Analysis And Research Of Harmonic Drive In Flexible Joint Of Robot

Harmonic drive is a common mode to transfer the motion in the flexible joint of a robot, and is provided with many advantages, such as small volume, light weight and high drive ratio. However, because harmonic drive mainly relies on elastic deformation of flex-spline to transfer motion, the flexibility of robot joint is more notable, which means low stiffness of joint, and vibration occurs during operation process, which lead to hard terminal positioning. So it’s significant to study the stiffness, load distribution, fatigue life and modal parameters. Based on referring to plenty of relevant reference material, this article research the basic theory and accomplish the simulation analysis according to the existing five-DOF lettering robot.(1) According to the fundamental principles of harmonic drive, based on establishing the kinematic model of harmonic drive, this paper build the formula of the tooth flank equation of flex-spline and circular-Spline, and accomplish the kinematics simulation of harmonic drive.(2) This paper plot the tooth flank equation of flex-spline and circular-Spline by matlab, and calculate the distribution of engagement flank clearance. By analyzing the deformation under the specific load, this paper calculate the stiffness of a single-tooth. According to the distribution of clearance and the stiffness of a single-tooth obtained, this paper give the regularities of engaging force distribution.(3) By establishing the finite element model of harmonic drive, this paper analyze elastic deformation, stress distribution and fatigue life of flex-spline under the condition of no load. By using the finite element method, this paper analyze the stress distribution and the deformation under the specific load, then calculate the stiffness of a single-tooth. Compared the elastic deformation and the stress distribution under different structure parameters, this paper point out that less thickness and length of flex-spline could reduce the deformation and stress. By simulation under the condition of on load, this paper calculate the stiffness of the flex-spline, which is useful for the research of robot joint.(4) By modal analysis with finite element method, this paper get first 12th order modes and resonant frequency. According to the influence under different load, it’s clear that the resonant frequency increases when load increases, but the influence is not so notable.