Research On Small Mobile Platform Of Farmland Soil Collection

Agricultural robot is a hotspot in the field of agricultural machinery.Some mature technologies of agricultural robots have been applied in agricultural production.At home and abroad,the research on mobile platforms of farmland operation robots has achieved preliminary results.Meanwhile,the research on mobile platforms for farmland soil collection has been rarely found.The collection of soil samples is an important step in the study of the physical and mechanical conditions of the soil.It is required to ensure the originality of the soil sample as much as possible.If the quality of the soil is not guaranteed,accurate research results cannot be obtained.To solve the above mentioned problems,this thesis presents a mobile robotic platform for farmland soil collection with compact structure,strong passability,high soil-sampling quality and efficiency.Platform details about mechanical design and implementation,control software design and coding,and preliminary field trials are given in the thesis.The main contents of this study are as follows:(1)In the design process of our mobile robot platform,differential steering is determined as the steering mode firstly.Secondly,the mechanical framework is proposed,including the main structure,the steering mechanism and the support rod.Thirdly,the motor requirement analysis and selection is conducted.The wheelbase of our mobile platform is determined to be 960 mm,the track is 600 mm,the power of the hub motor is 1000 W,and the maximum platform moving speed is 2m/s.Fourthly,the hardware circuit construction and the software coding of the control system are implemented.Here,both speed control switch and remote control handle are employed to carry out the motion control of the mobile platform.(2)On the basis of soil mechanics,the force of the earth borrower is analyzed.It was determined that the circumferential resistance torque was about 33 N·m and the vertical resistance was about 2888 N.The main technical parameters of the soil sampling device were determined by theoretical analysis,and the finite element analysis of the key components was carried out to verify the rationality of the structural parameter design.Determine the main technical parameters of the reduction gear,and check the root bending strength to meet the strength requirements.The hydraulic system is designed so that the hydraulic components can be well matched to complete the sampling operation.(3)Field trials of the mobile robotic platform for farmland soil collection are conducted to test its movement performance,soil collecting quality and efficiency.The results of the mobile performance test show that the platform's maximum obstacle climbing capability is 80 mm,the maximum climbing slope can reach 30°~35°,and the straight-line walking offset rate is about 0.755%.The sampling recovery test results show that the sampling recovery rate is about 95.8%.The shear strength tests show that soil samples taken by ring knife and our system share similar internal friction angle and cohesion.Under the confidence level of 0.05,the P value of the internal friction angle's variance is 0.866 at the depth from 0~20cm;at the depth from 0~10cm and 10~20cm,the P values of the cohesion's variance are 0.145 and 0.717,respectively.The comparison test results of soil sampling efficiency show that it takes only 3~5 minutes for each sampling plot.To sum up,the field experiments show that the smart mobile platform has good passability,can obtain satisfying undisturbed soil samples,is labor-saving and has high sampling efficiency.