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Linear Motor

January 11,2024

Linear motors  and servo motors are common industrial motors, and they are widely used in various modern industrial machinery production equipment. Although they are both motors, they are very different in terms of structure, working principle, application scenarios, etc. This article will introduce the characteristics of these two motors in detail.

Theoretically, any system with feedback (linear motors usually use Hall or linear grating feedback) should be a servo system. Therefore Linear motors are also a type of servo motors. Then, servo motors should be divided into two categories in a broad sense: rotary servo motors and linear servo motors.


The  linear motor  is a transmission device that directly converts electrical energy into linear motion mechanical energy without any intermediate conversion mechanism; it can be regarded as a rotating motor that is cut radially and developed into a plane, evolving from a stator The side that comes from the rotor is called the primary, and the side that evolves from the rotor is called the secondary; in practical applications, the primary and secondary are made into different lengths to ensure that the primary and secondary are within the required stroke range. The coupling between them remains unchanged; the linear motor can have a short primary and a long secondary, or a long primary and a short secondary.

Considering the manufacturing cost and operating cost, currently, a short primary and a long secondary are generally used.

The Servo motor refers to the engine that controls the operation of mechanical components in the servo system. It is an indirect transmission device that assists the motor. The servo motor can control speed and position accuracy very accurately and can convert voltage signals into torque and rotational speed. To drive the control object, closed-loop control.

Servo motors are prone to low-frequency vibration at low speeds. The vibration frequency is related to the load condition and driver performance. It is generally believed that the vibration frequency is half of the no-load take-off frequency of the motor. This low-frequency vibration phenomenon determined by the working principle of the servo motor is very detrimental to the normal operation of the machine. When the servo motor works at low speed, damping technology should generally be used to overcome the low-frequency vibration phenomenon, such as adding a damper to the motor or using subdivision technology on the driver. Most of the servo motors currently used in computerized embroidery machines are five-phase hybrid servo motors. The purpose is to reduce the step angle and improve control accuracy by using a high-phase stepper motor; however, the performance obtained by this method is limited. The improvement is limited and the cost is relatively high. The use of subdivision drive technology can greatly improve the operating quality of the servo motor, reduce torque fluctuations, suppress oscillations, reduce noise, and improve step resolution.

Linear motors have compact structure, low power loss, high rapid movement, high acceleration, and high speed (linear motors can achieve high-precision positioning control in different ranges from high speed to low speed by directly driving the load, such as in subway automatic Door)


Compared with rotating motors, linear motors mainly have the following characteristics:

1. Simple structure. Since the linear motor does not require additional devices to convert rotational motion into linear motion, the structure of the system itself is greatly simplified, and the weight and volume are greatly reduced;

2. High positioning accuracy. Where linear motion is required, linear motors can achieve direct transmission, thus eliminating various positioning errors caused by intermediate links. Therefore, positioning accuracy is high. If microcomputer control is used, it can be greatly improved. Positioning accuracy of the entire system;

3. Fast response, high sensitivity, and good follow-up. It is easy for a linear motor to support its mover with magnetic levitation so that a certain air gap is always maintained between the mover and the stator without contact. This eliminates the contact friction resistance between the stator and the mover, thus greatly improving the efficiency of the system. sensitivity, speed, and follow-up;

4. Safe and reliable work, long life. Linear motors can transmit force without contact, and the mechanical friction loss is almost zero, so there are few faults and maintenance-free, so they work safely and reliably and have a long life.

In short, the characteristics of linear motors are high dynamic characteristics and high rigidity. Compared with traditional linear transmission structures (such as screws and electric cylinders), they are maintenance-free, but the initial investment cost is relatively high. In practical applications, professional designers will consider the use of different servo motors from aspects such as equipment maintenance costs and the impact of production shutdown.

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