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针对现有光电传感器存在形式单一、跟踪精度不高、运行稳定性较差等不足,该文通过对光电传感器进行结构设计,设计了一种金字塔式和箱体式嵌套的粗-精跟踪光电传感器,其中箱体式可拆卸、单独使用,其内部的凹面镜利用反射作用有效减小了箱体高度,保证了跟踪过程中的跟踪精度和运行稳定性。在对该传感器的电路进行设计时,选取四运放集成电路LM324为核心,利用其比较作用来控制电机驱动执行机构,从而使聚光系统对准太阳。利用MATLAB/Simulink对模糊PID(proportional integration differentiation,比例-积分-微分)控制器建模和仿真,与PID控制相比,模糊PID控制曲线的响应时间较短,在0.1 s时给系统一个宽度为0.1的矩形脉冲干扰,在0.1~0.2 s之间系统的响应曲线、控制误差的响应曲线以及控制器的输出变化曲线呈现不同的变化;在0.2 s时,均达到稳定状态。通过分析可知,无论是否存在干扰,该控制方法均能使控制器迅速达到稳定状态,减少系统响应时间,从而减少系统的运行成本。该研究为太阳自动跟踪系统的稳定运行和跟踪精度的提高提供了参考。 相似文献
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大田农业节水物联网技术应用现状与发展趋势 总被引:3,自引:1,他引:3
物联网技术与农业领域应用的结合是推动传统农业向现代农业转型升级的重要驱动力,农业节水是中国农业发展长期关注的重点。以物联网技术感知层、传输层、应用层架构为主线,针对大田主要粮食作物水分需求,总结物联网技术在大田农业节水关键环节中的应用发展现状以及存在的局限性,并在大数据、云计算等现代信息技术发展基础上,结合新时期互联网+战略,对物联网技术快速发展态势下农业节水技术、服务、模式的未来发展趋势进行探讨,提出技术向服务转变、决策向预测转变、微观向宏观转变的发展思路。 相似文献
197.
This paper proposed a novel parallel piezoelectric four-axis force/torque sensor based on the bottleneck contradictions of elastic style multi-axis wrist force sensor, It introduces the sensor's structure and operating principle and discussed the selection and spatial layout of piezoelectric quartz wafer group.Then it derives the mathematic model of the sensor. The finite element model of the sensor is established, and the prototype of the sensor is manufactured. Finally, it obtains the input and output curve, voltage sensitivity, charge sensitivity and the coupling interference.The results indicate that the sensor has advantages of simple and rational structure, correct mathematic model, nice manufacturability, good linearity, good rigidity, and natural frequency greater than 30 kHz, less than 3% of the interference error without decoupling matrix.These can meet the requirements of sensor design. 相似文献
198.
G.B. Senay 《Agricultural Water Management》2011,98(4):606-618
Evapotranspiration (ET) can be derived from satellite data using surface energy balance principles. METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) is one of the most widely used models available in the literature to estimate ET from satellite imagery. The Simplified Surface Energy Balance (SSEB) model is much easier and less expensive to implement. The main purpose of this research was to present an enhanced version of the Simplified Surface Energy Balance (SSEB) model and to evaluate its performance using the established METRIC model. In this study, SSEB and METRIC ET fractions were compared using 7 Landsat images acquired for south central Idaho during the 2003 growing season. The enhanced SSEB model compared well with the METRIC model output exhibiting an r2 improvement from 0.83 to 0.90 in less complex topography (elevation less than 2000 m) and with an improvement of r2 from 0.27 to 0.38 in more complex (mountain) areas with elevation greater than 2000 m. Independent evaluation showed that both models exhibited higher variation in complex topographic regions, although more with SSEB than with METRIC. The higher ET fraction variation in the complex mountainous regions highlighted the difficulty of capturing the radiation and heat transfer physics on steep slopes having variable aspect with the simple index model, and the need to conduct more research. However, the temporal consistency of the results suggests that the SSEB model can be used on a wide range of elevation (more successfully up 2000 m) to detect anomalies in space and time for water resources management and monitoring such as for drought early warning systems in data scarce regions. SSEB has a potential for operational agro-hydrologic applications to estimate ET with inputs of surface temperature, NDVI, DEM and reference ET. 相似文献
199.
Landscape irrigation scheduling efficiency and adequacy by various control technologies 总被引:1,自引:0,他引:1
M.S. McCreadyM.D. Dukes 《Agricultural Water Management》2011,98(4):697-704
Automated residential irrigation systems tend to result in higher water use than non-automated systems. Increasing the scheduling efficiency of an automated irrigation system provides the opportunity to conserve water resources while maintaining good landscape quality. Control technologies available for reducing over-irrigation include evapotranspiration (ET) based controllers, soil moisture sensor (SMS) controllers, and rain sensors (RS). The purpose of this research was to evaluate the capability of these control technologies to schedule irrigation compared to a soil water balance model based on the Irrigation Association (IA) Smart Water Application Technologies (SWAT) testing protocol. Irrigation adequacy and scheduling efficiency were calculated in 30-day running totals to determine the amount of over- or under-irrigation for each control technology based on the IA SWAT testing protocol. A time-based treatment with irrigation 2 days/week and no rain sensor (NRS) was established as a comparison. In general, the irrigation adequacy ratings (measure of under-irrigation) for the treatments were higher during the fall months of testing than the spring months due to lower ET resulting in lower irrigation demand. Scheduling efficiency values (measure of over-irrigation) decreased for all treatments when rainfall increased. During the rainy period of this testing, total rainfall was almost double reference evapotranspiration (ETo) while in the remaining three testing periods the opposite was true. The 30-day irrigation adequacy values, considering all treatments, varied during the testing periods by 0-68 percentile points. Looking at only one 30-day testing period, as is done in the IA SWAT testing protocol, will not fully capture the performance of an irrigation controller. Scheduling efficiency alone was not a good indicator of controller performance. The amount of water applied and the timing of application were both important to maintaining acceptable turfgrass quality and receiving good irrigation adequacy and scheduling efficiency scores. 相似文献
200.
节能型日光温室温度控制系统的研究 总被引:2,自引:0,他引:2
利用单片机技术实现对温室内多点温度进行采集、处理及调节。通过温度传感器将非电量的温度值转换为电量输出,电A/D转换器对模拟信号进行数字化,经单片机处理后送显示器及执行机构,对温室内地下热交换系统、均温系统及排热系统的起停实现自动控制。 相似文献