Page 617 - Mechatronics with Experiments

CHAPTER 8

ELECTRIC ACTUATORS: MOTOR AND

DRIVE TECHNOLOGY

8.1 INTRODUCTION

The term “actuator” in motion control systems refers to the component which delivers the
motion (Figure 8.1). It is the component that delivers the mechanical power, which may be
converted from an electric, hydraulic, or pneumatic power sources. In the electric power
based actuator category, the motor and the drive are two power conversion components that
work together. In a motion control system, when we refer to the performance characteristics
of a motor, we always have to refer to it in conjunction with the type of “drive” that the
motor is used with, for the type of drive determines the behavior of the motor. The term
drive is generically used in industry to describe the power amplification and the power
supply components together.
The discussion in this chapter is limited to motor-drive technologies that can be used
in high performance motion control applications, that is involving closed loop position and
velocity control with high accuracy and bandwidth. Low cost constant speed motor-drive
components, which are used in mass quantities in applications such as fans and pumps, are
not discussed. To this end, we will discuss the following motor-drive technologies:
1. DC motors (brush-type and brushless type) and drives.
2. AC induction motors and field oriented vector control drives.
3. Step motors and drives:
(a) permanent magnet step motors,
(b) hybrid step motors,
along with full step, half step, and micro-stepping drives.
The operating principle of any electric motor involves one or more of the following
three physical phenomenon:

1. opposite magnetic poles attract, and the same magnetic poles repel each other,
2. magnets attract iron and seek to move to a position to minimize the reluctance to
magnetic flux,
3. current carrying conductors create electromagnets and act like a current-controlled
magnet.

Every motor has the following components,
1. a rotor on a shaft (moving component),
2. a stator (stationary component),

Mechatronics with Experiments, Second Edition. Sabri Cetinkunt.
© 2015 John Wiley & Sons, Ltd. Published 2015 by John Wiley & Sons, Ltd.
Companion Website: www.wiley.com/go/cetinkunt/mechatronics

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