| In most of China’s rice producing areas,due to the low temperature of the rice season,the planting mode of transplanting rice seedlings is used.The planted rice seedlings are cultivated in specialised and standardised ways,i.e.the agronomic method of planted rice seedlings,mainly dry seedlings in greenhouses,to improve the survival rate of seedlings and achieve stable and high yields.After decades of development,China has made great progress in planted seedling cultivation machinery,which can realize intensive mechanical operations such as spreading soil,sowing,mulching and watering,etc.However,due to the limitations in the frequency and scenarios of the use of machinery,agronomic aspects such as bed preparation in the greenhouse still rely heavily on manual work or the use of relatively primitive agricultural machinery.To address this problem,this paper designs an automatic levelling control system based on the1ZJP-2 seedbed leveller to improve the automation and operational quality of bed preparation implements,with the main research content as follows:(1)By studying the levelling requirements of the seedbed leveller,this paper adopts an electro-mechanical-hydraulic design idea and determines the overall scheme of the automatic levelling system with an electro-mechanical levelling device as the main part and a hydraulic compensation device as a supplement.The key components of the electromechanical device and the hydraulic compensation device are analysed and parametrically studied respectively.(2)The key components of the electromechanical levelling device are parametrically modelled and imported into ANSYS Workbench finite element simulation software to carry out static contact analysis on the stresses at the gear tooth mesh of the levelling gear,and compare the simulation results with the theoretical calculation values to check the structural reliability.The simulation results show that the maximum contact stresses obtained from static contact analysis are in good agreement with the theoretical Hertzian stresses.Meanwhile,the modal analysis of the overall gear pair was carried out to obtain its inherent frequency and vibration pattern,and through the vibration characteristics test of the whole machine,it was found that the main frequency of vibration of the whole machine is different from its inherent frequency,which is less likely to produce destructive resonance.(3)The overall control scheme of the automatic levelling system of the seedbed leveller is designed: the Mahony algorithm is used to fuse the attitude of the accelerometer and gyroscope inside the MPU6050 attitude sensor to obtain more realistic information on the attitude of the seedbed leveller;the STC15 series microcontroller is selected as the main controller and the incremental PID control algorithm is written inside it to complete the closed-loop control of the automatic levelling system.The hardware circuit of the automatic levelling system was designed in detail.(4)The Simulink simulation module was used to simulate the overall dynamic performance of the automatic levelling control system.The results show that the peak time of the automatic levelling system is 1.62 s,the overshoot is 1.5% and the adjustment time is 5.049 s,which has good response speed and accuracy;and the prototype of the automatic levelling system was mounted on a 1ZJP-2 seedbed leveller for comparative field tests: The test results showed that the mean value,root-mean-square error and stability of the attitude angle data of the operating equipment equipped with the electromechanical levelling device were better than those of the control group without the levelling system;the surface elevation information of the test plots was collected using a level to analyse the effect of the automatic levelling control system on the horizontal attitude of the operating equipment.The test results showed that the maximum height difference in the test plots was reduced by 2.4cm and the maximum mean standard deviation was reduced by 0.387 cm after the operation of the seedbed leveller with the automatic levelling system compared to the control group. |
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