Formation Mechanism And Construction Method Of Kinematic Characteristics Of Heald Frame Driven By Rotary Speed Change Mechanism

The dobby is the main shedding device in the weaving process that has been increasingly and widely used in modern looms.One of the key components of the heald shedding mechanism of the dobby is the modulator.This component determines the motion characteristics of the heald frame which directly affect the stability,reliability,and weaving quality of the loom during its operation.This dissertation is focused on the heald shedding mechanism of the rotary dobby.This study aims to construct motion characteristics of the heald frame that are more suitable for the weaving process.This was mainly done by optimizing the conjugate cam profiles of the modulator.The construction mechanism of the motion characteristics of the heald frame,the inverse solution and optimization method of the conjugate cam profiles,and the influence of various error factors on the dynamic behavior of the modulator have been thoroughly studied.(1)The movement principle of the heald shedding mechanism transmission process was analyzed.The kinematic model of the modulator,the eccentric mechanism,the motion transmission mechanism,and the heald frame were established in this study.The mathematical model of the heald frame movement driven modulator was theoretically deduced,and a set of effective methods for extracting the motion characteristics of the heald frame were also developed.(2)Based on the movement mechanism of the heald shedding mechanism transmission process and the motion characteristics of the heald frame,the influence of the conjugate cam profiles on the motion characteristics of the heald frame was analyzed.A mathematical model for the reverse solution of the conjugate cam profiles of the modulator was constructed based on the kinematic characteristics of the heald frame.The reverse solution method of the conjugate cam profiles of the modulator was then deduced.Sample analyses of the solution of the cam profiles were carried out,and the non-centrosymmetric cam profiles were finally obtained.(3)A method of using the particle swarm algorithm to optimize the reconstruction of the cam profiles was proposed.The objective,equations,and constraints for the optimization of the cam profiles were constructed.Calculations on the conjugate cam profiles reconstruction method were made for different motion characteristic curves of the heald frame and a comparative analysis was then carried out.(4)In view of the dynamics of the modulator of the dobby,a dynamic model of the modulator was constructed.Based on this model,the numerical solution method was established.Detailed dynamic calculations were carried out for the cam-link modulator based from some of the known key parameters that affect its dynamic performance.Finally,the main factors affecting the vibration characteristics and dynamic behavior of the modulator were analyzed.(5)An experimental prototype of a performance test bench for the dobby heald shedding mechanism was designed and developed.Detailed experimental methods were established and experiments on the kinematic characteristics and dynamic performance of the shedding mechanism were carried out.This study can provide a theoretical basis for the construction mechanism of the motion characteristics of the heald frame,and the analysis and design of the conjugate cam of the modulator.The results can also provide a reference for the design of dobby towards high speed and high precision weaving process.