Comparison between Servo Motor and Stepping Motor2016-11-09
Stepper motor as an open-loop control system, and modern digital control technology is essentially linked. In the current domestic digital control system, the stepper motor is widely used. With the emergence of all-digital AC servo system, AC servo motor is also increasingly used in digital control systems. In order to adapt to the trend of digital control, most of the motion control system using stepper motor or all-digital AC servo motor as the implementation of the motor. Although the two are similar in the control mode (pulse train and direction signal), but in the use of performance and applications there is a big difference. Are on the use of performance to make a comparison. 1 control accuracy is different Two-phase hybrid stepping motor step angle is generally 1.8 °, 0.9 °, five-phase hybrid stepping motor step angle is generally 0.72 °, 0.36 °. There are also some high-performance stepper motors that are subdivided by a smaller step angle. Such as the two-phase hybrid stepper motor manufactured by SANYODENKI, its step angle can be set to 1.8 °, 0.9 °, 0.72 °, 0.36 °, 0.18 °, 0.09 °, 0.072 °, 0.036 ° by DIP switch, Compatible with two-phase and five-phase hybrid stepping motor step angle. AC servo motor control accuracy by the motor shaft back-end rotary encoder to ensure. 2 low-frequency characteristics of different Stepping motor at low speed prone to low frequency vibration phenomenon. Vibration frequency and load conditions and drive performance, generally considered that the vibration frequency of the motor no-load take-off frequency of half. This stepper motor by the working principle of the low-frequency vibration of the phenomenon of the normal operation of the machine is very detrimental. When the stepper motor at low speed, the general should be used to overcome the damping technology to reduce the phenomenon of low-frequency vibration, such as in the motor damper, or the use of subdivision technology on the drive. AC servo motor running very smooth, even at low speed will not appear when the vibration phenomenon. AC servo system has a resonance suppression function, can cover the mechanical rigidity, and the system has a frequency analysis function (FFT), can detect the mechanical resonance point, easy to adjust the system. 3 frequency characteristics of different The output torque of the stepper motor decreases with the increase of speed, and it will drop sharply at higher speed, so its maximum working speed is generally 300 ~ 600RPM. AC servo motor for the constant torque output, that is, its rated speed (usually 2000RPM or 3000RPM) within the rated torque can be output in the rated speed above the constant power output. 4 overload capacity is different Stepper motors generally do not have overload capability. AC servo motor has a strong overload capacity. To Yasukawa AC servo system, for example, it has a speed overload and torque overload capability. Can be used to overcome the moment of inertia inertia moment in the load. Stepper motor because there is no such overload capacity, in order to overcome this inertia in the selection of torque, often need to select a larger torque of the motor, and the machine during normal work without the need for such a large torque, there has been torque Waste of the phenomenon. 5 Operating performance is different Stepping motor control for the open-loop control, start the frequency is too high or too large load prone to lose step or stall phenomenon, stop when the speed is too high prone to overshoot phenomenon, so in order to ensure its control accuracy, should be handled well Rise, slow down problem. AC servo drive system for closed-loop control, the drive can be directly on the motor encoder feedback signal sampling, the internal composition of the position loop and speed loop, stepper motor is generally not lost step or overshoot phenomenon, the control performance is more reliable. 6 Speed response performance is different Stepping motor acceleration from standstill to the working speed (usually hundreds of revolutions per minute) need 200 to 400 milliseconds. AC servo system acceleration performance is better, to Yasukawa AC servo motor, for example, from the static acceleration to its rated speed 3000RPM only a few milliseconds, can be used for fast start-stop control of the occasion. QQ picture 20160317113001.png In summary, the AC servo system in many performance is better than stepper motor. But in some less demanding occasions, often with a stepper motor to do the implementation of the motor. Therefore, in the control system design process to take into account the control requirements, cost and other factors, the selection of appropriate control motor.
