Control System Design Of Brushless DC Motor And Its Application On Unmanned Surface Vehicles

To improve the durability of the unmanned surface vehicles(usv), it has become a trend to use hybrid power supply and efficiency electric drives instead of fuel machines. With the background of rudder angle control in usv, this thesis deals with the control system design and torque ripple suppression of brushless dc motor(BLDC). The double closed loop control system is designed and a torque ripple suppression method based on discrete space vector(DSV) modulation combined with phase resistor voltage dropout compensation is proposed. Both the designed control system and the torque ripple suppression method are verified by experiments and simulations, respectively.A detailed introduction of commonly used topologies and conduction patterns is presented. The differences of selective sampling and other modes of sampling are analyzed. For the medium- and low-precision BLDC machines, deviance of the actual and the ideal positions of hall sensors installed on the shaft exists generally. Thus, in this thesis the zerocrossing detection of back electromagnetic force which is one of the key concepts in sensorless control of BLDC is combined with an encoder to implement calibration of the unbalanced hall signals. Double closed loop control of speed is designed on basis of the model of the motor, and discretization of the controllers is also covered. To suppress the torque ripple of BLDC during operation, the common and differential properties of the discrete space vector(DSV) modulation and the conventional 120-degree conduction mode is discussed. The torque ripple during commutation period is studied from the approach of sudden change of phase voltage. Theoretical inference shows that DSV modulation is applicable to replace the 120-degree conduction mode directly when the motor is operated in a low-speed range with certain load applied, moreover, the torque ripple suppression is satisfactory with DSV modulation. As for medium- and high-speed ranges, an extra controller must be introduced to ensure zero-current operation of the silent phase. To take advantage of the outstanding torque ripple suppression performance of the DSV modulation, a simple and easy compensation method is proposed in this thesis, which suppresses the torque ripple during commutation period to a certain degree. Validity of the proposed method is verified via simulation results.As a conclusion, the BLDC drive is applied in the rudder control system of the usv. A center controller assembled from three microchips is built, experiment and test results show that performance of the designed BLDC drive is satisfactory. To facilitate the tuning and monitoring process, as well as the following works such as parameter identification of the boat, control algorithms design and verification, a MATLAB based tuning and monitoring platform is created.