Frame Design And Optimization Of An Orchard Picking Operation Platform

The frame as the main load-bearing parts of the orchard picking platform,when the platform is driving on the orchard operation road,due to the unevenness of the orchard road,the frame will be subject to a variety of complex loads and the force of the operating mechanism and power mechanism on the frame.The static and dynamic characteristics of the frame under the action of various external forces are greatly tested,and the reasonable design of the frame structure is directly related to the safety,comfort and performance of the whole machine.Initially in the design of the frame mostly with the help of past experience and theory,the design process is cumbersome and complex,taking too long a period of time,it is difficult to develop new frames.And the design of the frame material redundancy,resulting in excessive frame mass,the machine fuel consumption increased,seriously hindered the development of China’s agricultural machinery.In today’s modern technology and economic development,the use of computer-aided design and optimization design has been a common practice.Many engineers in the frame design,will use the finite element method to analyze the structure of the frame,to understand the defects in the design of agricultural frame structure and optimization space,for modern agricultural frame structure design and optimization is of great significance.Taking the frame structure of orchard picking operation platform as the research object,the static and dynamic performance is analyzed comprehensively,and the frame structure parameters are optimized according to the analysis results.(1)The finite element modeling of the frame of the orchard picking work platform is carried out,and the static analysis of the frame is carried out for three typical working conditions: full load bending,full load bending and torsion,and emergency braking,to check whether the strength and stiffness of the frame are qualified,and to find out the weak points and optimization space of the frame structure.By analyzing the modal state of the frame structure,the engine harmonic response and the random vibration response caused by the unevenness of the road surface,the excitation of the engine and the unevenness of the road surface on the frame is combined to investigate whether the external excitation coincides with the modal inherent frequency of the frame structure,and the strength and stiffness state of the frame structure is derived.(2)Based on the results of the static dynamics analysis,on the basis of the original structure of the frame,the structural parameters that have a greater influence on the mass,structural static characteristics and structural modal characteristics of the frame are selected as design variables by using the sensitivity analysis method,the Kriging approximation model of the optimization objective and objective function of the frame is constructed based on the optimal Latin hypercube experimental design method,and the multi-objective genetic algorithm and hierarchical analysis method are proposed.The optimization method of the frame structure parameters of the orchard picking platform is combined with multi-objective genetic algorithm and hierarchical analysis.Through the comparison and analysis before and after optimization,the overall frame mass of the frame is reduced from 500.65 kg to 439.2kg,which is about 14%lower,and the 1st and 2nd order inherent frequencies of the frame rise to 20.79 Hz and21.16 Hz respectively,both of which reach above 20 Hz to effectively avoid the excitation of the frame by the unevenness of the road.(3)The durability simulation analysis of the optimized frame was carried out,and the original load spectrum of the frame was compiled by the pseudo-damage retention method,and the original load spectrum was compared with the accelerated load spectrum to investigate the efficiency and accuracy of the durability analysis of the frame with different pseudo-damage retention amounts.It was found that retaining 95%of the pseudo-damage amount can compress the original load spectrum time by nearly55%,and the efficiency of the frame durability simulation analysis can be improved by391%,and the error of the analysis results can be effectively controlled within 5%,which is the best editing scheme of the load spectrum in the pseudo-damage retention method.