Hybrid Structure Of Parallel Machine Tool

Parallel machine tools(PMTs), Which came forth in the middle of l990s, arealso called virtual axis machine tools(VAMTs). PMT is an aPPlication of spatialmulti-loop parallel machanism in the field of NC machine tool, is an combinationOtheome of mechanism theory robotic technology and numerical control technology,the PrototyPe of PMTs is parallel robotic manipulators. PMTs enjoy followingadvdsges over tr8ditional five-coordinates NC machine tools: high stiffness weightratio, high feed speed, high machining precision, high additional technology value etai. PMT has the characteristic of hardWare simple and software complex, is anelectromechanic product with high additional technology value, has very vastaPPlication vistas in industry.Aiming at the deficiency of traditional NC machine tool and parallel machinetool, the advantages of traditiona NC machine tool and parallel machine tool areused fOr reference, three hybrid type PMT, which combine serial structure withparallel structUre, are proposed in this dissertation tbIough type synthesis, InventionPatents have been aPplied for them. This three hybrid type PMTs possess suchadvantages as: simple structUre, good dexterity high machining precision, highmachinillg speed, position decouPling wth orientation, easy NC programming et al,can meet the need of numerical colltrol machining fOr large pwts with complexWes. Prototype synthsis, displacement analysis, singularity configuration,worksPace, kinematic model, dynamic model, dexterity analysis, accuracy analysis,stifness analysis, interpolation algorithm, machining simulation are studied deeplyand systematically for hybrid tyPe PMTs in this dissertation.Absolute coordinates of spherical joints on movable platfOrm are chosen asunknwn, a direct displacemeat analysis which is based on resultan eliminatiommethOd for 2nyS+2TPS tyPe PMTs is presented, the 7th degree inPut-outPul closedform equation with one wtwn is obtained, and all of the roots fOr all unknownsare gained. Numeric-symbolic technique is introduced in the procedure of resultantelimination, procedure of number-spobol manipulation is transformed into that ofmatrix manipulation. Because joini variables are treated as symbols and all structureparamCters are treated as real nuxnbers, the comPlexity of derivation for input-outPuteqUaion is reduced. The soluton is verified with a numerical example, its rsultswithoot extraneous roots agree with the original eqUaions. Forward displacementanalysis for lPS+3TPS,lPT+2TPS, lPPS+4TPS type PMTs are performed based onresult elimation method. Closed form solutions for forward displacement of thesehybrid type PMTs are derived, numerical examples are given for illustration.Method of inverse displacement analysis for hybrid twe PMTS is a1so given.An analytical method, which is based on surface analysis, for workspace -analysis of 6-SPS type PMTs is proposed in this dissertation. Topological diagramof workspace for 6-SPS type PMTs is derived, the equations of workspaceboundny surfaces for 6-SPS type PMTs are also derived based on the kinematiccharacteristic of the PMTs. The projection and section curve graPhs of workspaceboundary surfaces for 6-SPS tyPe PMTs are drawn. Results of analysis show that thetheoretic workspace of 6-SPS trpe PMTs is enveloped by 30 surface patchs. InPutand outPut ewtons of disPlacement analysis for double-octahedron variablegeometry miss PMTs are established, analytical expressions for determiningsinguledty configuration are derived. These analy'tical expressions are solved usinghomotOpy cofitinuation algorithJns, all solotions of singularity configuration areobtained. A numerical exarnple of singularity configuration analysis fordouble-octahedron variable geometry trUss PMTs is given., the equations ofworksPace boundary surfaces for double-octahedron variable geometry truss PMTsare derived based on surface analysis method. The projection and section curveg...