Application of Multifunctional Doppler LIDAR for ii Multifunction LIDAR Sensor System for Non-contact

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  • Application of Multifunctional Doppler LIDAR for Non-

    contact Track Speed, Distance, and Curvature Assessment

    Joshua Muñoz

    Dissertation submitted to the Faculty of the Virginia Polytechnic Institute and State University in

    partial fulfillment of the requirements for the degree of

    Doctor of Philosophy

    In

    Mechanical Engineering

    Mehdi Ahmadian, Chair

    Dong Ha

    Corina Sandu

    Saied Taheri

    Pablo Tarazaga

    October 30, 2015

    Blacksburg, Virginia

    Keywords: LIDAR, Health Monitoring, Vehicle Dynamics, Track Geometry

    Copyright©, Joshua Muñoz

  • ii

    Multifunction LIDAR Sensor System for Non-contact

    Speed and Rail Geometry Monitoring

    Joshua Muñoz

    Abstract

    The primary focus of this research is evaluation of feasibility, applicability, and accuracy of

    Doppler Light Detection And Ranging (LIDAR) sensors as non-contact means for measuring track

    speed, distance traveled, and curvature. Speed histories, currently measured with a rotary, wheel-

    mounted encoder, serve a number of useful purposes, one significant use involving derailment

    investigations. Distance calculation provides a spatial reference system for operators to locate

    track sections of interest. Railroad curves, using an IMU to measure curvature, are monitored to

    maintain track infrastructure within regulations. Speed measured with high accuracy leads to high-

    fidelity distance and curvature data through utilization of processor clock rate and left-and right-

    rail speed differentials during curve navigation, respectively. Wheel-mounted encoders, or

    tachometers, provide a relatively low-resolution speed profile, exhibit increased noise with

    increasing speed, and are subject to the inertial behavior of the rail car which affects output data.

    The IMU used to measure curvature is dependent on acceleration and yaw rate sensitivity and

    experiences difficulty in low-speed conditions.

    Preliminary system tests onboard a “Hy-Rail” utility vehicle capable of traveling on rail show

    speed capture is possible using the rails as the reference moving target and furthermore, obtaining

    speed profiles from both rails allows for the calculation of speed differentials in curves to estimate

    degrees curvature. Ground truth distance calibration and curve measurement were also carried

    out. Distance calibration involved placement of spatial landmarks detected by a sensor to

    synchronize distance measurements as a pre-processing procedure. Curvature ground truth

    measurements provided a reference system to confirm measurement results and observe alignment

    variation throughout a curve. Primary testing occurred onboard a track geometry rail car,

    measuring rail speed over substantial mileage in various weather conditions, providing high-

    accuracy data to further calculate distance and curvature along the test routes.

    Tests results indicate the LIDAR system measures speed at higher accuracy than the encoder,

    absent of noise influenced by increasing speed. Distance calculation is also high in accuracy,

    results showing high correlation with encoder and ground truth data. Finally, curvature calculation

    using speed data is shown to have good correlation with IMU measurements and a resolution

    capable of revealing localized track alignments. Further investigations involve a curve

    measurement algorithm and speed calibration method independent from external reference

    systems, namely encoder and ground truth data. The speed calibration results show a high

    correlation with speed data from the track geometry vehicle.

    It is recommended that the study be extended to provide assessment of the LIDAR’s sensitivity to

    car body motion in order to better isolate the embedded behavior in the speed and curvature

    profiles. Furthermore, in the interest of progressing the system toward a commercially viable unit,

    methods for self-calibration and pre-processing to allow for fully independent operation is highly

    encouraged.

  • iii

    Table of Contents

    Abstract ........................................................................................................................................... ii

    Table of Contents ........................................................................................................................... iii

    Table of Figures ............................................................................................................................ vii

    List of Tables ............................................................................................................................. xviii

    Outline.......................................................................................................................................... xix

    1 Introduction ............................................................................................................................. 1

    1.1 Motivation ........................................................................................................................ 1

    1.2 Objectives ......................................................................................................................... 1

    1.3 Approach .......................................................................................................................... 2

    1.4 Contributions .................................................................................................................... 5

    2 Background and Technical Review ........................................................................................ 7

    2.1 Rail Geometry Definitions ............................................................................................... 7

    2.2 Railroad Health Monitoring Practices and Techniques.................................................. 10

    2.3 Derivation of the Mid-chord Offset Relationship with Standard Curvature .................. 11

    2.4 LIDAR Technology........................................................................................................ 15

    2.4.1 LIDAR Technology Benefits and Risk ................................................................... 19

    2.5 Virginia Tech’s LIDAR Application.............................................................................. 21

    2.6 Track Speed Recording .................................................................................................. 22

    2.7 Distance Calculation ...................................................................................................... 23

    2.8 Curvature Calculation .................................................................................................... 24

    2.9 Influence of Lens Orientation and Vehicle Yaw on Speed Recording .......................... 26

    2.10 Lens orientation and speed output .............................................................................. 28

    2.11 Testing Schedule......................................................................................................... 30

  • iv

    3 Hy-Rail Vehicle Testing ....................................................................................................... 31

    3.1 System Setup .................................................................................................................. 31

    3.2 Speed Measurement Results........................................................................................... 34

    3.3 Distance Measurement Results ...................................................................................... 36

    3.4 Curvature Measurement Results .................................................................................... 37

    3.5 Wet Rail Testing............................................................................................................. 38

    4 Initial Rail Geometry Car Testing ......................................................................................... 41

    4.1 Test Setup and System Installation ................................................................................ 42

    4.2 Test Route ...................................................................................................................... 43

    4.3 Distance Calibration and Measurement Results............................................................. 43

    4.3.1 Tangent Track, GPS-Determined Distance Calibration.......................................... 43

    4.3.2 Ground Truth Calibration ....................................................................................... 48

    4.4 Speed Test Results ......................................................................................................... 51

    4.5 Curved Track Testing Results ........................................................................................ 51

    4.6 Inclement Weather Testing ............................................................................................ 57

    4.7 Effect of Special Track Work......................................................................................... 58

    5 Semi-Autonomous PXI LIDAR: Railway Geometry Car Testing .......................................