The Influence of the Cam Radial Displacement of a Harmonic Drive on the Angular Displacement of the Output Shaft

Harmonic drives are widely used in drives of machines that have high kinematic accuracy. These are the transmissions that largely determine precision characteristics of the drive. Manufacturing and installation errors of different parts may induce transverse oscillations of the wave generator leading to periodic changes in the angular position of the output shaft and therefore, to an increase in the composite deviation of the harmonic drive. The amplitude of the transverse oscillation of the wave generator depends on its frequency, hence a decision on the possible use of harmonic drives in high-accuracy drives can be made only based on the frequency-response characteristics of the composite deviation. To determine these characteristics theoretically, it is necessary to know the dependency of the rotation angle of the output shaft on transverse displacements of the cam. The authors propose a technique for determining this dependency with the aid of a 3D mathematical model of a harmonic drive. The calculations for the VZP-160 drive show that when transverse displacements of the cam increase, dual-wave gearing can become single-wave gearing. It is established that to calculate the rotation angle of the output shaft at dual-wave gearing, it is necessary to solve a problem of elastic interaction between elements of the drive. Simplified formulae used in various information sources can be used only for single-wave gearing with single-edge tooth contact.

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