Analysis of the concept of stepping motor holding torque and positioning torque
Stepper motor, also known as pulse motor, is based on the most basic electromagnet principle. It is an electromagnet that can rotate freely. Its action principle is to generate electromagnetic torque by changing the air gap permeability. Its original model originated from year to year. At the beginning of the year, attempts to control were applied to the electrode transport mechanism of the hydrogen arc lamp. This is considered to be the original stepper motor. At the beginning of the twentieth century, stepper motors were widely used in telephone automatic switches. Because Western capitalist powers compete for colonies, stepper motors are widely used in independent systems such as ships and airplanes that lack AC power. The invention of transistors in the late 1950s was gradually applied to stepper motors, making it easier to control digital. After the 1980s, the control method of the stepping motor was more flexible due to the appearance of a cheap microcomputer in a multi-functional posture. The biggest difference between a stepper motor and other motors for control purposes is that it receives the digital control signal electrical pulse signal and converts it into an angular displacement or linear displacement corresponding to it. It is itself an actuator that performs digital mode conversion. Moreover, it can control the open loop position, and input a pulse signal to obtain a specified position increment. Compared with the conventional DC control system, the so-called incremental position control system has a significantly reduced cost, and almost no system adjustment is necessary. The angular displacement of the stepper motor is strictly proportional to the number of pulses input and is synchronized with the pulse in time. Thus, as long as the number of pulses, the frequency and the phase sequence of the motor windings are controlled, the desired angle, speed and direction can be obtained. China's stepper motor started in the early 1970s. From the mid-1970s to the mid-1980s, it was the development stage of finished products. New varieties and high-performance motors were continuously developed. At present, with the development of science and technology, especially The development of permanent magnet materials, semiconductor technology and computer technology has made stepper motors widely used in many fields. As a special motor for control, the stepper motor cannot be directly connected to the DC or AC power supply, and a dedicated drive power stepper motor driver must be used. Before the development of microelectronics technology and special computer technology, the controller pulse signal generator was completely realized by hardware. The control system used separate components or integrated circuits to form a control loop. Not only the debugging and installation were complicated, but also consumed a large number of components, and once the type was set, To change the control scheme, you must redesign the circuit. This makes it necessary to develop different drivers for different motors, which has high development difficulty and development cost, and is difficult to control, which limits the promotion of stepping motors. Since the stepping motor is a device that converts electric pulses into discrete mechanical motions and has good data control characteristics, the computer becomes an ideal driving source for stepper motors. With the development of microelectronics and computer technology, hardware and software The combined control method has become the mainstream, that is, the control pulse is generated by the program to drive the hardware circuit. The single-chip microcomputer controls the stepping motor through software to better dig out the potential of the motor. Therefore, the use of single-chip microcomputer to control stepper motor has become an inevitable trend, and also in line with the digital age. Holding torque and positioning torque of stepping motor Maintaining the torque refers to the maximum torque that the motor can output when the motor's phase windings pass the rated current and is in the static lock state. It is one of the most important parameters when selecting a motor. The positioning torque refers to the torque generated by the permanent magnet material on the rotor of the hybrid motor when the motor windings of the motor are not energized and are in an open state. Generally, the positioning torque is much smaller than the holding torque. Whether or not there is a positioning torque is an important sign that a hybrid stepping motor is different from a reactive stepping motor. As an actuator, stepper motor is one of the key products of mechatronics and 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 it has applications in various national economic fields. A stepper motor is an actuator that converts electrical pulses into angular displacement. When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle (called the "step angle") in a set direction, and its rotation is step by step at a fixed angle. The angular displacement can be controlled by controlling the number of pulses to achieve the purpose of accurate positioning. At the same time, the speed and acceleration of the motor rotation can be controlled by controlling the pulse frequency, thereby achieving the purpose of speed regulation. The stepping motor can be used as a special motor for control, and it is widely used in various open-loop control because it has no accumulation error (100% accuracy). More commonly used stepper motors include reactive stepper motors (VR), permanent magnet stepper motors (PM), hybrid stepper motors (HB), and single-phase stepper motors. Permanent magnet stepping motor is generally two-phase, torque and volume are small, the step angle is generally 7.5 degrees or 15 degrees; reactive stepping motor is generally three-phase, can achieve large torque output, step angle is generally It is 1.5 degrees, but the noise and vibration are very large. The rotor of the reactive stepping motor is made of soft magnetic material, and the multi-phase excitation winding is arranged on the stator, and the torque is generated by the change of the magnetic permeability. Hybrid stepper motors are a combination of permanent magnet and reactive. It is divided into two phases and five phases: the two-phase step angle is generally 1.8 degrees and the five-phase step angle is generally 0.72 degrees. This stepper motor is the most widely used and is the stepper motor selected for this subdivision drive scheme. Some basic parameters of the stepper motor; Inherent step angle of the motor: It represents the angle at which the motor rotates each time the control system sends a step pulse signal. The motor is given a step angle value when it leaves the factory. For example, the value given by the 86BYG250A motor is 0.9°/1.8° (0.9° for half-step operation and 1.8° for full-step operation). This step angle It can be called 'the inherent step angle of the motor', it is not necessarily the true step angle of the actual working of the motor, and the true step angle is related to the drive. The number of phases of the stepper motor: It refers to the number of coil groups inside the motor. Currently, two-phase, three-phase, four-phase, five-phase stepping motors are commonly used. The number of phases of the motor is different, and the step angle is also 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°. When there is no subdivision driver, the user mainly chooses the stepping motor with different phase numbers to meet the requirements of the step angle. If you use a subdivision drive, the 'phase number' will become meaningless, and the user can change the step angle by simply changing the number of subdivisions on the drive. Holding torque (HOLDING TORQUE): It refers to the moment that the stator locks the rotor when the stepper motor is energized but does not rotate. It is one of the most important parameters of a stepper motor. Usually, the torque of the stepper motor at low speed is close to the holding torque. Since the output torque of the stepping motor is continuously attenuated as the speed increases, the output power also changes with the increase of the speed, so the holding torque becomes one of the most important parameters for measuring the stepping motor. For example, when people say that a 2N.m stepper motor, unless otherwise specified, is a stepper motor that maintains a torque of 2N.m. Positioning torque (DETENT TORQUE): It refers to the moment that the stator locks the rotor when the stepper motor is not energized. DETENT TORQUE has no unified translation method in China, which is easy to misunderstand. Because the rotor of reactive stepping motor is not permanent magnet material, it does not have DETENT TORQUE. Some features of the stepper motor: 1. The accuracy of a general stepper motor is 3-5% of the step angle and does not accumulate. 2. The maximum temperature allowed by the stepper motor appearance. If the temperature of the stepping motor is too high, the magnetic material of the motor will be demagnetized firstly, resulting in a torque drop and even out of step. Therefore, the maximum allowable temperature of the motor surface should depend on the demagnetization point of the magnetic material of different motors; in general, the demagnetization of the magnetic material The points are all above 130 degrees Celsius, and some even up to 200 degrees Celsius, so the external temperature of the stepper motor is completely normal at 80-90 degrees Celsius. 3. The torque of the stepper motor will decrease as the speed increases. When the stepper motor rotates, the inductance of each phase winding of the motor will form a back electromotive force; the higher the frequency, the larger the back electromotive force. Under its action, the motor decreases with increasing frequency (or speed), resulting in a drop in torque. 4. The stepper motor can run normally at low speed, but if it is higher than a certain speed, it cannot be started, accompanied by howling. The stepping motor has a technical parameter: the no-load starting frequency, that is, the pulse frequency that the stepping motor can start normally under no-load conditions. If the pulse frequency is higher than this value, the motor cannot start normally, and lost or blocked may occur. In the case of load, the starting frequency should be lower. If the motor is to be rotated at a high speed, the pulse frequency should have an acceleration process, that is, the starting frequency is low, and then rise to a desired high frequency (the motor speed is increased from a low speed to a high speed) at a certain acceleration. With its remarkable features, stepper motors play a major role in the digital manufacturing era. With the development of different digital technologies and the improvement of the technology of stepping motors, stepping motors will be applied in more fields. Liquid Crystal Display,Lcd Screen Displays,Calculator Lcd Display,Lcd Display For Car Bluetooth Dongguan Yijia Optoelectronics Co., Ltd. , https://www.everbestlcdlcm.com