Overview of Rotary Linear Machines: Principles, Classifications, and Drive Systems

Rotary linear machines (RLMs) are gaining significant attention due to their ability to achieve two degrees of freedom (2-DoF) motion into one actuation device. This capability offers numerous advantages, including high integration, compact structure, and enhanced reliability. As a result, RLMs hold promising application prospects in fields such as robotics, industrial automation, and marine multi-energy utilization systems, providing novel solutions for various challenges. However, there is a lack of comprehensive studies on the development history of RLMs, as well as systematic comparative analyses. This paper proposes a new classification of RLMs based on different flux-motion patterns, dividing them into two categories: longitudinal flux and transverse flux, aims to provide a thorough overview of the evolution, working principles, machine design, performance evaluation, and applications of RLMs, providing new perspectives and guidelines for practical implementations. Furthermore, a qualitative performance assessment and comparative study of different RLM types are presented, highlighting their respective strengths, weaknesses, and suitable application scenarios. Finally, the paper discusses the future research challenges and development trends in the field of RLMs, and suggests that transverse flux RLMs hold great promise for future applications in new energy, multi-energy utilization, and robotics due to integration.