Design Optimization of High-Torque BLDC Motors with Various Slot/Pole Combinations for Robotic Applications

Robots have been increasingly applied for harsh operating environments, such as disaster rescue, space exploration, and nuclear waste remediation. Robotic arms in such environments with extremely high/low temperatures and air pressure are prone to hardware failures, especially for joint motors and power electronic drives. Brushless DC (BLDC) motors are extensively used in robotic applications because they exhibit high reliability and efficiency. Thus, this paper presents a design optimization approach for high-torque BLDC motors for robotic applications to enhance the reliability and fault-tolerance capability based on a multi-objective genetic algorithm (MOGA). Owing to the inherent advantages of fractional-slot concentrated windings (FSCW) over distributed windings, this paper adopts BLDC motors with various slot/pole combinations. On the contrary, distorted flux distribution is one main drawback of FSCW, which may yield radial forces on the rotor. Moreover, the thermal behavior of the proposed slot/pole combinations is investigated, showing the resulting thermal stress. Finally, a broad comparison of the employed winding layouts is introduced to highlight the effect of the radial forces on the rotor deformation using finite element analysis (FEA). The higher the slot/pole combination, the higher the radial forces and rotor deformation.