An Introduction To Linear Motors

Title: An Introduction to Linear Motors

Linear motors, also known as linear motors, linear drives, or pushrod motors, have seen stable growth in industrial applications, proving that linear motors can be reliably used. In this article, we will provide a brief overview of the types of linear motors and their differences compared to rotary motors. The most commonly used types of linear motors are flat, U-slot, and tubular. The typical configuration of the coils is three-phase, with Hall elements for brushless commutation. A diagram illustrating the phase sequence and phase current of a linear motor using Hall commutation is shown.

Linear motors are often described simply as flattened versions of rotary motors, with the same operating principles. The mover (forcer, rotor) is made by compressing coils together using epoxy material. Additionally, the magnetic track consists of magnets (typically high-energy rare-earth magnets) fixed on steel. The motor's mover includes coil windings, Hall element circuit boards, thermal regulators (temperature sensors monitoring temperature), and electronic interfaces. In rotary motors, the mover and stator require rotary bearing support to ensure the air gap of the moving parts. Similarly, linear motors need linear guides to maintain the mover's position in the magnetic field generated by the magnetic track. Just as encoders in servo motors are mounted on the shaft to provide position feedback, linear motors require linear encoders to directly measure the load's position, thereby improving position accuracy.

The control of linear motors is similar to that of rotary motors. Like brushless rotary motors, the mover and stator have no mechanical connection (brushless). Unlike rotary motors, where the mover rotates and the stator's position remains fixed, linear motor systems can be either magnetic track-driven or thrust coil-driven (most positioning system applications use fixed magnetic tracks and moving thrust coils). Motors driven by thrust coils have a small weight and load ratio. However, they require high-flexibility cables and their management systems. Motors driven by magnetic tracks not only have to bear the load but also the mass of the magnetic track, eliminating the need for cable management systems.

Similar electromechanical principles are used in both linear and rotary motors. The same electromagnetic force that generates torque in rotary motors produces linear thrust in linear motors. Therefore, linear motors use the same control and programmable configurations as rotary motors. The shape of linear motors can be flat, U-slot, or tubular, depending on the specific application requirements and working environment.