Simulation Study On Load Meshing Performance Of Harmonic Gears Based On Flexible Wave Generato

Harmonic drive are widely used in aerospace,robotics,and precision measuring instruments because of their small size,high transmission accuracy,and large loadbearing capacity.During working process,the flexspline is forced by the wave generator to undergo periodic deformation to achieve the meshing motion with the circular spline.As a key component in the wave generator,the flexible bearing has an important effect on the meshing performance of the harmonic drive.In this paper,the finite element model of harmonic gear including flexible bearing wave generator is established,and the effects of ball position and radial stiffness of flexible bearing on load meshing performance are analyzed.Firstly,APDL in ANSYS is used to parametrically model the three-circular arc spatial tooth profile harmonic drive.The rigid wave generator is expressed by the isometric surface of the outer profile of the cam,and the contact analysis solution with the inner wall of the flexspline to obtain the no-load deformation of the gear ring and the position of the teeth of the flexspline tooth.The minimum circumferential side clearance between the teeth of the flexspline and circular wheels is calculated to obtain the side clearance distribution of the spatial tooth profile harmonic drive.Simulation of small load,rated load to instantaneous maximum permissible torque by applying gradually increasing angular displacement of the circular spline.The meshing forces and contact pressures under different load conditions are solved to evaluate the load meshing performance of spatial profile harmonic drive.The results show that the triarc spatial tooth profile harmonic drive has a wider tooth contact area in the axial and a more uniform mesh force distribution in the circumferential direction.Secondly,to investigate the effect of radial stiffness of flexible bearings on load engagement performance,a flexible wave generator containing cams,inner and outer rings of bearings,and discrete balls is established.The displacement conditions of the flexible wave generator are set with the actual operating conditions to simulate the load meshing performance of Harmonic drive under the same load conditions.The radial stiffness of flexible bearing is analyzed by the force of flexible bearing ball and the radial displacement of bearing outer ring under load condition,and the variation law of radial stiffness of flexible bearing with load is obtained.The effect of ball support position on the distribution of meshing force is compared through the analysis of the distribution of meshing force and the change of contact pressure.Based on the engagement force distribution under the action of two wave generators,the effect of radial stiffness of flexible bearings on the engagement performance is analyzed.The results show that the radial stiffness of the tooth in the ball-supported position is large and bears more meshing force.The greater the load,the greater the effect of the radial stiffness of the flexible bearing on the engagement force.The position of the tooth body in the cross section supported by the ball is where the contact pressure is greatest.Finally,based on the finite element model,the effect of the clearance between the flexible wheel and the wave generator and the clearance of the flexible bearing on the torsional stiffness is analyzed,and compared with the experimental results of the physical prototype torsional stiffness.The results show that the torsional stiffness increases with the number of meshing teeth.The torsional stiffness of Harmonic drive considering the effect of flexible bearing stiffness is closer to the experimental results.The clearance and windage conditions have the greatest effect on the torsional stiffness under small load condition.