Design And Experimental Research Of Attitude Adjustment And Walking Mechanism Of Mountain Crawler Tractor

China’s total land area is 9.6 million square kilometers,the hilly and mountainous area are about 6.66 million square kilometers,and accounting for 69.4% of the total land area.Due to the influence of many factors such as topography and landform,the level of agricultural mechanization in hilly and mountainous areas lags behind seriously,and the supply of mountain tractors that can meet the requirements for operations in hilly and mountainous areas are seriously inadequate.Therefore,this paper according to the design requirements of crawler tractors and the characteristics of slope contour operations,The attitude adjustment and walking mechanism of the mountain crawler tractor were studied,and a mountain crawler tractor with omnidirectional attitude adjustment function was designed to improve the stability and safety of the tractor’s slope operations.The main research contents of this article include:(1)Determination and stability analysis of omnidirectional attitude adjustment scheme of mountain crawler tractor.By comparing the five lateral attitude adjustment schemes,the lateral attitude adjustment scheme based on the "parallel four-bar" mechanism was determined,and designed a longitudinal attitude adjustment scheme based on the "double frame" mechanism;Finally,the omnidirectional attitude adjustment plan of the mountain crawler tractor was determined;Through a dynamic analysis of the tractor’s slope operation,the key factors affecting the tractor’s ultimate glide angle and ultimate tip angle were obtained.And through the dynamic analysis of the slope-tracking of the mountain track tractor after the attitude adjustment,the positive effect of the attitude adjustment device on the stability of the tractor is verified.(2)Design of key components of mountain crawler tractor.First,through the kinematic analysis of the lateral and longitudinal attitude adjustment devices of the mountain crawler tractor,the mathematical models of the key parameters that affect the lateral and longitudinal attitude adjustment angles were established respectively,thereby determining the main parameters of the lateral and longitudinal attitude adjustment devices of the mountain crawler.Then,by comparing and analyzing the characteristics of various types of walking systems and suspension forms,the overall scheme of the mountain crawler tractor walking system was finally determined,and the main size parameters of the walking device were theoretically calculated;Finally,the design of the mountain track tractor’s attitude adjustment hydraulic system and the selection of hydraulic components were completed.(3)Processing trial production and optimization of mountain crawler tractors.First,using SW software to carry out 3D modeling and virtual assembly of tractor parts;Then,completed the processing,assembly and trial production of mountain crawler tractor parts;Finally,the maximum attitude adjustment angle of the mountain crawler tractor was tested,and the test results showed that the maximum angles of the tractor’s attitude adjustment were 15.50°(lateral left),15.20°(lateral right),8.50°(vertical),and they all meet the design requirements.And optimized design of the track tensioning device,by comparing the advantages and disadvantages of the four track tensioning schemes,the hydraulic follow-up tensioning scheme based on "accumulator and manual pressure device" was determined,and the calculation and selection of various components in the tensioning scheme were completed.(4)Mountain track tractor attitude adjustment and pass test.First,a test experiment was conducted on the attitude adjustment of the tractor,and it was found that when the body of the mountain crawler tractor is inclined to the left or right by 0° to 15°,the body of the tractor can be leveled by the left or right attitude adjustment;Then,according to the relevant national standards,the passability of the mountain crawler tractor is tested and analyzed from the aspects of the prototype center of mass coordinates,ground pressure,straight-line driving performance,minimum turning radius and maximum span trench width.Through the measurement of the center of mass coordinates of the whole machine,the horizontal,vertical and height coordinates of the tractor’s center of mass are: 825 mm,-3mm,422 mm,and then the maximum tilt angle of the tractor’s limit uphill,downhill and transverse are: 60.0°,58.1°,56.7°,indicating that the tractor has good stability;By calculating the average ground pressure of the tractor,the average ground pressure of the tractor is 0.025 Mpa,indicating that the tractor has good passability on soft ground and peat swamp;Through the straight-line driving test of the tractor,the average yaw rate of the tractor on the grass is 5.50%,which is less than 6% of the national standard;Through the test of the minimum turning radius of the tractor,the minimum turning radius of the tractor on the loam road is: 1728 mm,indicating that the tractor has good steering maneuverability;Through the test of the maximum width of the tractor across the ditch,the maximum width of the tractor across the ditch is 600 mm,which is consistent with the theoretical analysis of the width of the trench across the tractor based on the static method.In summary,the indicators obtained by the test basically meet the requirements of the national standard.