Design and Optimization of Geometrical Parameters of Inductive Displacement Sensor

1
The 1st Workshop ReCIMiCo
Design and Optimization of Geometrical Parameters
of Inductive Displacement Sensor
Faculty of Technical Sciences University of Novi
Sad
Novi Sad, Serbia, 29th and 30th September 2008
2
Introduction

• Construction of the sensor
• Extending the linearity measurement range
• Improved model of the sensor
• Input impedance calculation
• Results
• Summary

1-12
3
The structure of the sensor
The first sensor element wA 1.52 mm, wB
0.51mm detects z-displacement
The second sensor element wA wB 0.51
mm detects x-displacement
2-12
4
Input inductance versus displacement

• When coil B moves above coil A in x-z plane, the
  coupling between
• coils changes, as well the input inductance LIN
  of the pair of coils
• Example coil B moves above coil A in direction
  of x-axis, for constant
• z-coordinate z 0.1 mm

3-12
5
Input inductance versus displacement

• When coil B moves above coil A in x-z plane, the
  coupling between
• coils changes, as well the input inductance LIN
  of the pair of coils
• Example coil B moves above coil A in direction
  of x-axis, for constant
• z-coordinate z 0.1 mm

3-12
6
Input inductance versus displacement

• When coil B moves above coil A in x-z plane, the
  coupling between
• coils changes, as well the input inductance LIN
  of the pair of coils
• Example coil B moves above coil A in direction
  of x-axis, for constant
• z-coordinate z 0.1 mm

3-12
7
Input inductance versus displacement

• When coil B moves above coil A in x-z plane, the
  coupling between
• coils changes, as well the input inductance LIN
  of the pair of coils
• Example coil B moves above coil A in direction
  of x-axis, for constant
• z-coordinate z 0.1 mm

3-12
8
Input inductance versus displacement

• When coil B moves above coil A in x-z plane, the
  coupling between
• coils changes, as well the input inductance LIN
  of the pair of coils
• Example coil B moves above coil A in direction
  of x-axis, for constant
• z-coordinate z 0.1 mm

3-12
9
Input inductance versus displacement

• When coil B moves above coil A in x-z plane, the
  coupling between
• coils changes, as well the input inductance LIN
  of the pair of coils
• Example coil B moves above coil A in direction
  of x-axis, for constant
• z-coordinate z 0.1 mm

3-12
10
Input inductance versus displacement

• When coil B moves above coil A in x-z plane, the
  coupling between
• coils changes, as well the input inductance LIN
  of the pair of coils
• Example coil B moves above coil A in direction
  of x-axis, for constant
• z-coordinate z 0.1 mm

3-12
11
Input inductance versus displacement

• When coil B moves above coil A in x-z plane, the
  coupling between
• coils changes, as well the input inductance LIN
  of the pair of coils
• Example coil B moves above coil A in direction
  of x-axis, for constant
• z-coordinate z 0.1 mm

3-12
12
Input inductance versus displacement

• When coil B moves above coil A in x-z plane, the
  coupling between
• coils changes, as well the input inductance LIN
  of the pair of coils
• Example coil B moves above coil A in direction
  of x-axis, for constant
• z-coordinate z 0.1 mm

3-12
13
Input inductance versus displacement

• When coil B moves above coil A in x-z plane, the
  coupling between
• coils changes, as well the input inductance LIN
  of the pair of coils
• Example coil B moves above coil A in direction
  of x-axis, for constant
• z-coordinate z 0.1 mm

3-12
14
New structure of the sensor
The first sensor element with inserted gaps in
coil A
Y segment of coil A, with inserted gap g
4-12
15
Input impedance of the sensor
Equivalent circuit of sensor element
5-12
16
Method of the partial inductance
A meander coil composed of elementary filaments
6-12
17
Mathematical model 1/2
Coil A of the first sensor element with inserted
gaps
7-12
18
Mathematical model 2/2
Equivalent circuit of the coil with inserted gaps
8 -12
19
Results The first sensor element
Dependance of input inductance LIN of
displacement for different gaps width
Normalized measured values of the input
inductance for different gaps width, z 0.1 mm

• Inserting the gap g 0.25 mm, the useful
  x-range is
• almost 90 wider range than for the
  structure without gap

9 -12
20
Results The second sensor element
Dependance of input inductance LIN of
displacement for different distance z
Enlarged part of curve for displacement in
vicinity of x 0.44 mm
10-12
21
Results The new structures

• New structures, with less turns N 8 and N 6,
  were analyzed

.
Simulated input inductance LIN for different
widths of segments of coil A, N8 and z0.1 mm
Normalized simulated input inductance LIN for
different number of turns N10, N8, N6
11-12
22
Summary

• An improved version of planar inductive
• sensor was analyzed
• A new simulation tool in MATLAB was
• developed for evaluation of input impedance
• of the sensor
• Inserting gap g 0.25 mm, the linear
• measurement range is extended for almost 90
• The linear measurement range is extended
• additionally by analyzing structures with less
• turns and wider conductive segments

.
12-12
23
.
THE END