Design of a harmonic drive test apparatus for data acquisition and control

Abstract

Harmonic drive gear reducers were developed during the mid-1950's and are used in many industrial and military applications. The harmonic drive is a compact, "in-line" gear reducer capable of producing reduction ratios of up to 320:1. The devices are known for their efficiency and precision, but they also possess undesirable qualities characterized by nonlinear behavior. These undesirable aspects include the presence of both static and dynamic friction, flexibility (compliance), and kinematic, or positional, error. In the thesis, the mechanical design of a test platform for the study of the system nonlinearities was developed and fabricated. Experimental testing through computer controlled data acquisition validated the apparatus as a system for the examination and control of kinematic error. A new model for kinematic error was developed for the test system. Observations were made concerning the way in which flexibility effects the magnitude of the kinematic error. PD control schemes were implemented in both motor state and local state feedback control efforts. The load state feedback effort successfully compensated for the effects of kinematic error during regulation of the load position. The experimental results were compared to a model and discussed in detail.