Design And Analysis Of Multimode-Mobile Parallel Mechanism

With the rapid development of science and technology and the multifunctional and adaptive requirements of mobile institutions in various fields of modern social life,the structural design and analysis of multi-mode mobile mechanisms have become hotspots in the field of mechanism and robotics in recent years.This paper proposes several structural design and singularity analysis methods for multi-mode mobile mechanisms,such as the existing multi-mode mobile mechanisms with few configurations,poor non-structural environment adaptability,and lack of a reasonable systematic structural design method.According to the requirements of multi-task,unstructured environment in real life,the structural design and motion analysis of multimode mobile mechanism are carried out.This paper focuses on the following aspects.(1)Based on the bionic principle and spiral theory,a design method of a multi-mode moving mechanism composed of rotating pairs is proposed.A type of motion pair(rotation pair)of the mechanism is used as the main model of the bionic structure design,and creatures with the same motion joint(motion pair)and different forms of motion are used as bionic objects.The equivalent structural unit is extracted and carried out based on spiral theory Configuration synthesis.Based on the 2R(rotating pair)as the basis,a spatial 3R motion branch chain is generated,and a spatial single-loop 6R mechanism is synthesized based on the position relationship of the motion pair axis of the spatial 3R motion branch chain.Finally,combined with the principle of spatial geometric symmetry,imitating the shape of living things,two plane single-ring mechanisms are arranged symmetrically in space to form a multi-mode moving mechanism.The kinematics performance of the mechanism in the three motion modes of gliding,crawling and rolling is analyzed,and the virtual prototype simulation is verified by Adams.The results show that the multi-mode mobile mechanism designed by this method can meet the working requirements of unstructured environment.(2)Based on the positioning points of the regular polyhedron and the computer-aided design method of space geometry,a design method of a multi-mode moving mechanism composed of moving pairs is proposed.The geometric regular polyhedron is used as the main model of the mechanism design,and computer software is used to carry out the topology design of the connecting branches of the mechanism.First,based on the geometric frame of a regular polyhedron,the relative positions of the spatial anchor points are determined,and then the branch chains are selected and constructed according to the different motion patterns,and the mobile pair is constructed based on the mobile pair P.Combining the principles of CAD and spatial geometric constraints,the simulation configuration of the connecting chains of the multi-mode moving mechanism is determined.Finally,the spatial positioning point is combined with the motion branch chain to construct a multi-mode moving mechanism,and the Euler formula is used to verify the rationality of the structural model design.The motion model of the mechanism was verified by Adams’ virtual prototype simulation,which proved the feasibility of this method in designing a multi-mode mobile mechanism.(3)Based on Grassmann’s line geometry and line graph theory,a design method for a multi-mode moving mechanism including a moving pair and a rotating pair is proposed.Based on the 3-RSR parallel mechanism as the design body,the similarity between the linear vector force branch and the force couple and the directional characteristics of the basic vector chain constraint of the linear vector force are analyzed by the line graph method.The overall degree of freedom of the mechanism is used to derive the mechanism branch chain.Degree of freedom type,with reasonable motion pairs to form branch chains.Combined with the actual motion mode,a mobile pair is added to the branch chain to realize the multi-motion mode of the mechanism,and Adams software is used to perform square gait simulation verification.(4)Aiming at the problem of singularity during the movement of multi-mode moving mechanisms,a method for studying the mechanism singularity during the movement was proposed.The singularity analysis of the multi-mode parallel movement proposed in the first three chapters is performed by using the spiral theory and the geometry theory of space lines,combining the physical meaning of the input motion spiral and output motion spiral.First,based on the time-sharing control of the motor,determine the singularity of the mechanism during the movement of the full R pair of multi-mode mobile parallel mechanisms in the three motion modes of sliding,crawling and rolling.For the multi-mode mobile parallel mechanism based on P pair,since the driving pair is P pair,the singularity of the mechanism during the movement is determined by the positional relationship between the input spiral and the output spiral in the space,and the correlation of the line geometry to determine the correlation of the spiral in space.Finally,for a multi-mode mobile parallel mechanism composed of R and P pairs,the motion spiral is represented by geometric algebra,and the singularity of the mechanism during the movement is determined by the correlation of the complete Jacobian matrix line vector of the mechanism.It provides a certain theoretical basis for the selection of motor control and drive of the multi-mode moving mechanism in different modes.