大型车辆空气悬架控制器的设计开发

以空气悬架为研究对象,构建带附加空气室空气悬架系统的1/4车辆振动模型,采用不依赖于被控对象精确数学模型的模糊控制策略,开发出空气悬架刚度可调的软件控制单元。     

Simulation of automatic control of an irrigation canal

Improved water management and efficient investment in the modernization of irrigation schemes are essential measures in many countries to satisfy the increasing demand for water. Automatic control of the main canals is one method for increasing the efficiency and flexibility of irrigation systems. In 2005, one canal in the irrigation scheme ‘Sector B-XII del Bajo Guadalquivir’ was monitored. This canal is representative of irrigation schemes in Southern Spain; it is divided into four pools and supplies an area of 5154 ha. Ultrasonic sensors and pressure transducers were used to record the gate opening and water levels at the upstream and downstream ends of each canal pool. Using the recorded data and the SIC (Simulation of Irrigation Canals) hydraulic model, two canal control options (local upstream control and distant downstream control) were evaluated using a PI (Proportional-Integral) control algorithm. First, the SIC model was calibrated and validated under steady-state conditions. Then the proportional and integral gains of the PI algorithm were calibrated. The controllers were tested using theoretical demand changes (constant outflow followed by a sudden demand increase or decrease) and real demand changes generated on the basis of a spatially distributed crop water balance that included a number of sources of variability (random and not random) in the determination of field irrigation timing and depth. The results obtained show that only the distant downstream controller was able to adjust quickly and automatically the canal dynamics to the varying water demands; it achieved this efficiently and with few spills at the canal tail, even when there were sudden and significant flow variations.     

An evaluation of the net radiation sub-model in the ASCE standardized reference evapotranspiration equation: Implications for evapotranspiration prediction

Net radiation (R_n) is a key component of the surface energy balance, but it is expensive and difficult to measure accurately. For these reasons, R_n is often predicted in evapotranspiration (ET) calculations with a model requiring measurements of incoming shortwave radiation, air temperature, and vapor pressure. We compared R_n predictions from the R_n sub-model used in the American Society of Civil Engineers (ASCE) standardized reference ET equation to mean R_n measurements from five 4-component reference net radiometers. The radiometers were part of a recent comparison study of multiple net radiometer models conducted over irrigated and clipped turfgrass in northern Utah (Blonquist et al., 2009). In the R_n model, net shortwave radiation is determined by direct measurement of solar radiation and an assumed value of albedo for the surface (0.23 for fully vegetated surfaces), and net longwave radiation is calculated with a Brunt (1932, 1952) approach for predicting net surface emissivity, calculated from near surface vapor pressure. Additionally, the ratio of measured incoming shortwave radiation to predicted clear-sky shortwave radiation is used as a surrogate variable for cloud cover in the net longwave radiation calculation. Relative to the reference R_n measurements (average of five 4-component net radiometers), modeled R_n was high during the day by an average of 8.6% and high in magnitude (more negative) at night by an average of 13.4% over hourly time intervals. Daily total R_n calculated by summing the hourly model predictions was always higher than the reference measurements, by an average of 8.1%, whereas daily total R_n calculated from the model over daily time intervals was closer to the reference measurements, 2% high on average. The model R_n error during the day was partly caused by the assumption in the model that surface albedo is a constant value of 0.23. Measurements showed albedo ranged from approximately 0.21 at solar noon to 0.30 near the beginning and end of the day, with a mean value of 0.23. However, most of the model R_n error was due to the prediction of net longwave radiation, where the empirical equation in the model typically yielded values that were too low in magnitude (less negative), by approximately 20% on average, but the error was dependent on time of day. The R_n error at night was largely caused by the inability to measure the surrogate for cloud cover at night, which relies on measurement of solar radiation from a previous time period of sufficient solar zenith angle. All five of the net radiometer models tested in the comparison study matched the mean of the reference net radiometers better than the ASCE model. When modeled hourly R_n was used to calculate ET over hourly time intervals, or when hourly ET values were summed to yield daily ET, ET was typically high, by 6% on average, relative to ET calculated from measured reference R_n. When modeled R_n was calculated over daily time intervals and used to calculate ET over daily time intervals, ET was more accurate, 1% high on average, relative to ET calculated over daily time intervals from measured reference R_n. While new models for R_n are being developed, the sub-model in the ASCE standardized reference ET equation has been in use for the past two decades in thousands of ET stations. As newer models are developed we hope to use this data set to evaluate them.     

Deficit irrigation and nitrogen effects on seed cotton yield, water productivity and yield response factor in shallow soils of semi-arid environment

A field experiment was conducted for 2 years to investigate the effects of deficit irrigation, nitrogen and plant growth minerals on seed cotton yield, water productivity and yield response factor. The treatment comprises six levels of deficit irrigation (Etc 1.0, 0.9, 0.8, 0.7, 0.6 and 0.5) and four levels of nitrogen (80, 120, 160 and 200 kg N ha⁻¹). These were treatments superimposed with and without plant growth mineral spray. Furrow irrigation treatments were also kept. Cotton variety Ankur-651 Bt was grown during 2006 and 2007 cotton season. Drip irrigation at 1.0 Etc saved 26.9% water and produced 43.1% higher seed cotton yield over conventional furrow irrigation (1.0 Etc). Imposing irrigation deficit of 0.8 Etc caused significant reduction in seed cotton yield to the tune of 9.3% of the maximum yield. Further increase in deficit irrigation from 0.7 Etc to 0.5 Etc significantly decreased seed cotton yield over its subsequent higher irrigation level. Decline in the yield under deficit irrigation was associated with reduction in number of bolls plant⁻¹ and boll weight. Nitrogen at 200 kg ha⁻¹ significantly increased mean seed cotton yield by 36.3% over 80 kg N ha⁻¹. Seed cotton yield tended to increase linearly up to 200 kg N ha⁻¹ with drip Etc 0.8 to drip Etc 1.0. With drip Etc 0.6-0.5, N up to 160 kg ha⁻¹ provided the highest yield, thereafter it had declined. Foliar spray of plant growth mineral (PGM) brought about significant improvement in seed cotton yield by 14.1% over control. The water productivity ranged from 0.331 to 0.491 kg m⁻³ at different irrigation and N levels. On pooled basis, crop yield response factor of 0.87 was calculated at 20% irrigation deficit.     

Effects of precipitation patterns and temperature trends on soil water available for vineyards in a Mediterranean climate area

The objective of this paper is to analyse the impact of temperature increases and irregular rainfall distribution, associated with climate change, on water availability for rainfed vineyards cultivated in a Mediterranean climate area. The study includes the analysis of the interrelations between precipitation distribution, temperature, evapotranspiration and runoff rates, and the resulting water storage in vineyards soils of the Penedès region (NE Spain). A hierarchical cluster analysis was applied to classify the years according to water availability. The influence of water stored into the soil on yield for some one of the main vine varieties cultivated in the area is analysed. A vineyard, representative of the land management practices in this area, was selected for soil moisture monitoring and runoff evaluations, as well as for grape yield, which was compared with yields recorded in other plots.According to rainfall distribution and water availability, the 12 analysed years represent five different situations: wet years with positive and negative water balance; dry years; years with average annual rainfall but irregularly distributed throughout the year leading to a negative water balance; and extreme situations. Significant water deficits were observed in years in which total rainfall amount was above the annual average in the area, being similar to those observed in dry years: in 8 of the 12 analysed years deficits higher than 100 mm (up to 309 mm) during the growing period (budbreak-harvest) were recorded. At annual scale, 42% of the analysed years recorded deficits ranging between 27.7 and 191.4 mm. In the driest years, and those with more irregular rainfall distribution, soil moisture contents below the wilting point were reached. The high intensity rainfalls, producing important runoff losses (in many cases out of the periods in which crop water needs are higher), together with the increasing temperature trends, which give rise to significant evapotranspiration increases (values up to 32% higher than the average were recorded during the study period), are the main responsible factors for the water deficits recorded during grape development. Winegrape yield was influenced by the water stored into the soil, bloom-veraison or during budbreak-bloom depending on the variety.     

车辆半主动悬架控制器的设计与研究

根据半主动悬架系统的研究现状,设计了嵌入式智能控制器,采用模糊神经网络控制算法,调节车辆半主动悬架系统阻尼系数,在8位单片机上实现了该算法,并且在实验室进行了台架试验,试验结果表明,所设计的控制器可以满足半主动悬架控制系统的要求.     

基于计算机网络的水肥一体机监控作业研究

针对我国传统的灌溉和施肥技术的水分利用率较低、农田管理效率低下的问题,基于计算机网络技术对水肥一体机的监控作业进行研究.该水肥一体机的主要组成包括设备模块、通信模块、数据模块、接口模块和用户模块.农作物生长状态主要受电导率(EC)和酸碱度(pH值)的影响,为了实现对这两项指标的控制和调节,对水肥一体机的监控软件进行设计...     

基于渠池蓄量平衡的闸前变目标水位算法

为了改善渠系下游常水位运行控制方式调节过程蓄量变化剧烈、增大水源供水压力的问题,保证渠系控制的安全、高效,提出了一种基于渠池蓄量平衡的闸前变目标水位的算法,该算法在蓄量变动小时采用下游常水位控制,蓄量变化超过阈值采用考虑约束条件的控制蓄量法.并以Natlab仿真验证法对南水北调中线输水渠道建立多渠段串联控制模型,分析比较控制效果.结果表明:基于渠池蓄量平衡的闸前变目标水位的算法运用效果良好,可实现下游常水位和控制蓄量运行方式的灵活、平稳转换;各渠池蓄量调节量显著减少,基本可以实现蓄量平衡,减小了对上游的需水压力;与下游常水位运行方式相比,其控制过程水位波动平缓闸门流量过程震荡较小,有效减小了闸门超调和回调操作,稳定时间有所延长但在总体调控过程中更为平稳.     

农机数据采集传输系统的设计与实现——基于CAN总线

随着CAN总线的发展应用,越来越多的农业机械开始装备使用CAN总线,采集农机CAN数据对于农机作业运行及故障维修的应用研究具有重要意义。农机CAN总线数据采集传输系统,能够实时采集、解析、传输农机CAN总线数据信息,且可将数据传输到PC机进行数据处理和数据分析。为此,详细介绍了基于单片机、CAN控制器及CAN收发器的农机CAN总线数据采集传输系统,并给出了硬件设计和软件实现。试验表明:该系统将发动机转速、油耗、经纬度、高程等数据解析并传输存储,在实际应用过程中,系统可靠性好,信息准确、运行正常。     

盐水灌溉对不同暖季型草坪草蒸散量的影响

草坪蒸散量是指导草坪合理灌溉的重要指标。以7属11种共13份暖季型草坪草品种（种源）为材料,采用盆栽结合盐水（20 g· L^-1 NaCl）灌溉的方法,研究盐胁迫对其蒸散量的影响及与抗盐性的关系。结果表明：对照和盐胁迫条件下,草种间蒸散量均有显著差异。对照条件下,草种间的日均蒸散量变异系数为22.28%,日均蒸散量最高为‘Pan1’巴哈雀稗（Paspalum notatum）（5.71 mm·d^-1）,最低为‘南京’狗牙根（Cynodon dactylon）（2.77 mm·d^-1）。盐水灌溉条件下,草种间的日均蒸散量变异系数为36.05%,明显高于对照,不同草种的日均蒸散量排序为：‘Diamond’沟叶结缕草（Zoysia materlla）（3.87 mm·d^-1）>‘S004’钝叶草（Stenotaphrum secundatum）（2.90 mm·d^-1）>‘兰引3号’结缕草（Zoysia japonica）（2.34 mm·d^-1）>‘Z080’结缕草（2.25 mm·d^-1）>‘Adalayd’海雀稗（P.varginatum）（2.20 mm·d^-1）>‘P011’双穗雀稗（P.distichum）（2.17 mm·d^-1）>‘南京’狗牙根（2.10 mm·d^-1）>‘Tifway’杂交狗牙根（2.00 mm·d^-1）>‘Pan1’巴哈雀稗（1.90 mm·d^-1）>‘B003’野牛草（Buchloe dactyloides）（1.84 mm·d^-1）>‘H001’牛鞭草（Hemarthria sibirica）（1.61 mm·d^-1）>‘E126’假俭草（Eremochloa ophiuroides）（1.57 mm·d^-1）>‘TifBliar’假俭草（1.50 mm·d^-1）。除‘Diamond’沟叶结缕草外,盐水灌溉下参试草种的蒸散量均有一定程度的降低,降幅从15.29%（‘S004’钝叶草）到66.74%（‘Pan1’巴哈雀稗）。相关性分析表明,盐处理下草坪草的蒸散量与草种的抗盐性成正相关。