| It is of great significance to study intelligent reconfigurable mechanism and robot with the ability of active adaptation to changeable environment and passive adaptation to emergencies,which is of great significance to the innovation and development of advanced manufacturing field and new generation robots in China.There are few existing multi-mode,reconfigurable structures.In the aspect of structural design,there is no systematic method.The configuration is often based on the designer’s sudden inspiration,and the driving mode is not ideal.The innovation design of multi-mode parallel mechanism is an important research content of mechanism.This paper introduces different types of multi-mode branched chain into the design of multi-mode parallel mechanism,and studies a kind of reconfigurable parallel mechanism with multi-mode characteristics,reduces the number of driving pairs and branch chains,and improves the adaptability of the mechanism to complex working conditions.The motion mode of the spherical 4R mechanism is analyzed.The influence of the structure parameters on the motion mode of the mechanism is studied.First,the parallel mechanism with 2R1T and 3R,2T1R and 2R1T modes are synthesized by using displacement manifold theory.The degree of freedom of the mechanism under different motion modes are analyzed by using the screw theory,and the feasibility of selecting the driving pair of the branch chain is analyzed.The new mechanisms can be control by using three driving pairs under the general configuration of two modes of motion.The freedom of the mechanism is 4 under the transformation of two motion modes.Based on this kind of mechanism,a parallel mechanism is designed to realize the mechanism change degree of freedom.Second,Based on the parallel mechanism with 2R1T and 2T1R motion mode,after the parallel mechanism of plane parallelogram and rotation pair are connected in series on the moving platform,a hybrid multi-mode branch chain is proposed.The motion mode of the series chain and the hybrid chain with multi-mode are analyzed.The paper analyzes the degree of freedom of the mechanism with series and hybrid multi-mode branch chain in the process of motion mode transformation by using the screw theory,and verifies the rationality of the selection of driving pair under different motion modes.When analyzing the rationality of the mechanism freedom and the selection of the driving pair,different linkages are selected as the moving platform,which simplifies the analysis process.The results show that the parallel mechanism with the hybrid branch chain has 3T,2T1R,2R1T,and 3R,2R1T,2T1R motin modes respectively.When the mechanism is in the general configuration of the three modes,the three driving pairs can control the mechanism.When the motion mode of the mechanism is transformed,it is necessary to move to the common configuration of two modes.When the mechanism is in the constraint singular configuration when the motion mode is transformed,an auxiliary driving pair is needed to realize the transformation of the mechanism motion mode.Third,this paper presents a method for the analysis of the motion mode of spherical 4R mechanism under the condition of uncertain structural parameters.Firstly,the kinematic equation of mechanism displacement is transformed into algebraic equation by half-angle formulas.Through the condition of factorization of the two variable algebraic equation,the conditions for the structural parameters of the mechanism are obtained when the kinematic equation can be decomposed by prime decomposition.Then,the kinematic equation is parameterized to determine the form of factorization.When the joint angle of mechanism equals π,the motion mode of the mechanism is determined.Finally,the motion mode of the mechanism which has different structural parameters is analyzed comprehensively.The equations of motion of bivariate polynomials of the spherical 4R mechanism are factorized and parameterized.The influence of different structural parameters on the motion mode is studied.The spherical 4R mechanism with two variable rotation axis motion modes is found.The instantaneous continuous axis of the connecting rod of the spherical 4R mechanism with different motion modes is analyzed.The double loop spherical mechanism which the instantaneous rotation axises of the connecting rod in the motion mode transformation configuration coincides is designed.When the instantaneous rotation axis of the 4R loop in the double loop spherical mechanism is collinear with the other two rotation pairs and is coplanar with the other rotation pairs,when the tangent plane of the axode formed by the instantaneous rotation axis of the spherical 4R loop coincides with the plane above,the spherical mechanism can realize the transformation of the motion mode.A double loop spherical mechanism with two motion modes is designed by using a 4R mechanism with multi-mode.According to the spherical 4R and spherical double loop mechanisms with different motion modes,the parallel mechanism with variable rotation axis and 3T1R motion mode is synthesized by using displacement manifold theory.Finally,combined with the rotation rehabilitation of ankle joint and simulation of ankle rehabilitation movement under pressure,the parallel mechanism with 3R and 2R1T motion modes is proposed to be used in ankle rehabilitation equipment.The fixture with two foot postures is designed,so that the rehabilitation device will not be in the transformation configuration of the two motion modes in 3R motion mode of ankle rotation rehabilitation.When the ankle is under pressure,that is,when the rehabilitation equipment is in 2R1T motion mode,the mechanism is far away from motion mode transformation configuration.The method of connecting the spring with the moving pair and the rotating pair of the rehabilitation mechanism is proposed,and then the motion mode transformation is realized without using the auxiliary driving pair. |
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