Open-Loop Control Of Stepper Motor

1.General composition of stepper motor open-loop servo system

The armature on and off times of the stepping motor and the power-on sequence of each phase determine the output angular displacement and movement direction. The control pulse distribution frequency can achieve the speed control of the stepping motor. Therefore, the stepper motor control system generally adopts open-loop control.

2.Hardware control of stepper motor

The stepping motor turns a corresponding step angle under the action of a pulse, so as long as a certain number of pulses is controlled, the corresponding angle that the stepping motor turns can be accurately controlled. However, the windings of the stepping motor must be energized in a certain order to work properly. This process of making the motor winding on and off in accordance with the control of the input pulses is called a ring pulse distribution.

There are two ways to achieve circular allocation. One is computer software distribution. A table lookup or calculation method is used to cause the three output pins of the computer to sequentially output a circular distribution pulse signal that meets the speed and direction requirements. This method can make full use of computer software resources to reduce hardware costs, especially the pulse distribution of multi-phase motors shows its advantages. However, because the software running will occupy the computer's running time, the total time of the interpolation operation will increase, which will affect the running speed of the stepper motor.

The other is hardware ring distribution, which uses digital circuits to build or special ring distribution devices to process continuous pulse signals and output ring pulses after circuit processing. Ring distributors built with digital circuits usually consist of discrete components (such as flip-flops, logic gates, etc.), which are characterized by large size, high cost, and poor reliability.

Post time: Mar-26-2021