| Traditional gear(such as cylindrical gears and bevel gears)transmission mechanisms usually have only one degree of freedom of motion.However,with the development of emerging fields,like artificial intelligence and bionic joint,the traditional gear mechanisms have been unable to meet the requirements of the emerging field for multi-degree of freedom transmission.Therefore,the thesis proposes a spherical gear with three degrees of freedom,which can realize the pitch,partial pendulum and rotary motion.The transmission devices with the spherical gear as the core have omnidirectional motion characteristics,which can easily realize the spatial motion that can be accomplished by combining several pairs of gears,so as to realize the lightweight design of transmission structure.The thesis mainly studies the spherical gear with three degrees of freedom,and analyzes its tooth surface generation principle,tooth surface contact characteristics and structure optimization and simulation of spherical gear,etc.The main research contents are as follows:1)By analyzing the structural characteristics and motion principle of the spherical gear,a kind of spherical gear with three degrees of freedom was proposed,which was formed by the intersection of ring teeth and spherical cone teeth.Based on the generating principle of plane involute and spherical involute,the tooth profile surface equations of annular tooth surface and spherical cone tooth surface were deduced respectively.The simulation model and 3D model of two tooth profile surfaces were obtained in software MATLAB and Pro/E,and then the 3D accurate modeling of spherical gear was realized.2)Based on the principle of differential geometry,the main curvature changes of the conjugate tooth surfaces of the ring tooth and the spherical cone tooth at the contact point were studied respectively,and it was deduced that the contact forms of the two tooth surfaces and their conjugate tooth surfaces were all point contact.According to the kinematic analysis of the ring tooth and the spherical cone tooth,the contact equations and contact points of the two tooth surfaces were obtained respectively.The finite element analysis of spherical gear pairs under different angles of meshing was carried out by Workbench.The results showed that the maximum stress value of the gear teeth followed a law of first decreasing and then increasing as the increase of angles of meshing of two spherical gears.3)According to the characteristics of the tooth profile of the spherical gear,the volume function and the contact ratio function of the spherical gear were derived,and the volume and the contact ratio functions of spherical gear were combined under multiple constraints to establish the multi-objective optimization function of the spherical gear structure.Based on the standard particle swarm optimization algorithm and the improved particle swarm optimization algorithm to optimize and analyze spherical gear,the analysis showed that the improved particle swarm optimization algorithm had a better effect.The result was that the volume of the spherical gear decreased by 18.98%,and the contact ratio of ring tooth and spherical cone tooth increased by 5.36% and 7.86%,respectively.4)The spherical gear universal joint mechanism was established according to the optimized spherical gear.Based on the coordinate transformation theory,the kinematics law of the spherical gear mechanism was analyzed,and the forward and inverse kinematics equations were obtained.The spherical gear universal joint mechanism was established in Pro/E and the motion simulation was carried out.The simulation results finally showed that the spherical gear mechanism transmission was accurate and stable. |
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