This presentation is a lecture about robotics sensors and simulation

1. Mechatronics, Robotics,
Sensors and Simulation
(500682)
Lecture 2: Mechatronic/Robotic System, Motors

2. Outlines
• Mechatronic/Robotic System
– Components, their Role and Types
– System Integration and Testing
– Signal Perspective
• DC Motors (Quick recap)
– Working
– Types
• Special Motors
– Servo Motors
– Stepper Motors

3. j.Iqbal@hull.ac.uk
Room: 303H RBB
Mech./Robotic
System

4. Mech. System – Closed-loop Perspective

5. Mech. System – Closed-loop Perspective
Controller Actuator Plant
Sensor
Ref.
Current
-
Control for Engineers
(500662)
Mech., Robotics, Sensors & Simulation
(500682)
Robotics & Automation
(601089)
Mechatronic Systems
(500680)

6. PID (Proportional Integral Derivative) Controller
P I D
u(t)
r(t)
r(t) u(t)

7. Overall Mechatronic System
Signal Generator Motor Driver
Test Signal
Arduino
Oscilloscope
Motor
Give Test I/p to System Record O/p from Sensor
Sensor Data

8. Signals Perspective

9. Mechatronic System in Operation
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
-0.4
-0.35
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
0
Time [sec]
Angle
[rad]
Desired
Measured
0 1 2 3 4 5 6 7 8 9 10
0
0.2
0.4
0.6
0.8
1
1.2
Time [sec]
Angle
[rad]
Desired
Measured
Step response Sinusoidal response
J. Iqbal, A.H. Khan, N.G. Tsagarakis and D.G. Caldwell, “A novel exoskeleton robotic system for hand
rehabilitation - Conceptualization to prototyping”, Biocybernetics and Biomedical Engineering, 2014, 34(2):79-89

10. MIMO Systems
S. Ullah, A. Mehmood, Q. Khan, S. Rehman and J. Iqbal, “Robust integral sliding mode
control design for stability enhancement of underactuated quadcopter”, International
Journal of Control, Automation and Systems, 2020, 18(7):1671-1678

11. j.Iqbal@hull.ac.uk
Room: 303H RBB
Motors

12. Parts of a Typical Motor
• Commutator
• Rotor
– Rotating portion of the motor
– Turns within the magnetic field
• Stator
– Stationary portion of the motor
• Bearing
– Allow free rotation of the motor shaft
Brushes
Electrical connector
between armature
and power
Commutator
Mechanical
rectifier converts
AC to DC
Rotor:
Armature
conductor are
connected to the
Commutator
Stator
Produces an
external flux
+ + + =
DC Machine

13. Types
• Motors convert electric energy to mechanical force or
motion
• Input:
– AC/DC electrical energy source
• Industrial robots:
– AC Servo motor
• Mobile robots, Domestic robots:
– DC motor
– DC Servo motor
– Stepper motor
• Output:
– Output is mechanical motion of the output shaft
– Rotation about or a translation along the shaft
M
O
T
O
R

14. Motor Accessories
• Motor (Armature)
• Shaft
• Gear Box
• Encoder (Position sensor)

15. j.Iqbal@hull.ac.uk
Room: 303H RBB
DC Motors

16. DC Motors
• Attractive for Robotics, Medical and Automotive
applications
– Can be small
– Efficient
– High and low torque
• Classification
– Brush DC motor
– Brushless DC (BLDC) motor

17. Brush DC Motors
• A typical Brush DC motor consists of
– An armature (or rotor)
– A commutator (split ring wrapping around the axle
which connect to opposite poles of a power source to
deliver positive and negative charges to the
commutator)
– Brushes
– Axle
– Field magnet

18. Brush DC Motors
• Principle
– The brushes charge the commutator inversely in polarity to
the permanent magnet
– This in turn causes the armature to rotate
– The rotation’s direction (c/w or anti c/w) can be reversed
by reversing the polarity of the brushes, (i.e., reversing the
leads on the battery)

19. Brush DC Motors
Video Content: https://www.youtube.com/watch?v=LAtPHANEfQo

20. Brush DC Motors
• Advantages 
– Generally inexpensive and reliable
– Simple two wire control
– If the brushes are replaceable, these motors also boast a
somewhat extended operational life
– They tend to handle rough environments reliably
– They need few external components or no external
components at all
• Disadvantages 
– Require periodic maintenance as brushes must be cleaned
– Sometimes replaced for continued operation
– (ruling them out for critical medical designs)
– Also, if high torque is required, brush motors fall a bit flat
– As speed increases, brush friction increases and viable
torque decrease
– Electromagnetic interference (EMI) generated by brush
arcing

21. Brushless DC Motors (BLDC)
• Principle
– No brush, no commutator
– A BLDC motor mounts its permanent magnets, usually
four or more, around the perimeter of the rotor in a
cross pattern
– More expensive but long life
– Come in compact packages (viable for a variety of
compact designs)
– BLDC motors are synchronous motors
– Efficiency is a primary selling feature for BLDC motors

22. Brushless DC Motors (BLDC)
Video Content: https://www.youtube.com/watch?v=bCEiOnuODac

23. DC Series Motors
• The field winding is connected internally in series to
the armature winding
• Advantages 
– High starting torque (∝ square of field current)
– Best suited for traction applications

24. DC Series Motors
• Disadvantages 
– Poor speed regulation:
* With the increase in the load → Speed of the machine decreases
* In comparison, DC shunt motor maintains almost constant speed
from no load to full load
– Should always require being loaded before starting the
motor
– ∴, they are not suited for applications where load on the
motor is completely removed

25. DC Shunt Motors
• The field windings are shunted to / connected in
parallel to the armature winding of the motor
• Since they are connected in parallel → the armature and
field windings are exposed to the same supply voltage
• The torque is ∝ to the armature current (𝐼𝑎)
• How to increase torque:
– Increase 𝐼𝑎
– by decreasing 𝐼𝑠ℎ
– i.e. increase 𝑅𝑠ℎ
– Use conductors with less dia (𝑅 = 𝜌
𝑙
𝐴
)
• The field winding must be wound with many turns to
increase the flux linkage

26. DC Compound Motors
• They are made up of both series the field coils and
shunt field coils connected to the armature winding

27. j.Iqbal@hull.ac.uk
Room: 303H RBB
Special
Motors

28. AC/DC Servo Motors
• Features
– An obvious choice when higher precision is required
– Can get a very high torque in a small and light weight
package
• Composition
– AC/DC Motor
– A gearing set
– A control circuit
– A position-sensor (Potentiometer/Encoder)
• Applications
– Toy car
– RC Helicopters
– Planes
– Robots
– Machines

29. AC/DC Servo Motors

30. AC/DC Servo Motors
• Features
– Servo motors do not rotate freely like a standard DC
motor
– Instead the angle of rotation is limited to 180° (or
so) back and forth
– Pulse Width Modulation (PWM) is used for the
control signal of servo motors
– When a servo is commanded to move, it will move to
the position and hold that position, even if external
force pushes against it. The servo will resist from
moving out of that position, with the maximum
amount of resistive force the servo can exert being the
torque rating of that servo

31. AC/DC Servo Motors
Video Content: https://www.youtube.com/watch?v=LXURLvga8bQ

32. Stepper Motors
• Features:
– A stepper motor can control the angular position of the
rotor without a closed-loop feedback
– It is simple, accurate and open-loop system
– Different method of motorisation to that of servo
• Working Principle
– A permanent magnet is used for rotor
– All the coils are not energised simultaneously
– Energised step by step (one after the other)

33. Stepper Motors
Video Content: https://www.youtube.com/watch?v=eyqwLiowZiU

34. Stepper Motors
http://www.piclist.com/images/www/hobby_elec/e_step1.htm

35. Stepper Motors
• Advantages 
– The rotation angle is proportional to the input pulses.
– Full torque at standstill
– Very low-speed synchronous rotation is possible to
achieve
– There are no brushes so it is reliable
– Speed is directly proportional to the frequency of the
input as pulses; hence a wide range of rotational speed
can be realised
– Low speed with high precision
• Disadvantages 
– Low efficiency
– Difficult to operate at very high speed
– May produce more noise
– For the smooth move, micro stepping is required