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1 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Sensors for Automotive Applications
ANSYS, Inc.
2 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Introduction
Hall Sensor
Variable Reluctance Sensor
Magneto-resistive Sensor
Flux Gate Sensor
Eddy Current Sensor
Summary
Contents
3 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
4 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
5 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
6 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
• 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
7 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
8 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Hall Effect Sensor – Meshing Tips
Sensor Air BoxRequired for Proper Meshing
Target Air BoxRequired for Proper Meshing
9 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
−=
= ∫
10 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Average top and bottom flux vs. angle
Spacing = 1, 2, and 3mm
Hall Sensor - Parametric Results
11 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
12 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Spacing = 3mm
Differential signal is too small
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
13 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Spacing = 1mm
Differential signal is detected
Hall Sensor - System Simulation
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
14 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
For speed control by determining output voltage
Consider varying flux linkage vs. time due to fringing, nonlinear materials, and speed of rotation
Variable Reluctance Sensor
Permanent magnet
CoilPole piece
15 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Variable Reluctance Sensor
16 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Variable Reluctance Sensor
Finite element model
(equivalent circuit)
Output voltage vs. time
Angle vs. Time
17 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
• 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
Magneto-resistive Sensor
18 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Input Parameters• Rotation angle of Wheel• Permeability of missing tooth
Magneto-resistive Sensor
RotAngle
$TeethMur
Magnetize M
19 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Output Parameters• The Angle of magnetic field on sensor
part
Magneto-resistive SensorSens_Fwd Sens_Back
=
∫∫−
VdvH
VdvH
x
y
/
/tan 1α
Qty ・ H ・Scalar ・ YGeom ・ Sens_Fwd ・ Integ
Qty ・ H ・ Scalar ・ XGeom ・ Sens_Fwd ・ Integ
/
Trig ・ Atan
Constant ・PI ・/Number ・ 180.0 ・*
[Add] → Ang_Fwd
Operation of Calculator.
20 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Exporting Lookup Table– Export as format of Table .– Data is manually processed by other tools. (e.g. Excel)– Reload as Table Export SML.
Magneto-resistive Sensor
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.
21 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
-15[deg] Magnetic Flux Density B
-13[deg] H vector near sensor.
Magneto-resistive Sensor
22 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Parametric results – α vs. rotation
Shows results for missing tooth
Magneto-resistive Sensor
-15[deg] ~ 15[deg] -30[deg] ~ 30[deg]
23 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
-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
24 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
System Model for Speed Control
Angle
speed
25 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
26 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
27 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
28 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Saturated Region
Linear Region Curve Shifts
Due To Influence of External Field
Parametric Analysis
29 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
• Waveform Distortion caused by traversing the B-H Curve
• Positive and Negative Areas are Equal
System Analysis
Cur
rent
(A)
Time (s)
30 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
External Field Shifts Curve Positively or Negatively
Positive and Negative Areas are No Longer Equal
Sinusoidal Response
Force = 3.72N
Cur
rent
(A)
Time (s)
31 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Cur
rent
(A)
Time (s)
Square Wave Response
32 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Differential Configuration System Simulation
33 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Differential Flux Gate Sensor System Output Voltage2.50
2.402.41
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 Sensor Response• External Field For Sensor 2 Changes from 0G to –2G at 2ms• Output Voltage Shifts Downward to Reflect the Change
Differential Results
34 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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 −− −= ω
35 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
36 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
37 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
The tested device is a pipe made of Inconel
Description of the Task
22 mm
1.3 mm thick
µ = 1.001
σ = 970,000
Skin depth:
0.6mmδ1.6mmδ
600kHz
100kHz
==
38 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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 ?
Description of the Task
10 mm
39 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
Description of the Task
SourceCoil
Pick up Coils
40 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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
41 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
Induced Currents
Results
42 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential
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