【作者】 罗海峰；

【导师】 汤楚宙；

【作者基本信息】 湖南农业大学 ， 种子科学与工程， 2013， 博士

【摘要】 油菜是我国最重要的油料作物,在我国农业生产中占有重要地位。油菜机械化收获是油菜生产中的重要环节,现有油菜收获机在收获过程中由于茎秆交叉而难以分行,增加了割台收获损失量。本文对油菜植株、角果等在收获过程中的物理表现特性进行测试研究,采用高速摄影技术手段对角果碰撞过程裂荚现象进行研究分析。设计一种茎秆分厢机械,在对其结构进行运动学、动力学分析基础上,借用adams、solidworks、matlab等软件对分厢器进行深入研究,最后对关键部件进行结构优化分析,该研究为油菜机械化收获装备的设计提供了理论依据。研究的主要内容和结果如下：1、对油菜植株田间特性进行了测试调查,结果表明植株茎秆直径在8mm附近分枝少,分枝离地高度较高,表现特性比较适合于机械化收获,有利于割台分枝收割,减少割台落粒损失。中等密度时,植株平均直径趋于平稳,植株高度中等,分枝较少,分枝离地高度较高等田间特性有利于机械化收获作业。成熟度、催熟剂喷施等因素对角果拉伸力学特性影响表明：中等密度的直播油菜直径处于8-10mm间,其角果抗拉能力受收获时间段的影响偏小,其适收期会有所延长,有利于提高机械作业利用率和作业时间跨度；催熟剂的实施对植株角果的抗拉能力影响较小,通过喷施催熟剂对提前油菜收获时间有着积极的作用。2、对油菜茎秆进行抗挤压特性测试试验,为分厢器的设计提供合适挤压点挤压高度等田间作业参数。结果表明：拉断试验表明偏角主要分布在40-60。范围内。离地高度为600mm,挤压偏角为30。,中等成熟阶段,挤压效果较好,回弹比小于20%,单位挤压力低于0.25N.mm-1。3、采用pco.1200高速摄影仪,对油菜角果收获时间段进行裂荚过程摄像分析研究,结果表明不同挤压位置时侧面挤压角果比『F面挤压角果力度较大,在200mm/s挤压速度时挤压力相对较小。对角果碰撞裂荚过程中高速摄像分析研究发现不同碰撞角度、不同摆放位置对角果裂荚有影响,自下而上的碰撞过程需要的碰撞速度相对较大,而自上而下碰撞需求的碰撞力较小。倒挂状态下需求的碰撞速度最小,自然状态下需求的碰撞速度较大,最大为水平状态下。4、采用“黑箱”方法对分厢器进行了系统设计,对分厢器进行功能分解和原理方案求解,再构建形态学矩阵计算得到合理的结构原理方案——往复向上扩张顶开式分厢,设计了整体结构布局图。5、运用理论力学运动学求解原理,对平行四杆机构和槽轮机构进行了运动学和动力学分析,研究发现：平行四杆机构在进行往复运动过程中,水平滑块上的推力F向左推的过程中,开始位于较大值,随着角度的增加受力逐步下降到一个较小的值,且一直稳定在一个较低的范围内；由于移动摩擦力的作用承担了部分助推力,滑块向右运动过程中受力偏小,但整体上基本对称。对槽轮角速度和角加速度变化规律以角度0.83。为对称点,呈M字形变化；圆柱销在滑槽中的相对速度和加速度分析表明,在0.83。对称点两侧呈V字形对称分布；推杆对滑槽径向压力从-45。开始变化到Φ1角度为-10.62。时,开始有一个逐步上升的过程,然后从-10.62。到0.83。急剧减少到一个最低点,再从0.83。向正向角度增大时实现下一个对称循环,整个过程呈M字形变化。6、在对分厢机构的关键部件进行结构优化分析中,优化得到滑块长度62mmm时受力最小；在不超过最大压力角的情形下,双向螺纹轴优化得到最小基圆半径为14mm；最合理双头螺纹过度圆弧的外切圆半径为37mm；滑块在经过过度圆弧其受力变化曲线为一开口向上的抛物线形状,幅度在0.4%左右；最后对分厢推杆的两侧布置结构进行分析优化,两侧斜推杆倾角θ=60°,主推杆总变形长度R=855mm时为最佳分厢角度,该状态下受力最小。7、运用adams软件对分厢机构关键部件的运动学和动力学进行仿真分析,采用solidworks软件中的simulation插件对推杆和槽轮机构进行有限元分析,研究结果如下：对机构顶端水平推杆进行运动学分析,推杆质心速度变化拟合方程为：y=0.0015x2-0.2598x+15.112(R2=0.9996);推杆质心加速度拟合方程为：y=-0.0001x2+0.0107x一0.4963(R2=0.9964);对推杆和槽轮进行有限元仿真分析,推杆在静态分析和疲劳分析中表明,原有设计的结构和材料完全符合强度要求；对槽轮有限元分析表明,最大应力集中在槽轮的滑槽底部靠近槽轮过渡圆弧处；在材料厚度方面,槽轮优化后得到厚度为4.44583mm,拨杆圆柱销连接侧面板厚度为8.63324mm,优化后质量相对下降55.54%和32.08%。最后对槽轮厚度优化值取整5mmm,拨杆侧面厚度9mmm,缺口圆盘5mm,拨杆圆柱销14mmm。8、对试制的样机进行田间分厢试验,试验结果表明：1)随着推杆上升速度的增加,成行稳定性下降。2)圆弧形推杆的损失率远远大于球形推杆,而成行一致性与成行稳定性相比较影响不显著。3)结果显示总损失率在顺倒伏和逆倒伏情形下变化不大,而侧向倒伏时损失率增加明显。4)早熟品种损失率大于中熟品种,中熟品种大于迟熟品种,成熟度对成行一致性和成行稳定性影响不显著。5)折枝率随推杆的上升速度增加而增加,在茎秆倒伏情况变化中,顺倒和侧倒对折枝影响相对较小,而侧倒伏时折枝比率增加较快,成熟度对折枝率的影响不大。6)对推杆上升速度(A)、推杆形状(B)、油菜成熟度(D)三种因素,以总损失率、成行一致性、成行稳定性为性能指标进行正交试验。正交试验极差分析表明影响总损失性能指标最主要因素D,其次是B和A,各因素主次顺序为D>B>A,优化组合为40mm/s推杆速度,作物侧倒伏,晚熟；作物倒伏性能对成行一致性影响的主次顺序为B>D>A,其最优组合为作物顺倒伏,晚熟,100mm/s推杆速度;作物倒伏对成行稳定性影响的主次顺序为B>A>D,较优水平分别为A1、B1、D2,最优组合为作物顺倒伏,40mmm/s推杆速度,中熟。7)对试验结果方差分析表明,作物成熟度不同水平对总损失影响显著,P=0.014<0.05,而推杆速度大小及倒伏情形对总损失不显著,A、B、D各因素对成行一致性与成行稳定性都不显著,但从P值大小顺序可以发现油菜成熟度是影响总损失的主要因素,油菜倒伏情形是影响成行一致性和成行稳定性的主要因素,但是影响不显著。更多还原

【Abstract】 Rape is one of the most important oil crops which occupies an important position in China’s agricultural production. Rape mechanized harvesting is an important part during the production, while rape harvesting machine at present has an increase of cutting table harvest loss due to the stem cross. The tests of physical characteristics have been done on rape plants and siliques in harvest, using high-speed camera technology to analysis the siliques split in collision. The paper is to design a stalk divider and provide theoretical basis for the design of rape mechanized harvesting equipment, on the basis of kinematics and dynamics analysis in its structure, using Adams, Solidworks, MATLAB software to study the stalk divider, finally carrying out the structure analysis on the key components. The main results are as follows.1) The field characteristics tests of rape plants show that plant diameter around8mm is suitable for mechanized harvesting due to fewer branches, branches higher above the ground. Those characteristics are beneficial to harvest mechanization, cutter dividing and reduce the shattering loss in cutting station. Medium-density planting exhibits the stable average diameter, medium plant height, fewer branches, and higher distance above the ground which give more advantages for mechanized harvesting. The study on the silique tensile mechanical properties affected by maturity, ripening agent shows that:the rape diameter with medium-density planting is between8mm-10mm, its silique resistance to tension capacity has little impact on harvest period which can improve the utilization of mechanical operations and working time span; Ripening agent has little impress on the plant silique tensile strength. Spraying a ripening agent has a positive effect on rape which can be harvested ahead of time.2)The tests of anti-extrusion characteristics of rape stalk have been conducted in order to provide a suitable work parameters of extrusion points and extrusion height for sub-compartment design. The results show that:the snap angle of inclination is mainly distributed in the range of40°-60°,The effect of stalk extrusion is better with600mm height from ground,30°extrusion deflection, medium maturity, in which the ratio of rebound is less than20%, the unit extrusion pressure is less than0.25N.mm-13)Pco.1200high speed camera has been used to analyze the silique break process in rape harvest period. The result show that different collision direction, different locating place have impact on the silique break. Collision direction from bottom to top need relatively large velocity, while from top to bottom need less collision force. Upside down state needs minimum collision speed, natural state needs larger collision speed and horizontal state is maximum. Test of extrusion silique results show that the extruding force from side direction is larger than from front direction, which the squeeze pressure is relatively smaller with200mm/s extrusion speed.4)The stalk divider is systematically designed by "Black box" method. Using functional decomposition and principle scheme solution, then building morphological matrix calculation to obtain the reasonable structural principle program-reciprocating upward stalk dividing, thus the overall layout structure has been designed.5) Kinematics and dynamics analysis have been used in parallel four-bar mechanism and the geneva wheel mechanism. The study found that:while parallel four-bar mechanism were in reciprocation process, the thrust F on the horizontal slider to the left the force had larger value at first, then the force gradually decreased to a smaller value in a stable lower range with the increase angle; Due to mobile friction bearing a part of the boost force, the force was small while slider movement to the right, but change tendency is overall symmetrical. The angular velocity and angular accelerated velocity of geneva wheel analysis showed that the symmetry angle was0.83°in M shape; Relative velocity and acceleration analysis for cylindrical pin in the chute showed that the symmetry angle was0.83°in V shape symmetry distribution; Radial pressure from push rod to the chute change from-45°to the φ1angle of-10.62°, at the beginning of the process it had a gradual rise, then decreased sharply from-10.62°to0.83°to a lowest point, a symmetric cycle from0.83°to the forward angle increase, the whole process changed in M-shape.6)The structure optimization analysis has been taken on the key components of the stalk divider, which the slider length is62mm the force is minimum. In the case of not exceeding the maximum pressure angle, bothway thread spindle has been optimized that minimum base circle radius is14mm. The circumscribed circle radius of37mm is most reasonable for bothway thread spindle. The force curve is a parabola shape slider change about0.4%while slider ran after excessive arc. Finally, the structure optimization analysis has been done for the push rod of divider in two sides, on both sides of the lifter angle is60°,the best deformation length of the main push rod is855mm because the force is in the minimum state.7)Kinematics and dynamics simulate analysis on the key components of stalk divider has been taken with Adams software, the finite element analysis has been done on push rod and geneva mechanism by the Solidworks software simulation, the results are as follows:through kinematics analysis on the level of the top push rod,the velocity change fitted equation of mass center of push rod is:y=0.0015x2-0.2598x+15.112(R2=0.9996)Acceleration change fitted equation of mass center of push rod is:y=-0.0001x2+0.0107x-0.4963(R2=0.9964)The finite element simulation analysis has been done for push rod and geneva wheel:the static analysis and the fatigue analysis on push rod show that the original design of the structure and material is completely in conformity with strength requirements; and the finite element analysis shows that the maximum stress concentrates in the transition circular arc of the geneva wheel; the optimal thickness of the geneva wheel is4.44583mm,the thickness of side panel connect to cylindrical pin of driving lever is8.63324mm, after optimization the relative quality drop55.54%and32.08%respectively. Finally, the thickness of the geneva wheel gets rounded to5mm, driving lever gets rounded to9mm, cutaway disk gets rounded to5mm, cylindrical pin of driving lever gets rounded to14mm. 8)The field trials have been conducted for prototype, the results show that:1) the rising rate of push rod increases, the in line stability decreases.2)the loss rate of arc-shaped push rod is greater than the spherical push rod, while the consistency and stability has no significant effect.3) the results show that the total loss rate changes little in sequence and opposite lodging while loss rate increases significantly in the case of side direction lodging.4) the loss rate of early maturing variety is greater than medium maturation variety and medium maturation variety is greater than the late-maturing varieties, maturity has no significant effect on the in line consistency and stability.5) the broken branches rate increase with the rising speed of push rod, the impact is relatively small in sequence and opposite direction lodging, while the broken branches ratio of side direction lodging increases rapidly, the maturity has little effect on broken branches rate.6) three factors of the ascending velocity of push rod (A), the push rod shape (B), rape maturity (D), three performance indexes of total loss rate, in line consistency, in line stability are designed in orthogonal test. The range analysis of orthogonal test shows that the most important factors of the total loss performance is D, followed by B and A. The factor order is D> B> A, that is optimal combination push rod speed40mm/s, crop side lodging, late maturity. The influence of crop lodging performance to in line consistency is B> D> A in turn, optimal combination along is in sequence lodging of the crop, late-maturity, push rod speed100mm/s. The influence of crop lodging to in line stability is B> A> D in turn, the optimum level is A1,B1, D2respectively, the optimal combination crop is in sequnce lodging,40mm/s push rod speed, and medium maturity.7) variance analysis shows that the different levels of crop maturity have much influence on the total losses (P=0.014<0.05), while the push rod speed and lodging situation have no significant impact on the total loss. The influence of factors (A, B, D) to in line consistency and in line stability is not significant, but rape maturity is the main factor affecting the total loss from the P value. Rape lodging situation is the main factor that affects the in line stability and consistency, but the effect is not significant.更多还原