| Soil is an important basic environment in crop production,and the ability to quickly and accurately obtain its mechanical physical properties and micro-topographic parameters is of great significance for the design of soil tillage components and the evaluation of the operation effect of tillage tools.Aiming at the practical problems of traditional in-situ soil measuring instruments,such as complicated use,labor-intensive manual measurement,and lack of devices integrating various soil mechanical and physical properties and micro-geomorphic parameter measurement functions,the design of farmland soil mechanical-physical properties and micro-geomorphic measurement devices was carried out.with experimentation.A four-wheel drive-differential steering chassis suitable for soil walking in farmland is designed as a mobile platform.The platform is equipped with a combined soil parameter measurement system and a surface micro-geomorphic measurement system.Its working principle was designed and analyzed,and the electronic control system matched with the mobile platform and the two measurement systems was developed and designed,and the mechanical and physical properties of farmland soil and the actual operation effect of the micro-geomorphic measurement device were verified through field experiments.The specific research conclusions are as follows:（1）The mechanical and physical properties of farmland soil and the overall structure and working principle of the micro-geomorphic measuring device are determined.Based on soil mechanical and physical properties and device design requirements,the overall structure,working principle and main technical parameters of the device were determined.The device mainly includes a farmland mobile platform,a combined soil parameter measurement system,a surface micro-geomorphic measurement system and an electric control system.During the measurement operation,the farmland mobile platform is used to carry the combined soil parameter measurement system and the surface micro-geomorphic measurement system,and walk to the target position under the control of the electronic control system.The combined soil parameter measurement system is used to measure soil shear strength related parameters such as soil firmness,soil moisture content,soil internal friction angle and soil cohesion;Geometric characteristic parameters such as groove type and ridge surface profile.The maximum measurement depth of the combined soil parameter measurement system is 150mm,and the standard scanning area of the surface micro-geomorphic measurement system is 1m2.（2）The design determines the structure and key parameters of the farmland mobile platform and its key components.The farmland mobile platform mainly includes the body,suspension and anti-vibration components,drive system,wheels and driving electronic control system hardware.The driving and steering mode of four-wheel independent drive-differential steering is determined and the overall structure of the mobile platform is designed.The main technical parameters are the external dimensions of 780×500×350mm,the body weight of 35kg,and the climbing angle of 20°.A parallelogram suspension shock absorber is designed,and a spring shock absorber with an elastic coefficient of 100lbs/in is selected according to the shock absorber model.Using the discrete element simulation method,the key parameters of the wheel are analyzed,and the wheel diameter,wheel width,and tooth height are used as the test factors,and the wheel resistance torque is used as the test index to carry out the BBD simulation test,and the optimal wheel parameter combination is obtained.The wheel diameter is 350mm,Wheel width 120mm,tooth height10mm.The driving force of the mobile platform is analyzed and calculated,and it is concluded that the torque required by the motor is 14.54N·m.（3）The structural design of the combined soil parameter measurement system was carried out.The combined soil parameter measurement system mainly includes cone infiltration measurement components,soil moisture content measurement components and connecting components.The principle of soil firmness measurement was analyzed,and the structural design of the conical penetration measurement component was carried out.The tensile pressure sensor and the membrane pressure sensor were selected and calibrated.The fitting coefficient of the vertical loading force and the output signal of the tensile pressure sensor reached 0.999,and the horizontal The fitting coefficient between the loading force and the output signal of the film pressure sensor is 0.971.The structural design of the soil moisture content measurement components was carried out,and the soil moisture content sensor was selected and calibrated.The fitting coefficient of the relationship between the soil moisture content sensor and the soil sample moisture content reached 0.950.The modeling research on parameters related to soil shear strength such as soil internal friction angle and cohesion was carried out.Taking vertical resistance,horizontal resistance and soil moisture as the input layer variables,and internal friction angle and cohesion as the output layer variables,using The BP neural network algorithm is used to construct the prediction model,and the prediction models are respectively constructed for the internal friction angle and cohesion.The prediction results of the validation set are2=0.96 and2=0.89 respectively.（4）A surface micro-geomorphic measurement system was developed.The system structure is mainly composed of lidar,electric push rod and ball screw slide.The working principle is to adjust the lidar to a suitable height and then the electric push rod drives the lidar to start sampling the geodesic surface in a line scanning manner.The lidar scanning field of view is set to 90°,the scanning angle resolution is set to 0.25°,and the scanning frequency is set to 50Hz.After compensation accuracy verification,the maximum absolute error at each height is 2.85mm,and the maximum average absolute error is 1.21mm.In order to eliminate the tilt error caused by the front and rear tilt of the car body,a tilt error compensation model is constructed.（5）The mechanical and physical properties of farmland soil and the electronic control system of the micro-geomorphic measuring device are designed.It mainly consists of two parts:driving electronic control system and measurement electronic control system.The overall control scheme of the driving electronic control system is analyzed,and its hardware circuit schematic diagram and software system program are designed.The microcontroller,motor drive module and remote control module models are determined.The four-wheel drive kinematic inverse solution function and the PID speed closed-loop control function are designed,and6)is 0.2,6)4)is 0.42,and6)(（9） is 0.008.The overall control scheme of the measurement electronic control system is analyzed,and its hardware circuit is designed.Schematic diagram and software system program.Determine the microcontroller module,Bluetooth module model.The important modules such as the three-way stepping motor drive module,the combined soil parameter measurement system measurement function,and the lidar scanning function in the two measurement systems are designed,and the software design of the We Chat applet is carried out.（6）Field test research was carried out to verify the mechanical and physical properties of farmland soil and the operation effect of the micro-geomorphic measuring device.The driving performance and measurement performance of the device are tested through field tests.The driving performance test results show that the driving deviation rate of the device is about 0.882%.Through the mobile performance test in four actual working conditions,the device can run smoothly in a variety of complex environments,the maximum climbing angle is about 20°,and it can cross The maximum furrow depth is 120mm;the measurement performance test results show that the combined measurement system can effectively measure the soil firmness value and soil moisture content value,with an average relative error of 5.84%and 3.99%,respectively.Combined with the mathematical model of soil shear strength parameters,it can be Effective calculation of soil internal friction angle and cohesion,the average relative errors are 8.20%and 10.40%,respectively.The surface micro-geomorphic measurement system can effectively detect surface features such as car surface flatness,furrow and ditch shape and ridge surface contour. |
