| The degree of mechanization in orchards in China is relatively low.Especially,there is a lack of operating machinery for orchards in hilly and mountainous areas.At present,the thinning of flowers and fruits,bagging,pruning and picking in orchards are mainly completed with the support of artificial ladders.The orchard operating platform is one of the important operating equipment for orchard production management,while the domestic platform only has the lifting function,not the leveling function,and cannot adapt to the hilly and mountainous terrain with large slope changes.Therefore,the design of a high-level automatic leveling operation platform that can be applied in orchards in hilly and mountainous areas is of great significance for improving the harvesting efficiency and operation safety in the orchards.The research content and results of this paper are as follows:1.Based on the comprehensive analysis of the structural characteristics and functional parameters of domestic and foreign orchard platforms,as well as the horticultural situation of domestic dwarf stock densely planted apple orchards,the requirements for platform design and vertical and horizontal leveling methods were determined.The mathematical relationship between the structures was established,and on this basis,the size parameters of each component,the thrust of the hydraulic cylinder and the leveling angle were optimized and determined.Besides,the hydraulic system was designed,and the key components were calculated and selected.2.A three-dimensional model of the platform was built in Solid Works according to the determined size parameters,and finite element simulation was conducted on the main components such as scissor lifting structure,longitudinal leveling structure,horizontal leveling structure and platform to analyze the distribution of stress and deformation under the maximum load.And simulation results were meet safety requirements.3.Conducted a tipping simulation experiment in ADAMS to analyze and compare the tilting slope of the platform under different postures,lifting heights,load and load positions.It was found that the maximum slope of the safe operation of the platform is 43.02°.According to the characteristics of the road surface in orchard,single-wave and continuous-wave obstacle roads were established,and the simulation results showed that the dynamic leveling error of the operation platform is within 0.75°.4.A mathematical model of the longitudinal and lateral leveling system was constructed and its stability was analyzed;conventional PID and fuzzy PID controllers were used for simulation,and the system’s step response curve and sine response curve were obtained.The results show that compared with conventional PID,the average response speed of fuzzy PID is 0.66 s faster,the average error is0.125° smaller,and the control has achieved better performance.5.After the prototype was produced and processed according to the optimized three-dimensional model,the basic functions and leveling performance were tested.The results revealed that the deviation in straight-line walking is within 1.1%,the radius of the turning space is within 1.5m.The longitudinal leveling error is within 0.4°,and the lateral leveling error is within 0.8°.This proved the correctness and feasibility of the structural design and control system.The leveling platform for orchard designed in this paper has good overall performance with satisfying anti-tilting ability,and the data meet the design requirements.The operation platform can always remain level when walking on uneven roads.It meets the requirements for the use in orchards in hilly and mountainous areas,promotes the development of mechanization in orchards in China.And provides the basic equipment for the development of automation and intelligence of orchards. |
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