Development Of Maize Stubble Harvesting Machine And Mechanism Analysis Of Its Key Components

Biomass like crop stalks and stubbles is important renewable and high-quality energyresource. Using the stalks and stubbles for power generation not only help to overcomeenergy shortage problem, but also reduce the emission of carbon dioxide. Utilization ofbiomass energy resource can help to reduce environmental pollution and mitigate energyshortage. Therefore, biomass has been applied to the development of circular economy,supplying clean energy and improving ecological environment. It has shown a great potentialdevelopment prospect. Maize stalk and stubble produced accounts for12%-15%of thetotal stalk, which is a huge biomass. But this resource has often been ignored, most of themare abandoned in the field. A root system of maize has a developed, layered and criss-crossfibrous structure. The main roots combined with soil forming a solid stubble-soil compositebody. Therefore, it is difficult to efficiently separate soil from maize stubble and collectsoil-removed maize stubble in mechanization.This work was supported by the National Hi-tech Project (863Project) of China (Grantno.2009AA043603-4,2009AA043604-2), by National Foundations of AgriculturalTechnology Transformation of China (Grant No.2009GB23600507), by the National NaturalScience Foundation of China (Grant No.51075185), by the Development Program ofScience and Technology of Jilin Province of China (Grant No.20100711), by National “985Project” in Jilin University and by Graduate Innovation Fund of Jilin University, China.(Grant No.20121093). The basic physical properties of maize stubble and soilenvironmental characteristics from stubble-soil composite body were extensivedlyresearched. Combining with the binding characteristics of root system with soil in the maizestubble, the picking-up mode and transporting mode of maize stubble were explored. Theseparating mechanism of soil from maize stubble was analyzed. Accordingly, a reasonabletechnical process was determined. In the working process, many of the involved key issues were analyzed by theoretical method. In addition, relevant mathematical models which canfurther optimize theoretical models were established. A maize stubble collecting machinewith multiple functions, including picking-up, transporting, separating soil from stubble andcollecingt stubble, was developed. The verification and correction of theoretical modelguided structural optimization of key components by a testing platform, the structural andmotioning parameters of machine were further optimized through test optimization design.Thus, the optimal combination of determined parameters was verified through experiments.Ultimately, the optimal parameters were obtained for improving working performance andquality of the machine.In this work, the basic physical properties of maize stubble, soil environmentalcharacteristics of stubble-soil composite body and binding characteristics of root system withsoil were studied. Based on a prototyping technology, the testing platform of maize stubblecollecting machine was set up to provide a good test condition for further theoretical analysisand experimental research. The motion track, velocity and acceleration of blades forpicking-up and pushing stubble were researched and analyzed. The trochoidal condition formotion track of the blade endpoint was obtained, and the motion track of stubble picked-upwas analyzed. Accordingly, the necessary condition that stubble could enter the first-levelthrowing and transporting mechanism were found. Then, the collision process of maizestubble with dam-board was analyzed, and found the necessary condition that stubble anddam-board could generate collision phenomenon. Finally, the separation mechanism of rootsystem and soil from stubble-soil composite body was analyzed and researched by thethree-dimensional stress principle. So imitating various mode of action (such as squeezing,rubing, comb-threshing, vibration, impacting, sieving) during treating stubble in theproduction and living process by human, he complex structure of stubble-soil compositebody could be destroyed, and as a result, complete separation of soil from maize stubbleeffectively can be achieve.The whole system modal parameters (natural frequencies and structural shapes) andstructural dynamic characteristics were obtained by combining theoretical modal analysiswith experimental modal analysis method. Based on the theoretical analysis results, in order to analyze the working performance of separating mechanism with new bionic roller andconcave, the effects of three major parameters (rotation speed of bionic roller, clearancebetween roller and concave, and cornerite of baffle) of the bionic roller and baffle on the rateof soil separation from maize stubble and the loss rate of stubble in working process wereexamined by means of three-factor quadratic regression orthogonal rotary method, and foundthe optimal combination of the major parameters. Consequently, relevant mathematicalmodels and experimental verification were carried out. Finally, the major parameters ofmachine were set to the best condition. The working performance and quality of the wholesystem were tested in field. The experimental results showed that, on average, the rate of soilseparation was95.57%, rate of stubble loss was4.58%at the forward speed of0.46m/s, therate of soil separation was93.23%and rate of stubble loss was4.46%at the forward speedof0.65m/s were achieved.