltage
  levels and communicate information to a computer.

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Ultrasonic Sensing TX

• Composed of two modules Ultrasonic transmitter
  module and Ultrasonic receiver module
• Ultrasonic TX- Emits an ultrasonic pulse at 40
  kHz
• We provide a 40khz square wave at TTL level by
  sending out periodic pulses from the PIC
• Problem this wave is not strong enough for the
  ultrasonic receiver to receive a distinguishable
  from noise
• Solution-Use an LM318 circuit to amplify the
  signal to 20Vrms(max rating on sensor)

http//www.hobbyengineering.com/H4093.html
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Ultrasonic Sensing RX

• Ultrasonic RX- Will receive 40khz signals, and
  process into signal readable by the PIC
• The RX sensor will receive a signal between
  .039-1.47V, initially we wanted to amplify the
  signal and then use a rectification circuit
• However this was not necessary because the
  signal, could be sent to the comparator(LM339),
  and could be measured against a threshold
  voltage, and the PIC can accurately read the
  signals fast enough therefore the circuit was
  simplified the circuit and costs were reduced

http//www.hobbyengineering.com/H4093.html
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Originally-planned Rx Signal Pathway
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Some Changes!
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Wireless Communication

• Wireless communication is accomplished usinga
  Linx HP3 RF Tx/Rx pair at 903.37 MHz. All
  sensors transmit on the same frequency.
• When not in use, transmitters power down to
  conserve use of spectrum (an ethical obligation)
  and all other sensors to communicate.
• Errors due to interference are detected and
  rejected by a 5-byte communications protocol
• Byte 1 Start byte (0xAA)
• Byte 2 Device ID
• Byte 3-4
• Byte 5 A hash of the last 4 bytes verifying
  integrity
• Predicted error rate is one in 65025
  transmissions (two bytes start and hash would
  have to randomly be correct.

http//www.linxtechnologies.com/Products/RF-Module
s/HP3-Series-Multiple-Channel-Radio-Frequency-Modu
le/
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Providing Power

• Power is provided by a 120VAC-to-30VDC AC Adapter
  from a wall source.
• Problem Need 15 volt rails along with 5 and
  GND.
• Original solution Use resistive divider plus
  voltage-following Op Amps to buffer voltages.
• This solution does not adequately source enough
  current
• Better solution Use two voltage regulators (a
  15 and a 5) to pick off the ground and 5
  levels.

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Software

• Software was designed that reports for all
  sensors 4 quantities
• Raw echo time delay data.
• Estimated physical distance.
• Time of last sensor report.
• Occupied or Available state of each sensor.

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Calibration and Testing Overview

• The ultrasonic sensor records a time measurement
  (in non-SI units iteration count through a wait
  subroutine) of the echo delay.
• To extract distance information from this,
  calibration is required.
• This calibration was performed under normal and
  adverse circumstances.
• Transmitted ultrasonic beam has a characteristic
  emission profile, adding dependence

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Calibration Data
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Calibration Under Adverse Conditions
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Beam Emission Profile

• Beam emission spectrum is shown.
• The emission profile is not in a straight line,
  but has an angular distribution.
• -6 dB point of intensity is at roughly 30 degrees.

http//info.hobbyengineering.com/specs/t400s16.pdf
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Limits of Detection Due to Angled Surfaces
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Triumphs over Challenges

• Overcoming the learning curve associated with new
  hardware and unfamiliar ICs.
• Addressing the signal-to-noise problems
  associated with the ultrasound sensor
• Required careful empirical calibration of the
  threshold at which a sensor signal was considered
  detected.
• The sensors are quite sensitive to variance in
  excitation frequency.
• Minimizing the impact of signal noise on the
  circuit
• Bypass capacitors
• Avoiding noisy integrated circuits
• Avoiding noise-generating signals when detection
  was in progress

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Triumphs over Challenges (Cont)

• Re-designing elements of the circuit to improve
  performance or account for previously unknown
  bugs
• Improvements to the ultrasonic transmitter
• Re-design of the ultrasonic receiver signal
  processing pathway
• Replacement of circuits providing power to obtain
  increased sourcing of current

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Opportunities for learning (technical)

• A primary non-technical objective of the project
  was to learn. Some lessons
• Microprocessor programming
• Incorporating transducers within a sensor
• Error-rejecting, robust wireless communication
• Hardware-software interfacing via RS-232
• Printed Circuit Board Design/Implementation
• Thread-safe, event-driven software design

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Opportunities for learning (other)

• Working and learning autonomously in a very
  loosely-structured environment
• Communicating technical issues effectively
  between partners and to course staff
• Allocating time to the project as appropriate
• Sharing project responsibility
• Obtaining necessary materials
• Identifying and recruiting the assistance of
  knowledgeable experts as necessary

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Future Directions

• We produced a prototype base station and two
  prototype sensor systems to demonstrate the
  system could operate as a multi-sensor system.
• This could easily be scaled up as-is by simply
  powering on more sensors.
• Spectrum-friendly communications protocol
  protects against errors due to internal
  interference, but some upper limit exists before
  reporting to the base station becomes a problem.
• This could be mitigated by decreasing the
  frequency at which each sensor reports to the
  base station.

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Future Directions (Cont)

• Range of wireless transmission is limited in a
  full-scale implementation repeaters to
  communicate across and between floors would be
  required.
• Empirically observed that a prototype transmitter
  and communicate between parking garage floors
  near a stairwell even out of line-of-sight.
• Software would need to be generalized to include
  displays for more than 2 sensors at a time.

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Acknowledgements

• We wish to acknowledge the following people for
  their helpful assistance
• P. Scott Carney, Senior Design Lab Instructor
• Tony Mangognia, Supervising TA
• Mark Smart, who provided valuable insights with
  respect to PC board design
• ECE Parts Shop Staff
• ECE Machine Shop Staff
• Other ECE 445 project teams with which fruitful
  conversations were had
• University of Illinois ECE Department for
  financial support

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Questions

• We would be happy to entertain questions or
  comments at this time!
• Is there something of particular interest to you
  upon which we can elaborate?
• Is there a technical point on which you would
  like clarification?
• Are they are any ideas you would like to discuss
  at this time?
• Other questions can be addressed to Daniel
  Parente at parente2_at_uiuc.edu or Kamran Mazhar at
  mazhar.km_at_gmail.com if you dont want to ask now!
• Lecture slides are available at request or from
  the ECE 445 Website. We are Project 21 from Fall
  2007. http//courses.ece.uiuc.edu/ece445

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Supplemental Figure Power Circuit