BLDCM Sensorless Control System Based On DsPIC

The brushless DC motor not only has its light weight, small volume and simple structure, but also has the advantage of high efficiency, reliable operation and excellent speed control performance. It has a short development history, while with the continuous development of brushless DC motor in the field of motor industry, aerospace and household electrical appliances, researchers take the more and more high request to its control technology. In order to not only reduce the size and the weight of brushless DC motor, but also apply to some special occasions, people began to emphasize the brushless DC motor’s sensorless control technology, and also researched a variety of mature methods of sensorless control technology. These methods will be introduced briefly in this article.At first, this paper outlines the brushless DC motor’s development process and its important applications, analyzes its structure and working principle and then column to write some basic equations according to brushless DC motor’s simplified mathematical model. This paper mainly introduces how to convert terminal voltage signal gained from brushless DC motor to the rotor’s position signal through a series of processes of hardware circuit and software program, and finally realize the brushless DC motor’s sensorless control technology. Because the zero point information of the back EMF can’t be detected in the condition of static or low speed, the high-frequency pulse injection method cooperated with the traditional three-step startup method is put forward to detect the motor’s position and finally realize the start of the brushless DC motor.On the base of the above theory, this paper builds a simulation platform based on Matlab/Simulink, and detailedly introduces the functions of each module. Aimed at brushless DC motor’s difficulty starting, it is solved by programming block from Simulink. Finally, a series of simulations are experimented and the feasibility of this design method is verified through a series of simulation debugging and analysis of simulation results.In the end, with the guide of the results from simulations, the whole hardware platform of the brushless DC motor’s sensorless control system are designed around the core controller dsPIC33F706, the communication circuit board ATmegal6 and the driver circuit board IPM whose model is 6MBP50RA120. The electric potential zero crossing detection circuit are analyzed emphatically, and the other models are also introduced in theory. Under the integrated development environment of MPLAP IDE v8.53, this paper completed the whole software design of the control system through a lot of on-line debugs and program. Experimental results measured by oscilloscope proved that the brushless DC motor can start from the static state and switch to sensorless state to complete current inside loop and speed outside loop, and the feasibility of the whole control system are verified.