Research On Header Profiling And Crop Height Measurement Method

In recent years,China has paid special attention to the development of agricultural machinery and equipment,and combine harvesters have played an important role in agricultural production as crop harvesting tools.With the continuous advancement of science and technology,combine harvesters are developing in the direction of large-scale,automated and intelligent.In the harvesting process,the combine harvester often has problems due to improper adjustment of the height of the header and the inability to adjust the speed of the harvester in time because of the change of crop height,resulting in food loss,header collision and blockage damage,and slow harvesting efficiency.Therefore,research on harvester header profile and crop height measurement methods is particularly necessary.This paper conducts in-depth research on the design of the harvester's header profile control system,sensor measurement data processing,automatic height control strategy of the header and crop height measurement based on binocular vision.The main contents include:? In order to solve the problem that the height adjustment of the harvester's header depends on the manual operation of the driver,a header profile measurement and control system is designed.Design and adopt the header height measurement scheme combining ultrasonic array sensor and mechanical profiling mechanism;design software and hardware system based on STM32,realize CAN bus communication,PWM drive electromagnetic valve,automatic control manual control switching and closed-loop control of header height and other functions.? In order to solve the problem that the measurement error of the header height is large,the sensor measurement data processing methods are studied.The sensor calibration is performed by the least squares method,and the relationship between the sensor output value and the actual header height value is obtained;According to the characteristics of the measured data of the ultrasonic sensor and the angle sensor,the double filtering method of limiting filter combined with median filtering and the moving average filtering method are selected respectively to denoise and smooth the measurement data.The superiority of threshold filtering based on wavelet transform in the measurement of ultrasonic sensor measurement data is analyzed.The adaptive weighted average fusion method based on historical data and the fusion method based on BP neural network are studied for the filtered data of the sensor.The simulation results show that the header height measurement data after sensor calibration,data filtering and sensor data fusion has higher precision than the original measurement data.? In order to solve the problem that the traditional control method cannot adapt to various terrains,the research on the height control strategy of the header is carried out.Modeling and analyzing the harvester to obtain the transfer function of the header height with respect to the drive current;The control effects and limitations of traditional control algorithms under different terrains are studied;A fuzzy adaptive PID control strategy is designed.The simulation and field trial results show that the fuzzy adaptive PID control method has faster response speed and more stable control effect and can adapt to different terrains.? In order to solve the problem that crop height measurement relies on manual measurement,a research on crop height measurement method based on binocular vision was carried out.The principle of binocular vision 3D reconstruction is analyzed;The stereo calibration and stereo matching technology of binocular camera were analyzed.A crop height measurement method based on disparity map is proposed.The test results show that binocular vision measurement is a feasible method for measuring crop height,and the measurement accuracy meets the requirements of normal operation.