Sensorless Open-Loop Speed and Torque Control of BLDC Motor

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Sensorless Open-Loop Speed and Torque Control of BLDC Motor

Girish Chandu Dhawak , Prashil Siddharth Sukhdeve , Aditya Abhimanyu Gawai , Mohit Gajanan Bawankar , Dr. Sachin Jolhe

DOI : 10.46335/IJIES.2026.11.3.2

Abstract—This paper presents a cost-effective, sensorless, open-loop speed and torque control architecture for a three-phase Brushless DC (BLDC) motor driven by the PIC18F25K22 8-bit microcontroller. Unlike conventional BLDC drive systems that rely on Hall-effect sensors or back-EMF zero-crossing detection, the proposed design achieves phase commutation solely through time-based PWM sequencing generated by the on-chip CCP modules. The high-side/low-side gate driver pair IR2102 controls IRFZ540 power MOSFETs rated at 100 V / 28 A, providing robust switching for each motor phase. A 16x2 LCD connected in 4-bit mode on PORTB displays real-time PWM duty cycle and estimated rotor speed, enabling operator monitoring without external instrumentation. The complete system is verified through Proteus simulation. Comparative analysis demonstrates that the proposed design achieves equivalent steady-state speed regulation under light-load conditions to sensor-based implementations, while reducing system BOM cost by eliminating Hall sensors and their associated signal-conditioning circuitry. The architecture is reproducible, pedagogically transparent, and constitutes a practical foundation for future closed-loop upgrades.