Designing a 3D Rotation Transducer Using LVDT Sensors

MINI PROJECT
Topic: Design of Transducer to measure
comparative rotation in 3D using LVDT
Submitted By
RanSher (1814110)
1
National Institute of Technology, Silchar

CONTENTS
 Introduction
 LVDT
 Design of Transducer
 Design of Transducer
 Working of Transducer
 Solutions for Challenges in Implementation
 Summary
2

INTRODUCTION
INTRODUCTION
 TRANSDUCERS: A transducer is an electronic device
that converts energy from one form to another. Common
examples include microphones, loudspeakers,
thermometers, position and pressure sensors, and antenna.
thermometers, position and pressure sensors, and antenna.
3

INTRODUCTION
INTRODUCTION
Transducers can be classified as:
 On the basis of transduction form used.
 As primary and secondary transducers.
 As primary and secondary transducers.
 As passive and active transducers.
 As analog and digital transducers.
4

LVDT
LVDT
 The linear variable differential transformer is a type of
electrical transformer used for measuring displacement.
 WORKING PRINCIPLE:
 LVDT works under the principle of mutual induction, and
the displacement which is an on electrical energy is
converted into an electrical energy. And the way how the
energy is getting converted is described in working of
LVDT in a detailed manner.
5

LVDT
LVDT
 It consists of a cylindrical former where
it is surrounded by one primary
winding in the centre of the former and
the two secondary windings at the sides.
The number of turns in both the
The number of turns in both the
secondary windings are equal, but they
are opposite to each other, i.e., if the
left secondary windings is in the
clockwise direction, the right secondary
windings will be in the anti-clockwise
direction, hence the net output voltages
will be the difference in voltages
between the two secondary coil.
6

LVDT
LVDT
 Case 1: On applying an external force which is
the displacement, if the core reminds in the null
position itself without providing any movement
then the voltage induced in both the secondary
windings are equal which results in net output is
equal to zero.
Case 2: Due to external force if the steel iron
 Case 2: Due to external force if the steel iron
core moves in the right hand side direction then
the emf induced in the secondary coil 2 is
greater when compared to the emf voltage
induced in the secondary coil 1.
 Case 3: Due to external force if the steel iron
core moves in the left hand side direction then
the emf induced in the secondary coil 1 is greater
when compared to the emf voltage induced in
the secondary coil 2.
7

LVDT
LVDT
DIS-ADVANTAGES
 Sensitive to a stray magnetic
field.
 Performance is affected by
vibrations.
 Temperature effects the
DIS-ADVANTAGES
 LVDT has High Range.
 LVDT is a frictionless device.
 LVDT has low hysteresis.  Temperature effects the
performance.
APPLICATIONS
Used in applications where
displacements ranging from
fraction of mm to few cm are to be
measured.
Acts as the secondary
transducers.
 LVDT has low hysteresis.
8

Design of Transducer:
measure comparative rotation in 3D
Design of Transducer: T0
 Design:
z-axis
LVDT 3
Explaination:
1. Three similar LVDT,
numbered with
LVDT1, LVDT2 and
9
x-axis
y-axis
LVDT 2
LVDT 1
LVDT 3
LVDT1, LVDT2 and
LVDT3 are kept at x-
axis, y-axis and z-axis
respectively.
2. They are binded in
such away that middle
portion of each LVDT
lies at the origin
ideally.

 Design:
z-axis
LVDT 3
Explaination cont.:
3. LVDTs can freely
rotate in any direction
about origin.
10
x-axis
y-axis
LVDT 2
LVDT 1
LVDT 3
about origin.
4. Initially, LVDT 3,
which lies on z-axis
has maximum
displacement of
core(let say L) and
LVDT 1 and LVDT 2
has zero
displacement of
core.

 Design:
z-axis
LVDT 3
Explaination cont.:
5. Any rotation about
origin will tend to
11
x-axis
y-axis
LVDT 2
LVDT 1
LVDT 3 origin will tend to
decrease the value of
L(displacement of
core of LVDT 3) and
tend to increase the
value of core
displacement of LVDT
1 and LVDT 2 .

Working of Transducer:
Working of Transducer: T0
 Working:
1. According to principle of LVDT, when core
of LVDT is displaced from the centre
machanically, the voltage difference of two
secondary coils becomes non-zero and
12
hence displaced position of core can be
measured easily.
2. Weight of the core is responsible for its
displacement from the centre. When LVDT
is vertical, it has maximum core
displacement whereas when it is
horizontal, it has minimum displacement.
3. Let’s displacement along x-axis, y-axis and
z-axis is denoted by , and .
x
d y
d z
d

 Working: State 1: LVDT 3(z-axiz) is fixed and LVDT1(x-axis)
and LVDT 2(y-axis) is rotated x-y plane.
Here, = 0
= 0 = L (let)
𝛼
z-axis
x
d
y
d d
rotation
13
= 0 = L (let)
Therefore, if 𝛼 is the angle with x,
Then,
cos 𝛼 = 𝛼 = 90
y
d z
d
α
α
x-axis
y-axis

 Working: State 2: LVDT 2 (y-axiz) is fixed Motion in x-z plane
OR
LVDT 1 (x-axis) is fixed, Motion in y-z plane.
Due to rotation in x-z plane, there will be increase in
and decrease while remains constant
z-axis
α
x
d
y
d
z
d
14
and decrease while remains constant
= L’ (let)
= 0
= L – L’ {since increase displacement of LVDT 1 will be same as decrease in LVDT 3 }
cos 𝛼 =
=
hence, 𝛼 =
y
d
z
d
α
y-axis
x-axis x
d
y
d
z
d
rotation

 Working: State 3: All LVDTs are rotated by angle 𝛼 .
Let say L’ is increase in displacement of LVDT1 and LVDT2 and it
is known that there is same decrease in LVDT 3, hence
= L’ (let)
z-axis
α
d
15
= L’ (let)
= L’
= L – L’ {since increase displacement of LVDT 1 will be same as decrease in
LVDT 3 }
cos 𝛼 =
=
hence, 𝛼 =
α
y-axis
x-axis
x
d
y
d
z
d
α

 Working: State 4: LVDT 1 , LVDT 2 and LVDT 3 are rotated by angle
α, β and γ respectively from x, y ,z axes .
Let say Lx’ and Ly’ are increase in displacement of LVDT1 and
LVDT2 and Lz’ is decrease in LVDT 3, hence
= Lx’ (let)
z-axis
γ
d
16
= Lx’ (let)
= Ly’
= L – Lz’ {since increase displacement of LVDT 1 will be same as decrease in
LVDT 3 }
cos 𝛼 =
=
hence, 𝛼 =
Similarly β = and γ =
α
y-axis
x-axis
x
d
y
d
z
d
β

 Working: • Three dampers is added at the centre
of the designed LVDT ,
• in such a way that when LVDT at any
time starts moving away from the
z-axis
γ
17
time starts moving away from the
central point in uncontrolled
acceleration,
• then damper comes into effect to start
damping force to stop or
• to oppose the LVDT in opposite
direction of its motion.
α
y-axis
x-axis
β

Implementation
Solutions for Challenges in
Implementation
 Centres of all three LVDTs should lie on origin initially, which is not
possible in real senario.
Solution: Although it is not possible, but it can be achieved to near
ideal value by reducing the thickness of LVDTs to minimum value.
18
 During rotation, centrifugal force comes into effect which causes vary
in actual displacement in cores of LVDTs.
Solution: Measurement readings should be taken during equilibrium
condition, which can reduce this error.
 Accuracy can be hampered by Temperature and Hysteresis.
Solution: Temperature must be kept constant by cooling and soft iron
core can be used for reduction in losses due to hysteresis.

Summary
Summary
 LVDT is a class of transducer, which works principle of
mutual induction and can measure the linear displacement
by determining difference in voltages.
 3 LVDTs can be to design a transducer which can measure
comparative rotation in 3D, by binding it to 3 perpendicular
comparative rotation in 3D, by binding it to 3 perpendicular
axes x, y and z with its centres kept at near origin.
 Rotating the designed transducer to some angles causes
displacement in core of LVDTs, hence these displacements
measured can be utilised to determine the angle of rotation
about any axes using cosine formula discussed earlier.
 There are many challenges in physical implementations
which can be solved by using suitable conditions and
favourable precautions.
19

THANK YOU
20
THANK YOU

Designing a 3D Rotation Transducer Using LVDT Sensors

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