来源：http://www.jnmcd.com 发布时间：2019-04-22 浏览：次
Micromotor is an actuator that converts electric pulse into angular displacement. When the micro-driver receives a pulse signal, it drives the micro-motor to rotate a fixed step angle in a given direction, and its rotation moves step by step at a fixed angle. So we can easily control the angle of motor rotation by controlling the number of pulses, and at the same time we can control the speed and acceleration of motor rotation by controlling the frequency of pulses.
There are three main types of micro motors in common use: variable reluctance type, permanent magnet type and hybrid type. The variable reluctance type consists of a fundamental rotor and a stator. The rotor has teeth or grooves. It always turns to the position with the lowest reluctance in the stator magnetic field. It can produce medium torque with a step angle of 0.9 15. The rotor of permanent magnet micro motor is made of cylindrical permanent magnet with teeth or slots on it. Torque ratio is small, with persistent torque, step angle 7.5 ~90. It is widely used in computer peripheral equipment and instrumentation industry. Hybrid micro-motor combines the advantages of permanent magnet micro-motor and variable reluctance motor. Hybrid stepping motor produces large torque, has persistent force when power is cut off, and the step angle is about 0.9 ~15.
See many people say that the micro motor stop subdivision is to improve positioning accuracy, in fact, this is not the main factor. In practice, subdivision can greatly improve the operation performance of the motor. Take two-phase hybrid micro-motor as an example. If the rated current of the motor is 5A, the winding energy phase current of the motor will change from 0 to 5A or from 5A to 0 every time it runs in conventional driving mode. The sudden change of the current will inevitably cause the vibration of the motor. If the subdivision technology is used, if it is 50 subdivision, the motor does not run a step, and its winding energy and current change is only 0.1A, which can greatly improve the vibration condition of the motor. At the same time, after subdivision, the output torque of the motor is increased in practice. Especially for the three-phase reacting motor, its torque is improved by about 30-40% compared with that without subdivision, which improves the resolution of the motor, reduces the step angle and increases the average of the step. Therefore, stopping subdivision of the micro-motor is really beneficial.
Take two-phase micromotor as an example, if the number of beats is N and the input of F pulses per second, the speed of the rotor is N, if the speed of the rotor is changed under the condition of F unchanged, then the speed of the rotor is changed. After the motor is subdivided, N increases, and the number of beats increases, thus reducing the step angle. This will make the speed of the motor run down. In order to maintain the normal working speed of the motor, the demand increases correspondingly. The number of pulses.
If the change of input pulse is only a part of the rated current in the corresponding winding, then the rotation of the rotor will only be a part of the original step angle. When the rated current dividend stops switching at several levels, the rotor completes an original step angle in several steps. After the step control of the phase current of the micro motor, the motor runs at a smaller unit step angle, thus reducing the step size and low frequency oscillation. In short, the idea of subdivision drive is to change the original simple on-off process of rotor current to gradually change the current magnitude and direction of each phase winding, so as to gradually change the space composite magnetic field inside the motor, so that the original step angle of the power mode can be changed into a current-following step wave, into a multi-step. Because of the high frequency of the common chopper, it can be neglected when the current swings at each stage, which is approximately regarded as DC output.
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