Improved Multiobjective Optimization of Tubular Slotless Permanent Magnet Linear Synchronous Motor for High-Performance Z-Axis Actuators

The z-axis actuator is a critical component in many high-end intelligent equipment, such as surface mount equipment. The tubular slotless permanent magnet linear synchronous motor (TPMLSM) is advantageous in these applications, offering both high thrust density and dynamic response. However, this topology is associated with challenges, including thrust fluctuation and substantial copper losses. To address these limitations, this article proposes an optimization scheme for the motor structure based on an improved multiobjective particle swarm algorithm. To improve efficiency, a simplified analytical model of magnetic field stratification is first developed for the slotless motor structure. The accuracy of this model is verified through comparison against finite element analysis results. The thrust fluctuation of a finite-length stator is then analyzed and the magnetic field distortion and winding inductance imbalance are mitigated by adjusting the length of the stator core, effectively suppressing thrust fluctuations caused by end effects. Building upon this, a multiobjective optimization model is proposed, using dimensionless proportional coefficients as optimization variables. This model simultaneously optimizes TPMLSM output thrust, operating temperature rise, and permanent magnet consumption, yielding a set of Pareto optimal solutions. Finally, based on the optimization results, an experimental prototype has been manufactured and extensively tested, clearly demonstrating the advantages of the proposed solutions.