Kinematic analysis, structural design and prototype verification for the single-stage nutation drive

Nutation drive has advantages of large transmission ratio, high load-bearing capacity and compact structure, making it a promising solution for precise transmission in various fields such as industrial robots, electric vehicles, and space explorations. However, the nutation drive would be difficult to adapt to the design requirements of different application scenarios because of lacking reliable and easy-to-use design methods. The primary reason for the lack of design methodology lies in the insufficient understanding in kinematic mechanism of the nutation drive. To solve this problem, the present work aims to reveal the motion transmission mechanism of nutation drive and to provide a universal structural design methodology. First, angular velocity analyses for two typical single-stage nutation drives are carried out, clarifying the velocity of each key component in the nutation drive. Second, the transmission ratios of two kinds of nutation drives are derived, respectively. Third, the relationships between the kinematic characteristics and structural parameters of single-stage nutation drive are established and a design process for key structural parameters is subsequently proposed. Then, a case study based on the proposed design methodology is conducted to yield the detail structure of a single-stage nutation drive. Finally, a prototype of single-stage nutation drive is fabricated and its transmission ratio is tested. The testing results show that the average transmission ratio of the nutation reducer is −14.89 and its relative error is just −0.70% compared with theoretical one, while the average fluctuation of the transmission ratio is 0.86 with a relative error of 5.76%. It means that the proposed nutation drive has the potential for stable transmission with low speed fluctuations. The proposed kinematic analysis model and design method is verified.