伺服系统中滑模变结构控制器的设计

针对伺服系统中包含非线性和参数不确定性问题,依据滑模变结构控制理论,提出了基于指数趋近率的滑模位置控制器设计方法,建立了被控系统的数学模型。最后给出了采用极点配置方法确定切换函数。     

荔枝果壳摩擦系数测量试验研究

依据自行设计的农业物料摩擦系数自动测量装置,针对不同品种、取样方向荔枝果壳以及不同斜面倾角,测得荔枝果壳-橡胶板、果壳-尼龙板之间的摩擦系数．结果表明,荔枝果壳-橡胶板的静摩擦系数为0．8202～O．8683,滑动摩擦系数为0．8184～O．8738;果壳-尼龙板之间的滑动摩擦系数为0．407～0．474;荔枝品种和取样方向对果壳静摩擦系数存在一定影响,对滑动摩擦系数影响不大．因此,在建模的时候可近似将荔枝果壳当成各向同性材料,这些为荔枝收获、加工、储运等设备的设计提供了参数依据．     

模幂运算的窗口NAF方法

将椭圆曲线的定点标量乘的窗口NAF方法应用在模幂运算中,通过采用预处理技术,与SMM算法进行组合得到一种新的求模幂乘算法窗口NAF方法.     

汽车转弯自动照明控制系统数据采集滤波方法

为了减少汽车转弯自动照明控制系统数据滤波处理中的延时,在滑动中值滤波方法基础上,提出了一种带补偿的限幅滑动中值滤波算法,通过补偿的方式跟随信号的变化趋势。该算法通过2个步骤完成滤波,先对数据进行带补偿方式的限幅处理,再进行滑动中值滤波处理。该算法综合了滑动中值滤波法的实时性以及限幅滤波法对偶然性干扰滤除的有效性,实现更准确的滤波。仿真与实测结果表明,与滑动中值滤波方法相比较,改进后的算法滤波能够实时地滤除数据中的干扰,处理时间可减少62%,滤波效果较好,且速度信号的数据滞后时间较短,实时性较高,满足系统设计要求。     

CLDAS融合土壤湿度产品在东北地区的适用性评估及订正

通过计算CLDAS的0-20cm土壤相对湿度融合产品与农业气象观测站逐旬10cm土壤相对湿度观测值的相关性和偏差,综合分析CLDAS在东北地区的适用性。结果表明：CLDAS融合土壤相对湿度能较合理地反映东北地区10cm深度土壤相对湿度的空间分布,但是在对极值的描述上有所欠缺,其中CLDAS对辽宁西部和黑龙江西南部的土壤相对湿度模拟偏高较明显,而在黑龙江的东北部地区对实际土壤相对湿度的模拟偏低;总体上,CLDAS融合土壤相对湿度资料在东北地区的适用性由西南向东北方向递减,在吉林和辽宁省的适用性更好。回归订正和7旬滑动平均订正法对CLDAS产品的误差订正表明,订正结果大大提高了CLDAS产品的精度,其订正后产品可以应用于土壤湿度干旱监测业务。     

Anti sliding pile performance under acid stress coupling

Anti sliding piles are an important engineering structure used extensively in landslide prevention. Their durability influences their work lives. In a laboratory model experiment of a cantilevered anti sliding pile under acid stress coupling, the pile body displacement variation is monitored continuously, and both concrete strength and neutralization depth are tested. The results indicate that the concrete strength decreases gradually under acid stress coupling, while the displacement increases continuously. The neutralization depth of the concrete in the anti sliding pile is linear to the square of duration in acid stress coupling.     

Fire-driven oak regeneration in French Mediterranean ecosystems

Regeneration by seeds for cork oak (Quercus suber) and companion oaks (holm oak Quercus ilex and downy oak Quercus pubescens) is likely to be poor in the fire-prone Maures massif (southern France) but the causes are poorly known. Our objective was to assess the effective recruitment for these three oak species and their temporal pattern of recruitment, in order to determine the main limitation factors and the regeneration window of each species. We studied oak recruits (height <3 m) in naturally regenerated populations according to a gradient of fire recurrence and in five main vegetation types including shrublands and mixed mature woodlands. Fire recurrence was the main explanatory factor of oak recruitment, either directly or through vegetation type and microsite characteristics. The results indicate nil to low recruitment for holm oak and downy oak in shrublands, especially those recurrently burned and dominated by Cistus species. Cork oak recruited better than the other oaks in medium and high shrublands dominated by Erica arborea. In contrast, recruitment was high for holm and downy oak in mixed oak stands and mixed pine-oak stands that have not burned for decades. Microsite conditions such as coverage by litter and shrubs influenced oak recruitment, whereas landscape configuration and stand basal area had no influence. Our results suggest that strategic shrub-clearing, oak planting and protection of mixed oak woodlands as seed sources would help maintaining oak populations in the woodland–shrubland mosaic.     

浅析欧式木窗截面基本形状

从人们对普及型欧式木窗的需要出发,介绍了实木窗基本截面形状对其使用性能的影响,在原理上对每个截面形状确定的基本方法进行了分析,阐述了在设计截面形状时应考虑的问题.     

走式不分行青饲机切割器滑切角分析与计算

在对切割器进行动力学分析的基础上,给出了青饲机切割器动态切割角的定义和计算公式;详细分析了机器以不同作业速度行走时,切割器旋转1周过程中动态滑切角的变化规律,可按照统一方法描述滑切角的特性。同时,做出了动态滑切角增减量的函数曲线,该函数曲线对青饲机切割器的研究设计有重要意义,可直观看出滑切角的变化趋势,即青饲机作业速度越大,动态滑切角的变化幅度也越大。     

基于农服平台的植保无人机任务分配与路径优化

为解决农业社会化服务平台下植保无人机“单基站-多无人机”模式任务分配调度的精细化匹配问题,建立了任务分配调度的两阶段混合整数规划模型。首先,引入了考虑温度影响下的农药药效可变时间窗、植保无人机农田中飞行模式选择、变动耗电速率等农业参数变量,在快速精准解决农户分散的植保需求条件下,求解出植保无人机任务分配调度的成本最小化目标;然后在保证其他参数不变的情况下,分别改变植保无人机的电池额定续航时间、农田中的飞行模式、温度对应的最佳药效可变时间窗和需求大小4个参数,研究了植保成本的改进情况。结果显示,各植保无人机搭载续航时间长的电池、在农田中选择长边转弯栅格形飞行、选用发挥最佳药效温度范围大的农药种类和提高单位时段平台服务量上限策略,分别可以降低40.02%、12.45%、21.17%和39.19%的植保成本。以上结果表明,引入了具体农业生产要素的混合整数规划的模型科学有效,更适用于农服平台的植保无人机任务分配调度。