Transcript Internal Sensors

Internal sensors
Josep Amat and Alícia Casals
Automatic Control and Computer Engineering Department
Program
Chapter 1. Introduction
Chapter 2. Robot Morphology
Chapter 3. Control
Chapter 4. Robot programming
Chapter 5. Perception
Chapter 6. Mobile robots. Architecture, components
and characteristics
Chapter 7. Robotics applications.
Robotization
Chapter 2. Robot Morphology
2.1 – Mechanical Structures. Classical
Architectures.
2.2 – Characteristics of a Manipulator. Definitions.
2.3 - Actuators. Pneumatic, Hydraulic and
Electrical.
2.4 – Movement transmission systems: Gearboxes,
movement transmission and conversion.
2.5 – Robot internal sensors. Position sensors, speed
and acceleration.
2.6 – End Effectors.
Components of a Robot
Environment
External
Sensors
User
Programming
Net
Internal
Sensors
Control Unit
Actuators
Mechanical Structure
Mechanical:
Detectors
Internal
sensors
Actuators
Mechanical structure
Position
sensors
Electromagnetic:
Detection from the variations
of the oscillation conditions of
an L – C sensor circuit
Detectors
Internal
sensors
Actuators
Mechanical structure
Position
sensors
Optical:
From the interruption of a light
beam, or reflection.
Detectors
Internal
sensors
Actuators
Mechanical structure
Position
sensors
Types of sensors
Angular
Linear
Types of sensors
Angular
Analog
Resistive (Potentiometers)
Digital
Vcc
R2
R
a
V = Vcc
R1 V = Vcc
0V
R1
R
a R
a
= Vcc
a0
a0 R
Types of sensors
Angular
Analog
Resistive (Potenciometers)
Inductive
( Resolver )
Digital
Ve = A sin (wt)
A is obtained through the lecture
in a look up table of arcsin and
arccos
Ve = A sin(wt ) cos a
Ve = A sin(wt ) sin a
A
e
D/A
Low resolution conversions
S1
S2
S1 = V cos a
A/D
S2 = V sin a
a
aX
a
A/D
High resolution conversions
mcontroler
Ve = V sin (wt)
aX
S1 = V sin(wt ) cos a
S2 = V sin(wt ) sin a
Possibility of obtaining the value of a by means of “tracking”
Types of sensors
Angular
Analog
Resistive (Potentiometers)
Inductive
Absolute
Digital
Incremental
( Resolver )
Optical Encoder Absolute
Fotoelectric sensor
2 paths
4 divisions
n paths
2n divisions
n optical barriers
Commercially
10 bits 1024 div.  Resol. 0.35º
12 bits 4096 div.  Resol. 0.088º
14 bits 16384 div.  Resol. 0.022º
Encoder diameters: de 50 a 175 mm
Ambiguity when reading the natural binary code
Elimination of the reading ambiguity using the Gray code
Example of a disc with the Gray code
Example of an angular encoder
Types of Sensors
Angular
Analog
Resistive (Potentiometers)
Inductive
Absolute
Digital
Incremental
( Resolver )
Commercially
10 bits 1024 div.  Resol. 0.35º
12 bits 4096 div.  Resol. 0.088º
14 bits 16384 div.  Resol. 0.022º
Signal obtained after
displacing the sensor
over a coded disc
1
2
3 4 5 6 7 8 9 10 11
Gray code
12
Commercially
10 bits 1024 div.  Resol. 0.35º
12 bits 4096 div.  Resol. 0.088º
14 bits 16384 div.  Resol. 0.022º
Gray code
Possibility of detecting the counting sense using two sensors
Incremental Optical Encoder
A
B
R
1 mark = 4 divisions
0
1
P
Q
200 x 4 = 800
P
Q
Computing resolution
r
q = 210 60 =
360
q = 170,6
Using a a
10 bits
encoder
directly
coupled to
the motor
axis
j = 60º
60
l = 2 p 1200
=
360
l = 1256 mm.
1256 mm.
r=
= 7,3 mm.
170,6
js
Measuring strategies
0j
0
1:1
Arm
j
0
360º
Encoder
Code j
Absolute
dn-1 . .
Incremental
dn-1 . . Counter
. . do
. . do
Measuring strategies
1:n
Arm
0
n=
360º
0
j
j
360º
Encoder
Code j
Absolute
dn-1 . .
Incremental
dn-1 . . Counter
. . do
. . do
Measuring strategies
0
Arm
n=
m
· · ·
360º
j
1:n
j
m
m=2
m=1
Encoder
0
360º
0
360º
Absolute + Inc.
dn+p-1 . . dn-1 · · Code j · · do
Incremental
dn+p-1 . . dn-1 · · Counter
· ·do
Encoder coupled to the arm with a transmission ratio: m x n
Computing resolution
r
q=8·
q = 8192
210
Using a 10
bits
encoder
coupled with a
1:64
transmission
ratio
j = 60º
=
l = 1256 mm.
x6 x8
1256 mm.
= 0,15 mm.
r=
8192
0 1 2 3
· · ·
199 200
With a 10 bits A/D converter
r’ = r/1024
l = 1256 mm.
1256 mm.
r=
= 0,006 mm.
204.800
r < 0,01 mm.
200 x 1024 = 204.800
Sinusoidal light obtained from
Moore interference
Types of sensors
Angular
Analog
Resistive (Potentiometers)
Inductive
( Resolver )
Incremental
Digital
Absolute
Analog
Linear
Digital
Resistive
Inductive ( Inductosyn )
LVDT
Optical rule
R
Sensing with a linear potentiometer
Types of sensors
Analog
Angular
Resistive (Potentiometers)
Inductive
Digital
( Resolver )
Incremental
Absolute
Analog
Linear
Digital
Resistive
Inductive ( Inductosyn R )
LVDT
Optical rule
Inductosyn sensor
0,2 mm
With two secondary sensors shifted 90º, the
resolution is: 0,2 / 28 < 0.001 mm *
* With an analog interpolation using a 8 bits ADC
Types of sensors
Angular
Analog
Resistive (Potentiometers)
Inductive
( Resolver )
Incremental
Digital
Absolute
Analog
Linear
Digital
Resistive
Inductive ( Inductosyn )
LVDT
Optical rule
LVDT
LVDT = Linear Voltage Differential Transformed)
LVDT
v
V1
V2
Linear sensing
displacements
V1
V2
V1 - V2
Types of sensors
Angular
Analog
Resistive (Potentiometers)
Inductive
( Resolver )
Incremental
Digital
Absolute
Analog
Linear
Digital
Resistive
Inductive ( Inductosyn )
LVDT
Optical rule
Incremental optical rule
Head reader
Absolute optical rule