基于DGPS定位与双闭环转向控制的农业自动导航系统

以东方红X-804拖拉机为平台,开发了一种基于RTK-DGPS定位和双闭环转向控制相组合的农业自动导航系统。系统主要包括RTK-DGPS接收机、姿态航向参考系统(AHRS)、转向控制器、电控液压转向装置和转向角检测传感器。设计了Kalman滤波器对定位数据进行平滑处理,同时实现航向角的校正。为实现自动转向,在拖拉机原有手动控制系统基础上加上电控比例液压阀,并设计电控单元。然后,推导了转向系统的数学模型,通过Matlab仿真工具箱得到传递函数的参数,设计了双闭环转向控制算法。最后,进行了算法验证试验和田间试验,结果表明,双闭环控制方法较好抑制了稳态时的震荡现象,方波信号的角度跟踪稳态时最大误差0.60°,平均误差0.40°,平均延时为0.20 s;设计的Kalman滤波器有助于提高定位系统的精度,横向跟踪误差不超过0.09 m,转向角度平均跟踪误差为0.43°,延时0.25 s。     

基于GNSS航向微分和MEMS陀螺仪的农机轮角测量方法

【目的】设计一种农机前轮转角测量方法,代替安装复杂的连杆式轮角传感器。【方法】采用GNSS天线测量航向和速度,MEMS陀螺仪测量车身和车轮的合转动速率,计算MEMS陀螺仪与GNSS航向微分差值,获得车轮转动速率;设计自适应卡尔曼滤波器进行信息融合和校正,获得车轮转向角,并进行性能验证和田间应用试验。【结果】与连杆式轮角传感器测量结果对比,轮角测量方法的拖拉机在偏离航线2.5和1.5 m进行上线时,平均绝对误差(MAE)分别为1.13°和0.87°,均方根误差(RMSE)分别为0.90°和0.68°,上线时间分别为29.4和23.5 s;以4 km/h田间导航应用时,MAE为0.44°,RMSE为0.87°,满足拖拉机旱地作业要求。【结论】GNSS航向微分和MEMS陀螺仪轮角测量方法与连杆式轮角传感器测量性能相当,能够替代轮角传感器用于较低速农业机械导航。     

自动导航拖拉机的农机具作业精度研究

针对自动导航拖拉机带农机具作业时农机具跟踪误差会被放大的问题，提出了1种能够提高农机具作业精度的拖拉机导航算法。采用路径跟踪误差最小的优化控制方法，研究拖拉机自动导航作业时引起机具误差大的因素及改进方法，设计具有农机具误差项的拖拉机模型预测控制算法，对该算法进行可行性试验及对比试验。试验结果表明采用带机具误差项的算法使农机具横向偏差平均降低了42.36%，横向偏差标准差平均降低了40.91%，航向角最大偏差平均降低了6.11%,航向角偏差标准差平均降低了31.04%。结果表明增加农机具误差项的模型预测控制算法能有效提升农机具的作业精度。     

基于RTK-GNSS和MEMS陀螺仪的车辆航向角测量技术

【目的】更好地满足车辆自动驾驶时航向角测量的精度要求。【方法】提出卡尔曼滤波算法,把实时动态–全球导航卫星系统(RTK-GNSS)测量出来的经纬度和高程经过高斯投影转换为高斯平面坐标,和微电子机械系统(MEMS)陀螺仪测得的累积航向角进行融合处理,最终得到车辆更为精准的航向角。【结果】融合后的航向角度曲线既保持了GNSS航向的整体变化趋势,也保持了陀螺仪航向的细部变化趋势,且较GNSS和陀螺仪所得曲线更为平滑,可以跟踪车辆180°调头的转弯动作。【结论】卡尔曼滤波算法可以实时在线且精准地测得车辆航向角数据,精度较GNSS测量结果提高80%以上。     

基于密度自适应的RANSAC非结构化环境下果园机器人导航

目的 提出一种基于多传感器融合的果园导航方案,解决果园机器人在GPS导航过程中受果树遮挡导致信号弱、定位效果差的问题。方法 通过16线激光雷达采集高精度的三维点云数据,利用Voxel grid filter滤波算法进行点云预处理,降低点云密度并去除离散点,将果树行通过欧几里类算法进行聚类,采用改进的随机采样一致性 (Random sample consensus, RANSAC) 算法拟合出果树行直线,根据平行直线的关系,推算得到导航线,并融合惯性测量单元(Inertial measurement unit, IMU)对果园机器人进行高精度定位。基于差速转向和纯追踪模型进行轨迹跟踪,实现果园机器人在果树行间自主导航以及自动换行的目标。结果 在将激光雷达和IMU的数据进行融合后,获取到果园机器人的准确位姿,当机器人以速度0.8 m/s在果园作业时,对比最小二乘法和传统RANSAC法产生的偏差,基于密度自适应RANSAC法产生的横向偏差不超过0.1 m、航向角偏差不超过1.5°,均为3种方法中的最小值。但当机器人速度增加到1.0 m/s时,各项偏差均明显增大。结论 本文提出的基于多传感器融合的果园机器人导航技术适用于大多数规范化果园,具有重要推广价值。     

Multi-GNSS precise point positioning for precision agriculture

The main objective of this research was to examine the feasibility of Multi-GNSS precise point positioning (PPP) in precision agriculture (PA) through a series of experiments with different working modes (i.e. stationary and moving) under different observation conditions (e.g. open sky, with buildings or with canopy). For the stationary test carried out in open space in the UK, the positioning accuracy achieved was 13.9 mm in one dimension by a PPP approach, and the repeatability of positioning results was improved from 19.0 to 6.0 mm by using Multi-GNSS with respect to GPS only. For the moving test carried out in similar location in the UK, almost the same performance was achieved by GPS-only and by Multi-GNSS PPP. However, for a moving experiment carried out in China with obstruction conditions, Multi-GNSS improved the accuracy of baseline length from 126.0 to 35.0 mm and the repeatability from 110.0 mm to 49.0 mm, The results suggested that the addition of the BeiDou, Galileo and GLONASS systems to the standard GPS-only processing improved the positioning repeatability, while a positioning accuracy was achieved at about 20 mm level in the horizontal direction with an improvement against the GPS-only PPP results. In space-constrained and harsh environments (e.g. farms surrounded with dense trees), the availability and reliability of precise positioning decreased dramatically for the GPS-only PPP results, but limited impacts were observed for Multi-GNSS PPP. In addition, compared to real time kinematic (RTK) GNSS, which is currently most commonly used for high precision PA applications, similar accuracy has been achieved by PPP. In contrast to RTK GNSS, PPP can provide high accuracy positioning with higher flexibility and potentially lower capital and running costs. Hence, PPP might be a great opportunity for agriculture to meet the high accuracy requirements of PA in the near future.     

多机协同导航作业远程管理平台开发

为实现对多机协同导航作业的实时远程监控,设计开发多机协同导航作业远程管理平台。该平台主要分为作业管理和调度管理2个模块。作业管理模块利用电子地图实现多机协同导航作业信息远程监测、作业进度实时分析以及作业质量在线评估;调度管理模块包括多信息获取和处理,以及通过电子地图进行精准定位,实现多机协同导航作业任务规划和路径规划。结果表明:该平台可以实时监测多机协同导航作业轨迹和作业信息,并且可以进行远程调度管理,远程通信丢包率≤0.3%,延时≤2 s,可以初步满足多机协同导航作业需求。     

Apparent electrical conductivity in dry versus wet soil conditions in a shallow soil

The general objective of this study was to evaluate the stability of patterns of apparent soil electrical conductivity (EC_a) in dry versus wet soil conditions in a shallow soil typically used for pastures in Mediterranean conditions of the southern region of Portugal. A 6 ha experimental field of permanent bio-diverse pasture was divided into 76 squares of 28 × 28 m. The soil electrical conductivity was measured using a Dualem 1S sensor under dry conditions (June 2007) and under wet conditions during the rainy season (March 2010). Soil samples, geo-referenced with GPS, were collected in a depth range of 0–0.30 m. The soil was characterized in terms of bedrock depth, moisture content, texture, pH, organic matter content, and macronutrients (nitrogen, phosphorus, and potassium). Pasture samples, also geo-referenced with GPS, were collected to measure the pasture dry matter yield. The statistical analysis of apparent electrical conductivity between dry and wet soil conditions resulted in a linear significant correlation coefficient (R = 0.88). The results also showed a significant correlation between apparent electrical conductivity and the relative field elevation (R = ?0.64 and R = ?0.66), the pasture dry matter yield (R = 0.42 and R = 0.48), the bedrock depth (R = 0.40 and R = 0.27), the pH (R = 0.50 and R = 0.49), the silt (R = 0.27 and R = 0.38) and soil moisture content (R = 0.48 and R = 0.45), in dry and wet conditions, respectively. A multi-variate regression was carried out using the following soil parameters that showed significant correlation with EC_a and that did not present multi-collinearity: pH, bedrock depth, silt and moisture content. The results showed, in dry and wet conditions, that the analysis was significant (R = 0.75 and R = 0.84, respectively). Overall, these results indicate the temporal stability of EC_a patterns under different soil moisture contents, which is relevant with respect to the time when a field should be surveyed and is important for using the electrical conductivity sensor, as a decision support tool for management zones in precision agriculture.     

基于UWB定位的农业机械辅助导航系统设计与试验

【目的】低成本实现南方中小型田块中农业机械田间精确定位,降低农机操作人员劳动强度、提高农机作业效率。【方法】采用超宽带(Ultra wide band,UWB)技术对作业机械进行实时定位,通过位置解算算法,得到定位标签的三维精确位置坐标;利用位置校正算法,修正作业机械车身倾斜引起的田间定位误差;设计基于AB线的路径规划算法,实时规划作业路径并计算作业偏差;通过可视化人机交互界面为农机操作人员提供实时辅助驾驶信息。【结果】水田环境中,分别以0.5、1.0和1.5 m/s的速度沿规划路径行驶时,系统平均横向定位偏差均小于7 cm;当行驶速度大于1.0 m/s时,利用位置校正算法平均横向定位偏差降低了52.79%,标准差降低了49.82%,最大横向定位偏差降低了50.04%。搭载辅助导航系统进行田间插秧试验,各行作业轨迹与自身行拟合直线的平均横向偏差为5.90 cm,标准差为3.64 cm;各行作业轨迹与其规划直线路径的平均横向偏差为6.98 cm,标准差为4.95 cm。【结论】辅助导航系统具有较高的定位精度和良好的稳定性,成本低且通用性强,能够满足南方中小型田块中农业机械田间作业要求。研...     

Effect of dry and wet storage at cool temperatures on the post-harvest performance of Ranunculus asiaticus L. flowers

A study was undertaken to assess the effect of different storage temperatures on senescence and postharvest performance of isolated flowers of Ranunculus asiaticus L.. The main aim of the work was to develop a cost-effective storage protocol to reduce the postharvest losses and to bring out the transportation of cut flowers of R. Asiaticus. The flowers were subjected to two different storage treatments, dry storage and wet storage, and their postharvest performance was compared under laboratory conditions. For this purpose, the buds were harvested at 8:00 AM at loose bud stage (Stage II of flower development). The harvested buds were cut to a uniform size of 15 cm and processed for dry or wet storage. For dry storage, the buds were packed after wrapping them in moistened filter papers and kept at 5°C and 10°C. For wet storage, the buds were held in distilled water in separate glass beakers kept at 5°C and 10°C, respectively. A separate set of buds each for dry and wet storage was kept at room temperature (15±2)°C. After 72 h storage, the buds were kept at room temperature in distilled water. The average life of an individual flower that opened fully was about 4–5 days. The buds kept under wet storage at 5°C and 10°C for 72 h maintained their premature status, while the buds held at room temperature for 72 h generally bloomed. All the buds stored dry maintained their premature status irrespective of storage temperature. Storage of buds for 72 h at 5°C, followed by transferring to distilled water improved the longevity by about 5 to 6 days. Cold storage treatment before transferring to holding solution improved floral diameter, membrane integrity besides maintaining higher fresh and dry mass of flowers, sugar content, soluble proteins, and phenols. Our results suggested that wet and dry storage of premature buds of R. asiaticus for 72 h at 5°C, followed by placing them in distilled water, improved the cut flower longevity and can be used as effective postharvest storage treatments for this beautiful cut flower.     

Evaluating corrections for a horizontal offset between sensor and position data for surveys on land

When regarding evolutions in land-based, motorized sensor data collection it can be generalized that the speed of surveying, sampling rates, digital communications speed and survey resolutions have increased over the last years. Possibilities for accurate positioning have been following pace. However, a spatial offset between sensor and position data can be necessary to avoid interference with the instrument or can be the result of using a sensor array. It can also be due to practical considerations such as mounting possibilities. Unfortunately a severe degradation of positional accuracy is possible when performing corrections for a spatial offset and quantification of the induced error is quite difficult. As a consequence, the actual positional accuracy of sensor measurements is therefore often omitted or unknown, and a correction may be neglected during data processing. In this paper, accounting for a horizontal (spatial) offset is researched by examining the use of several correction methods. To evaluate the degree of loss of positional accuracy and validate several correction procedures, global navigation satellite system (GNSS) data (with real-time kinematic correction) have been simultaneously collected, using a GNSS receiver that was mounted on an all-terrain vehicle and two other receivers that were mounted near the front and end of an elongated sensor sled. The sled was connected to the towing vehicle using a flexible connection. Since the positioning systems’ horizontal accuracies were about 20 mm, it was possible to quantify the horizontal error of the predicted positions for the different correction procedures considered. The best approach for high-resolution surveys, which make use of a connection to a cart or sled that can rotate around a pivot on the towing vehicle, was researched. The strengths and weaknesses of the applied corrections were also evaluated, allowing selection of an appropriate correction for a given survey implementation.     

3D LiDAR感知的植物行信息提取方法与试验

目的 针对林间或冠层下等卫星信号严重遮挡的区域，提出一种面向农业机器人导航环境感知的低成本3D激光雷达(LiDAR)点云信息处理与植物行估计方法。方法 利用直通滤波器滤除感兴趣区域外的目标无关点；提出均值漂移聚类、扫描区域自适应的方法分割每棵植物主干，垂直投影主干点云估算中心点；利用最小二乘法拟合主干中心，估计植物行。分别在开阔地的仿真果园与水杉树林进行模拟试验与田间试验，以植物行向量与正东方夹角为指标，计算本研究提出的方法识别的植物行信息与GNSS卫星天线定位测得的植物行真值间的角度误差。结果 采用提出的3D LiDAR点云信息处理与植物行估计方法，模拟试验和田间试验对植物行识别误差平均值分别为0.79°和1.48°，最小值分别为0.12°和0.88°，最大值分别为1.49°和2.33°。结论 车载3D LiDAR能够有效估计水杉树植物行。该研究丰富了作物识别思路与方法，为无卫星信号覆盖区域的农业机器人无图导航提供了理论依据。     

四川省粉煤灰中天然放射性含量及安全性评价

对四川省（ 含重庆）８ 个大、中型火力发电厂排出的干／湿粉煤灰中天然放射性核素的组成和含量进行了测定和分析;并调查了我省粉煤灰的综合利用情况。结果表明,四川省火力发电厂排出的粉煤灰中天然放射性核素主要由２３８Ｕ,２３２Ｔｈ,２２６Ｒａ,４０Ｋ４ 种核素组成,放射性比活度变化在０～１０９７９ ±１６６９（２３８Ｕ）,８２０５ ±２７８ ～２２４４７ ±１１７３（２３２Ｔｈ）,６３９２ ±２７５ ～２５５８ ±３８６（２２６Ｒａ）,１１７７２±１４７７ ～１１４７４３±３４５１（４０Ｋ）Ｂｑ／ｋｇ 。根据国家标准ＧＢ６５６６ － ８６,四川省火力发电厂粉煤灰用做建筑材料时,以江油（ 湿灰） 、内江、攀枝花、宜宾和雅安（ 湿灰） 调查点的灰样放射性比活度不超标,其余调查点的灰样均属超标范围,根据ＧＢ６７６３－ ８６ 中限制式计算,其最高用量不能超过建筑材料总重的６８６７ ％ ～６９５８ ％ （干灰） 和６８６９ ％ ～９１４０％ （ 湿灰） 。干粉煤灰的比放射性活度普遍高于湿灰。粉煤灰在农业上的利用具有潜在的优势,本文就此进行了较为详细的分析     

基于无线定位的温室生产平台自动导航

  目的  为了提高温室内车辆自动导航的精度，提出了一种基于超宽带定位和带有自调整函数模糊控制的路径跟踪方法。  方法  首先利用超宽带(UWB)模块构建无线定位系统，采用二元三次多项式对定位误差进行拟合，并修正测量点误差；其次结合带自调整函数解析式的模糊控制器，对横向偏差与航向偏差的权重进行动态调整，输出前轮转角；最后分别进行直线和矩形路径跟踪的实车试验，并与使用纯追踪方法的结果进行对比。  结果  在进行不同初始状态的直线路径跟踪时，平均偏差均值为22.4 cm，标准差为5.8 cm，稳态偏差平均值为5.4 cm，比纯追踪模型精度分别提升了28.4%、40.2%和34.9%；进行矩形路径跟踪时，平均偏差为14.4 cm，最大偏差为46.9 cm，相比于纯追踪模型精度分别提升了46.5%和53.5%，其中最大偏差主要出现在矩形的转角处。  结论  本研究提出的方法具有较好的稳定性和控制精度，能满足生产平台在温室内自动导航作业需求。图8表3参24     

土壤水分对寒地水稻生育特性和物质积累的影响

选用上育397和绥粳3号两个水稻品种,于分蘖期、穗分化期、抽穗后1～10d、抽穗后11～20d分别进行土壤水势为-30～-35kPa和-60～-65kPa的控水处理,研究了土壤水分对寒地水稻的生长发育、物质形成与分配规律的影响。结果表明,分蘖期控水对株高影响不大,土壤水势为-30～-35kPa时,使两个品种的茎数显著减少,上三片叶叶面积不同程度的降低。穗分化期控水使两个品种的株高显著降低,主要是极显著地降低了第二至第四节间的长度;土壤水势为-30～-35kPa时,上三片叶叶面积降低,而两个品种的茎数、穗数却极显著增加。抽穗前土壤水势为-30～-35kPa时,两品种在齐穗期茎、鞘、穗的干重均低于对照,各器官的物质输出率也有所降低,大多数控水强度大的处理降低幅度也大。抽穗初期土壤水势为-30～-35kPa时,上育397多数处理各器官的物质输出率低于对照,而绥粳3号多数处理各器官的物质输出率高于对照。不同水稻品种在不同生育阶段对不同程度水分胁迫反应不同,抽穗前期是水稻的需水敏感期,对水稻的生长发育、物质积累与输出影响最大。     

紫色土抗剪强度差异分析及土坎优化设计

选择钙质紫色土和中性紫色土为工程试样,通过室内多级三轴剪切试验测定了含水率和干密度交互作用对土坎稳定性重要指标——土壤抗剪强度指标的影响,确定了紫色土土坎坎高及外边坡稳定角的取值,以优化土坎设计.结果表明:干密度和含水率交互作用对土壤粘聚力的影响下,钙质紫色土和中性紫色土土坎土质的最优含水率分别为11%,8%,最优干密度分别为1.7,1.68g/cm3;在紫色土最优干密度和含水率下,考虑占地和稳定性因素,钙质紫色土土坎高度不宜超过2.0m,其外边坡坡度角可设计为80°;中性紫色土土坎高度不宜超过1.5m,其外边坡坡度角可设计为60°.本文旨在为紫色土区国土整治土坎修筑工程提供理论指导.     

Apparent electrical conductivity measurements in an olive orchard under wet and dry soil conditions: significance for clay and soil water content mapping

Mediterranean olive trees traditionally grow under rainfed conditions, on poor soils with steep slopes. Rainfall is mainly concentrated during autumn and winter and is characterized by intense rain pulses, separated by dry periods. The use of electromagnetic induction (EMI) techniques in these olive orchards might be questioned since EMI surveys are generally recommended to be performed under moist soil conditions. A 6.7 ha olive orchard was surveyed for EMI-based apparent electrical conductivity (ECa), both under wet and dry soil conditions. In addition, 48 soil samples were analyzed for soil texture and for soil water content (SWC) under both soil conditions. The relationships between ECa, soil texture and SWC, under both soil conditions were evaluated. Despite the significantly larger ECa values measured during the wet survey as compared to the dry survey, a similar spatial correlation structure was found, indicating temporally stable ECa patterns. Significant correlations (r) were found between both surveys for ECa (r = 0.67) and for SWC (r = 0.63). The correlation between SWC and clay content exceeded 0.60 for both surveys, and the correlation between ECa and clay content was twice as high under wet soil conditions as compared to dry soil. In both situations, the ECa surveys revealed the same patterns of soil texture, indicating that moist soil conditions are not an absolute prerequisite for the use of EMI to map the spatial variability of these soil properties. Nonetheless, measuring the ECa under different moisture conditions can provide additional information about soil moisture dynamics.     

Short- and long-term dynamic accuracies determination of satellite-based positioning devices using a specially designed testing facility

Short-term dynamic accuracy is one of the most significant parameters for agricultural application of satellite-based positioning on straight segments. This is an important characteristic of guidance devices for every user. Two standards are proposed for dynamic testing of satellite-based positioning devices for utilization in agriculture. Previous approaches were typically based on the use of RTK records as a reference for error calculation. A test procedure based on a highly precise testing facility was developed, having a mechanical offset of the test cart less than 0.002 m. The new mathematical approach for straight line segment definition, based on two representative points was developed. This approach enables error-free calculation of off-track errors and determination of U-turn influence based on two additional parameters. Long-term testing was performed (24 h), using a Garmin GPS 18 device for test validation. The obtained results showed that this method can be successfully used for testing dynamic characteristics of GNSS devices. The results were as follows: mean value of the off-track errors was −0.39 m, standard deviation of all measured off-track errors was 1.51 m, being 1.3 m in 95% of the measured off-track errors. The pass-to-pass average error was 0.90 m, being under 0.662 m in 95% of the detected passes. The designed facility and developed procedure can also be successfully applied to the testing of high precision devices, e.g., RTK.     

Comparing apparent electrical conductivity measurements on a paddy field under flooded and drained conditions

Every growing season, paddy fields are kept both flooded and drained for a significant period of time. As a consequence, these soils develop distinct physico-chemical characteristics. For practical reasons, these soils are mostly sampled under dry conditions, but the question arises how representative the results are for the wet growing conditions. Therefore, the apparent electrical conductivity (EC_a) of a 1.4 ha alluvial paddy field located in the Brahmaputra floodplain of Bangladesh was measured in both dry and wet conditions by a sensing system using the electromagnetic induction sensor EM38, which does not require physical contact with the soil, and compared both surveys. Due to the smooth water surface under wet conditions which ensured increased stability of the sensing platform, the results of the survey showed considerably reduced micro-scale variability of EC_a. Furthermore, the wet survey results more reliably furnished soil-related information mainly due to the absence of soil moisture dynamics. The differences between EC_a under wet and dry conditions were attributed to differences in soil texture, mainly the sand content variation having considerable effect on soil moisture differences when flooded following drainage. Accordingly, the largest differences between EC_a under wet and dry conditions were found in those parts of the field with a large sand content. Hence, the conclusion was that an EC_a survey on flooded fields has an added value to precision soil management.     

四川农区水土流失及其治理

四川省最严重的水土流失发生在东部盆地的紫色丘陵农区,泥土流失主要来自坡度≥６°的坡土。全省坡土面积３１６－６ 万ｈｍ２ ,占耕地总面积的４８ ％ ,坡土中坡度≥２５°的陡坡土占１７％ 。因此,坡土的水土流失治理是我省持续农业发展的重要基础。坡土水土流失治理,除陡坡土退耕还林种草外,还有８３％ 的坡土不仅要继续耕种,而且要持续稳定高产,治理难度大且任务艰巨。坡土水土流失治理的基本思路是以集雨拦洪（地表径流） 蓄水即治水为中心,旱、洪兼治;主要治理途径是：充分开发土壤、工程（ 以小微型蓄水工程为主） 、生物（ 森林） 三大“水库”的拦洪蓄水功能,有效集蓄和利用天然雨水资源,兴利除害,为持续农业创造良性生态系统。