This document discusses several techniques to reduce cogging torque in permanent magnet motors, which is an undesirable effect that prevents smooth rotor rotation. It describes classical and innovative techniques to minimize cogging torque through varying motor geometry while maintaining running torque. Some techniques discussed are skewing stator/magnets, fractional slots per pole, modulating drive current, and using optinet with magnets. Several industrial applications of cogging torque control are mentioned, like conveyor belts, CNC machines, and motorized vehicle braking. The document provides theoretical and practical justification for different cogging torque reduction techniques.

1. SHADAN WOMEN’S COLLEGE OF ENGINEERING AND TECHNOLOGY
Head of the Department :PROF. C.B.V. SUBBARAYUDU Internal guide : Ms. V. CHANDANA
Presented by:
RAFIYA BEGUM(12L51A0210)
RAVADA PAVITHRA(12L51A0211)
SINDHURA CHALASANI(12L51A0212)

2.  Cogging torque of
electrical motor is
the torque due to the
interaction between the
permanent magnets of
the rotor and the stator
slots of a Permanent
Magnet (PM) machine. It
is also known as ‘detent’
or “no-current” torque.
What is cogging torque??

5. This projects contains four momentary switches (normally open or
normally close) , each switch serves different operation
•Switch 1- for start motor clock wise rotation
•Switch 2- for start motor anti clock wise rotation
•Switch 3- for stop motor clock wise rotation
•Switch 4- for stop motor anti clock wise rotation

6.  Revolutions per minute is a measure of the frequency of rotation,
specifically the number of rotations around a fixed axis in one minute.
 A tachometer is an instrument measuring the rotation speed of a shaft or
disk, as in a motor or other machine. It is of two types contact and non-
contact type rpm.

7.  A conveyor belt is the carrying medium of
a belt conveyor system (often shortened to
belt conveyor).
 It counts the number of objects moving from
one end to the other end .
 A belt conveyor system consists of two or
more pulleys (sometimes referred to as
drums), with an endless loop of carrying
medium—the conveyor belt—that rotates
about them.
Conveyor Belt:

8.  It is a device emitting rays in infrared band, which cannot be seen by human eyes.
 An infrared sensor is an electronic device, that emits in order to sense some aspects of the
surroundings. An IR sensor can measure the heat of an object as well as detects the
motion
 The Main concept is simple, the IR led keeps transmitting IR infrared rays up to some
range (there is a potentiometer also in the design with the help of which you can alter the
range)

9. IR sensor :

10. Cogging torque is an undesirable effect that prevents the smooth rotation of
the rotor and results in noise.
The following are the ways to reduce cogging torque:
 Skewing stator stack or magnets
 Using fractional slots per pole
 Modulating drive current waveform
 Almost all the techniques used against cogging torque reduces the
motor counter-electromotive force and so reduce the resultant running
torque.
 In this example, optinet is used with Magnet in order to minimize the
cogging torque by varying the geometry yet maintaining a certain running
torque in a brushless dc motor.

11.  Providing a feedback signal of the torque/force
being applied to the physical process, and bringing
said feedback signal to a summation point with the
command signal inside the drive.
 Pole shifting is the major logic to operate.
 One of them has the high cogging torque rotor without
the pole shifting and the other has the low cogging
torque rotor with the pole shifting. They have been both
examined on a single PMSG separately.

12. • 12v step down transformer
• Bridge rectifier IN40007 diodes
• 1000uf capacitors
• 7805 regulator
• 330 ohms resistors
• Red led 2v

13.  Transformers convert AC electricity from one voltage to another with
little loss of power. Transformers work only with AC and this is one of
the reasons why mains electricity is AC.
 The transformer will step down the power supply voltage (0-230V) to
(0- 12V) level. Then the secondary of the potential transformer will be
connected to the bridge rectifier, which is constructed with the help of
PN junction diodes. The advantages of using bridge rectifier are it will
give peak voltage output as DC.

14.  When four diodes are connected as shown in figure, the circuit is called
as bridge rectifier.
 The input to the circuit is applied to the diagonally opposite corners of
the network, and the output is taken from the remaining two corners.
 The main advantage of this bridge circuit is that it does not require a
special centre tapped transformer, thereby reducing its size and
cost.

15.  Voltage regulators comprise a class of widely used Ics
 IC units provide regulation of either a fixed positive voltage, a fixed
negative voltage, or an adjustably set voltage.
 In this project regulated 12V, 750mA power supply, 7812 three terminal
voltage regulator is used for voltage regulation.

16.  Smoothing is performed by a large value electrolytic
capacitor connected across the DC supply to act as a
reservoir, supplying current to the output when the varying
DC voltage from the rectifier is falling.
 The capacitor charges quickly near the peak of the varying
DC, and then discharges as it supplies current to the
output.

17. Why Atmega8??????
 High performance, low power Atmel 8-bit
microcontroller.
Advanced RISC architecture.
High endurance non-volatile memory segments
In-system programming by on-chip boot program
True read-while-write operation
Peripheral features
Operating voltages 4.5 -5 volts
Atmega8 pin diagram:

18. L293D driver IC Description
•L293D is a typical Motor driver or Motor Driver IC
which allows DC motor to drive on either direction.
•L293D is a 16-pin IC which can control a set of two
DC motors simultaneously in any direction.
•The l293d can drive small and quiet big motors as
well
•With respect to our project L293D will drives the
conveyor belt.
•The L293D is a quadruple half H-Bridge
bidirectional motor driver IC.
• it can drive current up to 600 mA with voltage
range of 4.5 to 36 volts.

19. •As we know voltage need to change its direction for being able to rotate the
motor in clockwise or anticlockwise direction, Hence H-bridge IC are ideal
for driving a DC motor.
•The L4293D motor driver IC deals with huge currents, due to this reason,
this circuit uses a heat sink to decrease .
•These ICs are generally used in robotics.

21. D.C GEARED MOTOR:
 Free running Torque and
current are ideally zero.
 Increased load implies
increased torque.
 Power supplied by a motor
is the product of output shaft’s
rotational velocity &torque.
 can run in both directions.

22. IC LM358- LM358 consists of two
independent, high gain operational
amplifiers in one package.
 Important feature of this IC is that we do
not require independent power supply for
working of each comparator for wide range
of power supply. LM358 can be used as
transducer amplifier.
This IC can be operated on wide range of
power supply from 3V to 32V for single
power supply or from ±1.5V to ±16V for dual
power supply and it also support large
output voltage swing.
LM358 COMPARATOR:

23. •screen is an electronic display module and find a wide range of
applications. A 16x2 LCD display is very basic module and is very
commonly used in various devices and circuits.
•A 16x2 LCD means it can display 16 characters per line and there are
2 such lines. In this LCD each character is displayed in 5x7 pixel
matrix. This LCD has two registers, namely, Command and Data.

24.  To add LCD support to your C projects create a new project in AVR
Studio, then copy the following files to your project folder.
 lcd.c lcd.h myutils.h from then add them to your project by right
clicking project view and selecting “Add Existing Source File(s)…”
and then select the “lcd.c”.
 Similarly add “lcd.h” and “myutils.h” in Header Files section. Now you
are ready to start coding LCD applications !!!

27. • A metal detector is an electronic instrument which detects the presence
of metal nearby. Metal detectors are useful for finding metal inclusions
hidden within objects, or metal objects buried
• Metal detectors will detect ferrous (iron, steel, stainless steel) as well as
non-ferrous (copper, tin, gold, lead, silver, aluminum) as well as alloys (brass,
cuprous-nickel, pewter etc). Depending on the complexity of the circuit, a
metal detector will be able to discriminate between a lump of gold and an
aluminum ring-pull from a drink-can.

29. • When a metal object is placed inside the detecting
coil, some of the magnetic flux passes into the object
and creates a current called an ‘eddy-current’.
• This "uses-up" some of the magnetic flux and thus less
flux is available for the receiving coil.
• This produces a lower output from the coil and causes
the second transistor in the circuit to be turned OFF
slightly and the voltage on the collector rises.
• When a metal is detected, the copper coil flux
reduces; so that circuit will makes on buzzer.

30. AVR Studio 4 is a professional Integrated Development
Environment (IDE) for writing and debugging AVR applications in
Windows 9x/NT/2000/XP environments. you may obtain a copy of
AVR Studio 4 from one of 3 places:
1. Atmel Corporation: http://www.atmel.com
2. AVR Freaks: http://www.avrfreaks.net
3. Borrow a CD from your instructor
This will guide you through the steps required for
1. Executing the AVR Studio 4 Integrated Development
Environment(IDE)
2. Typing in a program,
3. Assembling the program, and
4. Simulating a program

31.  Step 1: Open AVR Studio 4 IDE. You should see the
program banner shown below:

33.  Step 3:click on the ‘new’ project
button
 Step 4: Type in a project name and
the initial file name:

34.  Step 6: Click on the “Next” button
 Step 7: Choose “AVR Simulator” for the Debug Platform
and then scroll down the right window to choose the
ATmega32 AVR processor. Select in the drop down list.
Choose Simulator and ATmega8
 Step 8: Click on the “Finish” button. You should then see
the IDE
 Step 9: Type in the program as shown in Figure 1. Note the
color-coded text. This is done automatically by the IDE and
helps you to make corrections as you go.
 Step 10: When you have completed the program save it. It
is also good practice to periodically save your program as
you type.
 Step 11: Assemble your program. You may do this by
selecting “Build” from the “Build Menu "or by striking the
[F7] key:

37.  Typical, the tool settings under Options – Target are all you need to start a new application.
 You may translate all source files and line the application with a click on the Build Target
toolbar icon. When you build an application with syntax errors, avr4 will display errors and
warning messages in the Output Window – Build page.
 A double click on a message line opens the source file on the correct location in a AVR4 editor
window.
 Once you have successfully generated your application you can start debugging.

38. • Cogging torque technique is used in Industrial conveyor
belt operations
• we can fix a motor with immediate stopping.
• It is helpful for CNC working motors
• For applications requiring motor & drive operation in
torque mode, in which a constant torque or resulting
force through a mechanism is desirable, this project is
useful.
• Conveyor belt with metal detector is used in shopping
malls, super markets & airports.
• This project finds its place in places where the things
wanted to be done automatically with utilization of power
in efficient and effective manner.

39. • By using this project, all industrial motors can be handle
with respect to cogging
• Now a days conveyor belt concepts is normally operated
but after wide usage of cogging technique, conveyor belt
can be used with CNC motors.
• CNC working motor can operate
• Sudden stop of electric motorized wheels vehicles can
operate with cogging torque logics.
• Every motorized application is eligible for cogging project.

40. • Several techniques may be adopted in designing surface-
mounted permanent-magnet motors in order to reduce the
cogging torque.
• This paper describes various classical and innovative
techniques, giving a theoretical and practical justification
for each of them.
•As a result, it is highlighted that some of industrial
applications are used to maintain motors perfectly with
respect to their requirement.

41.  [1] C. S. Joice, Dr. S. R. Paranjothi, and Dr. V. J. S. Kumar, “Practical
implementation of four quadrant operation of three phase Brushless DC
motor using dsPIC,” in Proc. IConRAEeCE 2011, 2011, pp. 91–94, IEEE.
 [2] P. Yedamale, Microchip Technology Inc., “Brushless DC (BLDC) motor
fundamentals,” 2003, AN885.
 [3] B. Singh and S. Singh, “State of the art on permanent magnet brushless
DC motor drives,” J. Power Electron., vol. 9, no. 1, pp. 1–17, Jan. 2009.
 [4] L. N. Elevich, “3-phase BLDC motor control with hall sensors using
56800/E digital signal controllers,” AN1916, Application Note, Rev. 2.0,
11/2005.
 [5] Afjei, O. Hashemipour, M. A. Sati, and M. M. Nezamabadi, “A new
hybrid brushless DC motor/generator without permanent magnet,” IJE
Trans. B: Appl., vol. 20, no. 1, pp. 77–86, Apr. 2007. [6] C. Xia, Z. Li, and T.
Shi, “A control strategy for four-switch three phase brushless DC motor
using single current sensor,” IEEE Trans. Ind. Electron., vol. 56, no. 6, pp.
2058–2066, June 2009.