Linear motor structure and working principle

The structure of the linear motor can be considered as forming a rotating electric machine in a radial direction and expanding the circumference of the motor into a straight line. The stator is equivalent to the primary of the linear motor, and the rotor is equivalent to the secondary of the linear motor. When the primary current is applied, a traveling wave magnetic field is generated in the air gap between the primary and secondary, and the action of the traveling wave magnetic field and the secondary permanent magnet The driving force is generated to realize the linear motion of the moving parts.

 

How linear motors work

 It is envisaged that a rotating motion induction motor is cut along the radius and flattened, which becomes a linear induction motor.

The primary is done very long, extending to the position that the movement needs to reach, and the secondary can be made very long; it can be primary fixed, secondary moving, secondary fixed, primary moving.

The magnetic flux generated in the stator after the AC power is supplied, according to Lenz's law, induces eddy currents on the metal plate of the moving body. Let the induced voltage causing the eddy current be E, the metal plate has the inductance L and the resistance R, and the eddy current and the magnetic flux density will generate a continuous thrust F according to the law.

Linear motor characteristics

 High-speed response Because the mechanical transmission parts such as the lead screw with large response time constant are directly canceled in the system, the dynamic response performance of the whole closed-loop control system is greatly improved, and the response is extremely sensitive and quick.

 High bit accuracy The line drive system eliminates the transmission error caused by the mechanical mechanism such as the lead screw and reduces the tracking error caused by the delay of the transmission system during interpolation. Through the linear position detection feedback control, the positioning accuracy of the machine tool can be greatly improved.

The elastic deformation, friction and wear of the transmission link and the motion hysteresis caused by the backlash increase the transmission rigidity.

Fast speed, short acceleration and deceleration
Unrestricted stroke length On the guide rail, the linear length of the motor can be extended infinitely.

Quiet, low noise Due to the elimination of the mechanical friction of the drive screw and other components, and the guide rail can be used rolling guide or magnetic pad suspension guide (no mechanical contact), the noise will be greatly reduced during the movement.

 High efficiency Since there is no intermediate transmission link, the energy loss during mechanical friction is eliminated.

Linear motor application
Linear motors are mainly used in three aspects:

 Applied to automatic control systems, there are many such applications;

 As a long-term continuous running drive motor;

It is used in devices that require large linear motion energy in a short time and short distance.

The U-shaped linear motor can be driven directly without turning the rotation into linear motion, and the mechanical structure is simple and reliable. The motor runs ultra-stationary, has no cogging effect, dynamic response speed is very fast, inertia is small, acceleration can reach 20G, speed reaches 10-30m/s, smooth motion at low speed 1μm/s, high rigidity, compact structure, optional straight line The encoder performs high-precision position control with positional accuracy depending on the selected encoder.

The stator rails can be connected as needed, so theoretically the length of the motor is not limited. The motor mover does not touch the stator and does not use the wear, jam, and backlash of the common screw ball and belt drive. Therefore, our linear motor can achieve maintenance-free long-term work. Our U-shaped linear motors are divided into iron cores and ironless cores. Iron core linear motors have larger output per unit volume. No iron core linear motors have no hysteresis and eddy current effects. The movement is smoother and faster, and the magnetic loss is less. , fever is small.

Such linear motors are particularly suitable for: robots, actuators, linear platforms, optical fiber alignment, precision machine tools, semiconductor manufacturing, vision systems, electronic component plug-ins, factory automation, etc., which require high speed and accuracy for motion systems. Application.

In addition, various linear motors such as voice coil linear motors, flat linear motors, linear motor inverted pendulums, and two-dimensional linear motor platforms are available to meet different needs.