| Ratooning rice is a kind of rice that can be harvested twice after planting,which is the most potential rice planting mode for increasing grain yield and also a powerful means to achieve poverty alleviation.With the accelerating process of agricultural mechanization,the operation technology of mechanized harvesting of ratooning rice is still relatively weak.The straight rolling rate is generally 40～50%,and the turning area is as high as 80～90%,which seriously affects the yield of second season(the yield of the rolling area in second season is less than 10%).The traditional stubble righting methods of ratooning rice are mainly artificial assistance,which has a high labor intensity and low efficiency,thus it is not suitable for large area planting.The problem of high rolling rate caused by mechanical harvesting in the first season of ratooning rice has become the core problem that restricts the promotion of the planting of ratooning rice and affects the yield and income of farmers in the second season.In this paper,a stubble righting device and the height adaptive control system during the first harvest season of the ratooning rice were designed,which could realize the integrated operation of machine harvesting and stubble righting,and could adjust the height automatically according to the change of the complex field terrain.The main research work includes:(1)The effect of stubble righting angle on the yield of the second season was investigated."Yue Guang rice" planted in the growing area of Dai Zhuang,Jurong City,Jiangsu Province was taken as the experimental object.To verify the feasibility of stubble righting in the rolling area of crawler-type harvester and determine the ideal stubble righting interval,after the first harvest in August,the stubble left in the rolling area of the ratooning rice was righted to a certain angle with the ground to explore the effects of different righting angles on the yield of the second harvest season in November.The mechanical properties of the stems in the rolling area were analyzed.Through several groups of experiments,the average load of the stubble in the rolling area was 176.4N under axial tension,31.7N under cantilever bending,and 29.5N under radial compression.The calculated elastic modulus and shear modulus of the stem of ratooning rice stubble were 25.3MPa and 9.0MPa respectively.These mechanical properties provided data support for subsequent DEM-MBD coupling simulation.(2)The 4LZ-6.0 multifunctional crawler-type harvester was taken as the carrier,a kind of eccentric parallel four-link type stubble righting device was designed based on the width of crawler,the overall structure and working principle of stubble righting device were described.It was mainly composed of righting teeth,angle regulating plate and rotating shaft.The effective working range of the teeth was the same as the width of the crawler,and the stubble righting angle ranging from 0° to 90°.The spatial layout and hydraulic system of the height adjustment mechanism were optimized to meet the requirements of high efficiency and high performance of the operation of righting the ratooning rice stubbles.(3)The bidirectional coupling simulation of DEM-MBD was realized by EDEM and Recur Dyn.The coupling simulation experiment was carried out by setting different working parameters of the stubble supporting device for regrowing rice and combining with single factor test method.The effects of the stubble righting operation in the rolling area were analyzed under different stubble righting angle,rotation speed and forward speed,taking the righting success rate and stubble broken rate as evaluation indexes.Through coupling simulation test,the working parameter range of the device was obtained,and the ideal righting operation effect with low damage was realized.(4)According to the work requirements of the stubble righting device on the complex road surface in the field,ultrasonic sensors were used to obtain the height change information of stubble righting device,and a grey prediction fuzzy PID controller was designed for the stubble righting device combining with grey prediction,fuzzy theory and PID controller.The selection of various components of the hardware system was determined,the manual / adaptive control process was designed,and the manual / adaptive control system of the height of the rice stubble righting device with BODAS RC28-14 as the main controller was developed,which realized the automatic adjustment of the height of the stubble righting device.Through the field test,the influence on the righting operation effects when the height adaptive control system was turned on / off were compared.The test results showed that the height adaptive control system was turned on,the righting rate was higher than that of the test group without the height adaptive control system,and could effectively avoid the collision between the device and ground,thus improved the field trafficability and adaptability of the ratooning rice combine harvester.(5)Based on the working parameter range of stubble righting angle,rotation speed,forward speed determined in the DEM-MBD coupling simulation,the field experiment was carried out with righting angle,rotation speed and forward speed as experimental factors,and the righting success rate and the yield of the second harvest season as evaluation indexes.Three factors and three levels quadratic regression orthogonal rotation combined test method was used to further verify the performance of the device.The results showed that when the stubble righting angle was 45°,the rotating speed was 55r/min and the forward speed was 0.75m/s,the righting rate could reach up to 85.5% and the yield could reach 246.7 Jin/mu in the second season.In the experimental group,the yield loss in the area without righting in rolling area was about 70.2%,and the yield loss in the area without righting after rolling was 38.4%.The experimental results show that the error between the success rate of field test with optimal parameter combination and the theoretical success rate is 1.1%,and the error between the field test and the theoretical output is 2.9%. |
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