International Journal of Power Electronics and Drive Systems (IJPEDS) Vol. 16, No. 1, March 2025, pp. 106~116 ISSN: 2088-8694, DOI: 10.11591/ijpeds.v16.i1.pp106-116  106 Journal homepage: http://ijpeds.iaescore.com Rounding function-based zero crossing detection for a sensorless BLDC motor control Musa Mohammed Gujja 1 , Dahaman Ishak 1 , Muhammad Najwan Hamidi 1 , Mohamed Salem 1 , Mohamad Nazir Abdullah 1 , Khalil Alluhaybi 2 1 School of Electrical and Electronic Engineering, Universiti Sains Malaysia, Penang, Malaysia 2 Department of Electrical Engineering, College of Engineering, Taibah University, Al-Madinah Al-Munawwarah, Saudi Arabia Article Info ABSTRACT Article history: Received Jul 3, 2024 Revised Sep 12, 2024 Accepted Oct 23, 2024 Permanent magnet brushless DC (PMBLDC) motors are favored for their low maintenance, high reliability, and efficiency, making them ideal for industrial, domestic, military, aerospace, and robotics applications. Sensor less control is the most preferred technique for PMBLDC motors due to its reliability and cost-effectiveness, eliminating the need for physical sensors. A crucial aspect of sensor less control is accurately detecting the point of zero crossing of the back electromotive force (BEMF) signals. Traditional methods, such as rotor position estimation, input observers, and AI-based strategies, can suffer from high ripples and computational inefficiencies. This paper introduces an approach using the rounding function to determine the point of zero crossing, aiming to enhance precision and reduce computational overhead. The rounding function converts continuous BEMF signals into discrete signals, minimizing ripples and facilitating accurate zero-crossing detection. This method improves detection accuracy while simplifying computation demands. Validation was performed through a MATLAB Simulink simulation and an experiment using the F28379D microcontroller, gate driver, and a six-switch inverter. The results demonstrate the effectiveness of the proposed approach, showing agreement between experimental and simulation outcomes. Keywords: BEMF sensing BLDC motor Feedback circuit Rounding function Sensor less control Zero crossing This is an open access article under the CC BY-SA license. Corresponding Author: Dahaman Ishak School of Electrical and Electronic Engineering, Universiti Sains Malaysia Nibong Tebal, Penang 14300, Malaysia Email: dahaman@usm.my 1. INTRODUCTION Permanent magnet brushless DC or PMBDC motors are widely used for various applications due to their high speed, low maintenance, small size, and reliability. Typically, PMBLDC motors rely on Hall effect sensors for rotor position detection enabling commutation. This commutation sequence is essential for strategizing different control techniques for PMBLDC motors, as noted in [1]-[9]. However, having sensors increases overall cost, complexity, and potential reliability issues. To overcome the drawback of sensor-based control, sensor less control techniques, which estimate rotor position using electrical signals such as BEMF, have garnered significant attention. Back electromotive force or BEMF is the voltage generated by the rotating motor, which is proportional to the rotor speed and can be used to infer the rotor's position. A critical aspect of sensor less control is accurately detecting the zero-crossing point of the BEMF signals. Several methods for detecting BEMF zero-crossing have been proposed and explored through simulations. For instance, zero-crossing detection using pulse width modulation (PWM) was explored by [10], who developed a technique that detects rotor position through PWM-based zero-crossing detection to drive the motor. To enhance position estimation, flux linkage estimation was studied by [11], who integrated converter-