Reserch On Collaborative Optimization Of Screw Type Shift-box Mechanism

Shift-box mechanism is one of the main components of the high speed rice transplanter whose function is to complete the task of horizontal seedling feeding in the process of transplanting,and its performance which directly related to the stability of the work performance.The performance of the shift-box mechanism depends on the configuration of structural parameters.Shift-box mechanism with good structural parameters can make the speed of the rice seedling transplanting stable and has low vibration,and ensure the uniformity of seedling transplanting.Therefore,parameters optimization of rice transplanter is one of the key issues during the design of shift-box mechanism.In this paper,the parameters optimization of the screw shaft box mechanism was a multi-objective,variable-coupled and nonlinear complex problem.The optimization design of the screw shaft box mechanism involves the interaction of many subjects such as dynamics,kinematics and structural mechanics.According to the fact that traditional methods of optimization design are increasingly difficult to meet the general design requirements and carry out the research on multidisciplinary design optimization of screw shaft box mechanism.The research contents are summarized as follows:(1)This paper studies the relevant knowledge such as the framework of multidisciplinary optimization design,the solution strategy and the sensitivity analysis.It was found that the relaxed collaborative optimization method was more suitable for the MDO of screw shaft shifting mechanism after the methods which commonly used in mechanical field were carefully analyzed and compared.(2)The research was divided into three sub disciplines(dynamics,kinematics,structural mechanics)based on the characteristics of screw type shift-box mechanism and MDO system decomposition theory.The optimization target,optimization variables and constraints were determined to build the discipline optimization model by analyzing the decomposed disciplines.The optimal algorithm for each discipline was determined to optimize each discipline individually.(3)On the basis,because of low computational efficiency and convergencedifficulty of MDO problems in the process of optimization of the single discipline simulation model,the approximate model was used to replace the simulation model The optimal latin hypercube design was used as a DOE method to obtain sample points and construct theKriging approximate model of the screw shaft box mechanism.Furthermore,the accuracy requirements of approximate mode were determined to be met by the error analysis.(4)Based on collaborative frame and Kriging model,the integrated platform for MDO of screw type shift-box mechanism was established by using Isight software.The optimization results show that,the first natural frequency is increased from 236.428 Hz to259.534 Hz,which is increased by 9.77%.The anti vibration performance of the screw shaft is effectively improved.The maximum acceleration is reduced to 9.838e4mm/s~2 by9.013e4mm/s~2,which is decreased by 8.39% and the stress wear is reduced.The weight of the mechanism is reduced to 2127.17 g by 1848.31 g,which is reduced by 13.07%and makes the structure more compact and reduces the manufacturing cost.As a result,stability and precision of mechanism operation is obviously improved in such conditions that the weight of mechanism is reduced,which effectively improve the comprehensive performance of the shift box mechanism.