| With the vigorous development of the national economy and the improvement of living standards,the planting area and output of garden fruits in China are showing an increasing trend.The orchard transfer platform meets the needs of the orchard industry development,and it has been rapidly developed and applied due to its advantages in reducing labor intensity,improving operating efficiency,reducing labor costs,and reducing fruit damage.However,during the working process of the orchard transfer platform,vibration phenomena caused by factors such as road surface incentives and uneven movement of the crawler chain links,resulted in serious vibration damage problems during fruit transportation,which reduced the economic income of fruit farmers.For the purpose of analyzing the vibration situation of the orchard transfer platform under the operation,improving the fruit damage caused by excessive vibration under the work of picking and transportation,our study establish a multibody dynamic rigid-flexible coupling model of orchard transfer platform using Recurdyn software based on self-developed electric tracked orchard transfer platform,which is suiTab.for orchard operation in southern hilly and mountainous areas.Further,a three-dimensional random pavement model and an impact pavement model are established based on the analysis of the working conditions of the orchard transfer platform.This study carry out vibration testing of fruit transfer vehicles in different vehicle and operation conditions.By means of Ansys software,we established finite element structure dynamic model of the orchard transfer platform,and carried out the structural vibration analysis of the orchard transfer platform.In order to improve the vibration degree of the orchard transfer vehicle,we studied the reduction of vibration according to the vibration characteristics of the orchard transfer platform.Our study adopted the method of dynamic vibration absorber to control the vibration at the carriage,reduce the damage to fruits during transportation.Our study could help to improve the income of orchard farmers,promote the development of orchard industry,and provide a theoretical basis for the development of orchard transfer platforms with high vibration performance.The main research contents and conclusions of this article are as follows:?1?According to the geometric structure parameters of the electric track-type orchard transfer platform trial prototype,the Solidworks software was used to establish a three-dimensional geometric model of the orchard transfer platform.With the help of Recurdyn multi-body dynamics software,the rigid part model of the chassis of the orchard transfer platform,the carriage part,the crawler walking part,and the flexible model of the lifting plate system were established.According to the structure of the orchard transfer platform,a motion pair was created to connect the various parts of the car body,and a multi-body dynamic rigid-flexible coupling model of the orchard transfer platform was constructed.Based on the analysis of the working conditions of the orchard transfer platform,the white noise method was used to describe the road surface roughness,and the road surface roughness model was established by using the Matlab-simulink.We used Matlab software to solve the elevation data of the three-dimensional random pavement and edit the program,in order to realize the generation of node vector matrix and element vector matrix.Finally,a three-dimensional random pavement model was established using the triangular mesh method,and impact pavement model was established with the help of the Recurdyn software ground module.?2?Based on the multi-body dynamic rigid-flexible coupling model and pavement model of the orchard transfer platform,according to the research status of the orchard transfer platform's operational performance test,the vibration test of the orchard transfer platform under different vehicle conditions and operating conditions was carried out.The vibration test results under different vehicle conditions showed that:?1?The vibration acceleration in the y direction at the orchard transfer platform is much greater than the x and z directions.?2?The vibration of the carriage at different positions is different.The main manifestation was that the vibration at the center of the carriage is less than the edge,the rear end vibration is greater than the front end,and the vibration at the left and right sides of the carriage is basically the same.?3?The driving speed and load have a significant impact on the vibration at the carriage.In the driving speed range of 2-4km/h,the vibration acceleration in the y direction increases as the vehicle speed increases;The acceleration in the y-direction decreases with increasing load.The research results are consistent with the general law of vehicle vibration,and further confirm the correctness and feasibility of the multi-body dynamic rigid-flexible coupling model of the orchard transfer platform.The vibration test results under different driving conditions showed that:?1?In the test of different driving conditions,the vibration condition of the orchard transfer platform on the hard road was stronger than that of the orchard cultivated land.When passing the obstacle,the vibration acceleration changes greatly,and the maximum acceleration of the measuring point reached to 13.258m*s-2.?2?In climbing conditions,the vibration at the front end of the driving direction is stronger than the test points at the rear.The maximum point of cabin vibration was at 3 and 9,and the root mean square value of vibration acceleration in the y direction was 2.305m*s-2.?3?In steering driving conditions,the vibrations at test points located inside the steering are stronger than those at the outer test points.The maximum point of cabin vibration was at 7,and the root mean square value of vibration acceleration in y direction was 2.061m*s-2.?3?Structural vibration characteristics analysis is the basis of vibration control.In order to calculate the vibration characteristics of the structure of the transfer platform and understand the steady-state response of the transfer vehicle structure under driving conditions,the finite element structural dynamic model of the orchard transfer vehicle was established with the help of Ansys software.Modal analysis and harmonious response analysis of the car body part of the orchard transfer platform were carried out,and the first six-order modal frequencies and their modes were obtained by modal analysis.The results indicated that the vehicle structure of the transfer platform did not occur large bending deformation,and the vehicle structure could basically avoid the damage of large deformation caused by vibration.The steady-state response of the transfer platform structure under driving conditions was obtained by means of the harmonic response.The frequency response function of the displacement at the carriage showed that when the external load excitation frequency is 50.4Hz,the upper surface of the carriage is strongly vibrated.Meanwhile,the vibration displacement amplitude is 5.6842*10-7m,and the vibration acceleration reached to 5.701*10-2m/s2.Combined with the frequency and mode shapes of the first six orders of the transfer platform structure,it can be seen that the second order mode of the orchard transfer platform structure will play a major role in the resonance phenomenon in driving conditions.?4?The vibration test of the orchard transfer vehicle mastered the vibration conditions of the orchard transfer vehicle in different car conditions and operating conditions,including the vibration acceleration and the root mean square value of acceleration.In order to improve the vibration phenomenon caused by factors such as road surface excitation and uneven movement of crawler chain links during the work of the transfer vehicle,dynamic vibration absorbers were used to control the vibration according to the vibration characteristics of the orchard transfer platform.According to the steady-state response of the transfer platform structure under driving conditions,a dynamic vibration absorber was designed for the second-order mode shape of the vehicle structure.We confirmed that the power shock absorber was installed at the removable door at the front and rear of the transfer vehicle.With the aid of Ansys software modal analysis,the equivalent quality identification was used to obtain the equivalent quality of the main vibration system of the orchard transfer platform with installed dynamic shock absorber.What's more,an equivalent single-degree-of-freedom system for the transfer platform structure vibration system with installed dynamic shock absorber was established.The dynamic shock absorber was designed based on the fixed-point theory.The dynamic shock absorber was designed as following:mass m=3.4kg,stiffness k=282062.24N/m,and damping c=361.62N·s/m.According to the parameters of the dynamic shock absorber,a dynamic shock absorber model was established based on the finite element model of the transfer platform,and the numerical simulation of the vibration reduction model was carried out.The steady state response of the orchard transfer platform structure under the load of simple harmonic law was also analyzed.The results suggested that with the installing of dynamic vibration absorber,the maximum vibration displacement amplitude on the upper surface of the cabin was3.8983*10-8m,which was reduced to 17%of the maximum value before vibration reduction.The maximum vibration acceleration was 1.234*10-2m/s2,which was decreased to 21.66%of the maximum before damping.Carrying out the verification of vibration reduction effect of orchard transfer platform.Taking the vibration reduction test of orchard cultivated land transfer condition as an example,the vibration of each test point on the upper surface of the car box after installing the power vibration absorber significantly in the vertical direction,and the root mean square value of vibration acceleration is basically reduced to half before vibration reduction,and the root mean square value of vibration acceleration at the center test point of the upper surface of the carriage is 5.003 m/s2,which is reduced to 48.86%before vibration reduction.The vibration acceleration of the test points in horizontal and lateral also decreased slightly,the vibration absorption test of the orchard transfer platform proves that the dynamic vibration absorber can control the vibration phenomenon of the orchard transfer platform during the working process,and the vibration reduction effect is remarkable. |
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