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  • Alexander Reiterer Fraunhofer Institute For Physical Measurement Techniques (IPM)

    Laser Scanning Technology for Pavement Monitoring – A New Approach

  • Alexander Reiterer Fraunhofer Institute For Physical Measurement Techniques (IPM)

    Laser Scanning Technology for Pavement Monitoring – A New Approach

    Outline  Fraunhofer IPM

     Principle of a Laser Scanner

     Concept of a Pavement Profile Scanner

     Realized Technical Specification

     Evaluation and Calibration

     Examples of Implementation

     Results

     Conclusion and Outlook

  • © Fraunhofer IPM / Folie 3

    Fraunhofer IPM The Institute

    Services

     Consulting – feasibility studies, technology-oriented market studies, technology assessment

     Development – components, systems and pilot production

     Support – implementing and maintenance of systems, technology transfer, coaching, workshops

    Staff: 225 Employees Operating budget 2012 € 13.7 million, thereof € 4.8 million industrial proceeds

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 4

    Fraunhofer IPM The Institute / Research Group “Laser Scanning LSC”

    Contact Wire

    Poles

    Clearance Profile

    Geometry

    Road Pavement

    Software

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 5

    Pavement Monitoring Motivation

     intact road infrastructure is an essential precondition for a functioning economy

     One of the principal parameters of a road surface is its evenness

     Based on the transverse profiles taken (generally in 1 m grids), the parameters of rut depth and theoretical water depth are calculated for the left and right wheel tracks.

    → Precise measurement / monitoring of the road surface necessary.

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 6

    Pavement Monitoring (evenness, material characteristics) State of the Art

    Measurement device for measurement of transverse profile with laser distance sensors mounted on a bar with a length of 3.3.m. → Dr. D. Wehrhan (Germany)

    High-speed cameras, optics and laser line projectors to acquire high-resolution 3D profiles of the road. → e.g. Pavemetrics (Canada).

    © Pavemetrics © Lehmann und Partner

    Disadvantages: bulky, expensive and unsafe (Laser Class 3B!)

    © Phoenix Scientific Inc.

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 7

    Pavement Monitoring (evenness, material characteristics) State of the Art

    Solution: Small, precise and safe (Laser Class 1!) device based on laser scanning technology.

    Requirements:

     relative precision of 0.3 mm.

     max. point distance of 5 mm (transversal).

     measurement independent from ambient light situation.

     measurement independent from surface structure (color, roughness, etc.).

     stable housing (IP67).

     eye safe (laser class 1).

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 8

    Laser Scanning Technology Principles

    45°-Mirror Mirror as Polygon

    Components of a laser scanner:

    → distance measurement module → angular measurement module → optical beam steering module

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 9

    Laser Scanning Technology Principles

     Technology (Distance Measurement)

    Pros Cons

    pulse-based - medium and long range (2 m – 5.000 m)

    - less accurate - slower data aquisition - higher noise

    phase-shift - more accurate - faster data aquisition - lower noise

    - medium range only (~ 100 m)

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 10

    Laser Scanning Technology Principles

     Phase Shift Method

    → fast method for distance measurement (millions points per second)

    → precise method for distance measurement (e.g. sub-mm for distances up to 5 m)

    → method for close-range

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 11

    Pavement Profile Scanner PPS Technical Specifications

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 12

    Pavement Profile Scanner PPS Technical Specifications

    relative precision of 0.3 mm.

    max. point distance of 5 mm (transversal).

    measurement independent from ambient light situation.

    measurement independent from surface structure (color, roughness, etc.).

    stable housing (IP67).

    eye safe (laser class 1).

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 13

    Pavement Profile Scanner PPS Technical Specifications

    Mirror as Polygon

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 14

    Pavement Profile Scanner PPS Technical Specifications

    Polygon Mirror

    Interfaces

    - Modulator - DCDC-Board - FPGA - …

    Laser and Detector

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 15

    Pavement Profile Scanner PPS Tests and Calibration Procedure

     Step 1: Evaluation of Distance Measurement Unit (Static Mode)

    - Measurement section of 4 m is used as reference - Continuing measurement of distance between scanner and target - Evaluation for different reference targets (reflectivity) → functional test and evaluation of precision of the distance measurement unit.

    magenta, cyan: intensity white, yellow: phase shift measurement plus distance green: difference between PPS and reference measurement

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 16

    Pavement Profile Scanner PPS Tests and Calibration Procedure

     Step 2: Evaluation of Scanner (dynamic mode, step-and-go)

    - Measurement section of 10 m is used as reference - Continuing measurement of distance between scanner and target - Evaluation for different reference targets (reflectivity) - Evaluation of angular values (evaluation of the encoder) - Evaluation of the internal reference phase → calibration: non-linearity is considered by a lookup-table.

    blue, magenta: distance (mean, standard deviation) red: intensity green: difference between PPS and reference measurement

    Distance

    Std

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 17

    Pavement Profile Scanner PPS Tests and Calibration Procedure

     Step 3: Evaluation of Scanner (dynamic mode, mounting height)

    - Measurement of vertical profiles of different reflectivity - Continuing measurement of distance between scanner and target - Reference values are measured by a Laser Tracker (AT901) - Evaluation of reference and scanner values → calibration: non-linearity depending on angular values are considered by a higher-order (4th) polynomial function.

    - Functional test under different light situation - Evaluation of air-sealed housing → functional test under real conditions.

     Step 4: Indoor/Outdoor Test of the Scanner

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 18

    Pavement Profile Scanner PPS Tests and Calibration Procedure

     Calibration Protocol

    PPS 101, SN: 114308-8 Light Grey 35% and 80% (*) Mean Grey 20% (*)

    Noise (std. dev. < 0.2 – 0.3mm)

    @ middle 0 deg. 0.17 mm 0.16 mm @ side 35 deg. 0.24 mm 0.24 mm

    (*) on norm target, reference system = Leica Laser Tracker AT901B

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 19

    Pavement Profile Scanner PPS Possible Implementations

    Lehmann und Partner Germany

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 20

    Pavement Profile Scanner PPS Possible Implementations

    Lehmann und Partner Germany

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 21

    Pavement Profile Scanner PPS Possible Implementations

    Austria Institute of Technology Austria

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 22

    Pavement Profile Scanner PPS Example (Schematic)

    Dr. Alexander Reiterer - alexander.reiterer@ipm.fraunhofer.de

  • © Fraunhofer IPM / Folie 23

    Pavement Profile Scanner PPS Results

    Dr. Alexa

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