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A stepper motor is a motor that rotates a shaft by taking steps (that is, moving at a fixed angle). Its internal construction allows it to know the exact angular position of the shaft through simple step counting without a sensor, making it suitable for a variety of applications.Speaking of stepper motors, Xiaowei believes that engineers in the intelligent transmission and electrical control industries should be familiar with them. Stepping errors will not accumulate for a long time, positioning can be improved, and the control is simpler than servo. However, the premise of stepping motor control is that the motor does not lose its step. How can the stepping motor not lose its step?
We know that a stepper motor is an open-loop control motor that converts electrical pulse signals into angular displacement or linear displacement. In the case of no out-of-step, the speed and stop position of the motor only depend on the frequency and number of pulses of the pulse signal and are not affected by load changes. When the stepping motor receives a pulse signal, the motor will operate according to the set The direction turns a fixed angle (step angle or step angle), and the open-loop control is achieved by controlling the angular displacement of the motor and the motor speed by controlling the number of pulses and pulse frequency. In addition, there is always a certain error between the angle turned by the stepper motor every step and the theoretical step distance, and there is always a certain error from one step to another. However, the number of steps per revolution of the stepper motor Similarly, in the case of no loss of synchronization, the step error will not accumulate for a long time.The above mentioned are all under the condition of not losing the step, but how can we not lose the step, first of all, we need to know the factors that cause the motor to lose the step, mainly include the following four points:1. The rotor acceleration is slower than the rotating magnetic field of the stepping motor;2. The average speed of the rotor is greater than the average rotation speed of the stator magnetic field;3. The motor load inertia is large;4. The stepper motor resonates.When the rotor The average speed of the rotor is higher than the average rotation speed of the stator magnetic field. This is because the time for the stator to be energized and excited is longer than the time required for stepping. The rotor obtains too much energy during the stepping process, resulting in excessive torque generated by the motor and causing The motor oversteps.The above causes of the stepping motor out of step are essentially caused by improper selection of the stepping driver. Only by choosing the correct and suitable stepping driver can the stepping motor exert its control characteristics. Selecting a suitable driver needs to match the driver with a current greater than or equal to the current of the motor according to the current of the motor. If low vibration or precision is required, subdivided drives can be used. For high-torque motors, use voltage-type drives as much as possible to obtain good speed performance. At the same time, for the driving power supply, many people directly use switching power supply as the driving power supply. However, it is generally best not to use switching power supply, especially for high-torque motors, unless a switching power supply with more than twice the required power is selected. Because the motor is a large inductive load when it is working, it will form an instantaneous pressure on the power supply terminal. However, the overload performance of the switching power supply is not good, and it will be shut down for protection, and its precise voltage stabilization performance is not needed, which may sometimes cause damage to the switching power supply and the driver. For the driving power of the stepping motor, a conventional ring or R-type transformer can be used to transform the DC power supply. The resonance of the stepper motor is because the pulse frequency received by the motor is equal to the natural frequency of the stepper motor, which is related to the subdivision of the driver. When we generally use stepper motors, the subdivision capability of the driver is very important, and the smaller the resonance range, the better. The large load inertia of the motor is caused by the overload of the motor, so you only need to pay attention not to overload the motor when using it.Suzhou Weiben Engineering Plastics Wintone Z33 is a special engineering plastic for wear-resistant and silent gears. Compared with traditional POM materials, Z33 has more Excellent wear resistance, fatigue resistance and quietness can help solve the problem that the POM eccentric wheel is easily worn and pierced after a period of use, and at the same time effectively reduce transmission noise. In addition, Z33 is resistant to acid and alkali, hot water and steam, and Excellent chemical resistance such as salt water also greatly broadens the application scenarios of micro-diaphragm pumps and various micro-pumps.How does a stepper motor decelerate?As a commonly used and widely used driving motor, stepper motors are usually used together with deceleration equipment to achieve ideal transmission effects; and deceleration equipment and methods commonly used for stepper motors, such as deceleration gearboxes, encoders, controllers, pulse signal etc.Pulse signal deceleration: The speed of the stepping motor is changed according to the change of the input pulse signal. Theoretically speaking, if a pulse is given to the driver, the stepper motor will rotate a step angle (a subdivision step angle when subdivided). In fact, if the pulse signal changes too fast, due to the damping effect of the internal back electromotive force of the stepping motor, the magnetic reaction between the rotor and the stator will not be able to follow the change of the power-on signal, which will lead to stalling and loss of steps.Reduction gear box deceleration: the stepper motor is used together with a reduction gear box. The stepper motor outputs high speed and low torque speed. When connected to the reduction gear box, the reduction ratio formed by the meshing transmission of the internal reduction gear set in the gear box will reduce the high speed output of the stepper motor. Reduce and increase the transmission torque to achieve the ideal transmission effect; the deceleration effect depends on the reduction transmission ratio of the gearbox, the larger the reduction ratio, the smaller the output speed, and vice versa.Curve index control speed: Exponential curve, in software programming, first calculate the time constant and store it in the computer memory, point to select when working. Usually, the acceleration and deceleration time of the stepper motor is more than 300ms. If the acceleration and deceleration time is too short, it will be difficult to realize the high-speed rotation of the stepping motor for most stepping motors.Encoder controlled deceleration: As a simple and practical control method, PID control has been widely used in stepper motor drive. It forms the control deviation e(t) according to the given value r(t) and the actual output value c(t), and forms the control quantity through linear combination of the proportion, integral and differential of the deviation to control the controlled object. In the literature, the integrated position sensor is used in the two-phase hybrid stepping motor. Based on the position detector and vector control, a PI speed controller that can be automatically adjusted is designed. provide satisfactory transient characteristics. According to the mathematical model of the stepping motor, the literature designs the PID control system of the stepping motor, and uses the PID control algorithm to obtain the control quantity, so as to control the motor to move to the specified position. Finally, it is verified by simulation that the control has good dynamic response characteristics. The use of PID controller has the advantages of simple structure, strong robustness and high reliability, but it cannot effectively deal with the uncertain information in the system.What reducer can the stepper motor be equipped with? What factors need to be paid attention to in the matching of stepper motor and reducer, and what kind of reducer can be used together?1. The reason why the stepper motor is equipped with a reducerThe stepper motor switches the frequency of the stator phase current, such as changing the input pulse of the stepper motor drive circuit to make it a low-speed motion. When the low-speed stepping motor is waiting for the stepping command, the rotor is in a stopped state. When stepping at low speed, the speed fluctuation will be large. At this time, if it is changed to high-speed operation, the speed fluctuation problem can be solved, but the torque will be insufficient. That is to say, the torque will fluctuate at low speed, and the torque will be insufficient at high speed, so a reducer is required.2. What are the stepper motors often equipped with reducers?The reducer is an independent component composed of gear transmission, worm transmission, and gear-worm transmission enclosed in a rigid shell. It is often used as a reduction transmission device between the prime mover and the working machine. The mechanism plays the role of matching speed and transmitting torque; there are many kinds of reducers, which can be divided into gear reducer, worm reducer and planetary gear reducer according to the transmission type; according to the number of transmission stages, it can be divided into single-stage and multi-stage According to the gear shape, it can be divided into cylindrical gear reducer, bevel gear reducer and conical-cylindrical gear reducer; according to the transmission layout, it can be divided into expansion reducer, split flow reducer and coaxial reducer machine. The reducer for stepper motor assembly includes planetary reducer, worm gear reducer, parallel gear reducer, screw gear reducer.
How about the precision of the stepper motor planetary reducer?
The accuracy of the reducer is also called the backlash. When the output end is fixed and the input end rotates clockwise and counterclockwise, when the output end produces rated torque +-2% torque, there is a slight angular displacement at the input end of the reducer. This angle The displacement is the backlash. The unit is "arc minutes", which is one sixtieth of a degree. The usual backlash values refer to the output end of the reducer. The stepper motor planetary reducer has the characteristics of high rigidity, high precision (within 1 minute for a single stage), high transmission efficiency (97%-98% for a single stage), high torque/volume ratio, and maintenance-free.The transmission accuracy of the stepper motor cannot be adjusted. The operating angle of the stepper motor is completely determined by the step length and the number of pulses, and the number of pulses can be counted completely. The concept of precision does not exist in digital quantities. One step is one step. Two steps are two steps. The accuracy that can be optimized at present is the gear backlash accuracy of the planetary reducer gearbox:1. Spindle accuracy adjustment method: the adjustment of the rotation accuracy of the planetary reducer spindle. If the machining error of the spindle itself meets the requirements, the rotation accuracy of the reducer spindle is generally determined by the bearing. The key to adjusting the rotation accuracy of the spindle is to adjust the bearing clearance. Maintaining a proper bearing clearance is critical to spindle component performance and bearing life. For rolling bearings, when there is a large gap, not only the load will be concentrated on the rolling elements in the direction of force, but also serious stress concentration will occur at the contact between the inner and outer ring raceways of the bearing, shortening the life of the bearing, and The center line of the spindle will drift, which will easily cause the vibration of the spindle components. Therefore, the adjustment of the rolling bearing must be preloaded, so that a certain amount of interference is generated inside the bearing, so that a certain elastic deformation is generated at the contact between the rolling body and the inner and outer ring raceways, thereby improving the stiffness of the bearing.2. Adjusting the gap method: The planetary reducer will generate friction during the movement process, causing changes in the size, shape and surface quality of the parts, and causing wear and tear, which will increase the gap fit between the parts. At this time, we need Adjust it within a reasonable range to ensure the accuracy of relative motion between parts.3. Error compensation method: the error of the parts themselves is properly assembled to make them cancel each other out during the running-in period, so as to ensure the accuracy of the equipment's movement trajectory.4. Comprehensive compensation method: Use the tools installed by the reducer itself to process the correct and correct worktable, so as to eliminate the comprehensive results of various precision errors.The transmission design of the intelligent toilet clamshell gearbox needs to produce a large torque output in a very small space, and at the same time, it must take into account the noise reduction of the transmission and the unexpected impact caused by the user's improper operation, as well as hundreds of thousands of times. fatigue life. Generally, there are two kinds of transmission designs for this type of gearbox, one is a combination of parallel shaft gear transmission + planetary gear transmission, the other is a combination of worm gear transmission + planetary gear transmission, and the portable smart toilet flip gearbox and There are also many differences in the design of heavy-duty clamshell gearboxes.
In the application of the plastic gears of the intelligent toilet flip gear box and the transmission gears of various reduction motors, Suzhou Weiben Engineering Plastics Wintone Z33 wear-resistant and silent gear special material can help you solve the following problems: 1. POM and PA66 gears are relatively noisy
, The problem of insufficient wear resistance and fatigue resistance.
2. PA12 and TPEE gears are too soft, the torque is too small, and the wear resistance is not enough. When the temperature is above 60 degrees Celsius, the torque drops faster.
3. The corrosion resistance of POM and PA66 gears is not enough, and the problem of broken teeth. POM gears and injection molded parts are prone to wear and dust.
4. The noise reduction performance of nylon 46 gears is not enough, and the size is greatly affected by water.
As a strong and wear-resistant engineering plastic, Z33 material has the most notable features in gear applications: wear-resistant, quiet, corrosion-resistant, tough and not affected by moisture. The typical successful applications of Z33 materials are: miniature reduction gearboxes, electric push rods, EPS gears for automobile steering systems, massager gears, gasoline engine cams, central motor gears for electric bicycles, electric shavers and other transmission gears.
------------------------------------------In the application of industrial gears, compared with traditional POM and PA66, Wintone Z33 has better wear resistance, fatigue resistance, and deformation resistance. While maintaining good rigidity, Z33 further improves elasticity and toughness (this This excellent mechanical property is maintained and reflected at -40 degrees Celsius, 0 degrees and 80 degrees Celsius), which can help solve the problem of gear broken teeth, and at the same time greatly reduce friction noise. After application, Wintone Z33 is also better than many POM and PA66 with wear-resistant modified specifications (such as polytetrafluoroethylene, silicone or molybdenum disulfide modification), and Z33 has good corrosion resistance, and can be used in many scenarios where it is exposed to various chemical substances. Harsh environments, such as gears on printing and dyeing textile machinery, retaining rings and sealing rings in hydraulic systems, etc., have successfully replaced some application fields of expensive PEEK, PA12, PVDF, PTFE, and PA46. In addition, Z33 has very little moisture absorption, and the overall performance is slightly affected by moisture. The whole package of Wintone Z33 does not need to be pre-baked before injection molding, and can be directly injected, and no water treatment is required after injection molding.
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