What is a stepper motor and the specific structure of a stepper motor?

Stepper motor is a kind of induction motor, its working principle is to use electronic circuits, direct current into time-sharing power supply, multi-phase sequence control current, use this current to supply power to the stepper motor, stepper motor can work normally, the driver is for the stepper motor time-sharing power supply, multi-phase timing controller Although stepper motors have been widely used, stepper motors can not be like ordinary DC motors, AC motors are used under conventional conditions. It must be composed of a double ring pulse signal, a power drive circuit, etc., and the control system can be used. Therefore, it is not easy to use stepper motors well, and it involves many specialized knowledge such as machinery, motors, electronics, and computers.

As an actuator, stepper motor is one of the key products of mechatronics, which is widely used in various automation control systems. With the development of microelectronics and computer technology, the demand for stepper motors is increasing day by day, and they are used in various fields of the national economy. A stepper motor is an actuator that converts electrical impulses into angular displacements.

In layman's terms: when the stepper driver receives a pulse signal, it drives the stepper motor to rotate at a fixed angle (i.e., the stepping angle) in the set direction. You can control the angular displacement by controlling the number of pulses, so as to achieve the purpose of accurate positioning; At the same time, you can control the speed and acceleration of the motor by controlling the pulse frequency, so as to achieve the purpose of speed regulation.

Stepping motor

A micro motor that converts an electrical pulse signal into an angular displacement to control the rotation of the rotor. It is used as an actuator in an automatic control device. Each time a pulse signal is inputted, the stepper motor takes a step forward, so it is also called a pulse motor.

Stepper motors are mostly used in the peripherals of digital computers, as well as in devices such as printers, plotters, and disks. The driving power supply of the stepper motor is composed of a variable frequency pulse signal source, a pulse distributor and a pulse amplifier, whereby the driving power supply provides pulse current to the motor windings. The running performance of the stepper motor depends on the good coordination between the motor and the drive power supply.

The advantages of stepper motor are that there is no cumulative error, simple structure, easy to use and maintain, low manufacturing cost, and the ability of stepper motor to drive load inertia is large, which is suitable for small and medium-sized machine tools and places with low speed accuracy requirements, and the disadvantage is that the efficiency is low, the heat is large, and sometimes it will "lose step". There are three basic types of stepper motors: electromechanical, magnetoelectric and linear.

Speed measurement method of stepper motor:

A stepper motor converts a pulse signal into angular displacement or linear displacement.

First, the overload is good. Its speed is not affected by the size of the load, unlike ordinary motors, when the load increases, the speed will decrease, and the stepper motor has strict requirements for speed and position when used.

Second, it is convenient to control. The stepper motor rotates in "step" units, and the digital characteristics are more obvious.

Third, the structure of the whole machine is simple. The traditional mechanical speed and position control structure is more complex and difficult to adjust, and the structure of the whole machine becomes simple and compact after the use of stepper motor. The tachometer motor converts the speed into voltage and transmits it to the input as a feedback signal.

The speed motor is an auxiliary type motor, which is installed at the tail end of the ordinary DC motor, and the voltage generated by the speed motor is fed back to the DC power supply to achieve the purpose of controlling the speed of the DC motor.

Applications of stepper motors:

It is mainly used in digital control systems, with high precision and reliable operation. Closed-loop control is also possible if position detection and speed feedback are used. Stepper motors have been widely used in digital control systems, such as digital-to-analog conversion devices, CNC machine tools, computer peripherals, automatic recorders, clocks, etc., and are also used in industrial automation production lines, printing equipment, etc.

It turns like a person walking, jumping step by step, not like a traditional continuous movement.

A motor is something that converts electrical energy into mechanical energy.

A stepper motor is a type of motor that converts an electrical impulse signal into a corresponding angular displacement or linear displacement. Each time a pulse signal is inputted, the rotor rotates an angle or a step forward, and its output angular displacement or linear displacement is proportional to the number of pulses input, and the rotational speed is proportional to the pulse frequency. Therefore, stepper motors are also known as pulse motors.

The stator and rotor cores of progressive motors are made of silicon steel sheets. There are six magnetic poles on the stator, and each of the two opposing poles is wound with the same phase winding, and the three-phase winding is connected into a star shape as the control winding. There are no windings on the rotor core, only four teeth, and the tooth width is equal to the width of the stator pole shoe.

Because of the wide application of stepper motors, the control of stepper motors is also more and more studied, if the stepper pulse changes too fast when starting or accelerating, the rotor cannot follow the change of the electrical signal due to inertia, resulting in stalled or out-of-step due to the same reason when stopping or decelerating. In order to prevent stalling, out-of-step and overstepping, and increase the working frequency, it is necessary to control the speed of the stepper motor.

The stator and rotor cores of the stepper motor are made of silicon steel sheets.

There are six magnetic poles on the stator, and each of the two opposing poles is wound with the same phase winding, and the three-phase winding is connected into a star shape as the control winding. There are no windings on the rotor core, only four teeth, and the tooth width is equal to the width of the stator pole shoe.

A stepper motor is an open-loop control element that converts an electrical pulse signal into angular or linear displacement.

Type of stepper motor.

There are three main types of structure-based stepper motors:

Variable reluctance stepper motors: they have an iron-core rotor that is attracted by the stator pole and provides motion through the minimum magnetoresistance between the stator and the rotor.

Permanent magnet stepper motors: They have permanent magnet rotors that are repelled or attracted to the stator depending on the applied pulse.

Hybrid synchronous stepper motors: They are a combination of variable reluctance and permanent magnet stepper motors.

In addition to this, stepper motors can also be classified into unipolar and bipolar depending on the type of stator winding.

Let's understand the structure and working principle of stepper motor.

There are three main types of stepper motors in construction: variable reluctance (VR), permanent magnet (PM) and hybrid stepping (HS).

Reactive formula: There are windings on the stator and the rotor is composed of soft magnetic materials. The structure is simple, the cost is low, the step angle is small, the dynamic performance is poor, the efficiency is low, the heat generation is large, and the reliability is difficult to guarantee.

Permanent magnet type: The rotor of the permanent magnet stepper motor is made of permanent magnet material, and the number of poles of the rotor is the same as that of the stator. It is characterized by good dynamic performance and large output torque, but this kind of motor has poor accuracy and large step moment angle (generally or 15°).

Hybrid: The hybrid stepper motor combines the advantages of reactive and permanent magnet type, with multi-phase windings on the stator, permanent magnet materials on the rotor, and multiple small teeth on the rotor and stator to improve the step moment accuracy. It is characterized by large output torque, good dynamic performance, and small step angle, but the structure is complex and the cost is relatively high.

According to the winding on the stator, there are two phases, three phases and five phases and other series. The most popular is the two-phase hybrid stepper motor, which accounts for more than 97% of the market share, and the reason for this is that it is cost-effective and works well with a subdivision driver. The basic step angle of this kind of motor is step, and after the half-step driver is matched, the step angle is reduced to, and the step angle can be subdivided up to 256 times (microstep) after the subdivision driver is matched.

Due to friction and manufacturing accuracy, the actual control accuracy is slightly lower. The same stepper motor can be equipped with different subdivision drives to change the accuracy and effect.

There are many ways to classify stepper motors, and the most common way to classify them is according to the structure of the rotor and stationator.

According to the rotor structure, stepper motors are divided into: permanent magnet type, reactive type, and hybrid type. The permanent magnet rotor is a permanent magnet, the reactive rotor is a silicon steel sheet, and the hybrid type is a combination of permanent magnet and reactive, which is a silicon steel sheet sandwiched with a permanent magnet.

The cost of permanent magnet type is low, the step angle is large, the common step angle is etc., the noise is low, the shape is generally round, the outer diameter of the common shape size is 4 55mm, the output torque is relatively small, the magnet is generally ferrite, the shell is steel plate stamping and welding, and the oil-impregnated bearing. The reactive rotor is only pressed into the motor shaft on a silicon steel sheet, and the step angle is smaller than that of the permanent magnet type, but it is noisy and is rarely used now. The hybrid type combines the characteristics of permanent magnet type and reactive type, small step angle, common step angle angle, low noise, large torque, most of them are square, and the flange size is commonly 16 150mm, which is the mainstream product on the market at present.

Stepper motors are divided into single-phase, two-phase, three-phase, five-phase stepper motors according to the fixed substructure, and some stepper motors driven by two-phase unipolar drives are also called four-phase stepper motors. Single-phase stepper motors are generally only used for watch movements, two-phase stepper motors are the absolute mainstream products in the market, commonly used step angle sum, three-phase stepper motor step angle sum, five-phase stepper motor step angle sum, three-phase and five-phase stepper motor run smoother than two-phase stepper motor, high-speed torque attenuation is slower, but now the driving performance of two-phase stepper motor continues to improve, and the running smoothness and three-phase and five-phase stepper motor are getting closer and closer, but if you have to have a high-resolution stepper motor, it is better to have three-phase and five-phase stepper motors, But the cost is higher and the versatility is poor.

There are three basic 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).

1), whole step drive: the stepper motor driver according to the pulse direction command to the two coils of the two-phase stepper motor cycle excitation (i.e., coil charging set current), each pulse of this driving mode will make the motor move a basic step angle, that is, degree (a total of 200 step angles in a circle of the standard two-phase motor).

2) Half-step drive: when single-phase excitation, the motor shaft stops to the whole step position, after the driver receives the next pulse, if the other phase is excited and the original is in the 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.

The half-step method has the advantages of double the accuracy and low vibration at low speeds.

3) Subdivision drive: The subdivision drive mode has the advantages of low speed vibration and high positioning accuracy. Segmented stepper motor drives are widely used in stepper applications where low-speed operation is sometimes required (i.e., the motor shaft sometimes operates below 60 rpm) or where 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. The precision control effect produced under the subdivision needs to look at the driver's ability to control the current, which is uneven, and the accuracy of the motor cannot be determined by looking at the subdivision alone.

However, the integrated stepper motor is now in use, which is relatively simple for the application and subsequent installation.

When it comes to starting into the motor, I believe most people are a little unclear, but for electricians, this is one of the important accessories of the motor. Let's introduce the working principle of the stepper motor!

What is a stepper motor.

A stepper motor is an open-loop control element stepper motor device that converts the electrical pulse signal into angular displacement or linear displacement. In the case of non-overload, the speed of the motor, the position of the stop only depends on the frequency of the pulse signal and the number of pulses, and is not affected by the change of load, when the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle in the set direction. 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 the motor can be controlled by controlling the pulse frequency, so as to achieve the purpose of speed regulation.

The working principle of the stepper motor.

When an electric current flows through the stator windings, the stator windings produce a vector magnetic field. This magnetic field causes the rotor to rotate by an angle so that the direction of the pair of magnetic fields of the rotor coincides with the direction of the magnetic field of the stator. When the vector magnetic field of the stator rotates by an angle.

The rotor also rotates at an angle with this magnetic field. With each input electrical impulse, the motor rotates an angle to take a step forward. The angular displacement of its output is proportional to the number of pulses input, and the rotational speed is proportional to the pulse frequency.

Change the order in which the windings are energized, and the motor will be reversed. Therefore, the rotation of the stepper motor can be controlled by controlling the number of pulses, the frequency and the energizing sequence of each phase winding of the motor.

All kinds of motors that are commonly seen have iron cores and winding coils inside. The winding has resistance, and the loss will be generated by energizing, and the loss is proportional to the square of the resistance and the current, which is what we often call copper loss, if the current is not a standard DC or sine wave, it will also produce harmonic loss; The iron core has a hysteresis eddy current effect, and losses will also occur in the alternating magnetic field, and its magnitude is related to the material, current, frequency, and voltage, which is called iron loss.

Both copper and iron losses manifest themselves in the form of heat generation, which affects the efficiency of the motor. The stepper motor generally pursues positioning accuracy and torque output, the efficiency is relatively low, the current is generally relatively large, and the harmonic component is high, and the frequency of current alternation also changes with the speed, so the stepper motor generally restores the return plexus in the heating situation, and the situation is more serious than the general AC motor.