Unraveling the Vibration Mechanism in Robotic Harmonic Drive: Coupled Dynamics Under Cyclic Inertial Loading and Installation Errors

As a key component in robots, the harmonic drive directly impacts the reliability and lifespan of the whole system. Due to the cyclic inertial loading and installation errors, the harmonic drive possesses unique but complicated vibration features. This study proposes a novel dynamic modeling method for the harmonic drive to unravel its coupled vibration mechanism and frequency distribution characteristics. To represent the gear meshing force between flexspline and circular spline, as well as the contact roller forces of the thin-wall bearing, two contact mechanics models are developed. Actual excitations are modeled by considering installation errors and cyclic inertial loading. A dynamic model considering translational and torsional directions is then established to unravel the coupled vibration of the primary components in the harmonic drive. Through theoretical and simulation analyses, the vibration features of the harmonic drive exhibit almost no meshing frequency components. Experiments under different transmission ratios and input speeds confirm the effectiveness of the proposed dynamic model. The verified theoretical interpretation of vibration features has provided fundamental insights into the dynamic behavior of harmonic drive.