Fast and Reliable Pavement Profile Scanning. Alexander Reiterer Fraunhofer Institute For Physical Measurement Techniques (IPM)

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1 Fast and Reliable Pavement Profile Scanning Alexander Reiterer Fraunhofer Institute For Physical Measurement Techniques (IPM)

2 Fast and Reliable Pavement Profile Scanning Alexander Reiterer Fraunhofer Institute For Physical Measurement Techniques (IPM) 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

3 Fraunhofer-Gesellschaft Facts and Figures Foundation 1949 Mission Applied research of direct use to businesses and for the benefit to society Objectives promoting innovations % external level of financing Size More than 20,000 employees 66 Fraunhofer institutes Annual research volume of 1.9 billion Fraunhofer IPM / Folie 3

4 Fraunhofer-Gesellschaft In Freiburg, in Kaiserslautern, in Germany and Worldwide Freiburg is the largest Fraunhofer location by the number of employees and revenues. The Fraunhofer-Gesellschaft operates globally. Each of the 66 Fraunhofer institutes has a large scope of action. Itzehoe Lübeck Bremerhaven Hamburg Oldenburg Bremen Rostock Hannover Berlin Potsdam Teltow Braunschweig Magdeburg Cottbus Oberhausen Paderborn Hall Dortmund Schkopau e Leipzig Duisburg Kassel Schmallenberg Dresden St. Augustin Erfurt Jena Aachen Freiberg Euskirchen Gießen Chemnitz Wachtberg Ilmenau Darmstadt Würzburg Bayreuth Erlangen Bronnbach St. Ingbert Kaiserslautern Fürth Nürnberg Saarbrücken Karlsruhe Pfinztal Ettlingen Stuttgart Straubing Freising Freiburg Augsburg Garching München Oberpfaffenhofen Kandern Prien Efringen- Holzkirchen Kirchen Fraunhofer IPM / Folie 4

5 Fraunhofer IPM The Institute Staff: 225 Employees Operating budget million, thereof 4.8 million industrial proceeds Services Consulting feasibility studies, technology-oriented market studies, technology assessment Development components, systems and pilot production Support implementing and maintenance e of systems, technology transfer, coaching, workshops Fraunhofer IPM / Folie 5

6 Fraunhofer IPM The Institute / Research Group Laser Scanning LSC Contact Wire Clearance Profile Road Pavement Poles Geometry Software Fraunhofer IPM / Folie 6

7 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. Fraunhofer IPM / Folie 7

8 Pavement Monitoring (evenness, material characteristics) State of the Art Lehmann und Partner Pavemetrics Phoenix Scientific Inc. Device for measuring transverse profiles with laser distance sensors mounted on a bar (with a length of 3.30 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) Disadvantages: bulky, expensive and unsafe (Laser Class 3B!) Fraunhofer IPM / Folie 8

9 Pavement Monitoring (evenness, material characteristics) State of the Art Requirements (Formulated by the German Federal Highway Research Institute - BASt): 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) Solution: small, precise and safe (Laser Class 1!) device based on laser scanning technology Fraunhofer IPM / Folie 9

10 Laser Scanning Technology Principles Components of a Laser Scanner distance measurement module angular measurement module optical beam steering module Technology (Beam Steering Methods) 45 -Mirror Mirror as Polygon Fraunhofer IPM / Folie 10

11 Laser Scanning Technology Principles Technology (Distance Measurement) pulse-based phase-shift Pros. - medium and long range (2 m m) - more accurate - faster data acquisition - lower noise Cons. - less accurate - slower data acquisition - higher noise - medium range only (~ 100 m) Fraunhofer IPM / Folie 11

12 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 Fraunhofer IPM / Folie 12

13 Technical Specifications Fraunhofer IPM / Folie 13

14 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 Fraunhofer IPM / Folie 14

15 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. Fraunhofer IPM / Folie 15

16 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. Step 4: Indoor/Outdoor Test of the Scanner - Functional test under different light situation - Evaluation of air-sealed housing Functional test under real conditions Fraunhofer IPM / Folie 16

17 Evaluation Master-Profile-Frame with geometric obstacles Reference system: Leica Laser Tracker AT 900 Fraunhofer IPM / Folie 17

18 Evaluation Fraunhofer IPM / Folie 18

19 Evaluation Point cloud model - grey overlay with raw data from the laser scanner (in orange) and overlay with the references points of the Master Profile Frame (in red). Fraunhofer IPM / Folie 19

20 Evaluation Laser Tracker PPS Fraunhofer IPM / Folie 20

21 Possible Implementations Lehmann und Partner Germany Fraunhofer IPM / Folie 21

22 Possible Implementations Lehmann und Partner Germany Fraunhofer IPM / Folie 22

23 Possible Implementations Austrian Institute of Technology Austria Fraunhofer IPM / Folie 23

24 Example (Schematic) Fraunhofer IPM / Folie 24

25 Results (3D Information) Fraunhofer IPM / Folie 25

26 Results (Intensity Information) Fraunhofer IPM / Folie 26

27 Results (Processing) - 2,0 % - 2,3 % - 2,5 % Fraunhofer IPM / Folie 27

28 Conclusion and Outlook Summary laser scanning device which is able to monitor the pavement with an (relative) precision of mm eye safe technology (laser class 1) robust technology used as a reference instrument by the German Federal Highway Research Institute (BASt) Outlook improvement of resolution of intensity channel (~0.5 1 mm) improvement of measurement frequency up to 2 MHz measurement device for both geometry and crack monitoring Fraunhofer IPM / Folie 28

29 Good ideas for better solutions Visit us on the Internet at Fraunhofer IPM / Folie 29