Shulou(Shulou.com)06/01 Report--

28BYJ-48 is a 4-phase permanent magnet accelerating stepper motor, which is shown in figure 9-3:

Figure 9-3 external indecency of stepper motor

Let's first explain the concept of "4-phase permanent magnet". The external structure of 28BYJ-48 is shown in figure 9-4. First, take a look at the inner ring. There are six teeth under it, which are identified as 05.This is called a rotor, which is literally meant to migrate. Each tooth of the rotor has eternal magnetism, which is a permanent magnet. This is the concept of "permanent magnet". If you look at the outer ring, this is the stator, which is motionless. In practice, it is fixed with the shell of the motor. There are eight teeth under it, and each tooth is wrapped with a coil winding, and the windings on the opposite teeth are connected in series, that is to say, the two windings facing each other will always be turned on or off at the same time. In this way, four phases are formed, which are marked as A-B-C-D on the map. This is the concept of "four phases".

Figure 9-4 external structure diagram of stepper motor

Now let's analyze its mission:

Assuming that the shape of the starting end of the motor is shown in figure 9-4, the migration changes counterclockwise, and the starting end is the opening and closing of the B phase winding and the conduction of the B phase winding, then the conduction current will be magnetized on the upper and lower stator teeth, and the magnetism on the two stator teeth will have the strongest attraction to the 0 and 3 teeth on the rotor, as shown in the figure. The No. 0 tooth of the rotor is at the top, and the tooth No. 3 is at the bottom and is in equilibrium. At this time, we will find that there is a very small angle between the No. 1 tooth of the rotor and the upper right stator tooth, that is, a winding of phase C, and a slightly larger angle between the No. 2 tooth and the left stator tooth, that is, the phase D. it is clear that this angle is twice the angle between the No. 1 tooth and the C winding, and the situation on the left side is the same.

Next, we disconnect the B-phase winding and turn on the C-phase winding, so it is clear that the upper right stator tooth will have the greatest attraction to the rotor No. 1 tooth, while the lower left stator tooth will have the greatest attraction to the rotor No. 4 tooth. Under the influence of this attraction, rotor No. 1 and No. 4 teeth will be aligned to the upper right and lower left stator teeth. The rotor turns the angle of the angle between the No. 1 tooth and the C phase winding in the original end shape.

Then, disconnect the C-phase winding and turn on the D-phase winding, the process is completely opposite to the above situation, and finally the rotor No. 2 and No. 5 teeth will be aligned with the stator D winding, and the rotor will turn around the above abnormal angle.

Then it is very clear that when the A-phase winding is turned on again, that is, after completing a four-rhythm operation of B-C-D-A, the No. 0 and No. 3 teeth of the rotor will be aligned to the upper and lower left and lower right stator teeth from the original alignment to the upper and lower right stator teeth, that is, the rotor turns over the angle of a stator tooth. And so on, another four-rhythm, the rotor will turn another tooth angle, eight four-rhythm rotor will turn a good circle, and a single rhythm makes it easy to calculate the angle of the rotor, that is, 360 degrees / (84th) = 11.25 degrees, this value is called stepping angle. The above task form is the single four-beat form of the stepper motor-single-phase winding electrified four rhythms.

Let's explain a task form with better function, that is to pull out a double winding conduction rhythm between every two rhythms of a single four beats to form an eight-beat form. For example, in the process of conducting from phase B to term C, suppose the rhythm of phase B and C is opposite, at this time, because the stator teeth of B and C windings have the opposite attraction to their nearby rotor teeth at the same time, this will cause the middle line of the two rotor teeth to shine on the middle line of the B and C windings. That is, the newly pulled rhythm causes the rotor to turn over half of the step angle in the above single-four-beat form, that is, 5.625 degrees. In this way, the accuracy of the transfer transformation is doubled, while the rotor transfer cycle requires 8: 8: 64 beats. In addition, the newly added two-end rhythm will add another gravity between the two rhythmic gravitation of the original single four beats, which can greatly add all the torque input of the motor and make the motor more "energetic".

In addition to the above single four-beat and eight-beat task form, there is also a double four-beat task form-double winding electrified four rhythms. In fact, it is to take out the four beats in which the two windings in the eight-beat form are electrified at the same time, while abandoning the four beats in which the lost single windings are electrified. The step angle is the same as that of single four beats, but because it is turned on by two windings at the same time, the torque will be larger than that of single four beats, so we won't explain too much here.

The eight-beat form is the best task form of this kind of 4-phase stepper motor, which can carry forward the functions of the motor as much as possible, and it is also the form chosen in most practical projects, so we focus on explaining how to use the single-chip microcomputer program to master the motor task according to the eight-beat form.

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