Find how the subdivision of a stepper motor driver works

The number of subdivisions refers to the actual step angle when the motor is running at a fraction of the basic step angle angle.

The function of the subdivision is entirely generated by the drive by precisely controlling the phase current of the motor. Nothing to do with the motor.

To put it simply. Originally, the driver gave 1 phase current motor travel angle (two-phase motor).The subdivision function is to refine the phase current.

Like what. I turn the drive to 10 subdivisions. It is to turn this phase current to 1 10.

So that the motor can only walk.

That's probably how it works. It's just that what I said didn't make it very clear. After all, I'm still a beginner. Hope you understand...

Changing the energizing order under the action of a pulse? You misunderstood, the so-called subdivision control, is like, in a step angle cycle, I let the control voltage remain unchanged at certain points, when it is unchanged, the motor is also stopped, in this way, it is like I have more points that can make the motor stop, just like a step angle is divided into many.

When controlling, only when the motor really goes to a step angle will the phase sequence be changed and commuted.

。The language is unclear...

Enlighten yourself ...

It turns out that your motor driver contains a single-chip microcomputer, and yours should be some kind of integrated stepper motor unit with a controller, right?

The subdivision we are talking about refers only to the control of the simple motor, and the step angle of the motor is further subdivided, and the subdivision you are talking about is actually to set the drive unit, how many pulses do I use to make a turn! As for what you asked, the principle in the drive, it should be controlled by a program, and I haven't touched this.

It should be different for different manufacturers.

I use a permanent magnet hybrid stepper motor, in a step angle, equivalent to a synchronous motor, as long as I stop the stator magnetic field at a certain value, then the rotor also stops at that position accordingly, this is the principle of step angle subdivision.

As for the induction stepper motor, I don't know if it can be subdivided (from the principle analysis, it shouldn't be), but the permanent magnet hybrid motor can.

The drive of the stepper motor is generally L298N, which is a double "H" bridge structure.

How the stepper motor sets up the subdivision.

For example, if A is aligned with a certain tooth, B is energized, and the tooth is aligned and turned 15 degrees, then AB is energized at the same time, and the attraction of the two electrodes is the same, then the tooth pair is on the midline of AB, and the rotation is excessive. Changing the current ratio of the two phases of AB can change the position.

Hardware: If the motor is not large, it will be driven by L298N, and if it is large, it should be driven by a MOS tube.

Take the four-phase four-wire as an example: the power-on sequence is: a-b-c-d-a, and the eight-beat operation mode is a-ab-b-bc-c-cd-d-daMore subdivisions need to control the proportion of phase current, and the hardware is more complicated.

Stepper motor driver subdivision is a drive control technology developed in the mid-seventies that can significantly improve the overall performance of stepper motors.

It is by controlling the current in the windings of each phase, so that they rise or fall according to a certain law, that is, a plurality of stable intermediate current states are formed between the zero current and the maximum current, and there will also be a plurality of stable intermediate states in the direction of the corresponding resultant magnetic field vector, and rotate according to the subdivision step. The amplitude of the resultant magnetic field vector determines the magnitude of the rotational moment of the stepper motor, and the direction of the resultant magnetic field vector determines the magnitude of the step angle after subdivision. The subdivision drive technology further improves the angle accuracy and running smoothness of the stepper motor.

The main structure of the stepper motor driver has the following parts:

1. a circumferential distributor. According to the requirements of the input signal, the switching waveform signal processing of the motor in different states is generated. PWM modulation is performed on the switching signal waveform generated by the circumferential distributor and filtering and shaping of the related waveform.

2. Protection circuit. When the winding current is too large, a shutdown signal is generated to shut down the main circuit to protect the motor driver and motor winding.

3. Sensors. The position and angle of the motor are monitored in real time, and the generation of the signal is dissipated.

Stepper motor subdivision drive technology is a drive control technology developed in the mid-seventies that can significantly improve the comprehensive performance of stepper motors.

The stepper motor subdivision drive technology was first proposed by American scholars at the annual meeting of incremental motion control systems and devices in the United States. Initially, the control of the phase current of the stepper motor was realized by hardware, and the phase current of each phase winding was controlled by n transistors forming n parallel circuits, and the phase current was controlled by the combination of transistor conduction numbers.

The domestic stepper motor subdivision drive technology has been greatly developed in the mid-nineties, mainly used in industry, aerospace, robotics, precision measurement and other fields, such as CNC machine tools, tracking satellite photoelectric theodolite with the use of stepper motor subdivision drive technology, greatly improving the control and measurement accuracy.

To understand subdivision, we must first understand the concept of step angle: it represents the angle at which the control system rotates for each step pulse signal. The value of a step angle is given when the motor leaves the factory, such as the value given by the FY86EL402A motor to indicate that the half-step work is the whole step work, this step angle can be called the 'inherent step angle of the motor', it is not necessarily the real step angle when the motor actually works.

To put it simply, the number of subdivisions means that the true step angle of the motor when it is running is a fraction of the intrinsic step angle (whole step). As can be seen from the above table, when the stepper motor driver works in the state of 10 subdivisions, its step angle is only one-tenth of the 'inherent step angle of the motor', that is:

When the driver works in the non-subdivided whole step state, the control system sends a step pulse every time, and the motor rotates; And when working in 10 subdivision states with the subdivision driver, the motor only rotates, which is the basic concept of subdivision.

A more accurate description of the subdivision characteristics of the driver is the number of running beats, which refers to the number of pulses required for each rotation of the gear pitch when the stepper motor is running. The FY86EL402A motor has 50 teeth, if the number of running beats is set to 160, then the stepper motor needs a total of 50 160 8000 steps to rotate one revolution; The corresponding step angle is 360 ° 8000. Please note that if the number of running beats is set to 30, the number will be broken down according to the correspondence in the table above, not an integer.

The subdivision function is generated entirely by the stepper driver by precisely controlling the phase current of the motor, independent of the motor.

How the stepper motor sets up the subdivision.

The subdivision of the stepper driver is used to match the pulse equivalent of the controller, if the number of subdivisions can be set more, the more convenient the user application, now the digital stepper driver such as Wuzhou Technology EZM872 can basically achieve any setting.

The essence of the stepper motor driver subdivision setting is to match the pulse equivalent of the controller, but after the stepper motor is subdivided and controlled, the vibration and noise of the motor can be improved, but the subdivision setting of the driver is too high, and the control frequency sent by the controller is relatively high. For example, if 500 subdivisions are selected, when the motor speed is 1rps, the control frequency of the controller must reach 100kHz.

The first; Stepper motors have a wide range of applications in control systems. It can convert pulse signals into angular displacement, and can be used as electromagnetic brake wheels, electromagnetic differentials, or angular displacement generators, etc.

Stepper Motor Driver Selection Guide.

1. Classification of working modes of stepper motor drivers.

There are basically three types of stepper motor drive modes: full step, half step, and subdivision. The main difference is the accuracy of the control of the motor coil current (i.e., the excitation method).

Whole-step drive. The same kind of stepper motor can be equipped with both whole half-step driver and subdivision driver, but the operation effect is different. The stepper motor driver excites the two coils of the two-phase stepper motor in a pulse-direction signal, and each pulse of this drive mode will cause the motor to move a basic step angle, i.e., degrees (a standard two-phase motor has a total of 200 step angles in one turn).

Half-step drive (2 subdivisions).

In the case of single-phase excitation, the motor shaft stops to the whole step position, and after the driver receives the next pulse, if it gives another phase excitation and keeps the original successive excitation state, the motor shaft will move half a step angle and stop in the middle of the two adjacent whole step positions. In this way, the two-phase coil is single-phased, and then the biphasic excitation stepper motor rotates in half-steps per degree of pulse.

Segment-driven. The subdivision drive mode has the advantages of minimal low-speed vibration and high positioning accuracy. It can be used in stepper motor applications where low speed operation is sometimes required or positioning accuracy is required to be less than a degree. The basic principle is to carry out precise current control of the two coils of the motor according to the sine and cosine steps respectively, so that the distance of a step angle is divided into several subdivision steps.

3. System control: The stepper motor can not be directly connected to the DC or AC power supply to work, and a special (12) must be used to adjust the rotation direction of the two-phase stepper motor after powering up in a simple way, only need to connect the motor with the driver

The control principle of the stepper driver is divided into two control modes: analog control and digital control, of which analog control is divided into hysteresis comparison and analog PI control. The analog control is performed by the MCU as a ring distributor, providing the current waveform of the stepper motor at different angles, and then the hysteresis loop comparison circuit and the analog PI circuit generate the corresponding control pulses to realize the control of the stepper motor.

The basic principle is to sample the bus voltage and the current of the stepper motor in real time through the current and voltage sensor, and then realize the precise control of the stepper motor through the control algorithm. The biggest difference between analog control and digital control: digital control can effectively suppress the vibration, noise and heat generation of the stepper motor, especially under low subdivision conditions, the digital stepper drive system can have high performance.

Innex Electric has launched EZM, EZD, EZN series drive systems with high-performance 32DSP control, which are widely used in various automation equipment and instrumentation.