As an industrial control accounting machine, PLC has modular structure, flexible equipment, high-speed processing speed, accurate data processing ability, and excellent control ability of PLC for stepping motor. It can end the control of stepping motor by using its high-speed pulse output function or motion control function.
The characteristics of the stepping motor: (1) The angular displacement of the stepping motor is strictly proportional to the number of input pulses. There is no accumulated fault after the motor works for one week, and it has excellent following ability. (2) The open-loop digital control system composed of stepping motor and driver circuit is very simple, cheap and reliable. At the same time, it can also form a highly functional closed-loop digital control system with the viewpoint response link. (3) The dynamic care of stepping motor is fast, easy to start and stop, positive rotation and speed change. (4) The speed can be smoothly scheduled within an appropriate and wide plan, and the large torque can still be ensured at low speed. (5) The stepper motor can only be operated by pulse power supply. It cannot directly use communication power supply and DC power supply.
The highest stepping frequency that the stepping motor can take care of without losing step is called "claim frequency"; Similarly, "continuous frequency" refers to the highest step frequency at which the system control signal suddenly turns off and the stepping motor does not overshoot the direction. The claimed frequency, connecting frequency and output torque of the motor should be consistent with the rolling inertia of the load. With these data, you can effectively control the stepping motor with variable speed.
When PLC is selected to control the stepping motor, the pulse equivalent, the upper limit of pulse frequency and the maximum number of pulses shall be calculated according to the following formula, and then the PLC and its corresponding function module shall be selected. The frequency required for PLC high-speed pulse output can be determined according to the pulse frequency, and the bit width of PLC can be determined according to the number of pulses. Pulse equivalent=(step angle of stepping motor × Pitch)/(360 × Transmission speed ratio); Upper limit of pulse frequency=(moving speed × Stepper motor fraction)/pulse equivalent; Maximum number of pulses=(moving interval × Stepper motor fraction)/pulse equivalent.
PLC is selected to control the operation of stepping motor through stepping driver, and then PLC is used more and more widely in stepping electric control. For example, in the control process of single and double axis movement, set the parameters such as movement interval, speed and direction on the control panel. After reading these set values, the PLC will operate the stepper motor drive after calculating the pulse and direction signals to achieve the intention of controlling the interval, speed and direction. It has been proved by the actual measurement that the operation function of the system is reliable, feasible and useful.
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