Introducing Kinematic Fundamentals of Strain Wave Gear for Robotic Arm Joint

Robotic arms play an important role in factory automation. A key mechanical component in robotic arm joint is a gear speed reducer called strain wave gear. This paper presents the kinematic fundamentals of strain wave gear. Three topics will be covered. First, systematic method to calculate gear ratio for different types of the strain wave gear. Second, the unique tooth geometry used for strain wave gears to maintain the conjugacy of meshing teeth. Third, typical materials and manufacturing process to make such gears. The topics are from the authors’ research in strain wave gear. This paper’s goal is to break the barrier between applications in robotic arm industry and engineering education in academia. From teaching effectiveness evaluation questionnaire, 87% students established the basic concepts after one lecture. 33% students can correctly calculate the speed ratio after one lecture. Homework practices are needed for the students to use the gear ratio equation correctly.