stepper motor (3)
TRANSCRIPT
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STEPPER MOTOR
Presented by: 1) Supriya Rakshit
2) Monika Soni
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Contents1. Introduction2. Comparison Between Servo & Stepper Motor
3. Types Of Stepper Motor
a. Variable Reluctance Stepper Motorb. Permanent Magnet Stepper Motor
c. Hybrid Stepper Motor
4. Applications
5. Advantages & Disadvantages
6. Simulation in Matlab
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1. Introduction A stepper motor is a pulse-driven motor that changes
the angular position of the rotor in steps.Rotor
Stator
Coils
2
1
S
N
1
2
Outside Casing
Stator
Rotor
Internal components of a Stepper
Motor
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Cont. A stepper (or, stepping) motor is an electromechanical
device which converts electrical pulses into discretemechanical movements.
Stepper motors work on the principle of
electromagnetism. There is a soft iron or magnetic rotor
shaft surrounded by the electromagnetic stators. The
rotor and stator have poles which may be teethed or not
depending upon the type of stepper. When the stators are
energized the rotor moves to align itself along with the
stator (in case of a permanent magnet type stepper) or
moves to have a minimum gap with the stator (in case of
a variable reluctance stepper). This way the stators are
energized in a sequence to rotate the stepper motor.
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2. Compare With a Servo Stepper motors are similar to servo motors as we can
perform position control with both. However, Servo motors require some form of analog
feedback whereas stepper motors are often open loop.
Stepping motors can be used in simple open-loop
control systems; these are generally adequate forsystems that operate at low accelerations with staticloads, but closed loop control may be essential for highaccelerations.
For high accelerations with variable loads, all rotor
information is lost, and we require closed loop for
accurate control
Servo motors are not subject to this problem
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3. Types Of Servo MotorPERMENANT MAGNET
MOTOR
VARIABLE RELUCTANCE
MOTOR
STEPPER MOTOR
HYBRID MOTOR
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Cont.
Permanent Magnet Employ permanent magnet
Low speed, relatively high torque
Variable Reluctance Does not have permanent magnet
Low torque
Hybrid multi-toothed stator poles and a permanent magnet
rotor
High static and dynamic torque
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PERMANENT MAGNET MOTOR
Cutaway diagram of a typical
permanent magnet stepper
motor.
Canstack rotor that is used in
permanent magnet stepper motors.
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The rotor and stator poles of a permanent magnet stepper are not
teethed. Instead the rotor have alternative north and south polesparallel to the axis of the rotor shaft.
When a stator is energized, it develops electromagnetic poles.
The magnetic rotor aligns along the magnetic field of the stator.
The other stator is then energized in the sequence so that the
rotor moves and aligns itself to the new magnetic field. This way
energizing the stators in a fixed sequence rotates the stepper
motor by fixed angles.
The resolution of a permanent magnet stepper can be increased
by increasing number of poles in the rotor or increasing the
number of phases.
Cont.
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The variable reluctance stepper has a toothed non-magnetic softiron rotor. When the stator coil is energized the rotor moves to
have a minimum gap between the stator and its teeth.
VARIABLE RELUCTANCE STEPPER
MOTORS
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The teeth of the rotor are designed so that when they arealigned with one stator they get misaligned with the next
stator. Now when the next stator is energized, the rotor
moves to align its teeth with the next stator. This way
energizing stators in a fixed sequence completes the
rotation of the step motor.
The resolution of a variable reluctance stepper can be
increased by increasing the number of teeth in the rotorand by increasing the number of phases.
Cont..
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A hybrid stepper is a combination of both permanentmagnet and the variable reluctance. It has a magnetic
teethed rotor which better guides magnetic flux to
preferred location in the air gap.
HYBRID MOTOR
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The magnetic rotor has two cups. One for north polesand second for the south poles. The rotor cups are
designed so that that the north and south poles
arrange in alternative manner. Check out the insight
of a Hybrid Stepper Motor.
The Hybrid motor rotates on same principle of
energizing the stator coils in a sequence.
Cont.
http://www.engineersgarage.com/insight/how-stepper-motor-workshttp://www.engineersgarage.com/insight/how-stepper-motor-workshttp://www.engineersgarage.com/insight/how-stepper-motor-workshttp://www.engineersgarage.com/insight/how-stepper-motor-works -
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4. APPLICATIONS Stepper motors are also used for cruise control, military
antenna positioners, automated sensing devices
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1.Step motors are used inside
medical scanners, multi-axis
stepper motor microscopic or
nanoscopic motion control ofautomated devices, dispensing
pumps,
2.samplers, and chromatograph
auto-injectors. Also found insidedigital dental photography, fluid
pumps, respirators, and blood
analysis machinery.
Cont.
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Stepper motors are incorporatedinside PC based scanning
equipment, data storage tape
drives, optical disk drive head
driving mechanism, printers,bar-code printers, scanners.
Stepper motors in cameras for
automatic digital camera focus
and zoom functions.
Cont..
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The rotation angle of the motor is proportional to the
input pulse.
The motor has full torque at standstill (if the windings
are energized).
Precise positioning and repeatability of movement sincegood stepper motors have an accuracy of 3 to 5% of a
step and this error is non-cumulative from one step to the
next.
Excellent response to starting/stopping/reversing.
Very reliable since there are no contact brushes in the
motor. Therefore the life of the step motor is simply
dependent on the life of the bearing.
5. STEPPER MOTOR ADVANTAGEC
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The stepper motors response to digital input pulses
provides open-loop control, making the motor
simpler and less costly to control.
It is possible to achieve very low speed synchronousrotation with a load that is directly coupled to the
shaft.
A wide range of rotational speeds can be realized as
the speed is proportional to the frequency of the input
pulses.
Cont..
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Require a dedicated control circuit
Use more current than D.C. motors
High torque output achieved at low speeds
5. STEPPER MOTOR disadvantage
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6. SIMULATION cIRCUIT
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Output Waveforms
Phase Current of A
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Cont.
Phase Voltage
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Torque
Cont.
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Cont.
Angular Speed
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Cont.
Angular Position
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Thank You