Electric Drives and Electromechanical Systems
by Richard Crowder, Published by Butterworth-Heinemann-Elsevier
ISBN 0-7506-6740-0, paperback, 292 pp, $39.95
EN-Genius Reviewer: Dennis L. Feucht

This book presents a survey of mechanical components and system-level motor and motion-control components from an industrial control perspective. The author is from Southampton, England. For an electronics engineer, the book has value in its coverage of the various mechanical components used in motion systems. Some of the more complicated components, such as harmonic or cycloid gearboxes, lack what I would have liked in detail, though the basic ideas behind them are presented. Some details, like shaft sizing, are helpful in alerting the EE to some of the less obvious aspects of mechanical design. The industrial-systems emphasis is manifested in the discussion of motor sizing. The commonly-used kinds of motion sensors are briefly presented, mixed in with analog-to-digital conversion and what aliasing is. These concepts are apparently presented for awareness, not comprehension by the reader. Axial- and radial-field motors are followed by thyristor converters and motor linear amplifier drivers. PWM and the 4-switch bridge receive greater attention and some math, as do regenerative drives.

Permanent-magnet synchronous (PMS) or "dc brushless" motors get a chapter, along with their drives. Some practical design details are presented, though not enough to provide a solid foundation in motor-drive design as such. The succeeding chapter on induction motors fills in some of what is lacking in motor control principles such as vector or field-oriented control.

A chapter introducing step-motors and their open-loop control is followed by less common kinds of actuators: voice-coil motors, limited-angle torquers, and piezoelectric and shape-memory alloy motors. No model useful for design is developed, but the basic idea is presented. Switched-reluctance motors are given more attention, to the point of deriving the basic torque equation.

The final chapter is titled "Controllers for Automation." Treatment of control includes digital control though, again, only the basic ideas are presented. The s- and z-domains show up, with transfer functions for basic motor torque and speed control loops. Programmable logic controllers and their relay-logic ladder diagrams also appear. The book ends with industrial networking and network architecture.

In attempting to cover so much ground, such a book would be either gigantic in size (which this one is not), superficial, or selectively deep but lacking in background development. This book tends toward the third possibility with much of the second. For instance, in describing robot arm kinematics, transformation matrices are offered, but without much explanation of their significance, nor the mechanical theory upon which they are based. The reader benefits from this book mainly by being brought to the level of awareness of various components, techniques, and principles. Consequently this book might primarily serve as a brief and light introduction to motion systems for engineers who know nothing about them.

The book has numerous typographical and grammatical errors and needs to be edited. Some obsolete terminology, such as "back emf." is used.

I just might keep this book in my engineering library for reference when I need to be refreshed regarding mechanical components. Although what is presented on them lacks engineering depth, the motion-control designer usually does not want to become a mechanical engineer in order to complete an industrial motion-system project, and this book has just enough useful information to sometimes help fulfill that need.