Circuit Design of Motor Monitoring System Built with NI Virtual Instrument

Single chip microcomputer STM32L151CCU6

Photocoupler

In order to improve the practicability and reliability of the switched reluctance motor control system, a monitoring system is built using NI virtual instrument, which can monitor and adjust the important parameters of the motor in real time. The program uses the PC and DSP equipped with the data acquisition card as the hardware foundation. The LabVIEW software is used to process the signals transmitted by various sensors in real time, and simultaneously record and display the data, and then use the corresponding algorithm to complete the analysis of the data. . The data was obtained using a PCI-6143 data acquisition card and programmed in LabVIEW 8.6 as the development environment. Considering that the system may be used in a 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 SRW with a power of 150 W.

Position signal detection

The rotor position sensor may fail when operating under very harsh conditions. In this case, no position sensor can achieve a safer way of working. The more common method currently used is to derive the angle of the motor by measuring the flux linkage and current. However, it is necessary to obtain the flux linkage value and current value of the SRM at different positions in advance as the basis for the judgment of the subsequent operation. If the system needs to be retrofitted without position sensor technology in the future, in order to accurately determine the rotor position, an absolute position encoder needs to be fixed on the rotor shaft. The absolute position encoder outputs the Gray code, which needs to be processed to obtain the 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 rotational speed information. However, absolute position encoders are expensive and relatively easy to damage relative to photoelectric position sensors, and are not suitable for applications where vibration is severe. The circuit structure of the experimental motor is shown in Figure 2. Among them, R1~R4 are small resistors connected in series with the motor four phases, and R5 is a voltage dividing resistor for measuring the winding voltage.