Fachhochschule Lausitz, Senftenberg Systems Engineering MASTER THESIS SAMPATH KUMAR UPPU

FH Lausitz/ SE Sampath Kumar, Uppu

Investigation of Magnetic Pattern of Vehicles and Correlation to Demands of Detection Systems

20.10.2004

Fachhochschule Lausitz, Senftenberg

Systems Engineering

MASTER THESIS

SAMPATH KUMAR UPPU

(Matriculation Nr.212835)

Supervisors:

Prof. Dr.-Ing. E. Stein,

FH Lausitz, Senftenberg

Dr. H. Grüger

Fraunhofer Institute for Photonic Microsystems, Dresden

Prof. Dr.-Ing. B. K. Glück

FH Lausitz, Senftenberg



20.10.2004

Contents Introduction

Problem definitionImportance of this thesis work

Measurement of Earth’s field by using fluxgate sensor Theoretical explanation Advantages of fluxgate sensor

Experimental Set-up and measurement procedure Measurement results

Comparison of vehicle signatures and equipotential lines Interpretations of the results

Discussions Conclusion

Future prospects



20.10.2004

Problem Definition: With the increase of traffic on the roads the current traffic detection

systems(Inductive loops) which are placed just below the earth‘s surface are not reliable.

Finding the appropriate vehicle recognition system.

Aim of the Project: The fluxgate sensor implementation in traffic detection system.

Finding the the appropriate sensor location and its direction of placement.



20.10.2004

Earth’s magnetic field The earth’s magnetic field vector



20.10.2004

Vehicle disturbance in Earth‘s field:

Ferrous object disturbance in uniform field:



20.10.2004

Comparison of different magnetic elements with their operational range:

Fluxgate-Sensors

SQUIDS MR-Sensors

10 10 10 10 0 -3 -6 -9 10 10 3 6

10 9

Magnetic Field strength H in A/m

Bio magnetism

10 10 10 10 -6 -9 -12 -15

10 10 -3 0

10 3

Magnetic flux density B in T

Compass systems

Earth field

Potential free current measurement

Permanent magnets

Magnetic coils

Hall-Elements



20.10.2004

Comparison of low field magnetic sensors with the same resolution:



20.10.2004

Sensor Type Measurement Range

Resolution Current Consumption

Hall sensor ±50mT 0.1mT 20mA

Magnetoresistive sensor

± 10mT/ ±1mT 200µT/20µT 10mA

IMS fluxgate sensor ±200µT 1µT 35mA

Comparison of different magnetic sensors:



20.10.2004

Working Principle of Fluxgate Sensor:



20.10.2004

Layout Diagram of FGS1/COB07:



20.10.2004

Characteristics: Two sensor axes are arranged in orthogonal directions. The differential arrangement of fluxgate system filters

out the even harmonics from the output signal. With the differential arrangement the sensitivity will be

twice as that of the single axis fluxgate sensor. The output voltage is linear. Low drift in sensitivity. The excitation current required by ferromagnetic core to

drive into saturationregion is 30-35mA.



20.10.2004

Advantages: The sensor is not affected by weather

conditions such as rain, fog, snow, wind etc., and dirt.

There is no problem to detect the vehicle even when the vehicle is projected into adjacent lane.

This sensor needs very low maintenance. With this sensor both moving and standing

vehicles can be detected.



20.10.2004

Experimental Set-up:

Measurement of Vehicle Signature

VW Passat B3

Variant

Driving Direction

8 x Sensor



20.10.2004

Blockdiagramm of Hardware

Fluxgate-Sensor

External Power Supply

USB

Software

CPU

Magnetic field

Passat

-1,4

-1,2

-1

-0,8

-0,6

-0,4

-0,2

0

0,2

0,4

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

16cm

-By-

µT



20.10.2004

300 250 200 150 100 50 0 50 100 150 200 250 300 350

Measurement Procedure:

40

60

80

100

120



20.10.2004

Offset measurement:



20.10.2004

Depth 120cm-Bx-µT

-4

-3

-2

-1

0

1

2

3

-600 -400 -200 0 200 400 600 800 1000

Distance(cm)

Bx-

µT

115cm

82cm

49cm

16cm

-16cm

-49cm

-82cm

-115cm

Measurement Results



20.10.2004

Depth 120cm-By-µT

-4

-3

-2

-1

0

1

2

3

4

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

By-

µT

115cm82cm49cm16cm-16cm-49cm-82cm-115cm

Measurement Results



20.10.2004

Depth 120cm-Bz-µT

-6

-5

-4

-3

-2

-1

0

1

-600 -400 -200 0 200 400 600 800 1000

Distance(cm)

Bz-

µT

115cm

82cm

49cm

16cm

-16cm

-49cm

-82cm

-115cm

Measurement Results



20.10.2004

0

2

4

6

8

10

12

14

0 20 40 60 80 100 120 140

depth of the sensor(cm)

B-m

gn

itu

de

-µT

16cm

49cm

82cm

115cm

Comparison of magnitude field strength with respect to distance:



20.10.2004

0

2

4

6

8

10

12

14

16

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

B-m

ag

nit

ud

e-µ

T 115cm

82cm

49cm

16cm

-16cm

-49cm

-82cm

-115cm

0

1

2

3

4

5

6

7

8

9

10

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

B-m

ag

nit

ud

e-µ

T 115cm

82cm

49cm

16cm

-16cm

-49cm

-82cm

-115cm

Magnitude variation for different depths:

Z-40cm depth

Z-80cm depth



20.10.2004

0

1

2

3

4

5

6

7

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

B-m

ag

nit

ud

e-µ

T

115cm

82cm

49cm

16cm

-16cm

-49cm

-82cm

-115cm

Z-120cm depth

The sensors in the middle(16cm, -16cm) are showing more deviation and which are away from the center are showing less deviation of the field.

This effect is beneficial when a sensor has to detect vehicles in a single lane of traffic with other lanes present.

Magnitude variation for different depths:



20.10.2004

Sensor in the middle-16cm-Bx

-8

-6

-4

-2

0

2

4

6

8

10

-600 -400 -200 0 200 400 600 800 1000

Distance(cm)

Bx

-µT

40cm-depth

120cm-depth

Comparison of sensor signatures for different depths:



20.10.2004

Sensor in the middle-16cm-By

-2

-1,5

-1

-0,5

0

0,5

-600 -400 -200 0 200 400 600 800 1000

Distance(cm)

By

-µT

40cm-depth

120cm-depth




20.10.2004

Sensor in the middle-16cm-Bz

-14

-12

-10

-8

-6

-4

-2

0

2

-600 -400 -200 0 200 400 600 800 1000

Distance(cm)

Bz-

µT

40cm-depth

120cm-depth




20.10.2004

Sensor in the middle-16cm-B-magnitude

-2

0

2

4

6

8

10

12

14

-600 -400 -200 0 200 400 600 800 1000

Distance(cm)

B-m

ag

nit

ud

e-µ

T

40cm-depth

120cm-depth




20.10.2004

-6

-4

-2

0

2

4

6

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

Z-11

5cm

-µT

BxByBzB-mag

-4

-3

-2

-1

0

1

2

3

4

5

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

-115

cm-µ

TBxByBzB-mag

Comparison of magnetic fields for a depth of 120cm:



20.10.2004

-6

-4

-2

0

2

4

6

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

82cm

-µT

BxByBzB-mag

-5

-4

-3

-2

-1

0

1

2

3

4

5

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

-82c

m-µ

TBxByBzB-mag




20.10.2004

-8

-6

-4

-2

0

2

4

6

8

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

49cm

-µT

BxByBzB-mag

-6

-4

-2

0

2

4

6

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

-49c

m-µ

TBxByBzB-mag




20.10.2004

-6

-4

-2

0

2

4

6

8

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

16cm

-µT

BxByBzB-mag

-6

-4

-2

0

2

4

6

8

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

-16c

m-µ

T

BxByBzB-mag




20.10.2004

Equipotential lines:

Figure 21

Figure 22

Analysis of Equipotential lines:

–Vehicle presence:

Figure 24



20.10.2004

Signal distortion due to the 50Hz power line cycle

Magnetic noise(Barkhausen noise).

Resistance noise(long cable): Calculated by Nyquist.

The measurements are taken by passing the car in steps of 20cm over the sensors. The position accuracy is ±1cm.

The Passat may not be driven exactly in the middle of the ramp. The variation is ±2.5cm.

Forward and Backward measurements.

Accuracy limitations in measurements:



20.10.2004

-3

-2

-1

0

1

2

3

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

16cm

-Bx-

µT

-1,4

-1,2

-1

-0,8

-0,6

-0,4

-0,2

0

0,2

0,4

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

16

cm

-By

-µT

-6

-5

-4

-3

-2

-1

0

1

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

16

cm

-Bz-

µT

-1

0

1

2

3

4

5

6

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

16

cm

-B-m

ag

.-µ

T

Interpretations of the results:

Overlapping of Passat on the signature:



20.10.2004

-4

-3

-2

-1

0

1

2

3

-600 -400 -200 0 200 400 600 800 1000

distance(cm)

Bx

-µT

115cm

82cm

49cm

16cm

-16cm

-49cm

-82cm

-115cm

Vehicle Direction:



20.10.2004

Vehicle Detection:

•Positioning the sensor:



20.10.2004

Figure28

Advantage of taking Bz for Vehicle Detection:

B-Magnitude=√ (B2x+B2

y+B2z)

–To get the third-axis field the sensor is to be rotated by 90°.



20.10.2004

Sensors are to be placed symmetrically. The waveforms at the outputs of the sensors are identical. Vehicle’s velocity:

• Vehicle length calculation: Velocity and the magnitude variation

• Vehicle classification:

Discussions:

• Velocity measurement:



20.10.2004

Some applications of vehicle presence in daily life:

Car Wash Entry/Exit Drive-through System Loading Dock Gate closing Traffic Detection Intelligent parking Lots Toll Ways



20.10.2004

Conclusion:• Achieved results:

Analysis of Bx, By, Bz, B-magnitude.

Drawing Equipotential lines.

Sensor which is very close: Earth’s field+ Remanence.

Appropriate depth for the proper signature of the vehicle is 100cm or 120cm.

Analysis of equipotential lines:

z-axis field is suitable for the vehicle detection.



20.10.2004

Correlation to Demands of Detection System

Noise correlation technique: Extract the actual signal from the embedding

Differential arrangement of fluxgate system: Twice the sensitivity

Power line cycle filter: Noise is reduced Signal to noise ratio is improved

With this method of measurement: Vehicle signature is much accurate



20.10.2004

• Future Prospects:

Finding length of the vehicle.

Classification of vehicles.

In this project the magnetic field in x, y, z directions are measured and from those B-magnitude is calculated.

Analyzing the Earth’s magnetic field vector () : Bx, By and Bz

Comparing the results with different vehicles.



20.10.2004

THANK YOU FOR YOUR ATTENTION

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Fachhochschule Lausitz, Senftenberg Systems Engineering MASTER THESIS SAMPATH KUMAR UPPU

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