A linear motor is a transmission that converts electrical energy directly into linear motion mechanical energy without the need for any intermediate conversion mechanism. It can be seen as a rotary motor cut in radial direction and developed into a plane.
Linear motors are also called linear motors, linear motors, linear motors, and push rod motors. The most common types of linear motors are plate and U-slot, and tube type. The typical composition of the coil is three phases, with Hall elements implementing brushless commutation.
The diagram linear motor clearly shows the inner winding of the actuator (rotor). Magnets and tracks. The mover uses an epoxy material to press the coil. Moreover, the magnetic track is to fix the magnet on the steel.
Linear motors are often simply described as rotating machines that are flattened and work in the same way. A forcer (rotor) is made by compressing a coil together with an epoxy material; a magnetic track fixes a magnet (usually a high-energy rare earth magnet) on the steel. The motor's movers include coil windings, Hall element circuit boards, thermistors (temperature sensors to monitor temperature), and electronic interfaces. In a rotating electric machine, the mover and the stator require a rotary bearing to support the mover to ensure an air gap of the relative moving part. Similarly, linear motors require linear guides to maintain the position of the mover in the magnetic field generated by the track. Just like the encoder of the rotary servo motor is installed on the shaft, the linear motor needs to feedback the linear position feedback device--linear encoder, which can directly measure the position of the load to improve the position accuracy of the load.
The linear motor controls the same as the rotary motor. Like a brushless rotary motor, the mover and the stator have no mechanical connection (brushless). Unlike the rotary motor, the mover rotates and the stator position remains fixed. The linear motor system can be a magnetic track or a thrust coil. The system application is fixed track, thrust coil movement). In a motor that moves with a thrust coil, the weight and load ratio of the thrust coil is very small. However, there is a need for highly flexible cables and their management systems. Motion motors that use magnetic tracks not only have to bear the load but also have to bear the mass of the tracks, but they do not need a cable management system.
Similar electromechanical principles are used on linear and rotary motors. The same electromagnetic force generates torque on the rotating motor and generates a linear thrust effect on the linear motor. Therefore, the linear motor uses the same control and programmable configuration as the rotary motor. The shape of the linear motor can be flat and U-shaped, and tubular. Which configuration is best suited to the actual application specification and work environment?
Linear motor working principleThe side evolved from the stator is called the primary, and the side evolved from the rotor is called the secondary. In practice, the primary and secondary are manufactured to different lengths to ensure that the coupling between the primary and the secondary remains constant over the desired range of travel. The linear motor can be a short primary length secondary, or it can be a long primary short secondary. Taking into account manufacturing costs and operating costs, a linear induction motor is used as an example: When the primary winding is fed into an AC power source, a traveling wave magnetic field is generated in the air gap, and when the secondary is cut by a traveling wave magnetic field, an electromotive force is induced and a current is generated. This current, which interacts with the magnetic field in the air gap, generates electromagnetic thrust. If the primary is fixed, the secondary performs a linear motion under the action of thrust; otherwise, the primary performs a linear motion. Linear motor drive control technology A linear motor application system must not only have a good linear motor, but also must have a control system that can achieve technical and economical requirements under safe and reliable conditions. With the development of automatic control technology and microcomputer technology, more and more linear motor control methods.
The study of linear motor control technology can be basically divided into three aspects: First, the traditional control technology, the second is the modern control technology, and the third is the intelligent control technology.
Traditional control techniques such as PID feedback control and decoupling control have been widely used in AC servo systems. PID control contains information in the dynamic control process and has strong robustness. It is the most basic control method in the AC servo motor drive system. In order to improve the control effect, decoupling control and vector control techniques are often used. Under the condition that the object model is determined, unchanged and linear, and the operating conditions and operating environment are fixed, the use of traditional control techniques is simple and effective. However, in high-performance applications where high-precision microfeeds are used, changes in the structure and parameters of the object must be considered. Various nonlinear effects, changes in the operating environment, and environmental disturbances such as time-varying and uncertainties can achieve satisfactory control results. Therefore, modern control technology has attracted much attention in the research of linear servo motor control. Common control methods include: adaptive control, sliding mode variable structure control, robust control and intelligent control. Mainly combines the existing mature control methods such as fuzzy logic, neural network, PID, and H∞ control to learn from each other to obtain better control performance.
Linear Motor Benefits(1) The structure is simple. The tubular linear motor directly generates linear motion without intermediate conversion mechanisms, greatly simplifies the structure, reduces the movement inertia, greatly improves the dynamic response performance and positioning accuracy; at the same time, it also improves reliability, saves costs, and makes manufacturing and maintenance more efficient. Simple. Its initial sub-level can directly become a part of the organization. This unique combination makes this advantage further manifested.
(2) Suitable for high speed linear motion. Because there is no constraint of centrifugal force, ordinary materials can also achieve higher speeds. And if the gap between the primary and secondary air cushions or magnetic mats is preserved, there will be no mechanical contact during movement, and therefore the moving part will be free from friction and noise. In this way, the transmission components are not worn, which can greatly reduce the mechanical losses and avoid the noise caused by the streamers, cables, gears, pulleys, etc., thereby increasing the overall efficiency.
(3) High primary winding utilization. In the tube type linear induction motor, the primary winding is a cake type, there is no end winding, and thus the winding utilization is high.
(4) No lateral edge effect. The lateral effect refers to the weakening of the magnetic field at the boundary due to the transverse breaking, while the cylindrical linear motor does not open transversely, so the magnetic field is evenly distributed in the circumferential direction.
(5) It is easy to overcome the problem of unilateral magnetic pull. Radial pull forces cancel each other out, basically there is no problem of unilateral magnetic pull force.
(6) Easy to adjust and control. By adjusting the voltage or frequency, or changing the secondary material, different speeds and electromagnetic thrusts can be obtained, suitable for low-speed reciprocating operation.
(7) strong adaptability. The primary core of the linear motor can be encapsulated with epoxy resin, has good anti-corrosion, moisture-proof performance, easy to use in the environment of moisture, dust and harmful gases; and can be designed into a variety of structures to meet the needs of different situations .
(8) High acceleration. This is a linear motor drive and offers a significant advantage over other screw, timing belt and rack and pinion drives.
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