Jones on Stepping Motors

Index

• Abstract
• Introduction
• 1. Types of Stepping Motors
• 2. Stepping Motor Physics
• 3. Basic Control Circuits
• 4. Current Limiting
• 5. Microstepping
• 6. Mid-Level Control
• 7. High Level Real-Time Control
• old 5. Stepping Motor Control Software
• old 6. A Worked Example
• Other Sources of Information

Abstract

This tutorial covers the basic principles of stepping motors and stepping motor control systems, including both the physics of steppers, the electronics of the basic control systems, and software architectures appropriate for motor control.

Introduction

Stepping motors can be viewed as electric motors without commutators. Typically, all windings in the motor are part of the stator, and the rotor is either a permanent magnet or, in the case of variable reluctance motors, a toothed block of some magnetically soft material. All of the commutation must be handled externally by the motor controller, and typically, the motors and controllers are designed so that the motor may be held in any fixed position as well as being rotated one way or the other. Most steppers, as they are also known, can be stepped at audio frequencies, allowing them to spin quite quickly, and with an appropriate controller, they may be started and stopped "on a dime" at controlled orientations.

For some applications, there is a choice between using servomotors and stepping motors. Both types of motors offer similar opportunities for precise positioning, but they differ in a number of ways. Servomotors require analog feedback control systems of some type. Typically, this involves a potentiometer to provide feedback about the rotor position, and some mix of circuitry to drive a current through the motor inversely proportional to the difference between the desired position and the current position.

In making a choice between steppers and servos, a number of issues must be considered; which of these will matter depends on the application. For example, the repeatability of positioning done with a stepping motor depends on the geometry of the motor rotor, while the repeatability of positioning done with a servomotor generally depends on the stability of the potentiometer and other analog components in the feedback circuit.

Stepping motors can be used in simple open-loop control systems; these are generally adequate for systems that operate at low accelerations with static loads, but closed loop control may be essential for high accelerations, particularly if they involve variable loads. If a stepper in an open-loop control system is overtorqued, all knowledge of rotor position is lost and the system must be reinitialized; servomotors are not subject to this problem.

Stepping motors are known in German as Schrittmotoren, in French as moteurs pas à pas, and in Spanish as motor paso a paso.

Other Sources of Information

Web Sites

Other Motor Control Web Pages

• Advanced Micro Systems Stepper Motor Basics
  an excellent tutorial from a maker of motors and controllers.
• motioncontrol.com
  a commercially operated gateway to motion control resources on the web
• Ian Harries on Stepping Motors (archived version June 8, 2011)
  with a nice set of information on reverse engineering salvaged motors and a number of example applications.
• Euclid Research MotionScope demo
  excellent illustrations of physical behavior of some real motors.

Motor Manufacturers

• Advanced Micro Systems (1.8 degree per step, large permanent magnet motors)
• Astrosyn. (UK)
• Electrocraft (formerly Eastern Air Devices Inc.) (midsize motors and linear actuators)
• MyMotors & Actuators The Faulhaber Group (very small pancake-format motors)
• Gunda Electronic GmbH (German) (Google's English translation)
• Haydon Switch and Instrument, Inc.
• IntelLiDrives (high-resolution linear and 2-d planar stepping motors)
• Lin Engineering (100 to 800 steps per revolution)
• MicroMo Electronics (very small motors)
• Mitsumi (Japan)
• Parker Hannifin Corporation (motors and controllers)
• Phytron, Inc. (motors and controllers)
• Portescap Inc.
• Shinano Kenshi Corp. (SKC)
• Micro Precision Systems (remarkably small motors and controllers)

Controllers

• Advanced Micro Systems
• Astrosyn. (UK)
• Advanced Micro Systems Inc.
• Alzanti Limited (UK)
• Arrick Robotics
• Control Technology Corporation
• E-Lab Digital Engineering, Inc.
• Simple Step LLC
• Netmotion

Distributors

• ACP&D Limited (UK) (UK version) (distributor for COLIBRI integrated motor/controllers and maker of COBRA linear and planar stepping motors)
• Alzanti Limited (UK)
• Circuit Specialists (USA)
• Electro Sales Inc. (northeast USA)
• MESA Systems Co. (USA) (distributor for COLIBRI integrated motor/controllers)

Surplus and Hobbyist Suppliers

• ALL Electronics (new and surplus)
• DIY Electronics (kits, Hong Kong)
• EIO's Stepper Motor Page (surplus)
• PC Gadgets (the Gadgetmaster interface)
• Surplus Center (mostly heavy industrial surplus, Nebraska)
• C & H Surplus (Surplus, California)

Motor Design, Selection and Prototype Fabricaton Services

• Yeadon Engineering Services, (Michigan)
  YES is the contact for the Small Motor Manufacturer's Association.

Other Web Pages

• The Art of Motion Control;
  Bruce Shapiro's stepper-controlled machine-shop and artist's studio.
• EIO's Stepper Motor Page;
  a surplus dealer, but listed here because of their extensive index of information about stepping motors.
• Fractional Horsepower Motor Manufacturers;
  an index maintained by Industrial Quick Search.
• Schmitz Engineering Liaison;
  a rotary shaft position encoder distributor offering consulting services on encoder use. Roger Schmitz wrote Encoder Output Choices for System Designers for MOTION Magazine.

Books

Handbook of Small Electric Motors

William H. Yeadon and Alan W, Yeadon, eds.
McGraw-Hill, c2001.
LC number: TK2537 .H34 2001

Stepping motors: a guide to modern theory and practice

Acarnley, P. P.
P. Peregrinus on behalf of the IEE, 1984, c1982.
LC number: TK2537 .A28 1984
A third edition has recently been released.

Stepping motors and their microprocessor controls

Kenjo, Takashi
Oxford University Press, c1984.
LC number: TK2785 .K4 1984

As of Dec 22, 2010, Google found about 12,700 references to this material from outside the University of Iowa. compare this with 890 on Feb 14, 2008 and 539 on Dec. 15, 2003.

Last Modified:Wednesday, 28-Jul-2021 09:09:17 CDT.