Statistical analysis of the influence of tooth geometry in the performance of a harmonic drive
The objective of this research is to determine the influence of gear tooth geometrical variations in the performance of a double wave harmonic drive through statistical analysis. This work incorporates state of the art analytical and numerical models to evaluate kinematic error, load capacity, bending fatigue strength, and pitting. The geometric variables considered in this study include gear modulus, pressure angle, and tooth correction factor. The statistical analysis follows a three-level full-factorial design of experiments. Nonlinear dynamic simulation is accompanied by finite element analysis to estimate contact and bending stresses. Largest bending fatigue strength is also determined. Results demonstrate that gear modulus is the geometric parameter with prevalent influence on the kinematic error, and pitting life is rather high for all geometric variables considered.
Deformation analysis of the flexspline of harmonic drive gears considering the driving speed effect using laser sensors
Accurate description of the elastic deformation of the flexspline is the foundation for optimization design of the structure and conjugate profiles of the harmonic drive gear. This paper proposed an experimental method to investigate the effect of the driving speed on the deformation characteristics of the flexspline. First, an experimental apparatus that integrates a special-fabricated micro-displacement platform and a pair of laser displacement sensors is developed, and the radial displacement of the flexspline is measured in vertical and horizontal directions. Next, the deformation analyses of the flexspline at different driving speeds are performed with our method and the conventional method, and the comparison results reveal that the radial displacement of the flexspline is actually composed of both harmonic and random components, and the amplitude decreases and tends to zero with the increase of the driving speed, especially near the closed end of the flexspline. Last, the mechanisms of the inherent multi-frequency and amplitude attenuation characteristics of the radial displacement of the flexspline are discussed. It is indicated that the impact and friction existing in the flexible bearing of the wave generator is likely responsible for the existence of the random component, and the assumption of linear distribution of the flexspline deformation along the rotating axis is invalid under high speed condition. Our research promotes the further study on the contact-impact problem of the flexible bearing of the wave generator and the transfer characteristic of the elastic deformation of the flexspline.
Chinese theories of theater and performance from Confucius to the present
Through the writings of noted Chinese philosophers, scholars, artists, and critics from the time of Confucius to the present, this rich compendium provides a fascinating guided tour of China's evolving conceptions of theater and performance. The book's more than sixty selections are arranged chronologically to provide a historical overview of four major periods: antiquity to the Song dynasty (fourth century B.C.E.-1279 C.E.); the Yuan dynasty (1271-1368) and Ming dynasty (1368-1644); the Qing dynasty (1644-1911); and the rest of the twentieth century.The writings collected here treat the origins, aesthetic principles, and functions of theater. Some are virtual manuals on playwriting and performance techniques; some describe the practices, conditions, and government policies concerning theatrical performance. Many of the selections forcefully dispute the myth that Chinese theater is valuable in performance but lacking in literature--the fact is that there is an equal, if not more prominent, emphasis on theme and content. What emerges from the writings in "Chinese Theories of Theater and Performance from Confucius to the Present" is a highly evolved and sophisticated aesthetic.The texts are enhanced by Faye C. Fei's extensive introductions and annotative notes that provide essential background and contextual information. She has provided accurate and engagingly written translations of the texts, making the majority of them available in English for the first time. The anthology will appeal to teachers and students of theater and performance, artists interested in Chinese theater and arts, and scholars and historians of Asia. Literary critics, aestheticians, philosophers, and social scientists will also find the volume of interest, since Chinese conceptions of the theater and performance are closely connected to China's general outlook on the humanities.Faye C. Fei is Assistant Professor of Dramatic Arts, Macalester College.