Search

Harmonic drives are the core components to enable movement in industrial robots. Unfortunately, the deformation of flexspline causes obvious partial axial load on gear engagement. This synthetic error leads to a series of additional problems, such as the deterioration of transmission quality, and the reduction of both precision and fatigue life. This study focuses on a harmonic drive with a double circular-arc tooth profile. A coordinate transformation is carried out based on the kinematics of harmonic drives. On this basis, the conjugate tooth profile of a circular spline is derived. A simulation model is developed based on the motion relationship for harmonic transmission. The effect of inhomogeneity of the load distribution on the surface of the gear teeth was investigated using the partial axial-load index. The effect of different factors on the partial axial load is analyzed. To reduce the effect of partial axial load of flexspline, we select a suitable material and wall thickness. For a certain practical range, both tooth width and chamfering of the flexspline teeth help reduce the partial axial load and increase the flexspline length. These conclusions enable improvements of future designs of reliable flexspline.

Harmonic drive is an indispensable device for robotic joint, and transmission accuracy of harmonic drive is one of its most important performance indexes. Due to the unsystematic research on the accuracy of harmonic drive, the accuracy consistency of harmonic drive is poor, and the prediction accuracy is seriously insufficient. This study focuses on modeling of transmission error system and prediction of transmission accuracy. Through tracing analysis of transmission error of harmonic drive, a transmission error model including manufacturing, assembly and tooth profile error is established. Based on Rayleigh distribution of error sources and considering multi-tooth meshing effect of harmonic drive, the transmission accuracy prediction model is built. Tooth profile error is measured by gear measuring center, dimension error and geometric tolerance are gauged by coordinate measuring machine. The transmission accuracy of three types harmonic drive (SHG14, SHG20 and SHG25) is measured by harmonic transmission error test bench under rated conditions. The comparison results show that the difference between the predicted and experimental values is less than 15%, which proves the validity of the accuracy prediction model. Prediction method play a crucial role for accuracy control of harmonic drive system.

In the bolt tightening control, when the input torque is given, the complicated friction phenomenon at the bolted joint interface will lead to the non-uniqueness of the pre-tightening force. Moreover, due to the coupling effect of uncertain physical factors such as the geometric tolerance, assembly error, bolt tightening sequence, etc., an inclination angle of the bolted joint interface will appear, so the pre-tightening force becomes more complex. To this problem, firstly, a friction model with an inclination angle is established from a micro-macro perspective. Then the finite element method is used to analyze the bolt tightening behavior with different inclination angles. Finally, the correctness of this model is verified by the tightening experiment. The results show that surface topography parameters D and G and an inclination angle β have significant effects on the friction coefficient, because surface topography affects the real contact area and contact load distribution, resulting in the change of friction coefficient, thus affecting the bolt pre-tightening force.

Harmonic reducer is the core part of robot joint, its tooth shape design theory and meshing characteristics will directly affect the motion control accuracy and vibration characteristics of robot. This paper studies the meshing process of the circular spline and flexsplines of the harmonic reducer based on the double arc profile and the elliptical wave generator. The main innovation of this research is to take the input angle of the wave generator as an independent variable, which more clearly represents the enveloping process and meshing interval distribution of the tooth profile. The results show that the secondary meshing process of the double circular arc tooth profile exists on both sides of the long axis of the wave generator. But the second conjugate contact interval is small, so the optimization of tooth shape should focus on the first conjugate interval. This study provides a theoretical basis for the design of tooth profile parameters of harmonic reducer.

The research focus on a domestic Double Tauren EDM machine, Analysis of the deformation of the spindle head Y axial and Z axial in the machine tool by simulation analysis. The 3D model is built and simplified by Solid works software, then analysis the static deformation by ANSYS software. In considering the effect of gravity, get the Y axial and Z axial displacement of the spindle head installation datum centroid point O. By changing the stroke of the Y axis and the Z axis, the deformation data corresponding to different travel are obtained. According to the stroke-displacement simulation data, the stroke-deformation curve is fitted, and the corresponding mathematical expression is obtained for the error compensation.