Circuit Design of Motor Monitoring System Based on NI Virtual Instrument

　　In order to improve the practicality and reliability of the switched reluctance motor control system, a monitoring system was built using NI virtual instruments, which can monitor and adjust the important parameters of the motor in real time. The solution uses a PC equipped with a data acquisition card and a DSP as the hardware basis. The LabVIEW software is used to process the signals transmitted by various sensors in real time, record and display various data at the same time, and then the corresponding algorithm is used to complete the data analysis. The data is obtained by using a PCI-6143 data acquisition card and programming with LabVIEW8.6 as the development environment. Considering that the system may be used in a relatively harsh working environment, in order to achieve real-time control more safely and effectively, the DSP is used as a backup processor for the PC. The experimental prototype is an 8/6-pole SRM with a power of 150 W.

　　Position signal detection

　　When working under very harsh conditions, the rotor position sensor may fail. In this case, a safer working mode can be achieved without position sensors. At present, the more common method is to deduce the angle of the motor by measuring the flux and current. However, this requires obtaining the flux and current values ​​of the SRM at different positions in advance as the basis for subsequent judgment during operation. If the system needs to be transformed into a position sensorless technology in the future, in order to accurately obtain the rotor position, an absolute position encoder needs to be fixed on the rotor shaft. The output of the absolute position encoder is Gray code, which needs to be processed to obtain ordinary binary code. Of course, in steady-state operation, the absolute position encoder can also completely replace the photoelectric position sensor to provide more accurate speed information. However, compared with the photoelectric position sensor, the absolute position encoder is expensive and easy to damage, and is not suitable for occasions with severe vibration. The circuit structure of the experimental motor is shown in Figure 2. Among them, R1~R4 are small resistors connected in series with the four phases of the motor, and R5 is a voltage divider resistor for measuring the winding voltage.