| With the development of precision manufacturing,precision positioning technology as its core technology is widely used in the construction industry,defense industry,MEMS,and medical fields.Its positioning accuracy affects the overall level of precision manufacturing.Due to the existence of gaps between rigid motion pairs and friction,wear and other factors,the precision positioning platform based on the traditional parallel mechanism has been unable to guarantee high positioning accuracy for a long time.However the compliant mechanism has no friction,wear within the mechanism.Characteristics have been widely used in the design of precision positioning platforms in recent years.This paper considers the characteristics of the compliant mechanism and the parallel mechanism comprehensively.A kind of 3-PRC type flexible parallel mechanism which was based on 3-PRC type rigid parallel mechanism was designed by introducing flexible branch chains.Then improved by flexible hinge replacement method,a precision positioning platform was designed that uses a centralized compliance-type full-flexible parallel mechanism as a transmission component.Based on this,a continuous structure topology optimization method is used to optimize the design,and a new distributed flexibility full-flexible parallel precision positioning platform is developed.Afterwards,in this paper,static and dynamic simulations of the above three kinds of precision positioning platforms are performed.The research shows that the precision positioning platform based on distributed flexibility full compliant parallel mechanism has obvious advantages in the stiffness characteristics,anti-jamming ability and vibration resistance of the mechanism,and has a high positioning accuracy.The specific research content is as follows:First,in this paper,the 3-PRC compliant parallel mechanism was designed and analyzed using flexible hinge replacement method.The degree of freedom of the rigid 3-PRC parallel mechanism was analyzed using the helix theory,and the Jacobian relationship matrix between the input and output of the mechanism was derived based on the principle of microkinetics.Kinematics analysis was performed on this mechanism.On this basis,the flexible branch chain was introduced,after two kinds of precision positioning platforms with 3-PRC type flexible parallel mechanism and concentrated compliance type full compliant parallel mechanism as transmission components were designed by flexible hinge replacement method.Static simulation analysis was performed on them respectively,last corresponding displacement cloud maps and stress cloud maps were obtained.Second,in this paper,a topological optimization method of continuum structure is used to design a precision positioning platform with distributed compliant full compliant parallel mechanism as the transmission component.In order to prevent the occurrence of mechanism singularity,a 3-PRC centralized compliance-based full-flexible parallel mechanism was used as a prototype.The minimum overall flexibility of the mechanism was set as the objective function,and the volume was a constraint condition.A topology optimization method was used to design a 3-PRC type distribution flexibility type full compliance parallel mechanism.At the same time,a corresponding precision positioning platform was constructed and the optimized mechanism was analyzed by statics to verify the effectiveness of the design method.Third,in this paper,the static stiffness of three different precision positioning platforms is analyzed by combining theoretical modeling method and finite element simulation.Each flexible hinge is connected by series and parallel connection to build a single flexible branch stiffness matrix,and then three flexible branches are connected in parallel to build the total stiffness matrix of the flexible parallel mechanism,thus establishing a static stiffness model of the flexible parallel precision positioning platform.On this basis,finite element analysis was used to analyze the static stiffness of the three types of mechanisms.The results show that the static stiffness of the distributed compliance full compliant parallel precision positioning platform is the largest among the three,and has better static performance.Finally,in this paper,the system dynamics model of the 3-PRC flexible parallel mechanism is obtained by using the finite element analysis method,and the modal analysis of the three mechanisms is performed.The flexible hinge structure is divided into multiple beam elements and its kinetic energy and elastic potential energy are obtained.The kinematics and dynamic constraints of the mechanism are combined to finally determine the dynamic equation of the system.The finite element analysis software is used to analyze the restraint modes of each platform.The results show that the distributed flexibility full-flexible parallel precision positioning platform has good dynamic performance and obvious advantages in anti-jamming ability and vibration resistance. |
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