Stepper Motor Angular Position Detection
For stepper motor angular position,usually using two detection methods:one method is to use the rotary transformer,the other is the use of photoelectric encoder.Absolute photoelectric encoder is a non-contact position feedback and measurement components,it has simple structure,high reliability,high resolution,high precision,small size,light weight and so on features.
When use it,make code and the mechanical axis coaxial connection,direct output the angle coding,the output code input to the microcontroller,after decoding can get the angle value,without any additional circuit,such as A / D conversion,zoom filter.The stepper motor control system using the photoelectric encoder is shown in Fig. 1,and the output of the photoelectric encoder in the figure 1 is fed back to the control circuit.The control circuit adjusts the angle of the stepping motor according to the feedback output.
Figure 1 uses the photoelectric encoder stepper motor control system
The stepper motor is driven by an electronic device,which is a stepper motor driver that amplifies the pulse signal from the control system to drive the stepper motor.The speed of the stepper motor is proportional to the frequency of the pulse signal.To control stepping pulse signal frequency to accurate speed the motor,control the number of stepping pulses to precisely position the motor.
Stepper motor drive control system consists of the following three parts:
The stepper controller is implemented by the microcontroller,while stepper drives amplify the pulses output by the microcontroller to drive the stepper motor.General system of single-chip control stepper motor system block diagram shown in Figure 2.Do not use DC
or AC frequency direct drive stepper motor,must use a dedicated stepper motor drive circuit,or with a separate component of the dedicated circuit.
Figure 2 block diagram of the stepper motor system
According to the motor starting current flow direction,the drive circuit is divided into unipolar drive circuit and bipolar drive circuit.Unipolar drive circuit to ensure that the motor winding current flows in one direction,suitable for reactive stepping motor;bipolar drive circuit through control unit,can make the motor winding current positive / negative flow,for permanent and hybrid stepper motor.