The following is a more complete statement of the stepper motor drive system: 1, system common sense: Stepper motor and stepper motor driver constitute the stepper motor drive system, the performance of the stepper motor drive system, not only depends on the performance of the stepper motor itself, but also depends on the quality of the stepper motor driver, the research of the stepper motor driver is almost synchronous with the research of the stepper motor, the stepper motor is a kind of electrical pulse into the angular displacement of the executive elements, When the stepper motor driver receives a pulse signal (from the controller), it drives the stepper motor to rotate a solid in the set direction

    The following is a more complete statement of the stepper motor drive system:

1. System knowledge:
    Stepper motor and stepper motor driver constitute a stepper motor drive system. The performance of the stepper motor drive system depends not only on the performance of the stepper motor itself, but also on the quality of the stepper motor driver. The research on stepper motor driver is almost synchronous with the research on stepper motor。

2. System Overview:
    Stepper motor is an actuator that converts electrical pulses into angular displacement. When the stepper motor driver receives a pulse signal (from the controller), it drives the stepper motor to rotate a fixed Angle (called the "step Angle") in the set direction, and its rotation is run step by step at a fixed Angle的。

3. System control:
    Stepper motor can not be directly connected to the DC or AC power supply, must use a dedicated drive power (stepper motor driver). The controller (pulse signal generator) can control the angular displacement 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.

4. Use:
    Stepper motor is a special motor for control, as an executive component, is one of the key products of mechatronics, with the development of microelectronics and computer technology (stepper motor driver performance improvement), the demand for stepper motor is increasing. The stepper motor has no accumulated error in its accuracy during operation, which makes it widely used in various automatic control systems, especially in open-loop control systems.

5, stepper motor according to the structure classification:
    Stepper motor is also called pulse motor, including reactive stepper motor (VR), permanent magnet stepper motor (PM), hybrid stepper motor (HB) and so on.
    (5.1) Reactive stepping motor:
    Also known as induction, hysteresis or reluctance stepper motor. The stator and rotor are made of soft magnetic materials, the stator evenly distributed on the large pole is equipped with a polyphase field winding, fixed and rotor periphery evenly distributed small teeth and slots, after energized by the change of magnetic permeability to produce torque. Generally three, four, five, six phases; Can achieve large torque output (large power consumption, current up to 20A, high driving voltage); Small step Angle (the minimum can be one-sixth of a degree); No positioning torque when power is off; The internal damping of the motor is small, and the single-step operation (refers to the pulse frequency is very low) has a long oscillation time; High startup and running frequency.
    (5.2) Permanent magnet stepper motor:
    Generally, the rotor of the motor is made of permanent magnet material, and the stator made of soft magnetic material has a polyphase excitation winding, and there are no small teeth and slots around the stator and rotor. After energizing, the permanent magnet is used to interact with the stator current and magnetic field to produce torque. Generally two or four phases; Small output torque (small power consumption, current is generally less than 2A, driving voltage 12V); Large step Angle (e.g. 7.5 degrees, 15 degrees, 22.5 degrees, etc.); There is a certain holding torque when the power is off; Low startup and operation frequency.
    (5.3) Hybrid stepper motor:
    Also known as permanent magnet reaction, permanent magnet induction stepper motor, a mixture of the advantages of permanent magnet and reaction. There is no difference between the stator and the four-phase reaction stepper motor (but the two magnetic poles of the same phase are opposite, and the N and S polarity generated by the winding of the two magnetic poles must be the same), and the rotor structure is more complex (the rotor is a cylindrical permanent magnet, with soft magnetic materials at both ends, and small teeth and slots around). Generally two or four phases; Positive and negative pulse signals must be supplied; The output torque is larger than the permanent magnet type (the power consumption is relatively small); The step Angle is smaller than the permanent magnet type (generally 1.8 degrees); No positioning torque when power is off; High start-up and operation frequency; It is a kind of stepper motor that develops rapidly at present.

6. Stepper motor is classified by working mode:
    Can be divided into power type and servo type two.
    (6.1) Power type: the output torque is large, and it can directly drive a large load (generally use reactive and hybrid stepper motors).
    (6.2) Servo type: The output torque is small, can only drive a small load (generally use permanent magnet, hybrid stepper motor).

7, the choice of stepper motor: generally use permanent magnet, hybrid stepper motor).
    (7.1) Select the type first, followed by the specific variety and model.
    (7.2) The performance indicators, dimensions, installation methods, pulse power supply types and control circuits of the three types of reactive, permanent magnet and hybrid stepper motors are different, and the price difference is also very large, which should be considered comprehensively when choosing.
    (7.3) Stepper motors with control integrated circuits shall be preferred.

8, the basic parameters of the stepper motor:
     (8.1) Motor natural step Angle:
    It represents the Angle of rotation of the motor for each step pulse signal sent by the control system. The motor is given a step Angle value at the factory, such as the 86BYG250A motor is given a value of 0.9°/1.8° (indicating that half step work is 0.9°, the whole step work is 1.8°), this step Angle can be called? Motor natural step Angle? It is not necessarily the actual step Angle when the motor is working, and the actual step Angle is related to the drive.
    (8.2) Number of phases of the stepper motor:
    Refers to the number of coil groups inside the motor, currently commonly used two-phase, three-phase, four-phase, five-phase stepper motor. The number of phases of the motor is different, and the step Angle is different, generally the step Angle of the two-phase motor is 0.9°/1.8°, the three-phase is 0.75°/1.5°, and the five-phase is 0.36°/0.72°. Increasing the number of phases of the stepper motor can improve performance, but the structure and drive power of the stepper motor will be more complex, and the cost will increase.
    (8.3) HOLDING TORQUE:
    Also known as the maximum static torque, is the maximum torque applied to the energized stepper motor shaft without continuous rotation at the rated static current. It is one of the most important parameters of the stepper motor, usually the moment of the stepper motor at low speed is close to the holding torque. Since the output torque of the stepper motor continues to decay with the increase of speed, and the output power also changes with the increase of speed, maintaining torque has become one of the most important parameters to measure the stepper motor. For example, when people say a 2N.m stepper motor, in the absence of special instructions, it means a stepper motor that maintains a torque of 2N.m.
    (8.4) Step accuracy:
    It can be expressed by positioning error or step Angle error.
    (8.5) Torque and Angle characteristics:
    The recovery torque of the rotor of the stepper motor after leaving the balance position changes with the deviation of the Angle. The relation between static torque and offset Angle of stepper motor is called torque Angle characteristic.
    (8.6) Static temperature rise: refers to the temperature rise when the motor is stationary, and the maximum number of phases in the specified mode of operation is passed with rated static current to achieve a stable thermal equilibrium state.
    (8.7) Dynamic temperature rise:
    The motor runs no-load at a certain frequency and works according to the specified running time. The temperature rise achieved by the motor after the end of the running time is called dynamic temperature rise.
    (8.8) Torque characteristics:
    It represents the relationship between the motor torque and the field current when the single phase is energized.
    (8.9) Starting moment frequency characteristics:
    The relationship between starting frequency and load torque is called starting torque frequency characteristic.
    (8.10) Operating moment frequency characteristics/inertial frequency characteristics: omitted
    (8.11) Frequency rise and fall time:
    It refers to the time required for the motor to rise from the starting frequency to the highest operating frequency or from the highest operating frequency to the starting frequency.
    (8.12) DETENT TORQUE:
    It refers to the stator locking torque of the rotor when the stepper motor is not energized. There is no unified translation method of DETENT TORQUE in China, which is easy to misunderstand. The rotor of the reactive stepper motor is not a permanent magnet material, so it does not DETENT TORQUE.

9, some characteristics of the stepper motor:
    (9.1) The stepper motor does not accumulate errors: the accuracy of the general stepper motor is three to five percent of the actual step Angle, and does not accumulate.
     (9.2) When the stepper motor is working, the pulse signal is added to each phase winding in a certain sequence in turn (the way in which the winding is controlled by the ring distributor in the driver).
    (9.3) Even if it is the same stepper motor, its torque frequency characteristics are very different when using different drive schemes.
    (9.4) Stepper motors are different from other motors, and their nominal rated voltage and rated current are only reference values; And because the stepper motor is powered by pulse, the power supply voltage is its highest voltage, rather than the average voltage, so the stepper motor can work beyond its rating range. But the selection should not deviate too far from the rating.
    (9.5) The maximum temperature allowed on the surface of the stepper motor: the temperature of the stepper motor is too high, which will first demagnetize the magnetic material of the motor, resulting in a decrease in torque or even a loss of step, so the maximum temperature allowed on the surface of the motor should depend on the demagnetization point of the magnetic material of the different motor; Generally speaking, the demagnetization point of the magnetic material is above 130 degrees Celsius, and some are even as high as 200 degrees Celsius, so the external temperature of the stepper motor is completely normal at 80-90 degrees Celsius.
    (9.6) The torque of the stepper motor will decrease with the increase of the speed: when the stepper motor rotates, the inductance of each phase winding of the motor will form a reverse electromotive force; The higher the frequency, the greater the reverse electromotive force. Under its action, the phase current of the motor decreases with the increase of frequency (or speed), resulting in a decrease in torque.
    (9.7) The stepper motor can operate normally at low speed, but it cannot be started if it is higher than a certain frequency, and is accompanied by whistling. The stepper motor has a technical parameter: no-load starting frequency, that is, the pulse frequency that the stepper motor can start normally under no-load conditions, if the pulse frequency is higher than this value, the motor cannot start normally, and it may lose step or block rotation. In the case of load, the starting frequency should be lower. If you want to make the motor reach high speed rotation, the pulse frequency should have an acceleration process, that is, the starting frequency is low, and then it rises to the desired high frequency according to a certain acceleration (the motor speed rises from low speed to high speed).
    (9.8) The four-phase hybrid stepping motor is generally driven by a two-phase driver, so the four-phase motor can be connected into two phases using a series connection method or a parallel connection method. The series connection method is generally used in the case of low motor speed, and the driver output current required at this time is 0.7 times of the motor phase current, so the motor heat is small; The coupling method is generally used in the case of high motor speed (also known as high-speed connection), the required driver output current is 1.4 times the motor phase current, so the motor heat is larger.
    (9.9) The power supply voltage of the hybrid stepper motor driver is generally a wide range (such as the power supply voltage of the IM483 is 12 ~ 48VDC), and the power supply voltage is usually selected according to the working speed and response requirements of the motor. If the motor operating speed is high or the response requirement is fast, then the voltage value is also high, but note that the ripple of the power supply voltage cannot exceed the maximum input voltage of the driver, otherwise it may damage the driver.
    (9.10) The power supply current is generally determined by the output phase current I of the driver. If the linear power supply is used, the power supply current is generally 1.1 to 1.3 times that of I; If switching power supply is used, the power supply current is generally 1.5 to 2.0 times of I.
    (9.11) When the off-line signal FREE is low, the current output from the driver to the motor is cut off, and the motor rotor is in a free state (off-line state). In some automation equipment, if the direct rotation of the motor shaft is required in the case of continuous power of the drive (manual mode), the FREE signal can be set low to make the motor offline for manual operation or adjustment. After manual completion, set the FREE signal to high to continue automatic control.
    (9.12) The rotation direction of the two-phase stepper motor after being energized can be adjusted in A simple way by simply switching the A+ and A- (or B+ and B-) of the motor and driver wiring.

10, some characteristics of the stepper motor driver:
    (10.1) ASIC constituting the stepper motor driver system:
    A, pulse distributor integrated circuit: such as Sanyo company's PMM8713, PMM8723, PMM8714 and so on.
    B, including pulse divider and current chopper controller integrated circuit: such as SGS L297, L6506, etc.
    C, only contains power drive (or includes current control, protection circuit) driver integrated circuit: such as Japan new electric power Industry company MTD1110 (four-phase chopper drive) and MTD2001 (two-phase, H-bridge, chopper drive).
    D, the pulse divider, power drive, current control and protection circuit are included in the drive controller integrated circuit, such as Toshiba TB6560AHQ, MOTOROLA SAA1042 (four phase) and ALLEGRO UCN5804 (four phase).
    (10.2) "Segment Drive" Overview: Concepts:
    The "motor inherent step Angle" is subdivided into several small steps of the drive method, called subdivision drive, subdivision is achieved by the driver precisely control the phase current of the stepper motor, and has nothing to do with the motor itself. The principle is that when the stator is energized, the phase current does not rise to the position at one time, and the phase current is not reduced to 0 at one time (the winding current waveform is no longer an approximate square wave, but an approximate N-order step wave), then the magnetic field force generated by the stator winding current will make the rotor have N new equilibrium positions (forming N step angles). Latest technological developments:
    Research on subdivision drive technology is very active at home and abroad, and high-performance subdivision drive circuits can be subdivided to thousands or even arbitrary subdivisions. At present, it has been able to make the step Angle after subdivision uniform through complex calculation, greatly improve the pulse resolution of the stepper motor, reduce or eliminate vibration, noise and torque fluctuations, so that the stepper motor has more "servo-like" characteristics. Effect on the actual step Angle: When there is no subdivision driver, the user mainly relies on the selection of different phase number of stepper motors to meet their requirements for step Angle. If a subdivision driver is used, the user can greatly change the actual step Angle by simply changing the fine fraction on the driver. Number of phases? The effect on changing the actual step Angle is almost negligible. The relationship between the use of subdivision technology and the improvement of the accuracy of the stepper motor: the subdivision technology of the stepper motor is essentially an electronic damping technology, its main purpose is to weaken or eliminate the low-frequency vibration of the stepper motor, and improve the running accuracy of the motor is only an incidental function of the subdivision technology. The resolution of each pulse is improved when the motor is running after subdivision, but whether the running accuracy can reach or approach the pulse resolution depends on other factors such as the subdivision current control accuracy of the subdivision driver. Different manufacturers of subdivision drive accuracy can vary greatly; The higher the fine fraction, the more difficult it is to control the precision.
    The real segmentation of the drive has quite high technical requirements and process requirements, and the cost will be higher. Some domestic drivers use the motor phase current "smoothing" processing to replace subdivision, belongs to the "false subdivision", "smoothing" does not produce micro-steps, will cause the motor torque to decline. The real subdivision control will not only cause the motor torque to decrease, on the contrary, the torque will increase. The popular expression of the stepper motor drive system by the manufacturer is as follows:
    Stepper motor is a device that converts electrical pulse into discrete mechanical motion, and its matching driver together constitutes a controllable stepper motor motion system, which has good data control characteristics. When receiving the working instructions (switching pulse signals) from the controller (PLC, MCU and other programmable processors), the driver excises the stator winding in an orderly manner according to the working instructions, so that a pulsating, non-coherent magnetic field with real-time response is established inside the stator, and is used in the rotor with many small teeth around the rotor to generate rotational motion. That is, a pulse is applied and the motor rotates one step. In an ideal situation, the speed and cumulative rotation Angle of the rotor are fully synchronized with the pulse frequency and the number of pulses input by the controller, so that only the effective work instructions are provided to the stepper motor motion system in the specified time, the rotor will be accurately driven to the set Angle position, and will remain in the position until further work instructions come.
    Stepper motor two-way drive, inherent braking performance, output torque can be adjusted appropriately, power control, accurate position, high resolution, good digital interactive interface, and only the use of open loop control can achieve good results are its significant advantages. And compared with the servo system, it has the advantages of large output power per unit volume, small moment of inertia, no drift and starting peak surge phenomenon, no position accumulation error, and so on. It is a digital control motor with low cost.
    Because of the above inherent advantages, it has established its application status in many fields, and is widely used in many fields that need to control rotation Angle, speed, position and synchronization, such as office automation, security, medical equipment, textile machines, stage lighting, vending and ticket machines, mechanical automation, etc.

The following points should be noted when choosing a stepper motor:
    1. Generally, the stepper motor with a torque 50% to 100% greater than the actual need should be selected, because the stepper motor can not run over the load, even if it is instantaneous overload, it may cause out-of-step, stall or irregular back and forth motion in place.
    2, the upper controller input pulse current must be large enough (generally >10mA) to ensure that the photoelectric coupler is stable on, otherwise it will lead to the stepper motor out of step; If the input pulse frequency is too high, individual pulses will not be received, resulting in the stepper motor out of step.
    3, the starting frequency should not be too high, the acceleration process should be set in the starting procedure, that is, from the specified starting frequency, accelerate to the set frequency, otherwise it may be unstable, or even in an idle state.
    4, if the motor is not fixed, resulting in strong resonance, will also lead to stepping motor out of step.
    5, should understand the inherent weakness of the stepper motor: the input pulse frequency is too high, easy to lead to lost steps; Input pulse frequency is too low, easy to appear resonance; The torque decreases obviously when the speed is high.
    6, should understand the performance of the latest type of stepper motor, if necessary, the use of the latest control technology of the advanced stepper motor system, the advanced system can make the stepper motor at high speed to reduce the resonance, but also reduce the stepper motor back electromotive force technology, increase the motor torque at high speed.

The following points should be noted when choosing a stepper motor driver:
1, the use of stepper motor driver precautions

    1.1) The power supply voltage should be appropriate (overvoltage may cause damage to the drive module), the +/- polarity of the DC input should not be connected incorrectly, and the current setting value of the drive controller should be appropriate (not too large at the beginning);
    1.2) The control signal line is firmly connected, and the shielding problem should be considered in the industrial environment (such as the use of twisted pair);
    1.3) Do not connect all the lines at the beginning, you can first connect the most basic system, and confirm that the operation is good before completing the connection.
    1.4) The grounding end and floating end must be confirmed in advance.
    1.5) At the beginning of operation, carefully observe the sound and temperature rise of the motor, and immediately stop and adjust if any abnormality is found.

2, the lowest pulse width recognized by the general stepper motor driver and the highest accepted frequency under 2 subdivisions

    The lowest pulse width generally recognized is not less than 2 microseconds, and the highest accepted frequency under 2 subdivisions is about 40khz
    Do not work, lose step (perhaps the motor force is not enough), stop when walking, the size of the step, the vibration is large, the shaking is obvious, the chaos, the lack of equal.

The selection of stepper motor controller should pay attention to the following points:
    1, the driver circuit of the stepper motor works according to the control signal, and the control signal is generated by the MCU (or other such as PLC, etc.). Its basic principle functions as follows:
    (1.1) Control commutation sequence
    The process of current commutation is called pulse distribution. For example, the three-beat working mode of the three-phase stepper motor, each of which is connected in the order of A-B-C-D, and the power-on control pulse must be controlled in strict accordance with this order respectively for the on-off of A,B,C, and D phases.
    (1.2) Control stepper motor steering
    If the positive sequence commutation is given in the working mode, the stepper motor is turned forward, and if the commutation is carried out in the reverse sequence, the motor is reversed.
    (1.3) Control the speed of the stepper motor
    If you send a control pulse to the stepper motor, it will turn one step, and send another pulse, it will turn another step. The shorter the interval between the two pulses, the faster the stepper motor will turn. Adjusting the pulse frequency sent by the single chip microcomputer can speed regulate the stepper motor. 2, PLC and stepper motor driver wiring guide:
    Q0.0 -- -- -- -- > control pulse q0.2 -- -- -- - > L + -- -- -- -- > total control direction, dir, end and pul + L + +
    q0.0 -----> Control pulse and pul- connection q0.2-----> Control direction and dir- connection Note that pulse and direction are equal series 1k resistance

The selection of stepper motor IC should pay attention to the following two points:
    1. The selection of the latest motor IC products with high integration and mature technology is conducive to speeding up the replacement speed of electronic motion control products, reducing the difficulty of product development, expanding the practical application range of a single product, and improving the cost performance of the product.
    2, the current technology leading highly integrated motor IC products mainly include German TRINAMIC motion control products, Toshiba motor IC products, etc. The common characteristics of these manufacturers are small size, high integration, stable operation, cost-effective, stable and diversified supply channels.