Linear motor

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A linear motor is an electric motor that moves in a straight line instead of spinning. By “unrolling” the usual motor, the moving part travels along a path with ends, not in a continuous loop. Linear motors are used in many machines that need precise, fast, straight motion, such as CNC machines and industrial robots, and they are common in transportation systems as well.

How they work
A linear motor creates force when electric current interacts with a magnetic field. This Lorentz-type action makes a straight, sliding motion along the motor’s track. Different designs use either windings and a moving field (linear induction motors) or magnets on one side and windings on the other (linear synchronous motors). Some systems use permanent magnets, others use electromagnets. Position sensors help control the motion precisely.

Two main categories
- Low-acceleration linear motors: designed for longer travel with steady speeds. They’re used in maglev-type transports and similar ground-based systems.
- High-acceleration linear motors: designed to push objects to very high speeds over short distances. They’re used in high-speed launch systems, experimental propulsion concepts, and certain fast-moving devices.

Common types and comparisons
- Linear Induction Motors (LIM): have windings on one side and a conductive surface on the other. They’re robust and good for long, heavy moves.
- Linear Synchronous Motors (LSM): have an active winding on one side and magnets on the other. They’re often brushless and well-suited for high precision and high speed. The Shanghai maglev uses an LSM.
- Brushless linear motors (BLDC) are common in precision positioning systems. Brushed linear motors are older and cheaper but need more maintenance because the brushes wear out.

Typical uses
- Industrial automation: CNC machines, pick-and-place systems, semiconductor equipment, and precise positioning tasks.
- Transport and infrastructure: maglev systems, sliding doors, baggage handling, and large conveyors.
- Entertainment and research: roller coasters use LIMs to accelerate cars; telescopes use hybrid actuators with linear motors for precise mirror positioning.
- Special applications: some systems imitate recoil in training devices or enable rapid, high-force actuation in experiments.

High-level history
Concepts for linear motors date back to the 19th century. Early practical designs appeared in the early 20th century, with significant development in the mid-20th century. Since then, linear motors have found widespread use in industry, transport, and research, improving speed, precision, and reliability in many systems.

Why they’re useful
Linear motors provide direct, backlash-free motion with high speed and strong force, which reduces the need for gears or screws and lowers maintenance. They’re especially valuable wherever fast, accurate straight-line movement is essential.