Enhanced Speed Characteristics of High Torque Density BLDC Motor for Robot Applications Using POEW (Parallel Open-End Winding) Configuration

High torque density motors are widely used in humanoid, wearable, and rehabilitation robots due to their ability to reduce gear ratios, enhance back-drivability, and enable compact and efficient joint actuation. However, their inherently high back-EMF limits speed performance, and safety regulations restrict operating voltage to below 50 V in human-interactive environments. To address these challenges, we propose two innovative winding strategies—Parallel Connected Winding (PCW) and Open-End Winding (OEW)—and evaluate their combined implementation as a Parallel Open-End Winding (POEW) configuration. PCW reduces winding resistance and inductance by implementing two parallel winding paths, which also decreases back-EMF. OEW removes the neutral point and allows full voltage application to each phase. The combined POEW configuration achieves up to 3.5 times higher speed experimentally compared to conventional SCW, without any modification to the motor’s rotor or stator. Experimental torque constant measurements confirmed that all proposed winding configurations maintain torque output, with no significant variation. Although the motor constant slightly decreases in parallel configurations due to increased current and heat, the improvement in speed performance is significant. Therefore, the POEW topology provides a practical and effective solution for enhancing motor performance under voltage-limited conditions, especially in applications requiring both high torque and speed.