Automotive Sensor Simulation

1 © 2014 ANSYS, Inc. April 1, 2016 ANSYS Confidential
Sensors for Automotive
Applications
Mark Christini
Zed (Zhangjun) Tang

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

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
Introduction

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
Component 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
System Analysis

For speed control
Determine flux passing through 3D
Hall effect sensor
Rotate sensor and vary gap
Hall Effect Sensor
Gap between pole
piece and target wheel
Rotate about the Z axis through
one half of a tooth, or 30 degrees.
Permanent
magnet
Pole piece
Hall
sensors
IC chip

Flux in Hall effect sensor can be
determined by integrating
B(normal) on a surface
Hall Effect Sensor
Field in permanent magnet
& pole piece
Field in IC
and
Hall sensor

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
PolePiece
Cell Top
Cell Bot
Hall IC
21
cell_face
aveavediff
xave dAB
jjj
j
-=
= ò

Average top and bottom flux vs. angle
Spacing = 1, 2, and 3mm
Hall Sensor - Parametric Results

Hall Sensor - Simplorer Simulation
ICA:
EMSSLink1.GAP := 3
EQU
Difference := FLUXM2.FLUX - FLUXM1.FLUX
FLX
FLUXM1 FLX FLUXM2CONST
CONST2
Difference
COMP1
ECE
EMSSLink1
ROT
ROT_V
ω
+
Maxwell 3D LinkMaxwell 3D Link

Spacing = 3mm
Differential signal is too small
Hall Sensor - System Simulation
0.00 100.00 200.00 300.00 400.00 500.00 600.00
Time [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 Axis
FLUXM1.FLUX
TR Y1
FLUXM2.FLUX
TR Y1
Difference
TR Y2
COMP1.VAL
TR Y2

Spacing = 1mm
Differential signal is detected
Hall Sensor - System Simulation
0.00 100.00 200.00 300.00 400.00 500.00 600.00
Time [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 Axis
FLUXM1.FLUX
TR Y1
FLUXM2.FLUX
TR Y1
Difference
TR Y2
COMP1.VAL
TR Y2

• For speed control by determining output voltage
• Consider varying flux linkage vs. time due to fringing,
nonlinear materials, and speed of rotation
Permanent
magnet
Coil
Pole piece

Finite element
model
(equivalent
circuit)
Output voltage vs. time
Angle vs. Time

• 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
÷
÷
ø
ö
ç
ç
è
æ
=
ò
ò-
VdvH
VdvH
x
y
/
/
tan 1
a
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 è Export SML.
Export from Parametric Solutions Export from Imported Table
ECE- LINKECE- LINK
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
20.40m
0
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

System Model
for Speed Control
Angle
speed

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.
Fluxgate Sensor
Drive Coil Core

Arrows
Indicate
Magnetizatio
n 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
Magnetizatio
n 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
w 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 Sinusoid
20.00m
-20.00m
0
-10.00m
10.00m
80.00u 100.00u85.00u 90.00u 95.00u
External Field Source
EMF := 0
System Analysis
Current(A)
Time (s)
w Positive and
Negative Areas
are Equal
w Waveform
Distortion caused
by traversing the
B-H Curve

Sinusoidal Response
Force = 3.72N
w External Field Shifts Curve Positively or Negatively
w Positive and Negative Areas are No Longer Equal
Current(A)
Time (s)
Forceee = 3.72NNN

Current(A)
Time (s)
Square Wave Response

Differential Configuration
System Simulation

w Differential Sensor Response
w External Field For Sensor 2 Changes from 0G to –2G at 2ms
w 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-0032.00e-003 3.00e-003
Differential Results

Current density for unflawed and flawed cases very
different
Flaw changes stored energy, and thereby affects mutual
inductances of coils
Differential voltage calculated by:
Eddy Current Flaw Sensor
)( 2121 pudpuddriveroc LLNNIV -- -= w

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
Eddy Current Sensor

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
Description of the Task

The tested device is a pipe made of Inconel
22 mm
1.3 mm thick
µ = 1.001
σ = 970,000
Skin depth:
0.6mmδ
1.6mmδ
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

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
Source
Coil
Pick up
Coils

Maxwell set up:
• Solve the design with the crack as
vacuum
• Duplicate the design
• Change material property of crack to
inconel (to remove the crack) in the
second design
• Solve the second design without
adaptive meshing, importing final
mesh from original design
Solve twice with same mesh

Induced Currents
Results

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
Summary

Automotive Sensor Simulation

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