Configuration Synthesis And Optimization Method Of Parallel Metamorphic Cutting Mechanism

Cutting different shapes of large-scale technological hole in the complex surface of the ship is a key project in the machining progress for the engineering background of the modern shipbuilding manufacturing.Because of the structural changes of the ship and the replacement of shipbuilding materials,the existing cutting equipment can't meet the "high-performance"manufacturing needs and can't guarantee the machining accuracy and performance index etc of the holes machining task.Therefore,it is necessary to study a new machining method to solve the difficult cutting problem of the complex curve in ship,that is the digital agile cutting technology,and develop cutting mechanism and digital cutting equipment with high efficiency,high precision and high quality machining characteristics,which is an important issues to be solved for the ship manufacturing and has important theoretical significance and engineering value.The mechanism design and optimization of the CNC cutting equipment and the measure,redesign and NC machining integration of the spatial complex surface parts are regarded as two core elements in digital agile cutting technology field,the parametric modeling method for the hole contour and its cutting track of the spatial complex surface,and the configuration synthetic,the configuration-complete motion performance analysis and comprehensive evaluation optimization method,the kinematic optimization design and the virtual simulation application have been carried out on the parallel metamorphic mechanism.On the one hand,the NC machining integration of the complex surface curve,configuration synthesis and optimization theoretical method are established on the parallel metamorphic mechanism,On the other hand,it provides a new cutting mechanism for solving complex surface machining problems.The main contents of this paper are as follows:The parameterized models are established of the hole contour and its cutting trajectory in space complex surface.According to the requirement of digital agile cutting technology based on space surface,the parametric model of arc length are constructed,which is expressed by the spacial parameters transformed from general parameters;the hidden parameter model and the B-spline parameter model are established for the cutting contour of the regular curve and the free curve.Then,the parameter expressions of the hole contour are given completely after the general expression is deduced about the groove vector.On the basis of this,the geometric parameter model of the flame cutting track is constructed which is combined with the flame cutting process and the bias theory on the contour of the spatial curve.It is shown that the flame cutting medium in the continuous cutting has the characteristics of the variable track and the variable attitude motion.The NC parameter interpolation model of the flame machining track is generated by using the adaptive speed control theory and the prediction correction calculating method.A dynamic constrain distintegration method is proposed for the synthetic configuration of parallel metamorphic mechanism.First,The main structural components and comprehensive elements of are cleared about the parallel metamorphic mechanism.Then,the variable constraint spinor principle is achieved during its synthetic configuration design process.After three kinds of unconstrained primary branch chain units and the practical form of the metamorphic kinematic pair are constructed,and the dynamic constraint synthesis process and general steps are established on parallel metamorphic mechanism.According to the machining demand for spacial complex surface,the "two kinds of "feasible parallel metamorphic cutting mechanism" are given synthetically which are combined with the service environment of NC equipment manufacturing.The 3URS-PPPS is optimized as implementation configuration,its working mechanism is analyzed.The configuration-complete motion performance is studied on parallel metamorphic mechanism.Starting from a general parallel metamorphic mechanism,the instantaneous constraint change model of the topological structure metamorphic state is given under the framework of the configuration-complete motion performance analysis;In the first order motion level,the workspace acquisition process?velocity transfer mode and precision transfer model are constructed to steady state motion and complete motion,and transient power change model is given to metamorphic state;The acceleration transfer model,instantaneous acceleration and instantaneous impulse change model are established in the two order motion plane.For the optimal parallel metamorphic cutting mechanism,the configuration-complete performance model is constructed by combining the general model with the cutting demand.It not only verifies the validity of the configuration-complete performance model,but also provides a theoretical basis for the design of the structure scale parameter of the parallel metamorphic cutting mechanism.The continuous metric performance index and the instantaneous catastrophe performance index are constructed respectively to the steady state and metamorphic state,the configuration-complete motion performance index evaluation system and architecture are given out on the parallel metamorphic mechanism.Then based on the established single motion performance index,the fuzzy principal component analytical method is used to establish the comprehensive evaluation index of the configuration-complete motion performance.The optimizing design process of the motion performance is also given by the using of the adaptive genetic algorithm.At last,for the 3URS-PPPS type parallel metamorphic cutting mechanics,the local/global numerical simulation and fuzzy comprehensive evaluation simulation of eight indexes are determined in the cutting service environment.At same time,optimization design and simulation are carried out based on configuration-complete index and comprehensive dexterity index,and the simulation is proceeded by the contrast with the optimization parameters of the two parallel metamorphic cutting mechanisms to verify the validity of the constructed configuration-complete performance index and the practicality of the motion optimization design.Finally,the key technology research of virtual prototype design,processing and application is carried out for parallel metamorphic cutting mechanism.First,for 3URS-PPPS metamorphic configuration,the structure components of the mechanical system on parallel metamorphic cutting mechanism is constructed which is based on its motion optimization design parameters,and the feasible form of virtual prototype is obtained.The simulation of the cutting task trajectory generation is carried out for variable angle groove holes on complex surface with large space.At the same time,a continuous machining path on the three working stages of the straight mouth,attitude adjustment and groove in high-performance parallel metamorphic cutting mechanism is produced which is combined with the avoidance path planning method of the avoiding singularity and singularity,and the adaptive speed interpolation simulation of the machining path is proceeded on the straight mouth and groove.The driving characteristics of the cutting mechanism in the virtual flame machining are obtained by dynamic simulation of ADAMS,which provides the basis for the lectotype manufacture of the engineering prototype and the subsequent dynamics closed-loop control.