Technical Report Documentation Page
1. Report No.FHWA/TX-10/0-6004-2 / 2. Government Accession No. / 3. Recipient's Catalog No.
4. Title and Subtitle
A Portable Profiler for Pavement Profile Measurements – Final Report / 5. Report Date
October 2009
Published: August 2010
6. Performing Organization Code
7. Author(s)
Roger S. Walker and Emmanuel Fernando / 8. Performing Organization Report No.
Report 0-6004-2
9. Performing Organization Name and Address
The University of Texas at Arlington
The University of Texas System
Arlington, Texas 76019
The Texas Transportation Institute
The Texas A&M University System
College Station, Texas 77843-3135 / 10. Work Unit No. (TRAIS)
11. Contract or Grant No.
Project 0-6004
12. Sponsoring Agency Name and Address
Texas Department of Transportation
Research and Technology Implementation Office
P. O. Box 5080
Austin, Texas 78763-5080 / 13. Type of Report and Period Covered
Technical Report:
October 2007–August 2009
14. Sponsoring Agency Code
15. Supplementary Notes
Project performed in cooperation with the Texas Department of Transportation and the Federal Highway Administration.
Project Title: Develop a Portable Profiler for Maintenance and Construction Applications
URL: http://ranger.uta.edu/~walker/Reports/recent_research_reports.htm
16. Abstract
This report provides a summary of work performed on Texas Department of Transportation (TxDOT) Research Project 0-6004. The project was initiated to develop a single path, easy to use, portable profiler. Such a device was developed. The profiler measurements from the device provide TxDOT an instrument that can easily be mounted or removed from the front or rear bumper of typical TxDOT vehicles. The profile generated is compatible with existing TxDOT formats. Two separate certification tests were successfully conducted on both a full-size TTI pickup truck and a TxDOT full-size van at the inertial profiler certification track located at the Texas A&M Riverside Campus. The project was conducted by Dr. Roger Walker of the University of Texas at Arlington and Dr. Emmanuel Fernando of the Texas Transportation Institute at Texas A&M University.
17. Key Words
Profiler, Profile Measurement Laser, Surface Pavement Profile / 18. Distribution Statement
No restrictions. This document is available to the public through NTIS:
National Technical Information Service
Springfield, Virginia 22161
http://www.ntis.gov
19. Security Classification.(of this report)
Unclassified / 20. Security Classification.(of this page)
Unclassified / 21. No. of Pages
70 / 22. Price
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
A Portable Profiler for Pavement Profile Measurements – Final Report
by
Roger S. Walker, Ph.D., P.E.
The University of Texas at Arlington
and
Emmanuel Fernando, Ph.D., P.E.
The Texas Transportation Institute, Texas A&M University
Report 0-6004-2
Project 0-6004
Project Title: Develop a Portable Profiler for Maintenance and Construction Applications
Performed in cooperation with the
Texas Department of Transportation
and the
Federal Highway Administration
October 2009
Published: August 2010
THE UNIVERSITY OF TEXAS AT ARLINGTON
The University of Texas System
Arlington, Texas 76019
TEXAS TRANSPORTATION INSTITUTE
The Texas A&M University System
College Station, Texas 77843-3135
DISCLAIMER
The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Texas Department of Transportation (TxDOT) or the Federal Highway Administration (FHWA). This report does not constitute a standard, specification, or regulation. The United States Government and the State of Texas do not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of this report. The engineer in charge of the project is Dr. Roger S. Walker, P.E. #31514.
ACKNOWLEDGMENTS
Researchers would like to acknowledge Mr. Phillip Hempel, the Project Director, Todd Copenhaver, and Dr. German Claros of the Texas Department of Transportation. Acknowledgments are also due Gerry Harrison at the Texas Transportation Institute at Texas A&M University, and Jareer Abdel Qader, Brandon Skinner, and Tuan Nguyen at the Transportations Instrumentations Lab at the University of Texas at Arlington for their part on this project.
vi
TABLE OF CONTENTS
LIST OF FIGURES viii
LIST OF TABLES ix
BACKGROUND AND OBJECTIVES 1
Introduction 1
Pavement Profiling Methods 1
PORTABLE PROFILER 2
Profiler Components 2
Instrument Module 3
SOFTWARE DEVELOPMENT 7
UTA Profiling Method 8
Phase Removal Techniques 10
UTA Profiler Program 11
INITIAL TESTING OF PROTOTYPE PROFILER MODULE 14
INVESTIGATION OF ALTERNATIVES FOR MOUNTING PORTABLE PROFILER MODULE 19
CERTIFICATION TESTING OF PORTABLE PROFILER SYSTEM 25
PORTABLE PROFILER COMPARISONS 30
REPORT SUMMARY 34
REFERENCES 37
APPENDIX: INSTALLING AND USING THE PORTABLE PROFILER 39
viii
LIST OF FIGURES
viii
Figure 1. LMI’s Selcom Road Lasers (from LMI Sales Literature). 3
Figure 2. Distance Measuring Assembly Used on TTI Profiler. 4
Figure 3. Block Diagram of Portable Profiler Design. 5
Figure 4. Printed Circuit Board for Portable Profiler Signal Interface. 6
Figure 5. Signal Interface Board Schematic. 7
Figure 6. Profiler Instrument Package. 8
Figure 7. Connecting the Profiler Instrument Module. 8
Figure 8. UTA Profile Computation Process. 9
Figure 9. Results of Applying a Reverse Filter to a Filtered Signal. 11
Figure 10. Part A of UTA-Profiler Program Flow Diagram. 12
Figure 11. Part B of UTA-Profiler Program Flow Diagram. 13
Figure 12. Unfiltered Reference Profiles on SH6 CRCP Section. 14
Figure 13. Unfiltered Reference Profiles on SH47 Hot-Mix Asphalt Section. 15
Figure 14. Prototype Profiler Module Mounted in Front of Test Vehicle. 17
Figure 15. Repeatability of Inertial Profile Measurements on SH6 Test Segment. 18
Figure 16. Repeatability of Inertial Profile Measurements on SH47 Test Segment. 18
Figure 17. Profiler Module Mounted at Side of Test Vehicle Using Suction Cups. 21
Figure 18. Profiler Module Mounted at Rear of Test Vehicle Using Suction Cups. 22
Figure 19. Profile Repeatability on SH6 Section with Suction Cup Mounting System. 23
Figure 20. Profile Repeatability on SH47 Section with Suction Cup Mounting System. 23
Figure 21. Components of Portable Profiler System. 26
Figure 21. Portable Profiler System on TTI Full-Size Truck. 26
Figure 22. Portable Profiler System on TxDOT Full-Size Van. 27
Figure 23. Profile Repeatability on Smooth Section (TTI Full-Size Truck). 28
Figure 24. Profile Repeatability on Smooth Section (TxDOT Full-Size Van). 28
Figure 25. Profile Repeatability on Medium Smooth Section (TTI Full-Size Truck). 29
Figure 26. Profile Repeatability on Medium Smooth Section (TxDOT Full-Size Van). 29
Figure 27. Test Setup for Comparative Evaluation of Portable Profilers. 31
Figure 28. Comparison of Portable Profiler IRIs on SH6 CRCP Project. 32
Figure 29. Comparison of Portable Profiler IRIs on SH6 PFC Project. 33
Figure 30. Comparison of Portable Profiler IRIs on SH21 Project (Type C Surface). 33
Figure 31. Comparison of Portable Profiler IRIs on SH47 Project (Type D Surface). 34
ix
LIST OF TABLES
Table 1. Instrument Module Components. 4
Table 2. Cross-Correlations between IRI-Filtered Reference Profiles. 16
Table 3. IRIs Computed from Unfiltered Reference Profiles. 16
Table 4. Repeatability of Profile Measurements from Test Module. 19
Table 5. Repeatability of IRIs from Test Module Profile Measurements. 19
Table 6. Accuracy of Profile Measurements from Test Module. 19
Table 7. Accuracy of IRIs from Test Module Profile Measurements. 19
Table 8. Profile Repeatability with Suction Cup Mounts. 24
Table 9. IRI Repeatability with Suction Cup Mounts. 24
Table 10. Profile Accuracy with Suction Cup Mounts. 24
Table 11. IRI Accuracy with Suction Cup Mounts. 24
Table 12. Profile Repeatability from Certification Tests. 30
Table 13. IRI Repeatability from Certification Tests. 30
Table 14. Profile Accuracy from Certification Tests. 30
Table 15. IRI Accuracy from Certification Tests. 30
Table 16. Projects Tested for Comparative Evaluation of Portable Profilers. 32
Table 17. 95 Percent Confidence Intervals of IRI Differences. 34
ix
BACKGROUND AND OBJECTIVES
Introduction
Texas Department of Transportation (TxDOT) Research Project 0-6004 was initiated to develop a single path, easy to use, portable profiler. The project was conducted by Dr. Roger Walker of the University of Texas at Arlington and Dr. Emmanuel Fernando of the Texas Transportation Institute (TTI) at Texas A&M University. During the project such a device was developed, tested, and profile from the device verified. The profiler module provides TxDOT a unit that can easily be mounted or removed from the front or rear bumper of typical TxDOT vehicles for measurements. The profile generated is compatible with existing TxDOT formats. This report provides a description of the portable profiler developed for the project, including its design and initial testing, comparison runs, and verification. The report includes descriptions of the sensors used, the portable profiler construction, and use. The appendix includes operational instruction and other information for mounting and using the device. Interim project report, Project 0-6004, Development of a Portable Profiler Interim Report was published in May 2009. The research plan as well as other project information was documented in the interim project.
Pavement Profiling Methods
Two generally known profiling methods or derivations of these methods are commonly used by today’s profilers. Further details of these methods are described in the interim report mentioned above. The first method was developed by Elson Spangler and William Kelly in the early 1960s (1). The method uses an accelerometer to measure the acceleration of the vehicle mass motion. The mass displacement is then determined by the double integration of the acceleration. The mass displacement (W-M)m with respect to the road is determined by a laser mounted with the laser measurement beam perpendicular to the road surface. The measured profile is then computed by summing Zm, the double integrated mass acceleration with the mass displacement, or (W-M)m, yielding Wm or measured road profile.
The second method, a variation of the first method, was developed by David Huft of the South Dakota Department of Transportation (SDDOT) (2). This method use a similar procedure but with a time-based profiling algorithm. For the Huft method, the vehicle mass acceleration,, and road-body displacement (W-M) are sampled with respect to time. The mass acceleration is then integrated with respect to time and added to the time sampled road-body displacements. Both the Spangler and Huft methods use a filtering process to attenuate the low frequencies or long wavelengths measured by the accelerometer. Because of the success of this system SDDOT began providing technical assistance to other states interested in building similar equipment and organized the Road Profiler Users Conference. This conference provided personnel from the various states with profilers a common time and place where they could discuss their experiences and problems in constructing and using these profilers. South Dakota did not patent this method, resulting in wide spread usage of this road profiling technology.
The portable profiler developed and described in this report uses a slight variation of the South Dakota method and is described in more detail later in the report. The major components used in the portable profiler are described next.
PORTABLE PROFILER
Profiler Components
The portable profiler computes road surface profile with the measurements from the following three sensors:
· a laser for road-body displacement measurements,
· a distance encoder, for measuring distance traveled and synchronizing the computed profile to this distance, and
· an accelerometer for measuring vehicle body displacements.
A fourth sensor, an infrared start sensor, is used for automated and precise starting of profile measurements useful for profile verification with known or reference profile and repeatability studies.
The portable profiler developed in this project uses an LMI SLS 5000 laser (Figure 1) for the road-body displacement measurements. A ± 4g Columbia Research SA107BHP accelerometer is used for measuring the vehicle body acceleration measurements. Synchronizing the computed profiles to distance traveled is required for pavement profiler applications. An Accu-Coder 260 encoder is used for this purpose. A portable distance mounting assembly (see Figure 2) was constructed at TTI on the project for easy attachment of the encoder to the measuring vehicle.
Figure 1. LMI’s Selcom Road Lasers (from LMI Sales Literature).
Instrument Module
A portable instrument module using the sensor components was designed and constructed. The sensors along with power, filter, and other required components in the module are listed in Table 1. Figure 3 provides a block diagram of the relationship between the components. Except for the distance encoder that is attached to the vehicle wheel, all sensors, power, and signal conditioning are housed inside the profiler instrument module, which is placed on the front or rear bumper of the profiler vehicle. During measurements, the data collected from these sensors are converted to digital values and then sent to a notebook PC located in the vehicle for computing profile. All communications between the sensors and PC is done via a USB cable. A printed circuit board was designed and constructed for the filter and other signal conditioning circuit. The board design and schematic are illustrated in Figures 4 and 5, respectively. Figure 6 illustrates the layout of the sensor components discussed in the instrument module. The instrument module is attached to the power, PC (via the USB), distance encoder, and infrared start signal via four connectors as illustrated in Figure 7.
The profiler is portable, small in size, and contains power, laser, and accelerometer sensors, signal conditioning, and analog to digital interface components. The unit is designed to run off the vehicle’s 12 volt power source.
Figure 2. Distance Measuring Assembly Used on TTI Profiler.
Table 1. Instrument Module Components.
A portable mounting bar was designed and developed for the instrument module. Alternate mounting procedures were investigated and discussed later in the section Investigation of Alternatives for Mounting Portable Profiler Module.
Figure 3. Block Diagram of Portable Profiler Design.
Figure 4. Printed Circuit Board for Portable Profiler Signal Interface.
Figure 5. Signal Interface Board Schematic.
SOFTWARE DEVELOPMENT
The profiler software or software module is a modified version of the UTA Ride Console program. Ride Console was developed on an unrelated project at UTA and has been used for a number of years on TxDOT’s and TTI’s profilers for both data collection and certification efforts. Several changes were made to the program for the portable profiler operations. Instructions for running the program are described later in this report. Both the source code and execute modules were made available to TxDOT.