Tham khảo tài liệu 'electric machines and drives part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Swarm Intelligence Based Controller for Electric Machines and Hybrid Electric Vehicles Applications 169 max max min iter__ max iter 37 Using the above equations a certain velocity can be calculated that gradually gets close to pbest and gbest . The current position searching point in the solution space can be modified by the following equation 1 Sk vk 1 i i i 38 Where vk Current velocity of agent i at iteration. v i k 1 Modified velocity of agent i r1 r2 random number distributed 0 1 Ski current position of agent i ffl weight function for velocity of agent i c1 c2 positive constants c1 c2 4 . max Initial weight min Final weight itermax Maximum iteration number iter Current iteration number. In 35 the losses formula is the cost function of the PSO. The particle swarm optimization PSO technique is used for minimizing this cost function. The PSO is applied to evaluate the optimal rotor flux that minimizes the motor losses at any operating point. Figure 3 presents the flowchart of the execution of PSO which evaluates the optimal flux by using MATLAB SIMULINK. The optimal flux is the input of the indirect rotor flux oriented controller. The indirect field-oriented controller generates the required two reference currents to drive the motor corresponding to the optimal flux. These currents are fed to the hysteresis current controller of the two-level inverter. The switching pattern is generated according to the difference between the reference current and the load current through the hysteresis band. Figure 4 shows a whole control diagram of the proposed losses-minimization control system. Fig. 4. The proposed losses minimization control system. 170 Electric Machines and Drives Simulation results In this section the proposed application is implemented numerically using MATLAB-SIMULINK to validate the performance of the proposed control strategy. The motor used in this study has the following parameters which were measured by using experimental tests. Table 1 shows