This chapter discusses sensors used in robot automation. It describes different types of sensors including velocity, acceleration, and position sensors. Velocity sensors measure medium to low frequencies and act as low-pass filters. Acceleration sensors measure the highest frequencies using piezoelectric, strain gage, or servo accelerometers. Position sensors include potentiometers, resolvers, optical encoders, and linear variable differential transformers (LVDT). The chapter concludes by discussing applications of robot sensors in industries like using contact sensors to detect welding seams or non-contact through-the-arc sensors to detect welding parameters.

1. CHAPTER 5:
SENSOR IN ROBOTS AUTOMATION

2. Learning Outcomes:
Upon completion this chapter, student should be
able:-
1. State the categories of sensor
2. Explain the velocity sensors, acceleration sensors
and the position sensors.
3. Explain the application of robot sensor in
industries

3. Contents
1. Introduction of robot sensor
2. Velocity and acceleration sensors
3. Position sensors
4. Application of robot sensor in industries

5. Introduction of robot sensor
 Sensors are devices that can sense and measure
physical properties of the environment
 e.g. temperature, luminance, resistance to
touch, weight, size, etc.
 A robot needs sensing to be an active participant in the
environment.
 Each sensor is based on a transduction principle, i.e. a
conversion of energy from one form to another.

6. Classification of sensors
 Proprioceptive (“sense of self”, internal state):
Measures values internally to the system (robot), e.g.
battery level, wheel position, joint angle, etc.
 Exteroceptive (external state): Observations of robot
environment, objects in it.
 Active: emit energy in environment
 More robust, less efficient
 Passive: passively receive energy from environment
 Less intrusive, but depends on environment e.g. light for
camera

7. General sensor classification

9. Sensor Characteristics
 Dynamic range: Ratio between lower and upper
limits, usually in decibels.
 Range: Difference between min and max.
 Resolution: Minimum difference between two values.
 Linearity: Variation of output signal as function of the
input signal.
 Bandwidth or frequency: The speed with which a sensor
can provide a stream of readings.
 Sensitivity: Ratio of output change to input change.
 Error/Accuracy: Difference between the sensor’s output
and the true value.

10. Velocity and Acceleration Sensor
 Velocity sensors:
 Used for medium to low frequency (1 to 1000 Hz)
measurements.
 Act as a low-pass filter (reduce high frequency signals)
 Traditional velocity sensors employ an electromagnetic sensor
to pick up the velocity signal
 Acceleration sensors:
 Used for the highest frequencies (100 Hz and up)
 Three types of accelerometers:
 piezoelectric
 strain gage ( piezoresistive)
 servo accelerometer

11. Tachometer
 A DC tachometer works in a similar fashion to the
Linear Velocity Transducer, except
 magnet is fixed (“stator”)
 “coil” of wire rotates inside the magnet
 produces a voltage proportional to the angular velocity

12. Incremental Encoders
 Two sensors (usually optical) are mounted such that
one is halfway blocked by the "solid" area (Channel A)
while the other is in the middle of the "clear" area
(Channel B).

13. Position Sensors
 Potentiometer
 Resolver
 Optical Encoders
 Relative position
 Absolute position
 Linear variable differential transformers (LVTD)

14. Potentiometer
 Resistance changes with the position of the dial
 potentiometers (“pots”) are electrical resistance
elements made in both linearly & rotary form
 a mechanical motion of the wiper changes the output
voltage in proportion to the wiper displacement

16. Resolver sensor
 Has a similar function principle as a stepper motor.
 It is a rotary electrical transformer basically
implemented for calculating the degrees of rotation.

17. Wheel / motor encoders
 Measure position, speed, direction
of revolution of the wheel.
 Odometry - wheel movements can
be integrated to get an estimate of
the robots position.
 Typical resolutions of 2000
increments per revolution.

18. Optical encoders
 Optical sensing of encoder
position is used
 A light source (LED or
light-emitting diode) is
placed on one side of the
encoder disk
 A light detector
(phototransistor) is on the
other side

19. Optical encoders
 Detecting absolute position

21. Linear variable differential
transformers (LVTD)
 LVDT measures linear motion traveled as a voltage
signal
 The sensor is based on the physical properties of
transformers and electromagnetic induction
 The transformer coil construction consist of a
primary winding between a pair of secondary coils on
either side

23. Application of robot sensor in
industries
 Various Types of Sensors for Robot Arc Welding
Stations:

24.  Figure 5(a) shows a contact type sensor
 A gas nozzle, or a finger, is used as a probe to detect
contact with the work piece
 The nozzle senses the existence, location, and
orientation, and, thereby, the location of the weld
seam.

25.  Figure 5(b) shows a non-contact type sensor referred
to as a through-the-arc sensor
 This sensor detects changes of welding parameters
while the torch is weaving during the arc welding
process
 This type of sensor is appropriate for welding of bigger
pieces with weaving when penetration control is not
necessary.

26. Group Discussion
Topic Industry
Application of robot sensor in industries
a. Types interfaces and groups of sensors used in industrial
b. Primary simple contact sensor commonly found in
robots automation system
c. State non-contact sensor used in industrial system
d. Difference between the simple sensor and complex
sensor interface
• Automotive
• Semiconductor
• Food

27. THANK YOU