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Ultrasonic Position Tracking System . Dave Sekowski Farhan Ismail Tunji Yusuf. Introduction. Design Objective System measures the position of an object in space in three dimensions Allows accurate tracking of ultrasonic equipped object Utilizes several reception units Design

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Ultrasonic Position Tracking System

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Ultrasonic Position Tracking System

Dave Sekowski

Farhan Ismail

Tunji Yusuf


Introduction

  • Design Objective

    • System measures the position of an object in space in three dimensions

    • Allows accurate tracking of ultrasonic equipped object

    • Utilizes several reception units

  • Design

    • Uses reverse concept of GPS

    • System consists of a transmitter, several receiver units and a base station

    • Base station actively manages transmitter

    • Base station later stores time values as RF signals arrive from reception unit

    • Counter values can later be used in trilaturation scheme to determine transmitter location versus receivers


Features

  • Portability

  • Multiple Applications

  • Expandable


Applications

  • Sports Related Usage

  • Motion Sensor and Capture

  • Firefighters

  • Miners


Original Design

  • Clock synchronized across PICs in each unit

  • Counter values referenced to unified clock

  • RF transmission includes data for receiver management

  • Mobile units using custom power supplies

  • Bluetooth output to PC for post processing


System Overview

  • Hardware

    • Can be broken down into three main component

      • Base Station Unit

      • Transmission Unit

      • Reception Unit

  • Software

    • VHDL codes for FPGA


Base Station Overview

  • FPGA

    • Responsible for control of the entire system

  • RF Linx Transmitter

    • Initiates Transmission Unit

  • RF Linx Receiver

    • Input signals from Reception Units


Base Station FPGA Board

  • Programmed in VHDL

  • Replaces PIC in system

  • Outputs logic high to RF transmitter for a window of time (~200ns)

  • Starts internal counter

  • Waits for signal from RF receiver


Base Station RF Transmitter

  • Waits for signal from the FPGA

  • Once received, transmits a modulated high from the base to the transmission unit


Base Station RF Receiver

  • A modulated signal from reception module RF transmitter is received here

  • Converted to digital output for FPGA in receiver

  • Once received the FPGA is instructed to stop its counter and load value into a register


Base Station


Transmission Unit Overview

  • RF Linx Receiver

    • Receives start signal from base station

  • FPGA

    • Responsible for control of the unit

  • Relay

    • Holds required voltage and frequency back

  • Ultrasonic Transmitter

    • Emits ultrasonic burst when prompted by FPGA


Transmission Unit RF Receiver

  • Listens for modulated high from the base station

  • Once received, a high is sent to the transmission unit FPGA


Transmission Unit FPGA Board

  • Programmed in VHDL

  • Replaces PIC in system

  • Once signal is received from RF, the FPGA outputs a high to the relay


Transmission Unit Relay

  • Passes 20 Vpp AC 40 kHz square wave to the ultrasonic transmitter


Transmission Unit Ultrasonic Transmitter

  • The human hearing range ends at 23kHz

  • The ultrasonic transmitter emits a burst of sound pulse at 40kHz

  • Sound travels at 340.29m/s in air enabling us to resolve distances


Transmission Unit


Reception Unit Design

  • Ultrasonic Receiver

    • Takes initial output from transmission unit

  • High Pass Filter

    • Used to attenuate any low frequencies

  • Amplifier

    • Signal is amplified

  • Comparator

    • Changes analog signal to a near-digital square wave

  • RF Linx Transmitter

    • Output sent to base station


Reception Unit Ultrasonic Receiver

  • Ultrasonic transmitter sends out high voltage, 40 kHz square wave signal

  • Distance attenuates the signal amplitude

  • Ultrasonic receiver receives a low voltage, 40 kHz sine wave signal


Reception Unit High Pass Filter

  • Constructed using 0.1uF capacitors and 10k resistors

  • Acts as voltage divider

  • The impedance of the capacitor goes up as frequency goes down thus attenuating low frequencies


Reception Unit Amplifier/Comparator

  • Because of the low voltage signal amplification circuit is needed

  • Gain ~ 905x

  • Amplified signal ran thru comparator

  • Comparator performs analog to digital conversion

  • RF transmitter outputs signal from comparator to the base station


Reception Unit


Software Overview

  • FPGA

    coded

    in

    VHDL


Transmission Unit State Machine


Base Station State Machine


Test/Measurements

  • Oscilloscope reading of signal when relay is off

  • 20 Vpp 40 KHz


Test/Measurements

  • Oscilloscope reading at output of relay

  • (note: distortion)


Test/Measurements

  • Oscilloscope reading of signal at ultrasonic receiver


Test/Measurements

  • Output of high pass filter


Test/Measurements

  • Output of Amplifier


Test/Measurements

  • Output of the Comparator


Test/Measurements

  • Output to the antenna from RF transmitter


Test/Measurements

  • Input of RF receiver at Base Station


Test/Measurements

  • Output of RF receiver

  • (note: trigger set at 3.175V)


Test/Measurements

  • Table of distance between the ultrasonic transmitter and receiver vs the voltage read at the receiver side


Test/Measurements

  • Table of Ultrasonic transmitter and receiver tilt angle vs voltage read at the receiver


Obstacles

  • Programming/Using the PICs for each of our units

  • Having multiple receivers operating at different frequencies

  • Overcoming ambient noise from the environment

  • Finding a proper timing cycle that allowed our device to be as accurate as possible


Recommendations

  • Machine shop RF transmitters and receivers

  • Custom mount ultrasonic and RF antennas

  • Increased importance on filtration system


Future Plans

  • Incorporating multiple receivers

    • Sending Data on same frequency

    • Use multi-channel RF system

  • Setup data processing interface

    • Hyper terminal to PC for external post processing

    • Onboard trilateral calculation with custom LCD display

  • Interchange transmitter and receiver operation

  • Customize power supplies for mobility


Credits

  • Professor Jon Makela: for keeping it real

  • Purvesh Thakker: for patiently waiting in lab dejected and alone during weekly reviews…

  • The many caffeinated beverage we consumed – Red Bull gives you wings

  • The standup comedy that kept us up those long nights – that IS how we do business

  • Jake “ECE 385 monster” Foster: VHDL guru


Thank You

  • Any Questions?


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