In a straight line module application is between the stepper motor or servo motor
stepper motor is a kind of discrete movement of the electric drill speed reducer, it has the nature of the contact and the modern digital control technology. In the current domestic digital control system, stepping motor is widely used. With the emergence of digital ac servo system, ac servo motors are increasingly used in the digital control system. In order to adapt to the development trend of digital control, motion control systems mostly adopt stepper motor or all-digital ac servo planetary gear motor as the executive motor. Although both similar on control mode ( Pulse sequence and direction signal) , but in the use of performance and applications on there is a big difference.
1） Different control precision
where two-phase hybrid stepper motor step Angle is commonly 3. 6° , 1. 8° , five step away from the Angle of the hybrid stepping motor is commonly 0. 72 ° , 0. 36° 。 There are also some high-performance stepper motor step Angle is smaller. Control precision of the ac servo motor by the motor shaft after the rotary encoder. Panasonic digital ac servo motor, for example, in line with standard 2500 encoder of the motor, drive due to the internal used four frequency multiplication technology, the pulse equivalent to 360 & deg; / 10000 = 0. 036° 。 For with 17 encoder of the motor, drive each receive 217 = 131072 pulse motor turns a circle, i. e. the pulse equivalent of 360 & deg; / 131072 = 9. In 89 seconds. Step is from Angle of 1. 8° 1/655 of the pulse equivalent of stepper motor.
2） Low frequency characteristics of different
stepper motor at low speed is easy to appear low frequency vibration phenomenon. Vibration frequency is associated with load and drive performance, it is generally believed half frequency vibration frequency for the motor no-load takeoff. This determined by the working principle of stepper motor in low frequency vibration phenomenon is very bad for the normal operation of the machine. When the stepper motor work in low speed, general damping technology should be adopted to overcome the low frequency vibration phenomenon, such as add damper on motor, or drive the segmentation technology, etc. Ac servo motor running smoothly, even in the low speed also won't appear when the vibration phenomenon. Ac servo system has a resonance suppression function, can cover mechanical rigidity, and the system has the function of frequency resolution ( FFT) , can detect the mechanical resonance point, is advantageous for the system adjustment.
3） The torque-speed characteristics different
stepper motor output torque increases with speed decreases, and at a high speed when they fell sharply, so its maximum operating speed is in commonly 300 ~ 600 RPM. Ac servo motor for constant torque output, that is, in its rated speed ( General is 2000 RPM and 3000 RPM) Less than, can be rated output torque, in for a constant power output above the rated speed.
4） Overload capacity of different
step motor is generally not have overload ability. Ac servo motor has a strong ability of overload. Panasonic ac servo system, for example, it has the speed overload and torque overload capacity. The maximum torque is three times the rated torque, can be used to overcome inertia load at startup moments of inertia moment. Stepper motor because there is no this kind of overload capacity, in order to overcome the inertia moment when selection, often need to select a larger torque of the motor, and the machine during the normal work and don't need that big torque, there is a moment of waste phenomenon.
5） Running performance different
stepper motor control for the open loop control, start frequency is too high or too much load step easy appear lost or blocked, stops frequently occur high speed overshoot phenomenon, so as to ensure the control accuracy, should handle the ascending and descending speed problem. Ac servo drive system for closed-loop control, the actuator can be directly to the motor encoder feedback signal sampling, internal position loop and speed loop, general won't appear step motor lose step or overshoot phenomenon, more reliable control performance.
6） Speed response performance different
stepper motor accelerate from 0 to speed ( Generally for a few hundred revolutions per minute) Need to 200 ~ 400 milliseconds. The acceleration of ac servo system performance is better.
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