Received: 4 August 2021 Revised: 6 September 2021 Accepted: 9 September 2021 DOI: 10.37917/ijeee.17.2.15 Early View | December 2021 This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2021 The Authors. Iraqi Journal for Electrical and Electronic Engineering by College of Engineering, University of Basrah. https://doi.org/10.37917/ijeee.17.2.15 https://www.ijeee.edu.iq 129 Iraqi Journal for Electrical and Electronic Engineering Original Article  Open Access Optimized Sliding Mode Control of Three-Phase Four-Switch Inverter BLDC Motor Drive Using LFD Algorithm Quasy S. Kadhim* 1 , Abbas H. Abbas 1 , Mohammed M. Ezzaldean 2 1 Electrical Engineering Department, University of Basrah, Iraq 2 Department of Electrical Engineering, University of Technology, Iraq Correspondence * Quasy S. Kadhim, Electrical Engineering Department, University of Basrah, Basrah, Iraq. Email: qusay.eifaan@uobabylon.edu.iq Abstract This paper presents a low-cost Brushless DC (BLDC) motor drive system with fewer switches. BLDC motors are widely utilized in variable speed drives and industrial applications due to their high efficiency, high power factor, high torque, low maintenance, and ease of control. The proposed control strategy for robust speed control is dependent on two feedback signals which are speed sensor loop which is regulated by Sliding Mode Controller (SMC) and current sensor loop which is regulated by Proportional-Integral (PI) for boosting the drive system adaptability. In this work, the BLDC motor is driven by a four-switch three-phase inverter emulating a three-phase six switch inverter, to reduce switching losses with a low complex control strategy. In order to reach a robust performance of the proposed control strategy, the Lévy Flight Distribution (LFD) technique is used to tune the gains of PI and SMC parameters. The Integral Time Absolute Error (ITAE) is used as a fitness function. The simulation results show the SMC with LFD technique has superiority over conventional SMC and optimization PI controller in terms of fast-tracking to the desired value, reduction speed error to the zero value, and low overshoot under sudden change conditions. KEYWORDS: Four Switch Inverter, Sliding Mode Speed Controller, Low Cost BLDC Motor Drive, LFD Algorithm, PI Controller. I. INTRODUCTION BLDC motor is a combining the advantages of DC motor with AC motor to produce a new special motor and it responds to the rapid development of power electronic technology, control theory, and permanent magnetic materials [1]. BLDC motors are widely utilized in variable speed drives and industrial applications due to their high efficiency, high power factor, high torque, low maintenance, and ease of control [2]. A BLDC motor produces to provide continuous torque by combining trapezoidal back EMF with square-wave currents [3]. A six-switch, three-phase inverter and three Hall-effect position sensors are used to give six commutation points for each electrical cycle in a traditional BLDC motor drive. In a fractional horsepower BLDC motor drive for household applications, cost minimization is critical. In recent years, elimination of driving components such as power switches was achieved. As a result, efficient algorithms should be created to get the desired results. For a three-phase BLDC motor drive, a four-switch, three-phase inverter (FSTPI) topology was recently developed and implemented. The key features of this topology are the reduction in the number of power switches, dc power supply, switching driver circuits, losses, and total price [4]. Conventional control approaches, on the other hand, are ineffective for current regulation in the four-switch architecture. Based on the independent control of the phases' current, [4] devised a new and effective current control strategy to achieve 120 rectangular currents. In order to maintain the BLDCM is stable under various condition such as variable loads, and parameters change, the control approach must be adaptable, resilient, accurate, and easy to apply [5,6]. Linear and nonlinear feedback controls are the two types of feedback controls available. The linear controller has been demonstrated to be an effective and simple control architecture in a study of linear control techniques such as Proportional-Integral-Derivative (PID) control in [7]. Nonetheless, traditional linear control has a number of significant merits. The linear control has several disadvantages, including the fact that it is only useful for slow-speed systems and is susceptible to uncertainties [7]. In light of these flaws, nonlinear controls such as model predictive control (MPC) [8], sliding mode control (SMC) [9] have been developed to