Stepper motor in industrial applications

Stepper motor in industrial applications

1. Presented by
Dr. R. RAJA, M.E., Ph.D.,
Associate Professor, Department of EEE,
Muthayammal Engineering College, (Autonomous)
Namakkal (Dt), Rasipuram – 637408
MUTHAYAMMAL ENGINEERING COLLEGE
(An Autonomous Institution)
(Approved by AICTE, New Delhi, Accredited by NAAC, NBA & Affiliated to Anna University),
Rasipuram - 637 408, Namakkal Dist., Tamil Nadu, India.
Stepper Motor in Industrial Applications

2. List of Contents:
Introduction
Construction
Stepper Motor Step Calculation and Working
Multiple Steppers Motor
Driving Techniques
Types of Stepper Motor
How to Select a Stepper Motor?
Advantages and Disadvantages of Stepper Motor
Industrial Applications of Stepper Motor
(i) Stepper Motor Drives for Robotic Applications

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3. Introduction
Stepper Motor:
Selection between a servomotor and stepper motor quite will be challenged with
balancing of several design factors of the cost consideration, torque, speed,
acceleration and drive circuitry are the important role in selecting the motor for
the application.
What is Stepper Motor:
A step motor or stepping motor is called a stepper motor in which the single
rotation is divided into a number of steps. Each step is being calculated by an
angle. The step angle can be varied as per the design of the motor.
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4. Construction:
It has a permanent magnetic rotating shaft called the rotor and stationary
electromagnets surrounding the rotor called the stator.
Also, It has typically 100 electromagnet poles of north and south poles
generated either by a permanent magnet or an electric current.
Each permanent magnetic pole is having a natural stopping point and the
position of the poles is placed in the stepper motor position itself accurately and
precisely.
This is the convenient features of the stepper motor in that the poles of the
stepper motor is allowed to position accurately without any positional feedback.



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5. Contd..
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6. When we want to increase the resolution will achieve the smallest rotation
movement designed for a stepper motor contains a large number of magnetic
poles.
Basically, the incremental step size of the motor is fixed to the cylinder greaves
rotation based on the number of electromagnet poles.
Therefore moving to an accelerate position is simply a matter of sending the
commends to the pole of the stepper motor.

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7. Stepper Motor Step Calculation:
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A Stepper motor has 200 rotor teeth and 200-400 four steps for the revolution of
the motor shaft. To determine the resolution of rotation of the motor we can
perform a little maths.
If the stepper motor has 200 incremental steps and we know four rotations is equal
to a circle where 360 degrees, 360 deg/200 steps = 1.8 degrees. And 360 deg / 400
steps = 0.9 degrees a four-step rotation.

8. Position 1:
The rotor is started at the top of the electromagnet pole which is current
energies with the current flowing through a wire. In order to move the stepper
motor in clockwise the top of the electromagnet pole will be deactivated.
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Contd..

9. Position 2, 3, and 4:
Now the top of the electromagnet will be deactivated and the right side
electromagnet is activated carrying a rotor to move 90 degrees clockwise and
align with the active magnet as shown in position 2.
Now it is continued to deactivate and activate the electromagnetic poles around
the stator and position 3 and 4 carrying rotor to realign with each new
electromagnet pole to enable to rotate the rotor 90 degrees in clockwise in each
time.
This eventually completes a 4
th
360 degree of rotation. Hence, remembering the
basic properties of like magnetic pole repels and low and unlike poles attract
depending on the power source current is applied to an electromagnetic pole
coil wire.
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Contd..

10. It causes like and unlike magnetic attraction and retraction forces in the
permanent magnet to rotate the motor.

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11. In the real word, the stepper motor incorporates a large number of
electromagnet poles on the stator and rotor to increase the resolution.
With the increase in the number of electromagnet poles, the operation is
basically the same as the example providing 90-degree rotation.
The pules are given as below,

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Contd..

12. Multiple Steppers Motor:
Refer to the below mentioned animated working principle of stepper motor with
multi-step action.





Frame 1: The rotor is designed in the upper position 1 with top stator electromagnet
-1 will be activated. It attracts the nearest geared pole in the rotor. Then the rotor
starts rotating. They will be slightly offset from the right electromagnet

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13. Frame 2: The top electromagnet 1 is deactivated, and the right side electromagnet 2
will be activated, pulling the teeth into alignment with it. i.e consider we have 100
steps motor. It gives 3.6 deg (360/100=3.6) of rotation for each steps.
Frame 3: The bottom coil 3 is energized (1 and 2 will be deactivated); hence another
3.6° rotation occurs.
Frame 4: The left electromagnet 4 in the stator is energized (1,2 and 3 will be
deactivated), hence we get another 3.6° rotation.
Again the top coil of stator 1 will be enabled, then the same process continues. By
energizing and de-energizing of the stator’s electromagnet, we get 360° rotation.
By fastening the electromagnetic polarization we can increase the speed of the
motor.

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Contd..

14. Driving Techniques:
Stepper motor driving techniques can be possible with some special circuits due
to their complex design.
There are several methods to drive this motor, some of them are discussed
below by taking an example of a four-phase stepper motor.
Single Excitation Mode:
The basic method of driving a stepper motor is a single excitation mode. It is an
old method and not used much at present but one has to know about this
technique.
In this technique every phase otherwise stator next to each other will be
triggered one by one alternatively with a special circuit. This will magnetize &
demagnetize the stator to move the rotor forward.

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15. Full Step Drive
In this technique, two stators are activated at a time instead of one in a very less
time period. This technique results in high torque & allows the motor to drive
the high load.
Half Step Drive
This technique is fairly related to the Full step drive because the two stators will
be arranged next to each other so that it will be activated first whereas the third
one will be activated after that.
This kind of cycle for switching two stators first &after that third stator will
drive the motor. This technique will result in improved resolution of the stepper
motor while decreasing the torque.

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16. Micro Stepping
This technique is most frequently used due to its accuracy. The variable step
current will supply by the stepper motor driver circuit toward stator coils within
the form of a sinusoidal waveform.
The accuracy of every step can be enhanced by this small step current. This
technique is extensively used because it provides high accuracy as well as
decreases operating noise to a large extent.

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17. Types of Stepper Motor
Permanent magnet stepper
Hybrid synchronous stepper
Variable reluctance stepper

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18. Permanent Magnet Stepper Motor
Permanent magnet motors use a permanent magnet (PM) in the rotor and
operate on the attraction or repulsion between the rotor PM and the stator
electromagnets.
This is the most common type of stepper motor as compared with different
types of stepper motors available in the market. This motor includes permanent
magnets in the construction of the motor.
This kind of motor is also known as tin-can/can-stack motor.
The main benefit of this stepper motor is less manufacturing cost. For every
revolution, it has 48-24 steps.

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19. Variable Reluctance Stepper Motor
Variable reluctance (VR) motors have a plain iron rotor and operate based on
the principle that minimum reluctance occurs with minimum gap, hence the
rotor points are attracted toward the stator magnet poles.
The stepper motor like variable reluctance is the basic type of motor and it is
used for the past many years.
As the name suggests, the rotor’s angular position mainly depends on the
magnetic circuit’s reluctance that can be formed among the teeth of the stator as
well as a rotor.

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20. Hybrid Synchronous Stepper Motor
Hybrid stepper motors are named because they use a combination of permanent
magnet (PM) and variable reluctance (VR) techniques to achieve maximum
power in small package sizes.
The most popular type of motor is the hybrid stepper motor because it gives a
good performance as compared with a permanent magnet rotor in terms of
speed, step resolution, and holding torque.
But, this type of stepper motor is expensive as compared with permanent
magnet stepper motors. This motor combines the features of both the permanent
magnet and variable reluctance stepper motors.
These motors are used where less stepping angle is required like 1.5, 1.8 & 2.5
degrees.

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21. How to Select a Stepper Motor?
Before selecting a stepper motor for your requirement, it is very significant to
examine the torque-speed curve of the motor.
So this information is available from the designer of the motor, and it is a
graphical symbol of the torque of the motor at a specified speed.
The motor’s torque-speed curve should match closely the necessities of the
application; or else, the expected system performance cannot be obtained.
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22. Advantages and Disadvantages of Stepper Motor
Advantages :
Simple construction
Can work in an open-loop control system
Maintenance is low
It works in any situation
Reliability is high
Disadvantages:
The Torque of a motor will declines fast with speed
Operation of this motor is not easy at very high speeds.
The dedicated control circuit is necessary
As compared with DC motors, it uses more current
If the motor is not controlled properly then resonances can occur




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23. Industrial Applications of Stepper Motor
3D printing equipment
Robotic arm
Textile machines
Printing presses
Gaming machines
Medical imaging machinery
Small robotics
CNC milling machines
Welding equipment.,,etc.

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24. Stepper Motor Drives for Robotic Applications
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25.  A stepper motor is a digital electromechanical system wherein each electrical
pulse input moves the rotor by a discrete angle called the step angle and hence
the name stepping motor.
Stepper motors are used universally for numerous applications in industrial
areas.
 Robotics is one of the areas where the use of stepper motor is of utmost
importance. Robotic applications require precise movements for accuracy.
A stepper motor is suitable for robotic applications because its movement
comprises of discrete steps.
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26. It moves by a discrete angle called the step angle in each step. Stepper motors
are used in commercial and industrial applications because of their high
reliability, low cost, high torque at low speeds and a simple construction that
operates in almost every environment.
The drive system of a stepper motor controls its movement. A versatile drive
system will allow accurate control of the movement of a stepper motor so that it
can be used in robotic applications.
Many authors have proposed driver circuits for stepper motors; however the
design circuitry proposed doesn’t have a user-friendly approach.

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27. Two-phase permanent magnet stepper motor drive model
The stepper motor driver is simulated using MATLAB Simulink’s Sim Power
Systems simulation engine.
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28. Parameters dialog box for permanent magnet stepper motor
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29. Signal builder dialog box showing the step and direction.
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30. Simulation waveforms
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31. The stepper motor model consists of a permanent magnet stepper motor block, a
driver block, a signal builder block, a DC voltage and a scope that gives the
results of the simulation.


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32. Thank You
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