Optimally Designed BLDC Motor Equipped with Different Winding Layouts for Robotic Arms

Robots have shown promising prospects in numerous applications, such as space exploration, disaster rescue, and nuclear waste remediation. Due to harsh environmental conditions, robotic arms are vulnerable to joint failures, especially the faults with joint motors and power electronic drives. Thus, optimal design of the employed motors is paramount to achieve a reliable and fault-tolerant robotic arm. The employment of brushless DC (BLDC) motors in robotic applications is of particular interest, not only for high reliability but also for high efficiency and high torque-producing capability. BLDC motors can be equipped with distributed and fractional-slot windings; however, fractional-slot concentrated winding (FSCW) outperforms distributed winding owing to their notable advantages, e.g., high slot fill factor, short-end turns, and low cogging torque. On the other hand, the resultant flux distribution is highly distorted. Therefore, this research presents the design optimization of BLDC motors with two fractional-slot windings, namely, non-overlapped 18-slot/16-pole and overlapped 18-slot/10-pole, based on the finite element methodology (FEM). Selected motors are first designed based on the sizing equations and further optimized using a multi-objective genetic algorithm (MOGA). Finally, a thorough performance comparison of the proposed winding configurations is conducted to highlight the optimal slot/pole combination for robotic applications.

I. Introduction

Robots have been increasingly utilized in remote, hazardous, and safety-threatening environments owing to their enhanced safety, productivity, and flexibility [1] - [3]. In fact, the robot joint motors and their associated power electronic drives are prone to hardware failures due to the harsh environmental conditions [4], [5]. These failures may yield malfunction of the whole robotic arms and thus economic losses. Therefore, optimal design of the joint motors is crucial to enhance system reliability and further develop fault-tolerant methodology for the joint motors and drives [6].