Profiling of rough terrainby Carl Becker

SCOPE

� Introduction

� Literature survey

� Profiling methods

Profiling concepts� Profiling concepts

� Profiled terrains

� Simulations

� Conclusion

INTRODUCTION

� Simulations are used to verify designs

� Cost effective design verification, prior to prototype building

� Compare simulation results with actual field tests

� Simulation requirements� Model – may be simplified

� Constraints

� Input data

� Simulation is nothing like recycling� Simulation => Garbage in = garbage out

� Correct input data is very important

� Model => Land Rover Defender (validated by M Thoresson)

� Input => Profile of rough terrain

INTRODUCTION

�Three profiling concepts were built and verified

�Profile a section of the Belgian with each concept profiler�Compare profiles from concept profilometers

�Displacement Spectral Densities �Displacement Spectral Densities

�Obtain profiles of frequently used rough terrains�Profiles of the rough terrains at Gerotek test facilities

�Use profile as a Road Definition File in simulation with the use of a previously validated model

�Compare simulation results with actual field tests

LITERATURE SURVEY

� Profiling methods

� Inertial profilers (2-D)

� Laser profilers (3-D)

� Aerial photography (3-D)� Aerial photography (3-D)

Profiling methods

Inertial profilers

(2-D)

Profiling methods

Inertial profilers

(2-D)

High speed profiler

Profiling methods

Laser profilers

(3-D)

Vehicle Terrain

Measurement System

�DGPS

�Inertial Measurement

Unit

�Laser scanner

Profiling methods

� Aerial

photography

(3-D)

Profiling methods

•2-D and 3-D profilometers are available to profile

smooth roads at relative high speed

•Terrains to be profiled are too rough for available

profilometers

•All profilometers have errors•All profilometers have errors

� Gyro errors

� Laser errors

� GPS errors

� Errors caused by the dynamics of vehicle

Profilometer Requirements

It is required that the profilometers are capable of

the following;

� Profile rough terrain (vertical displacements > 25

mm).mm).

� Minimum profile width of 2.5 m.

� Profilometer must be light weight and easily

transported.

� Effective profiling with minimal resources

required.

Profilometer Concepts

� Mechanical profilometer

� Photogrammetric profiling

� Laser scanner

Mechanical Profilometer

A mechanical profilometer using arms pivoted to a reference

frame on one side with small wheels on the ends in contact

with the ground, nicknamed the Can-Can machine

Tilt sensor

Profiling arms Encoder

Potentiometers

Mechanical Profilometer

�Profiles a 3 m wide section

�Resolution = 10.18 mm x 100 mm

�Profile an obstacle < 100 mm high

�Accuracy less than 5 mm

�Profiling fast and effective

Profile of Belgian paving

� Mechanical profilometer

Photogrammetric Profilometer

�Survey control points on profiled terrain (Pro Mapping)

�Calibrate camera to determine the lens distortions, focal length and size of the image

�Sequential photos are taken perpendicular to terrain a with digital camera mounted on a tripod

�Photos overlap one another by 60%

�Mapping done by CAD Mapping on a digital photogrammetric workstation

Photogrammetric Profilometer

�Profiles a 2.5 m wide section, depending on height of camera

�Resolution = 10 mm x 10 mm

�Profile an obstacle > 150 mm high

�Accuracy 3 mm to 10 mm, depending on camera

�Profiling resource intensive

-0.4-0.2

00.2

0.40.6

0.81

1.2

-0.200.2

0.40.60.81

1.21.41.6

1.8

0

0.2

0.4

Width [m]

Concept D test section

Distance [m]

Hei

ght

[m]

Profile of Belgian paving

� Photogrammetric profilometer

� Distortion in camera lens

Laser Scanner Profilometer

�Laser Distance Sensor, S80-MH-5 Data Sensor, used to measure the profile of the

terrain from a vertical distance of 2m

�The Data Sensor is mounted in a purposely build gimball which is mounted on a

tripod

�The gimball enables the Laser Distance Sensor to rotate about two perpendicular

axes. The rotation is controlled by two Stepper motors

Stepper Motors

Laser

Laser Scanner Profilometer

�Profiles a 2.4 m wide section

�Resolution = ave 60 mm x 60 mm, limited by step size

�Profile an obstacle > 150 mm high

�Accuracy 7 mm

�Profiling time consuming, laser sensitive to profiled surface

500x360x58 mm

Profile of Belgian paving

� Laser scanner profilometer

Belgian paving

Displacement Spectral Densities

DSD calculated as follows:

With

( ) ( ) 2

2xx

X FS F

Fδ=∆

With

( )

( ) 2 *

X Fast Fourier Transformof the road profile x d

F Step in Frequency

X F X X

δ

δ δ δ

=∆ =

=

Belgian paving

Displacement Spectral Densities

10-2

100

102

/cyc

les/

m]

DSD of profiled tracks

Class A roadClass D roadClass H road50m Belgian paving, Photogrammetry40m Belgian paving, Laser40m Belgian paving, Can-Can

10-3

10-2

10-1

100

101

102

10-12

10-10

10-8

10-6

10-4

Spatial Frequency [cycles/m]

Dis

plac

emen

t S

pect

ral D

ensi

ty [

m2 /cyc

les/

m]

Displacement Spectral Densities

vs. Straight line fit

10-3

10-2

10-1

/cyc

le/m

]

Belgian paving PSD, Can-Can profile

Belgian paving, Can-Can profile

Inverse Power Law,Sx

= Ax-n

0.05 cycles/m

10 cycles/m

10-2

10-1

100

101

10-7

10-6

10-5

10-4

Spatial Frequency [cycles/m]

Dis

plac

emen

t S

pect

ral D

ensi

ty[m

2 /cyc

le/m

]

Profiled Terrains

� Fatigue Track

Profiled Terrains

� Corrugations

Profiled Terrains

� Potholes

Profiled Terrains

� Ride and Handling Track

� 4.2 km long, profiled in 1 day.

1000

400 600 800 1000 1200 1400 1600 1800 2000 2200

1000

1200

1400

1600

1800

2000

Profiled Terrains

� Ride and Handling Track� Close-up on low mobility Ride and Handling Track

Profiled Terrains

� Rough Track

� Profile top Plato of Rough Track (800 m)

3200 3300 3400 3500 3600 3700

800

850

900

950

1000

Profiled Terrains

� Rough Track

� Structural stiffness of Can-Can too low

Profiled Terrains

� Rough Track� Close-up of rough track

Profiled Terrains

The Can-Can Machine is considered an efficient

profilometer due to:

� “High” profiling speed and efficiency

� Ease of data processing� Ease of data processing

� Accuracy of the profilometer

� Low operating costs

Simulation Model

� Front Suspension

Simulation Model

� Rear Suspension

Simulation Model

� Complete Model on RDF Belgian paving

Simulation Model

� Simulation validation over a trapezoidal bump

(M Thoresson)

Simulation Model

Actual test @ 15 km/h Simulation @ 15 km/h

Simulation Model

� Simulation results FFT unfiltered

0.25

0.3

Simulation FFT and Land Rover FFT of Right Rear Body @ 15 km/h

Simulation Right Rear Body

Land Rover Right Rear Body

0 2 4 6 8 10 12 14 16 18 20

0

0.05

0.1

0.15

0.2

Frequency [Hz]

Am

plitu

de [

m]

Simulation Model� Simulation results filtered FFT (8 Hz low-pass)

0.3

0.35

Simulation FFT and Land Rover FFT of Right Rear Body @ 15 km/h

Simulation Right Rear Body

Land Rover Right Rear Body

0 1 2 3 4 5 6 7 8 9 10

0

0.05

0.1

0.15

0.2

0.25

Frequency [Hz]

Am

plitu

de [

m]

Simulation Model

Simulation Model

BS 6841

[m/s2]

Ride comfort

>2.5 Extremely

uncomfortable

RMS of the vertical accelerations

2.5

3

3.5

RMS_SIM_LFuncomfortable

1.25-2.5 Very

uncomfortable

0.8-1.6 Uncomfortable

0.5-1.0 Fairly

uncomfortable

0.315-0.63 A little

uncomfortable

<0.315 Not

uncomfortable

0

0.5

1

1.5

2

15 26 40 57 73

Speed [m/s]

RM

S [

m/s

^2]

RMS_SIM_LF

RMS_Landy_LF

RMS_SIM_RR

RMS_Landy_RR

RMS_SIM_LR

RMS_Landy_LR

Conclusion

� Three profilometers verified

� Can-Can Machine most efficient profilometer

� Obtained accurate 3-D profiles of frequently

used test tracksused test tracks

� Straight line approximation for DSD not valid

approximation

� Good correlation between actual tests and

simulations on profiled terrain

Questions?