The measuring device in the traditional asynchronous motor control system mostly uses the photoelectric digital pulse encoder, and it is susceptible to interference in the process of use, which reduces the reliability of the system and is not suitable for the harsh working environment. In view of the above shortcomings, this paper proposes the speed-free sensor control of spatial pulse width modulation (SVPWM), which uses modern digital signal processing technology to realize complex flux linkage and speed control. And based on DSPTMS320F2812, vector control of asynchronous motor speed sensor is realized.
1 spatial pulse width modulation principle
For an asynchronous motor, the three-phase alternating current loaded onto the stator generates a rotating magnetic field that interacts with the induced magnetic field of the rotor to produce torque that causes the rotor to rotate. Spatial pulse width modulation converts the three-phase current vector of the stator from coordinates into two equivalent and orthogonal components, one of which corresponds to the field current and the other of which corresponds to the torque current. The space vector control is to control the magnitude, frequency and phase of the three-phase current of the stator, to maintain the magnetic field component at the maximum allowable value, and to adjust the torque current component to control the magnitude of the torque. And by controlling the switching mode of the inverter, the stator voltage space vector of the motor moves along a circular path, thereby significantly reducing the torque ripple [1]
2.1 Rotor flux estimation
In the rotor-field oriented vector control system, the accurate estimation and control of the rotor flux linkage is one of the key factors affecting the motor control performance. The rotor flux linkage is estimated to be either voltage or current. The traditional voltage model algorithm is simple, and it is less affected by the variation of the motor parameters, but the observation accuracy is low at low speed and the error accumulation and drift problems of the pure integral link are serious. The traditional current model does not involve pure integral terms. The low-speed observation performance is stronger than the voltage model method, but it is not as good as the latter at high speed, and is greatly affected by the rotor time constant [2].
2.2 Speed estimation principle
The speed of the speed sensorless vector control system is estimated based on the rotor flux linkage output from the flux linkage estimation model.
3 control system design
Based on the principle of speed sensorless vector control, TMS320F2812 is selected as the hardware of the core controller design control system, and the software program is written on the compilation platform of CCS2000.
3.1 hardware design
The speed sensorless vector control system is also composed of a main circuit and a control circuit. The system constitutes a three-phase inverter circuit with IGBT power devices. The rectifier circuit, the filter circuit, the drive protection circuit and the IGBT are combined to form a main circuit of the AC-type universal frequency converter. The control core is composed of TMS320F2812 as the core. The DSP is responsible for sampling the three-phase current of the motor, realizing the algorithm of speed sensorless vector control, and finally outputting the PWM drive three-phase inverter bridge [3].
3.2 software design
The system software is written in C language, mainly including the main program and the timer underflow terminal subroutine.
4 Conclusion
With the development of various control theories, digital signal processors (DSPs) and their widespread use in motor control, the development of motor control technology has entered a new phase. It can be seen from the research in this paper that the brushless DC motor control system with TMS320F2812 as the core has high control precision, strong real-time performance, low system power consumption, and can realize very rich control functions. These are traditional control systems. Unmatched, fully embodies the superiority of DSP control.
