Actuator Report: Stepper Motor
Steve [email protected]
(916) 662-4244
Utah State UniversityMarch 11, 2010
AgendaOverviewImpact of engineeringPrinciple of operationTypesImplementationApplicationMajor specificationsLimitationsPurchasingReferences
Typical Stepper Motorhttp://en.wikipedia.org/wiki/Stepper_motor
OverviewStepper motors are brushless electric
motors that operate through a radial array of steps
The step sizes vary from motor to motor and can be used in control applications where a defined resolution is helpful with motor manipulation
OverviewStepper motors have become widely
implemented in many ways due to their controllability without any form of feedback loop
Even without feedback, a stepper motor may be controlled to a good degree of precision
Impact of EngineeringThe functionality of stepper motors has
been so widely accepted that they have revolutionized the usefulness and ease of implementation of electric motors
They can be used in stable and reliable control system that function with great precision and accuracy
Principle of OperationVoltage applied to
the motor causes the rotor to incrementally spin
More voltage causes more increments to be bypassed around the circle
Typical Stepper Motorhttp://en.wikipedia.org/wiki/Stepper_motor
TypesPermanent Magnet stepper motors
maintain a permanent magnet within the housing
Variable Reluctance stepper motors with iron rotors have rotor points attracted to stator magnet poles
Hybrid Synchronous stepper motors are the combination of the previous two for better performance
ImplementationStepper motor control
varies almost as widely as the stepper motors themselves
Control implementation is heavily dependent upon internal configuration and application needs
Stepper Motor Controlhttp://www.tigoe.net/pcomp/code/category/
arduinowiring/51
ImplementationDrive circuitry for bi-polar
stepper motors can be complicated but may be worth the additional torque that the actuator would be able to provide once configured properly Stepper Motor Control
http://www.tigoe.net/pcomp/code/category/arduinowiring/51
ImplementationHalf-stepping and micro-
stepping are two implementation modes where the angular resolution may be increased with little change to the control circuitry
Stepper Motor Controlhttp://www.tigoe.net/pcomp/code/category/
arduinowiring/51
ApplicationCountless types of stepper motor
configurations are in use today all throughout the world
A wide variety of markets can take advantage of them for precise control actuation
ApplicationSmaller high precision
stepper motors are often used for common actuation tasks
Their small enclosures are easy to mount to hardware and at low speeds can provide high torque
Stepper Motorshttp://news.thomasnet.com/IMT/archives/
2006/07/scavenge_materials_to_build_tinker_your_own_c
nc_machine.html
ApplicationRobotic systems can take
advantage of a stepper motor’s quick response and high precision without the constant need of a feedback loop
Where needed they can also interface with belts and drive trains
Stepper Motorhttp://www.designworldonline.com/uploads/ImageGallery/G4.Handler.stepper.motor.gif
Major SpecificationsMotors tend to vary widely in response
and must be characterized in order to properly control and implement them in a design
Stepper motor characteristic equations are a good start to understanding their behavior, as long as the control circuitry is also taken into account
LimitationsStepper motor resolution is completely
dependent upon the number of teeth on the rotor
As motor velocity increases, there is also a marked decrease in the total torque output which can comprise certain implementations of the actuator
LimitationsDifferent tooth constructions in the
motors can lead to varied efficiencies and controllability
More complicated motor designs also may require more complicated control electronics with amplifiers and many input lines
PurchasingStepper motors may be readily purchased
from many online retailersSmall electronic stepper motors are found
at digikey.com or mouser.comLarge-application stepper motors may be
obtained from specialty manufacturers and retailers