Sensors for Automotive Applications -...

© 2010 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary

Sensors for Automotive Applications

Mark Christini Zed (Zhangjun) Tang ANSYS, Inc.

© 2010 ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary

Contents

• Introduction • Hall Sensor • Variable Reluctance Sensor • Magneto-resistive Sensor • Flux Gate Sensor • Eddy Current Sensor • Summary


Introduction

• Sensors are electromechanical devices that use magnetic field for sensing

• Velocity sensors for antilock brakes and stability control • Position sensors for static seat location • Eddy current sensors for flaw detection


Component Analysis

• Use specific magnetic solvers to understand the basic physics of the sensor – Vary Geometry, Material Properties, Environmental Conditions – Understand Key Factors that most Significantly affect Performance

• Statistical, Monte Carlo, Sensitivity, Design of Experiments – Use Optimization Tools to Refine Design

• Quasi-Newton, Genetic, Pattern Search – Create a Model of the Sensor for use in System Simulation


System Analysis

• Use System Simulation to understand the Sensor’s impact on the whole system – Design a robust sensor using appropriate technology – Don’t Over-Design unnecessarily – Consider Variations


Hall Effect Sensor

Gap between pole piece and target wheel

Rotate about the Z axis through one half of a tooth, or 30 degrees.

• For speed control • Determine flux passing

through 3D Hall effect sensor

• Rotate sensor and vary gap

Permanent magnet

Pole piece

Hall sensors

IC chip


Hall Effect Sensor

Field in permanent magnet & pole piece

Field in IC and

Hall sensor

• Flux in Hall effect sensor can be determined by integrating B(normal) on a surface


Hall Effect Sensor – Meshing Tips

Sensor Air Box Required for Proper Meshing

Target Air Box Required for Proper Meshing


Differential Hall Sensor

Gap between pole piece and target wheel

Target Wheel

Permanent

Magnet

Pol

e P

iece

Cell Top

Cell Bot

Hall IC

21

cell_face

aveavediff

xave dAB

ϕϕϕ

ϕ

−=

= ∫


Hall Sensor - Parametric Results

• Average top and bottom flux vs. angle • Spacing = 1, 2, and 3mm


Hall Sensor - Simplorer Simulation

ICA:

Link1.GAP := 3

EQU

Difference := FLUXM2.FLUX - FLUXM1.FLUX

FLXFLUXM1 FLX FLUXM2CONST

CONST2

Difference

COMP1ECE

EMSSLink1

ROT

ROT_Vw +

Maxwell 3D LinkMaxwell 3D Link


Hall Sensor - System Simulation

0.00 100.00 200.00 300.00 400.00 500.00 600.00Time [ms]

0.00

0.02

0.04

0.06

0.08

0.10

0.12

Flux

[vs]

0.0000

0.0010

0.0020

0.0030

0.0040

0.0050

Y2

Curve Info Y AxisFLUXM1.FLUX

TR Y1

FLUXM2.FLUXTR Y1

DifferenceTR Y2

COMP1.VALTR Y2

• Spacing = 3mm • Differential signal is too small


Hall Sensor - System Simulation

• Spacing = 1mm • Differential signal is detected

0.00 100.00 200.00 300.00 400.00 500.00 600.00Time [ms]

0.00

0.03

0.05

0.08

0.10

0.13

0.14

Flux

[vs]

0.00

0.03

0.05

0.07

0.10

0.13

0.15

0.17

0.20

0.21

Y2

Curve Info Y AxisFLUXM1.FLUX

TR Y1

FLUXM2.FLUXTR Y1

DifferenceTR Y2

COMP1.VALTR Y2


Variable Reluctance Sensor

Permanent magnet

Coil

Pole piece

• For speed control by determining output voltage • Consider varying flux linkage vs. time due to fringing, nonlinear

materials, and speed of rotation



Finite element model

(equivalent circuit)

Output voltage vs. time

Angle vs. Time


Magneto-resistive Sensor

– For speed control of gear wheel – Resistance changes with the angles which the magnetic field which crosses the direction of current accomplishes – Use Maxwell to determine average

magnetic field angle: α – In Simplorer, look-up table of α vs.

rotation gives resistance


• Input Parameters – Rotation angle of Wheel – Permeability of missing tooth

RotAngle

$TeethMur

Magnetize M



• Output Parameters – The Angle of magnetic field on sensor part

Sens_Fwd Sens_Back

=

∫∫−

VdvH

VdvH

x

y

/

/tan 1α

Qty ・ H ・Scalar ・ Y Geom ・ Sens_Fwd ・ Integ Qty ・ H ・ Scalar ・ X Geom ・ Sens_Fwd ・ Integ / Trig ・ Atan Constant ・PI ・/ Number ・ 180.0 ・* [Add] → Ang_Fwd

Operation of Calculator.



• Exporting Lookup Table • Export as format of Table . • Data is manually processed by other tools. (e.g. Excel) • Reload as Table Export SML.

Export from Parametric Solutions Export from Imported Table

ECE - LINKECE - LINK

編集

Part for One round is copied

Result table file : ±30[deg] and ±15[deg]

Result table file : Merged as Complete one round.



-15[deg] Magnetic Flux Density B

-13[deg] H vector near sensor.



• Parametric results – α vs. rotation • Shows results for missing tooth

-15[deg] ~ 15[deg] -30[deg] ~ 30[deg]



-20.40m

20.40m0

0 40.00m20.00m

MRSensor.Sensitivity

Sensor output Voltage.

28.00u

29.00u

28.50u

0 40.00m20.00m

VM1.V [V] + -2.50

-9.92

10.00

0

0 40.00m20.00m

VM6.V [V]

Amplified Output.

System Model with Sensor


Angle

speed

System Model for Speed Control


Fluxgate Sensor

• For static position indication • A fluxgate sensor contains a

small core designed to be easily saturated

• Inductance is affected by the magnitude of an external field created by drive coil

• The value of inductance can change by 10 times or more

• This circuit provides an output voltage that is proportional to the magnitude and the direction of an externally applied field.

Drive Coil Core


Arrows Indicate Magnetization Direction

• Typical Flux Gate Sensor Applications include:

• Proximity Sensing

• Magnetic Field Measurement (Navigation, Geomagnetics)

• Speed & Position Sensing

• Sensor has Linear Response Characteristic

Fluxgate Sensor


Arrows Indicate Magnetization Direction

Typical B-H Curve

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

-8.0E+05 -6.0E+05 -4.0E+05 -2.0E+05 0.0E+00 2.0E+05 4.0E+05 6.0E+05 8.0E+05

H (A/m)

B (T

)

Sensor is Driven Between Linear and Saturated Regions of the B-H Curve

Saturated Region - Low Inductance

Saturated Region - Low Inductance

Fluxgate Sensor Basics


Saturated Region

Linear Region Curve Shifts

Due To Influence of External Field

Parametric Analysis


oi_p

oi_m Bz

Fluxgate_Sensor_1

E2

E1

R1

Sensor Current Response to a 2.5V, 100kHz Sinusoid20.00m

-20.00m

0

-10.00m

10.00m

80.00u 100.00u85.00u 90.00u 95.00u

External Field Source

EMF := 0

System Analysis

Cur

rent

(A)

Time (s)

Positive and Negative Areas are Equal

Waveform Distortion caused by traversing the B-H Curve


Sinusoidal Response

Force = 3.72N

External Field Shifts Curve Positively or Negatively Positive and Negative Areas are No Longer Equal

Cur

rent

(A)

Time (s)


Cur

rent

(A)

Time (s)

Square Wave Response


Differential Configuration System Simulation


Differential Sensor Response External Field For Sensor 2 Changes from 0G to –2G at 2ms Output Voltage Shifts Downward to Reflect the Change

Differential Flux Gate Sensor System Output Voltage 2.50

2.40 2.41

2.42

2.43

2.44

2.45

2.46

2.47

2.48

2.49

1.00e-003 4.00e-003 2.00e-003 3.00e-003

Differential Results


Eddy Current Flaw Sensor

Current density for unflawed and flawed cases very different

Flaw changes stored energy, and thereby affects mutual inductances of coils

Differential voltage calculated by: )( 2121 pudpuddriveroc LLNNIV −− −= ω


Eddy Current Sensor

• For flaw detection in structures without altering the physical makeup of that structure

• Eddy Current Probes are based on the principle of artificially creating induced current in the target material, from which we are able to detect if any defect is present


Description of the Task

• This is a multi-parametric Eddy Current problem

• Goal: sweep the probe at every location on the pipe and reconstruct cartography of the flux patterns

• Comparing simulated and tested results allows testers to have a better understanding of the measurements taken in the field



• The tested device is a pipe made of Inconel

22 mm

1.3 mm thick

µ = 1.001

σ = 970,000

Skin depth:

0.6mmδ1.6mmδ

600kHz

100kHz

==



• The vertical slot crack blocks all the induced current. This crack should be easy to detect

• The horizontal surface crack only alters current paths. This crack is more difficult to detect

• Will the probe be able to detect the signal due to the surface crack ?

10 mm



Source Coil

Pick up Coils

The Probe works at 2 frequencies: 100 kHz and 600 kHz

We need to solve each problem twice

Note: this is not the exact geometry used by customer


Solve twice with same mesh

Maxwell set up: 1. Solve the design with the

crack as vacuum 2. Duplicate the design 3. Change material property of

crack to inconel (to remove the crack) in the second design

4. Solve the second design without adaptive meshing, importing final mesh from original design


Results

Induced Currents


Summary

• Several examples of sensors were given including: – Hall, VR, Magneto-resistive, Flux Gate, and

Eddy Current • These were used for speed, position and flaw

sensing • Both component and system level simulations

were necessary to understand the coupling interaction and complete performance of most sensors

Sensors for Automotive Applications -...

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