The power press punch punching machine servo uncoiler straighter feeder manufacturer believes that the stepper motor is a discrete motion device, which has an inherent connection with modern digital control technology. At present, stepper motors are widely used in domestic digital control systems. With the emergence of all-digital servo systems, servo motors are increasingly used in digital control systems. In order to adapt to the development trend of digital control, most motion control systems use stepper motors or all-digital servo motors as executive motors. Although they are similar in control (pulse train and direction signal), they are quite different in performance and application.
(1) Different control precision
The power press punch punching machine servo uncoiler straighter feeder manufacturer believes that the rotary encoder at the back end of the motor shaft ensures the control accuracy of the motor. For a motor with a standard 2500-line encoder, due to the quadruple frequency technology used in the servo driver, the pulse equivalent of the motor is 360/10000=0.036. For a motor with a 17-bit encoder, every time the driver receives 217=131072 pulses, the motor rotates One week, that is, its pulse equivalent is 360/131072=9.89 seconds. It is 1/655 of the pulse equivalent of a stepper motor with a step angle of 1.8.
(2) The moment-frequency characteristics are different.
The power press punch punching machine servo uncoiler straighter feeder manufacturer believes that the output torque of the stepper motor decreases with the increase of the speed, and will drop sharply at a higher speed, so the limit working speed is generally 300 ~ 600 rpm. The servo motor is a constant torque output, that is, it can output the rated torque within its rated speed range (generally 2000 rpm or 3000 rpm), and it is a constant power output above the rated speed.
(3) Different low frequency characteristics.
power press punch punching machine servo uncoiler straighter feeder manufacturers believe that stepper motors are prone to low-frequency vibration at low speeds. The vibration frequency is related to the load condition and the performance of the drive, and it is generally considered that the vibration frequency is half of the no-load take-off frequency of the motor. This low-frequency vibration phenomenon is determined by the working principle of the stepping motor, which is very detrimental to the normal operation of the machine. When the stepper motor works at low speed, damping technology should generally be used to overcome the phenomenon of low frequency vibration, such as adding dampers to the motor or using subdivision technology to the driver.
The power press punch punching machine servo uncoiler straighter feeder manufacturer believes that the servo motor runs very smoothly, and there is no vibration even at low speed. The servo system has a resonance suppression function, which can make up for the lack of mechanical rigidity. The system has a frequency analysis function (FFT), which can detect the resonance point of the machine and facilitate system adjustment.
(4) Different running performance.
power press punch punching machine servo uncoiler straighter feeder manufacturers believe that the control of stepper motor is open-loop control. If the starting frequency is too high or the load is too large, it is easy to lose step or stall, and when the speed is too high, it is easy to overshoot. Therefore, in order to ensure its control accuracy, it is necessary to deal with the problem of speed-up and speed-down. The servo system is closed-loop control, the driver can directly sample the feedback signal of the motor encoder, and form a position loop and a speed loop internally, so that the stepper motor will not lose step or overshoot, and the control performance is more reliable.
(5) Different speed response performance.
power press punch punching machine servo uncoiler straighter feeder manufacturers believe that it takes 200 to 400 milliseconds for the stepper motor to accelerate from standstill to working speed (usually several hundred revolutions per minute). The acceleration performance of the servo system is good. It only takes a few milliseconds for the servo motor to accelerate from a standstill to a rated speed of 3000RPM, which can be used in control occasions that require rapid start and stop.