Working Principle and six differences between stepping motor and servo motor

by:V&T Technologies     2020-01-18
There are six major differences between the working principle of stepping motor and servo motor. At present, there are too many names for stepping motor on the market, and many people are a little confused. Some are called Stepping Motor or motor, there is also a servo motor, also called servo motor, so many names, I think everyone has been blinded, today stepper motor manufacturers take you to understand, what is a stepper motor, what is servo motor and what is the difference between them? If you want to distinguish, you must first understand the difference between the two. Ruite electromechanical popularized the working principle of stepping motor and servo motor. First, let's look at the principle of stepping motor. First, let's talk about the working principle: stepping motor is an actuator that converts electrical pulse into angular displacement. When the stepping driver receives a pulse signal, it drives the stepping motor to rotate a fixed angle (Called'Step angle') Its rotation runs step by step at a fixed angle. The angular displacement can be controlled by controlling the number of pulses, thus achieving the purpose of accurate positioning; At the same time, the speed and acceleration of the motor can be controlled by controlling the pulse frequency, thus achieving the purpose of speed regulation. The rotor inside the servo motor is a permanent magnet. The U/V/W three-phase electricity controlled by the driver forms an electromagnetic field. The rotor rotates under the action of this magnetic field. At the same time, the encoder provided by the motor feeds back signals to the driver, the driver adjusts the rotation angle of the rotor by comparing the feedback value with the target value. The accuracy of the servo motor depends on the accuracy of the encoder (Number of lines). Difference 1: The control mode is different. The stepping motor controls the rotation angle by controlling the number of pulses, and one pulse corresponds to one step angle. The servo motor controls the rotation angle by controlling the length of pulse time. Difference 2: the required working equipment and workflow are different. The power supply required by the stepping motor (The required voltage is given by the driver parameters), A pulse generator (Most of them are now using plates), A stepper motor, a driver ( The driver sets the step angle, such as setting the step angle to 0. 45 °At this time, give a pulse, the motor goes 0. 45 °); Its working flow is that stepping motor generally needs two pulses: signal pulse and direction pulse. The power supply required by the servo motor is a switch (Relay switch or relay board card), A servo motor; Its work flow is a power supply connection switch, and then connected to the servo motor. Difference 3: The low-frequency characteristics are different, and the stepping motor is prone to low-frequency vibration at low speed. The vibration frequency is related to the load and the performance of the driver. It is generally believed that the vibration frequency is half of the no-load take-off frequency of the motor. This kind of low-frequency vibration phenomenon determined by the working principle of stepping motor is very unfavorable to the normal operation of the machine. When the stepping motor works at a low speed, damping technology should be generally used to overcome the low-frequency vibration phenomenon, such as adding dampers to the motor or using subdivision technology on the driver. The AC servo motor runs very smoothly and will not vibrate even at low speed. AC servo system has resonance suppression function, which can cover the rigidity deficiency of machinery, and the system has Frequency analysis function (fft) The resonance point of the machine can be detected to facilitate system adjustment. Difference 4: the torque-frequency characteristics are different. The output torque of the stepping motor decreases with the increase of the rotating speed and decreases sharply at a higher rotating speed, so the highest working speed is generally 300 ~ 600r/MIn. AC servo motor is constant torque output, I . e. at its rated speed ( (Usually 2000 or 3000 r/min) Within, can output rated torque, constant power output above rated speed. Difference 5: different overload capacity, ruite stepping motor, stepping motor generally does not have overload capacity. AC servo motor has strong overload capability. Take Panasonic AC servo system as an example, it has speed overload and torque overload capability. The maximum torque is 3 times of the frontal torque, which can be used to overcome the inertial torque of the inertial load at the moment of startup. ( Because stepping motors do not have this kind of overload capability, in order to overcome this kind of inertial torque, it is often necessary to select motors with larger torque, however, the machine does not need such a large torque during normal operation, thus causing torque waste) Difference 6: The speed response performance is different. The stepping motor accelerates from rest to working speed (Generally hundreds of revolutions per minute)Need 200 ~ 400 ms. The acceleration performance of AC servo system is good. Taking Panasonic MSMA400W AC servo motor as an example, it accelerates from rest to its rated speed of 3000 r/min. Only a few MS are needed and can be used in control occasions requiring quick start and stop. To put it bluntly, there are many pairs, slow rotation speed, control angle, and many power line pins are stepping motors, and the power is often relatively low. However, it has high precision and fast speed, and can be applied to speed, position and torque control in many occasions. The power line is UVW three-wire, usually servo motor. And usually the number of poles does not exceed 5, and the power ranges from tens of Watts to tens of kilowatts. Related reading: Calculation of positioning accuracy of Rui Te stepping motor principle and research of stepping motor TAG stepping motor
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