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.
Stress state analysis of harmonie drive elements by FEM
In the paper, a solution to the problem of elastic deformation of thin-walled shell structures with complex shapes within the theory of geometrically non-linear shells has been presented. It is a modification of the Newton-Raphson method. In a variational formulation, the problem is based on a Lagrange’s functional for increments of displacements. The method has been applied to investigations of a harmonic drive, in particular to analysis of the stress state in the flexspline with a variable curvature as well as bearings of the generator. For verification of the obtained results, a more adequate FEM model calculated by ANSYS has been used.
A Novel Harmonic Drive With Pure Involute Tooth Gear Pair
Consider commercially available harmonic drives or strain wave gearings (all patented designs). The tooth profiles of the mating pairs of teeth of the noncircular (pitch curve) flex gear and circular (pitch circle) ring gears are nearly conjugate and noninvolute. Evidently none of them offers ideal gear kinematics. In this paper, we propose a new wave generator (or cam) to drive flex gears of harmonic drives with fully conjugate gear pairs of purely involute profiles. The cam profile is made of circular arcs at the two diametrically opposite contact zones and shifted elliptical curves for the other two zones. The geometric construction is done in such a way that tip interference is properly avoided for both engagement and disengagement with nominally stubbed or full depth tooth involute gears. We develop the theory of geometric and gearing conditions. We have also built a physical model in order to verify the geometry of tooth interference and other relevant gearing kinematics.