土壤离散元模型是离散元法研究土壤与触土部件相互作用的基础。为了获得西南区坡耕地紫色土离散元模型,本文基于堆积试验,采用EDEM2020软件中的Hertz-Mindlin with JKR接触模型,以休止角为响应值,结合土壤本征参数实测试验,对模型参数...土壤离散元模型是离散元法研究土壤与触土部件相互作用的基础。为了获得西南区坡耕地紫色土离散元模型,本文基于堆积试验,采用EDEM2020软件中的Hertz-Mindlin with JKR接触模型,以休止角为响应值,结合土壤本征参数实测试验,对模型参数进行标定。实测参数包括土壤密度、含水率、休止角、粒径分布、颗粒-颗粒静摩擦系数、颗粒-45钢静摩擦系数,利用Origin2021b软件图像数字化工具处理图像,得到实际休止角为34.11°,变异系数为0.452%。利用Design-Expert11软件设计了Plackett-Burman试验,对影响拟合休止角的9个参数进行筛选,得到4个影响显著参数,即颗粒表面能、颗粒-颗粒滚动摩擦系数、颗粒-45钢静摩擦系数、颗粒-45钢滚动摩擦系数。设计最陡爬坡试验进一步缩小模型参数取值范围,设计Box-Behnken试验,对模型进行分析优化,得到4个参数最优组合,即颗粒表面能0.134 J/m^(2),颗粒-颗粒滚动摩擦系数0.231,颗粒-45钢静摩擦系数1.045,颗粒-45钢滚动摩擦系数0.228。结果表明,仿真休止角与实际休止角相对误差为2.07%,一致性较好,可为紫色土离散元仿真研究提供参考。展开更多
According to these characteristics of the movement of the special platform servo,a new improved grey predictive PID control algorithm was proposed based on the grey predictive PID,and then the algorithm was simulated ...According to these characteristics of the movement of the special platform servo,a new improved grey predictive PID control algorithm was proposed based on the grey predictive PID,and then the algorithm was simulated by MATLAB.As a result that it can improve the response speed and stability of the system,and meet the demand of the system.展开更多
Internal temperature is crucial to plant growth in the greenhouse. We investigated the patterns of constructing and managing greenhouses in Chongqing, and developed an algorithm of heating temperature for closed winte...Internal temperature is crucial to plant growth in the greenhouse. We investigated the patterns of constructing and managing greenhouses in Chongqing, and developed an algorithm of heating temperature for closed winter plastic greenhouses under the conditions of no man-made illumination, no ventilation and hot wind machine as the heating equipment, which are the most adopted pattern of greenhouses in Chongqing area. The algorithm includes two functions of temperature outside the greenhouse, which calculate the values of the warming estimation coefficient (WEC) and the gap between temperatures inside and outside the greenhouse with the measured data of outside temperature, and then give the value of internal temperature; the heat rating of heating facilities required by a greenhouse can be determined by this algorithm with given values of floor area and internal temperature, measured outside temperature and calculated WEC. Verification of the algorithm demonstrates a desirable accuracy of estimation. Algorithms of computing heating temperature for greenhouses of different constructing and managing patterns and in different geographic conditions can also be derived in a similar way. This research presents a paradigm for developing a feasible method to fit out greenhouses with appropriate heating facilities, aiming at energy efficient and cost efficient production.展开更多
文摘土壤离散元模型是离散元法研究土壤与触土部件相互作用的基础。为了获得西南区坡耕地紫色土离散元模型,本文基于堆积试验,采用EDEM2020软件中的Hertz-Mindlin with JKR接触模型,以休止角为响应值,结合土壤本征参数实测试验,对模型参数进行标定。实测参数包括土壤密度、含水率、休止角、粒径分布、颗粒-颗粒静摩擦系数、颗粒-45钢静摩擦系数,利用Origin2021b软件图像数字化工具处理图像,得到实际休止角为34.11°,变异系数为0.452%。利用Design-Expert11软件设计了Plackett-Burman试验,对影响拟合休止角的9个参数进行筛选,得到4个影响显著参数,即颗粒表面能、颗粒-颗粒滚动摩擦系数、颗粒-45钢静摩擦系数、颗粒-45钢滚动摩擦系数。设计最陡爬坡试验进一步缩小模型参数取值范围,设计Box-Behnken试验,对模型进行分析优化,得到4个参数最优组合,即颗粒表面能0.134 J/m^(2),颗粒-颗粒滚动摩擦系数0.231,颗粒-45钢静摩擦系数1.045,颗粒-45钢滚动摩擦系数0.228。结果表明,仿真休止角与实际休止角相对误差为2.07%,一致性较好,可为紫色土离散元仿真研究提供参考。
基金supported by the Chongqing Scientific and Technological Innovating Program under grant CSTC2008AC1014
文摘According to these characteristics of the movement of the special platform servo,a new improved grey predictive PID control algorithm was proposed based on the grey predictive PID,and then the algorithm was simulated by MATLAB.As a result that it can improve the response speed and stability of the system,and meet the demand of the system.
基金a grant from the Major Programs of the Ministry of Science and Technology during the 10th Five-Year Plan Period from (2001BA04A)
文摘Internal temperature is crucial to plant growth in the greenhouse. We investigated the patterns of constructing and managing greenhouses in Chongqing, and developed an algorithm of heating temperature for closed winter plastic greenhouses under the conditions of no man-made illumination, no ventilation and hot wind machine as the heating equipment, which are the most adopted pattern of greenhouses in Chongqing area. The algorithm includes two functions of temperature outside the greenhouse, which calculate the values of the warming estimation coefficient (WEC) and the gap between temperatures inside and outside the greenhouse with the measured data of outside temperature, and then give the value of internal temperature; the heat rating of heating facilities required by a greenhouse can be determined by this algorithm with given values of floor area and internal temperature, measured outside temperature and calculated WEC. Verification of the algorithm demonstrates a desirable accuracy of estimation. Algorithms of computing heating temperature for greenhouses of different constructing and managing patterns and in different geographic conditions can also be derived in a similar way. This research presents a paradigm for developing a feasible method to fit out greenhouses with appropriate heating facilities, aiming at energy efficient and cost efficient production.
