Lightweight Design And Dynamic Characteristic Analysis Of Sprayer Boom

Highland gap boom sprayer can meet the needs of different crops in each growth period for spraying purpose,thus,it has become the necessary equipment for the field management.Sprayer boom,as the core part of the sprayer,its performance directly affects the stability of the sprayer and the uniformity of spraying.In this thesis,sprayer boom with 18m’s spraying swath was studied,aiming to conduct a lightweight design and improve its balance characteristics.Firstly,the balance characteristics of the original boom was studied,in connection with its inability to isolate high-frequency vibration and restore stability under step incentive and other problems,so as to optimize its isosceles trapezoid suspension.Through the optimization,the suspension could almost meet the requirements for design.Under the low-frequency incentive,sprayer boom was able to swing as the frame of the sprayer swings in order to be adapted with undulating and sloping ground;under the high-frequency incentive,suspension can effectively attenuate the vibration to keep the boom balanced.The optimization result showed that the maximum swing angle of the outer boom under the angle of 50rad/s was within one degree,and the balance effect was perfect.After that,the thesis set up a finite element model for the boom,and carried out static analysis on the outer boom and inner boom.The result showed that the elastic displacement of outer boom was large and the stress of the inner sprayer boom was relatively small,and there is still a plenty of space for optimization.Combined with the analysis result,the outer boom was conducted with the improvement for its partial structure.Based on the static analysis of the sprayer boom,a lightweight research was carried out to the outer and inner booms.The result showed that,through the optimization of its dimension,the quality of the outer boom was decreased by 13.9%,the maximum stress of each working condition was controlled within 200 MPa,and the maximum elastic displacement of each direction was controlled within 15 mm.For the inner boom,its quality was reduced by 59.5%,the maximum stress of each working condition was controlled within 150 MPa,and the maximum elastic displacement of each direction is controlled around 1mm.Under the premise that the strength and stiffness are satisfied,a better lightweight effect was obtained.Then,a free modal analysis was conducted to the outer and inner booms.The result showed that the frequency of the first two modes of the outer sprayer boom was relatively small,which ranges within 0 to 6.9Hz for the road incentive frequency.When sprayer was under operations,the outer sprayer boom may cause resonance which could lead to excessive elastic displacement to deteriorate the uniformity of spraying.The frequency of the first mode of the inner sprayer boom was 72 Hz,which is greater than the road incentive frequency,and there was less possibility for the resonance.Thus,it can be considered as rigid members for analysis directly.Based on the modal analysis result,a flexible modeling for the outer sprayer boom was established.Finally,the rigid flexible coupling simulation model of the sprayer boom was established.According to the requirements of GB/T 24680-2009 for the “Stability Test Method of Sprayer Boom used for Agricultural purpose”,field road simulation test for the boom sprayer was implemented,so as to make analysis on the dynamic characteristics of the boom under different operating speeds and loads.The result showed that the elastic displacement of the end of the sprayer boom and its vertical displacement are relatively small on the whole,and this could effectively guarantee the uniformity of spraying.The results obtained from the research in this thesis provided references for the design of other sprayer booms with various breadths.