Stepper motor is commonly used for positioning control, it can control the angle of rotation (relatively speaking, it can be distance) by the number of pulses output by the PLC, and the frequency of the pulse controls the speed of rotation of the stepper motor. However, it is used for occasions where the control accuracy is not very high, which is simple, economical and convenient to control; For occasions with high control accuracy requirements, servo control systems must be used.
Stepper system = stepper driver + stepper motor. The stepper motor is driven by a stepper driver, which is equivalent to a driving power supply, and it is controlled by external pulse signals and direction signals (in this case, Siemens PLC output pulses), which in turn control the rotation angle and speed of the stepper motor.
Stepper driver + stepper motor + Siemens PLC (CPU 222 CN).
1. Drive: The medium used by PLC to control the stepper motor is responsible for amplifying the pulse signal given by the PLC and transmitting it to the stepper motor, so that the motor runs according to the parameters given by the PLC and the driver.
Control the process. 2. Step angle: The angle at which each pulse rotates the stepper motor is 18°, this is generally not something that can be changed.
Example: If no subdivision is set, the control step angle is 1How many pulses does the PLC need to emit for a stepper motor of 8° to rotate (360°)?
Answer: 360° x=18° 1, so x = 200 pulses.
3. SubdivisionIn practical application, it is found that if the step angle is large, the angle of each rotation will be large, which will cause vibration, and the corresponding control error will also become larger. So the function of segmentation is introduced. This means that the step angle is increased by a few points through the DIP switch of the driver, so that the motor rotates more smoothly.
Example: The step angle is 18°, set 10 subdivisions, then every time the PLC sends out a pulse, the motor only rotates 018°, stepper motor rotates once (360°), how many pulses does the PLC need to emit?
Answer: 360° x = 018° 1, so x = 2000 pulses.
Summary: The larger the step angle, the fewer the number of pulses; The smaller the step angle, the higher the number of pulses.
1. Stepper driver.
Pffield Drive Description.
There are generally two types of direction control for stepper motors:
a) Pulse + direction: When the pulse is generated by the pul, the motor will rotate, and the direction is determined by the DIR.
b) Forward Pulse + Reverse Pulse: When the PU pulse is generated, it rotates forward; When the dir has a pulse generated, anyway. However, pul and dir cannot be pulsed at the same time.
2. Stepper motor.
When ab When the two-phase winding is replaced, the motor can be reversed.
Stepper motor parameters.
Wiring diagram with PLC
The signal voltage of this stepper motor is 5V, and the voltage used by Siemens PLC is 24V, so to access the driver, you need to connect 12k, 1 4W resistor, shown in the red part of the figure.
The Siemens PLC (CPU222) can output high-speed pulses in two ways:
1. PTO (duty cycle 50%)
2. PWM (duty cycle can be changed).
The above two high-speed pulse output instructions can be used to control the stepper driver, and then control the stepper motor, and then control the movement and speed of some specific equipment.