Spatial Three Degree-of-Freedom Parallel Mechanisms: Configurations, Performances And Applications

With the development of the theory of anvanced spatial mechanism and the technology of robotics,parallel mechanisms based parallel robots have been one important branch of robotic technology.Forthermore,the research activities of the theories and applications of parallel mechanisms and parallel robots is becoming much hotter.However,although many scholars have done the intensive investigations on the dimension synthesis,kinematics,dynimics,workspace and singularity of parallel mechanisms,most of the existing work regarding arallel mechanisms was built upon the concept of traditional Gough-Stewart mechanism type.Since full degree-of-freedom devices are not necessary for most industrial operations,i.e.the machining operations only require a maximum of five axes,and the motion of pick-and-place for the assembly of electronic elements only require a maximum of four degree-of-freedom,new configurations with less than six axes(degrees of freedom) would be more appropriate for industry and academia.Tripod is one type of parallel mechanism with three degrees of freedom,and it can implement the basic three axes machining,by combining with the XY gantry,it can conduct four degree-of-freedom or five degree-of-freedom machining.Therefore,tripod mechanism is targeted as the main configuration for the development of parallel manipulators.Because of the opposition and unitarity of serial mechanisms and parallel mechanisms in philosophy,the hybrid mechanisms can be built through the combination of parallel and serial mechanisms and play an important role in some specific application background.The thesis will do the deep investigations on the spatial three degree-of-freedom parallel mechanisms in the following aspects:1. propose sevseal types of novel configurations,2.develop some important approaches of for the modeling and optimization of performance indices,3.explore on the specific application fileds of proposed parallel/hybrid mechanisms.The main work of the full thesis is generalized as follows:Study on the theories and approaches for design optimization of spatial less degree-of-freedom parallel/hybrid mechanisms.Give the degree-of-freedom computing criteria of the parallel robotic mechanisms for more reasonable kinematic structures using Chebychev-Grubler-Kutzbach criterion.Study on topology of the spatial three degree-of-freedom parallel/hybrid mechanisms.The globan stiffness and other indices and built based on the guidance of the redefined Jacobian matrix.The integrated algorithm of multi-population genetic algorithm,radial basis function network and Pareto method are introduced for the multi-objective optimizations of performance indices.The Pareto-optimal frontier sets under some geometrical constraining is given.Design a tripod parallel kinematics structure,of which the end-effecter(the moving platform) has three independent motions—two pure translations and one pure rotation.The output link of a planar parallelogram mechanism will remain in a fixed orientation with respect to its input link,and the parallelogram can ensure the desired output,in terms of translation and rotation.The use of the parallelogram structure can greatly increase the stiffness of the legs.Jacobian matrix based global stiffness modeling and optimization is developed.Study on the error calibration and compensation with the proposed cooperative evolutional network.In this error model, all the error sources are considered as a single one which affects the precision of gripper through the bias of joint variables.A 3S(?)S+RPR typed compliant hybird micromanipulator with flexure joints which encompasses three degrees of freedom and can produce motion on a microscopic level is proposed.The detailed design of motion systems for the machine structure is introduced.The multi-objective optimizations of global stiffness,dexterity and manipulability are conducted.The integration of inverse kinematics and radial basis function network is poporsed to sovel the forward kinematics problem of the proposed compliant hybird micromanipulator.Through the researches of the integrated three dimensional accelerators and the marmot-like rescuing robotics,the application viewpoints of parallel/hybrid mechanisms are extended.A novel design of a multidimensional acceleration sensor is proposed based on 3RR(?)RR decoupling parallel mechanism for kinetic information acquisition,specifically for measuring human motions.The translational elements of three perpendicular legs are served as elastic body which is manufactured by aluminium alloy,The finite-element analysis of resultant stress,strain and deformations is conducted based upon different input conditions to show the reliability of the proposed sensor structure.The physical prototype is developed.The calibration experiment based on gravity is performed to validate the correctness of related principle and performances of the prototype itself.Mine rescue robot is a kind of intelligent robots which can work in a complex and dangerous underground environment and be used for detection human beings in many aspects.The performance requirements of robot rescue in hazard place of mine accident are analyzed.The marmot-like rescuing robot and its 4UPS+PU redundant driven hybrid mechanism of neck is proposed.The feasibility of its application in the underground environment of coal mining accidents for assitant rescuing is discussed. The simulations of kinematics and dymanics for the proposed 4UPS+PU mechanism are conducted based on the dummy prototyoe technology.