来源：/ 发布时间：2019-12-03 浏览：次
Some contents of stepping motor and BLDCM are sorted out in this paper, mainly from the performance characteristics of the motor to make some simple description, and some related to the control.
Stepping motor can be used as a special motor for control. It has no accumulated error and is widely used in various open-loop control. Generally, the accuracy of stepping motor is 3-5% of stepping angle, and does not accumulate. The torque of stepping motor will decrease with the increase of rotating speed. The stepper motor can operate normally at low speed, but it can not be started if it is higher than a certain speed, accompanied by a howl.
When the step driver receives a pulse signal, it drives the step motor to rotate a fixed angle according to the set direction, which is called "step angle". Its rotation is run step by step with a fixed angle. The angular displacement can be controlled by controlling the number of pulses, so as to achieve the purpose of accurate positioning; at the same time, the speed and acceleration of motor rotation can be controlled by controlling the pulse frequency, so as to achieve the purpose of speed regulation.
Stepping motor includes reactive, permanent magnet, hybrid and single-phase stepping motor. Reactive stepping motor is generally three-phase, which can achieve large torque output. The stepping angle is generally 1.5 degrees, but the noise and vibration are very large. The rotor magnet of reactive stepping motor is made of soft magnetic material. There are multi-phase excitation windings on the stator. The torque is generated by the change of magnetic conductivity.
Hybrid stepping motor is a hybrid of the advantages of permanent magnet and reactive. It is divided into two phases and five phases: the step angle of two phases is generally 1.8 degrees. The five phase step angle is generally 0.72 degrees.
Brushless DC motor
BLDCM has excellent linear mechanical characteristics, wide speed range, large starting torque, simple control method, using electronic commutation instead of mechanical commutation, no wear, sparks, noise greatly reduced and so on.
BLDCM is a typical mechatronics product, which is composed of motor body and driver. Brushless motor is a motor without electric brush and commutator, also known as commutator motor. As early as the 19th century when the motor was born, the practical motor is the brushless form, that is, the AC squirrel cage asynchronous motor, which has been widely used. However, there are many insurmountable defects in asynchronous motor, so the development of motor technology is slow. In the middle of the last century, the transistor was born, so the DC brushless motor using transistor commutation circuit instead of brush and commutator came into being. This new type of BLDCM is called electronic reversing DC motor, which overcomes the defects of the first generation of BLDCM.
The stator winding of BLDCM is usually made of three-phase symmetrical star connection, which is very similar to three-phase asynchronous motor. In order to detect the polarity of the motor rotor, a position sensor is installed in the motor. The driver is composed of power electronic devices and integrated circuits. Its function is to receive the start, stop and brake signals of the motor, to control the start, stop and brake of the motor; to receive the position sensor signals and the positive and negative reversal signals, to control the on-off of each power tube of the inverter bridge, to generate continuous torque; to receive the speed command and speed feedback signals, to control and adjust the rotation Speed; provide protection and display, etc.
DC motor has fast response, large starting torque, and the performance of providing rated torque from zero speed to rated speed. However, the advantages of DC motor are its disadvantages, because if DC motor wants to produce the performance of constant torque under rated load, the armature field and rotor field must be maintained at 90 ° constantly, which requires carbon brush and commutator. The carbon brush and commutator will produce sparks and carbon powder when the motor is rotating, which will not only cause damage to the components, but also limit the use occasions.
There is no carbon brush and commutator in AC motor, which is maintenance free, robust and widely used. However, to achieve the performance equivalent to that of DC motor, complex control technology must be used. Nowadays, with the rapid development of semiconductor, the switching frequency of power components is much faster and the performance of drive motor is improved. The speed of microprocessor is also faster and faster. It can realize the control of AC motor in a rotating two axis rectangular coordinate system, and properly control the current component of AC motor in two axes, so as to achieve similar DC motor control and have the same performance as DC motor.