Design and performance of high trafficability self-propelled device of blueberry harvester

The blueberry trees are cultivated densely in domestic, and there is not enough space for blueberry harvester passing. The imported blueberry harvester cannot play a role in domestic blueberry field. As a result, the blueberry harvester should be improved, especially the self-propelled device of blueberry harvester should be researched. The design goal of the self-propelled device was determined. The self-propelled device was driven by hydraulic pressure. It is composed of the walking frame, an engine, hydraulic components, a driving area, etc. The harvester can pass on the space 2 m×2 m (tree height × ridge distance) and its turning radius is small. The height of the walking frame could be adjusted automatically and the range of height variation was 0 - 400 mm. The device can be adapted to the trees height from 1 - 2 m. The device was driving by four wheels. Its working stability was reliable. The device can be matched to the existing picking and harvest system, as a result the picking efficiency of the harvester can be guaranteed. The structure of the self-propelled device was designed and its main technology parameters were determined. The working principle of the device was illustrated. The walking frame of the device under full loading was analyzed by finite element analysis. The model of the walking frame was established, which was simulated by ANSYS. The form and value of loading on the model were determined. Under the full load bending condition, the maximum stress was 53.61 MPa and the maximum displacement was 0.54 mm on the top of the frame. Under the full load torsion condition, the maximum stress was 183.24 MPa and the maximum displacement that was 3.41 mm happened on the front left arm. The strength of the walking frame met the requirement of mechanical performance under the two working conditions, and it had good load ratio and anti-torsion ability. The driving performance of the harvester was analyzed. It contained the walking performance and turning performance of the harvester and lifting performance of walking frame under full loading. The walking stability of the harvester on the slope was theoretically analyzed. The working posture of the harvester was analyzed, which contains longitudinal uphill and longitudinal downhill and cross slope driving. The experimental prototype of the harvester was accomplished. In order to test the matching performance between self-propelled device and harvesting system and the driving performance and the working stability of the harvester, the field experiment of the harvester was executed. The experiment condition and methods were determined. The control easiness of the vehicle device was guaranteed. The walking speed range was 0 - 11 km/h. The minimum turning radius was 3 160 mm. The lifting performance of the walking frame was reliable, which was fit for picking the trees of 1.1 - 2 m in height. The harvester had strong walking stability. The uphill and downhill and cross slope driving limit tipping angle of the harvester was 51°, 50° and 44°. The cross sliding driving limit angle of the harvester on different road surface was 40°. The experiment results met technical requirements, which was basically consistent with the theoretical values. The reason of the error between experiment value and theoretical values was discussed. The self-propelled device was well matched with the existing picking and harvesting system. The harvesting efficiency of the harvester was 6.95 kg/min and damage rate of the tree branches was 3.5%. The research on the self-propelled device of blueberry harvester can improve the mechanized harvesting level of small berries represented by blueberry in China, promote the matching between domestic blueberry planting agronomy and agricultural machinery, and provide theoretical basis and technical support for the improvement of small berry harvesters.