Robot vibrations caused by torque ripples in power transmission mechanisms.

Abstract

When an industrial robot with a power transmission mechanism such as a harmonic drive gear is operated, vibrations resulting from the torque ripple of the power transmission mechanism are frequently generated. However, few studies on robot vibration characteristics owing to torque ripples have been reported. In this paper, the vibrations of a horizontal two-link robot are investigated with consideration given to the torque ripple and the nonlinearity of the power transmission mechanism. In the numerical analysis, the torque characteristics are assumed to be the product of the nonlinear function of the torsional angle of the gear teeth and the torque ripple represented by means of the the Fourier series of the rotating angle of the input axis. Numerical simulation is carried out, and the effects of the torque ripple and the nonlinearity on the vibration characteristics of the robot are demonstrated. The experiment also shows that the torque ripple can cause a good deal of vibration.