BOOK_CONTENT
From Motors and Drives

Linear Motors
Linear motor systems operate basically the same as rotating motors. The difference, of course, is that linear motion is produced, rather than clockwise or counterclockwise motion.

There are two main components of the linear stepper motor-the platenand the slider (sometimes referred to as the forcer). The platen could be considered the stator of the motor. The slider could be considered a linear rotor. Figure 3-47 indicates a linear stepper motor.

The electromagnetic "teeth" extend over the entire length of the platen. The slider also contains "teeth" and has both permanent magnets and coils that are electrically charged. It should be noted that the platen and slider have tooth structures that almost match. The slight offset is what causes the slider to be attracted to the next available magnetic field in the platen. The slider, in many cases, will contain air bearings that assist in developing a slight air gap. This air gap is where the magnetic flux is developed, and would be considered common to any standard AC induction motor.

When the slider coils are energized, the linear stepper motor moves in 1/4 tooth steps. Extremely fine resolution can be obtained from this type of motor, in some cases up to 25,000 steps per inch. This type of motor is well suited for applications where fast acceleration and high-speed movements are required, but where low mass or weight is needed.

Speeds of up to 100 ips (inches per second) are possible, with movements in increments down to 0.00005 inches. The linear stepper motor system has its advantages in precision open-loop control, mechanical simplicity, reliability, applications where space is limited, and the ability for multiple motion (more than one slider can be applied onto one platen). In addition, this type of system is an alternative in applications where leadscrews (with backlash issues), belts, pulleys, and gears are not practical.

© 2003 ISA

Products & Services
Stepper Motors (rotary)
Stepper motors use a magnetic field to move a rotor in small angular steps or fractions of steps. They provide precise positioning and ease of use, especially in low acceleration or static load applications.
Motor Coils
Motor coils are used with motors, generators, stators, and armatures.
Linear Actuators
Electric linear actuators have an output rod that provides linear motion via a motor driven ball screw, lead screw, or ACME screw assembly. The actuator's load is attached to the end of a screw or rod and is often unsupported.
Piezoelectric Motors
Piezoelectric motors use a piezoelectric ceramic element to produce ultrasonic vibrations of an appropriate type in a stator structure. The consequent movement can either be rotational or linear depending on the design of the structure.

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