This paper deals with the direct torque control (DTC) of BLDC motor drives by using particle swarm optimization technique. BLDC motors have wide variety of advantages like higher speed ranges, higher efficiency, and better speed versus torque characteristics. Direct torque control (DTC) is one of the efficient methods used in variable frequency drives to control the BLDC motor. DTC offers many advantages like fast torque response, no need of coordinate transformation and less dependence on the rotor parameters. In DTC, the estimated flux magnitude and torque are compared with their reference values. The reference torque is generated from the output of the speed regulator (PI controller).Tuning PI parameters (Kp, Ki) are essential to DTC system to improve the performance of the system at low speeds. In conventional PI controller, the performance of the motor may cause unexpected torque disturbances. Particle swarm optimization (PSO) is proposed to adjust the parameters (Kp, Ki) of the speed controller in order to minimize torque ripple, flux ripple, and stator current distortion.The simulation results of BLDC drive employing conventional PI and PSO based PI controllers is compared and evaluatedunder various load disturbances in the MATLAB/simulink environment. KEYWORDS:BLDC motor, DTC, PI, PSO, MATLAB/simulink. I.INTRODUCTIONCurrent researches have been tailored towards developing brushless direct current motors, which are fast becoming alternatives to the conventional dc motor types. The Brushless Direct Current (BLDC) motors are gaining grounds in the industries, especially in the areas of appliances production, aeronautics, medicine, consumer and industrial automations and so on. The BLDC motors are typically permanent magnet synchronous motors that are well driven by dc voltage. Some of the advantages of a brushless dc motor over the conventional brushed dc motors are better speed versus torque characteristics, high dynamic response and high efficiency. Another vital advantage is that the ratio of torque delivered to the size of the motor is higher, and this contributes to its usefulness in terms of space and weight consideration. There are several methods to vary the speed of a BLDC motor over a wide range. Techniques for control of current include vector control, predictive control, dead-beat control, and direct torque control. The most modern technique is direct torque control method (DTC). The DTC offers many advantages like fast torque response, no need of coordinate transformation and less dependence on the rotor parameters. The conventional PI (proportional, integral) control method is widely used in motor control system due to the simple control structure and easiness of design. However tuning the parameters of PI controller is a difficult task. To enhance the capabilities of traditional PI parameter tuning techniques, several intelligent approaches have been suggested such as genetic algorithms (GA) and the particle swarm optimization (PSO).Particle Swarm Optimization is one of the modern a...

ABSTRACT:This paper presents a new direct torque control (DTC) strategy for BLDC motor based on speed behaviour of PI and SMC based DTC of BLDC motor. In conventional direct torque controlled BLDC motor drive, there is usually undesired torque and flux ripple. So tuning PI parameters(Kp, Ki) are essential to DTC system to improve the performance of the system. PI controller is widely used in motor control system due to the simple control structure. In conventional PI controller, the performance of the motor may cause unexpected torque disturbances. To overcome the problems with PI controllers, in this paper, sliding mode controller is proposed to resolve the speed tracking problem for DTC of BLDC motor drive. The simulation results of DTC of BLDC motor drive with PI & SMC controllers are compared in the MATLAB/simulink environment.KEYWORDS:PI and SMC controllers,BLDC motor, DTC, MATLAB/simulink. I.INTRODUCTIONBLDC motors have many advantages over brushed DC motors and induction motors. A few of those have better speed versus torque characteristics, high dynamic response, high efficiency, long operating life, noiseless operation. The permanent magnet brushless dc motor is gaining popularity because of its usage in computers, aerospace, military and robots. The BLDC motor is inherently electronically controlled and requires rotor position informationfor proper communications of the current. The only drawback of conventional dc motors is that they need a commutator and brushes which are subjected to wear& tear and require regular maintenance. In BLDC motors the functions of brushes and commutator were implemented by position sensor and inverter. There are several methods to vary the speed of the BLDC motor over a wide range. The most modern technique is direct torque control method (DTC).The DTC offers many advantages like fast torque response, no need of coordinate transformation and less dependence on the rotor parameters. The conventional PI (Proportional, Integral) control method is widely used in motor control system due to the simple control structure and easiness of design. However tuning the parameters of PI controller is a difficult task. In conventional PI controller, the performance of the motor may cause unexpected torque disturbances. In order to resolves the speed tracking problem for DTC of BLDC motor drive various approaches have been suggested such as sliding mode controller (SMC) and Fuzzy controller, ANFIS controllers etc The proposed sliding mode controller(SMC) is one of the modern controller used to solve speed tracking problemsfor DTC of BLDC motor drive.This controller works irrespective of the parameter variations and load torque disturbances. The SMC method is an excellent control technique and a promising approach for solving the conventional PI controller parameters problem. Purpose of the present work:The objective of the present work is to provide an alternative approach to solve speed tracking problems for DTC of BLDC motor drive.This method uses the principle of Direct Torque Control...