Design And Analysis Of Harmonic Autuator Based On Giant Magnetostrictive Material

With the development of intelligent manufacturing and continuous adjustment and upgrading of the social industry,intelligent robots continue to flow in non-industrial fields such as medical care,services,and entertainment.The compact and lightweight design of the robot’s modular joints is of great significance to the development of the intelligent robot industry.Most of the existing robot joints use driving motor as the power source,the wave generator spins and the flexible spline deformed meshing with the circular spline,realizing single-degree-of-freedom swing or rotation of the robot arm,which has a low space utilization and limited application in low-speed operation and quick response fields.In order to expand the traditional robot drive transmission mode and improve the compactness of the robot’s modular joints,smart materials are introduced to improve the design of the robot’s modular joint drive,thereby forming a new type of robot modular joint drive that integrates driving and transmission.In this paper,based on the principle of harmonic transmission,a giant magnetostrictive harmonic actuator that can directly force the the flexible spline deformed and meshed with the circular spline.The research results provided a theoretical basis for intelligent robots joint design.The main research contents of this article are as follows:(1)Introduced the principle of harmonic transmission,and combined with the design requirements of the actuator,then designed the structural parameters of the three basic components of the harmonic reducer.Analyzed and compared a variety of harmonic gear tooth shapes,based on the principle of gear meshing,the design and research of the tangent double arc tooth profile were introduced.Based on the shell theory and small deformation assumptions,the calculation model of the neutral layer deformation function of the flexible spline and the equivalent normal stress of the wave generator has been derived.To provide design basis for harmonic actuator,finite element analysis software is used to simulate and analyze the harmonic reducer.As a result,the radial deformation of the flexible spline and the normal stress distribution of the wave generator are determined.(2)Explained the design concept of the harmonic actuator,and combined with the deformation characteristics of the flexible spline,the layout of the actuator has been designed,and then the displacement coefficient of the actuator in different phases is calculated.In order to achieve a larger range of displacement output,flexible film and metal bellows are combined to assemble a hydraulic micro-displacement amplifying mechanism.Based on Kirchhoff-Love plate and shell theory and finite element method,the mechanism parameters and theoretical magnification of the amplifying mechanism are calculated.According to the displacement output requirements and the stability conditions of the structure,combined with the preload characteristics,the structure size of the magnetostrictive bar and the pre-compressed disc spring were designed.Based on the Ampere loop law,the calculation model of the coil axis magnetic field intensity was established,and the values of the coil length-to-diameter ratio and energy loss parameters were optimized.At Last,the distribution of magnetic field intensity was analyzed.(3)According to the mechanism of double-frequency effect of magnetostrictive materials,and established the bias magnetic field by combinig permanent magnet disc and segmented magnetostrictive rod.Established the calculation model of the magnetic flux per unit cross section of the magnetostrictive rod in the equivalent magnetic circuit by simplifing the magnetic circuit structure,then combined with Navier equation and Maxwell equations,the calculation model of vector magnetic potential and magnetic field intensity at any point in the coil is improved established.Based on the harmonic actuator electromagnetic analysis finite element model,the influence of different structural parameters of the bias permanent magnet disc on the magnetic field distribution is analyzed,which provides a reference for determining the reasonable driving magnetic field and bias magnetic field parameters of the harmonic actuator.(4)Studied the variational energy theory of magnetostrictive materials,and combined with the internal magnetic domain density function,the physical meaning of the differential form of Gibbs free energy density function is analyzed.Using the function approximation method,the nonlinear stretching strain function of the magnetostrictive material is solved,and the theoretical calculation model of the displacement output of the harmonic actuator is established.Introduced the magneto-mechanical coupling module,and established the electro-magnetic-mechanical multiphysics coupling model of harmonic actuator.According to the parametric scanning method of the finite element analysis software,the influence of different structural parameters of the bias permanent magnet disc on the displacement output and mechanical characteristics of the harmonic actuator were analyzed,and finally the design parameters of the driving coil and the bias magnetic field were determined.