Research On Modification Theories And Modification Methods For Design Defects In Noncircular Gear Transmission System

Noncircular gear transmission system(NGTS)is used to transfer variable motion between two axes,compared with cam and link mechanisms,it possesses many advantages,including stable transmission,compact structure,high precision,high transmission power,high transmission efficiency.Therefore,it is an indispensable part in industrial equipment,and is widely used in solution devices,automation instruments,light industrial machinery and other mechanical products.NGTS with design defects may significantly affects the reliability and safety of transmission system and further results in safety risk,for example,causing huge property losses and heavy casualties.Thus,it is imperative to study modification theories and modification methods for design defects in NGTS,which will be of great theoretical significance and practical value to NGTS.Based on analytical researches of constraint models,modification theories and modification methods for position function closure design defect,pitch curve with convex cusps design defect,pitch curve with concave cusps design defect,tooth profile machinability design defect,manufacturing procedure design defect,assembly physical connectivity design defect of NGTS are researched deeply and systematically in this dissertation,its main research contents and innovations are summarized as follows:(1)Through analysis on closure constraint and defect reason of NGTS position function,a minimization modification method of maximum modification error is proposed for the position function closure design defect.The modification method is based on proportional and controllable modification parameters and minimization optimization objective of maximum modification error.An analysis is conducted for a relationship between internal and external gear pitch curve curvature radius of internal meshing noncircular gears,and then a feasible region of controllable modification parameter is given to avoid interference of pitch curves.The interference of pitch curves is avoided and the minimization of maximum modification error is ensured by using the obtained feasible region,the minimization modification of maximum modification error for the closure design defect of noncircular gear is implemented.(2)A steepest rotation modification method is proposed for the pitch curve with convex cusps design defect of NGTS.The modification method is based on given arc length constraint of modification pitch curve.On the basis of an analysis of a relationship between given arc length constraint and modification accuracy,two results are obtained,one of which is a characteristic that the modification accuracy increases with the decrease of the given arc length,another of which is a relationship diagram between the modification accuracy and the given arc length.According to the characteristic and the relationship diagram,transmission accuracy and transmission performance of the modified noncircular gears are effectively ensured by selecting appropriate arc length constraint.(3)By analyzing characteristics of pitch curve concave cusps for NGTS,a plane curve with minimal rotary inertia characteristic is designed to meet given rotation time constraint based on variational theory.The planar curve is used as modification pitch curve and the constraint is refered to the given rotation time passed the modification pitch curve.The modification pitch curve is used to replace pitch curve with concave cusps of noncircular gear in a small neighborhood,then a minimal rotary inertia modification model of the pitch curve with concave cusps design defect is established.In order to avoid the generation of new concave cusps during the modification process,constraint conditions of the model parameters are analyzed and given according to the characteristics of the concave cusps.The pitch curve with concave cusps design defect is modified by the minimal rotary inertia modification model,and the introduction of new concave cusp design defect is avoided.(4)A neural network modification method is proposed for the tooth profile machinability design defect of NGTS.In this method,the nonlinear relationship between key design parameters of noncircular gear,design variables of shaper and design defect constraint of tooth profile machinability are mapped as the relationship between input and output of the neural network.Tooth profile undercut,tooth profile interference,tooth profile top cutting and other machinability design defects are identified and modified by using the classification model and corresponding modification strategy of design defects.As a result,machinability and transmission reliability of noncircular gear are improved.(5)Based on mathematical model of manufacturing procedure for NGTS,a genetic optimization modification method is proposed for the manufacturing procedure design defect under resource-constrained condition.The modification method is designed by introducing a defect identification factor and a local mutation operator in the traditional genetic algorithm.In this method,its rapid convergence and local search ability are enhanced by using general genetic optimization,including selection,mutation,and crossover,the genetic optimization modification of the manufacturing procedure design defect of noncircular gear is implemented.(6)By means of constraint analysis of assembly connectivity for NGTS,an immune bionic modification method is proposed for the assembly physical connectivity design defect.The modification method is based on an identification operator and a modification vaccine of design defect and a vaccine of identification and adjustment of sub-assembly.The identification operator and the modification vaccine are designed by vaccination strategy of immune bionic system.The sub-assembly can be identified automatically by using the designed vaccine of identification and adjustment of sub-assembly in the process of assembly sequence planning,the stable connectivity of sub-assembly and its accessory parts can also be ensured.Researches in this dissertation construct a technology system of modification theories and modification methods for design defects in NGTS.These modification theories and modification methods greatly improve design quality,design level and design efficiency of NGTS.Furthermore,they can reduce development cost and improve reliability of NGTS.Based on theories and methods propossed in this dissertation,NGTS with high quality and high reliability can be designed by designers with less design experience.