Towards Smoother Linear Locomotion Through Combined Linear Machine Structural Optimization Methods

Permanent Magnet Linear Synchronous Motors (PMLSMs) are the dominant actuation solution for high-end manufacturing equipment, such as semiconductor lithography systems, owing to their superior force density and direct-drive capabilities. However, the inherent thrust ripple—comprising cogging force, end effects, and harmonics—severely compromises their ability to achieve the nanoscale tracking accuracy required for precision metrology. This paper presents a comprehensive review of structural optimization techniques aimed at suppressing thrust ripple to ultra-low levels suitable for high-precision applications. The optimization methodologies are systematically categorized into Permanent Magnet (PM) modification, core structure optimization, end-effect mitigation, and topological innovations. Beyond analyzing individual techniques, this review critically evaluates the synergistic efficacy of combined optimization strategies, identifying complementary pairings that maximize ripple suppression while minimizing the trade-off with average thrust. Finally, the paper discusses the impact of manufacturing tolerances on optimization robustness, providing a roadmap for designing next-generation, high-fidelity linear motion systems.