Open loop control system refers to the control mode without position feedback device. The control system with power stepping motor as the driving element is a typical open-loop control system.
According to the required movement speed and displacement, the numerical control device outputs a certain frequency and number of pulses to the ring distributor and power amplification circuit, constantly changing the power supply state of each phase winding of the stepping motor, making the stepping motor of the corresponding coordinate axis rotate the corresponding angular displacement, and then passing through the mechanical transmission chain to realize the linear movement or rotation of the moving parts. The progress and displacement of moving parts are determined by the frequency and number of input pulses.
Open loop control system has the advantages of simple structure and low price. But usually, the output torque value will be limited, and when a high pulse frequency is input, it is easy to produce out of step, and it is difficult to achieve rapid control of moving parts. At present, the open-loop control system can not fully meet the increasing requirements of CNC machine tools for control power, fast motion speed and machining accuracy.
However, in recent years, stepper motors have been widely used in the drive control of small equipment with low torque, high precision and medium speed, especially in microelectronic production equipment.
