A Review on Structural-Electromagnetic Aspects of Two-Degree-of-Freedom Rotary-Linear Motors for Automation Applications

The two-degree-of-freedom rotary-linear motor (2DoFRLM), as a promising high-integration mechatronics device, can achieve rotary, linear, and helical motions with a single motor, which is suitable for automation applications fields such as robotic arms, drilling machines, and machine tools. Therefore, it has attracted the attention of both industry and academia, resulting in a large number of different topological designs with their own unique features and operating principles. This article comprehensively reviews the over four decades of literature in this field. The structures of common 2DoFRLMs are introduced, and the motors are classified into three categories based on their winding structure and electromagnetic relationships. Then, the operating mechanisms of different types of motors are systematically analyzed, and their characteristics, applications, and performance are compared. Finally, the recommendations are offered for possible future developments.