Development of a row guidance system for an autonomous robot for white asparagus harvesting

The special cultivation features of white asparagus pose new challenges to the research and development of the row guidance control. This paper presents a row tracking system of a two-layer structure for an autonomous robot developed to harvest white asparagus. At the low level, two independent speed control loops are suggested to ensure the actual revolutions of the drive motors to follow their demanded values. A cascade control structure, consisting of an inner orientation error controller and an outer lateral offset controller, is proposed for the high level to drive the robot to track the desired trajectory. The most important advantage of the cascade structure is that the inner loop directly regulates the most significant error (the orientation error), which minimizes the impact of the external disturbances upon the outer loop. Moreover, the cascade scheme allows the orientation angle to be limited within a given range. That ensures a collision-free tracking. The controllers are designed based on the traditional proportional-integral-derivative (PID) algorithms. The control parameters are selected by using root locus analysis, which guarantees the system stability. The effectiveness of the proposed control regime is evaluated by numerical simulations and validated by experiments. The experimental results demonstrate that with the suggested row guidance strategy a satisfactory tracking accuracy of ±0.5 cm is achieved.     

论中国水稻生产能力

 发展水稻生产是确保我国粮食安全的关键。为了解我国水稻的生产能力,分析测算了我国水稻生产的现实生产力、现实生产能力和潜在生产能力,探讨了我国水稻单产徘徊的原因,提出了提高水稻生产能力的科技对策。研究结果表明,我国水稻现实生产能力和潜在生产能力分别可达2.2618亿t和25390亿t,分别比现实生产力高3 428万t和6 200万t。为进一步提高我国水稻生产能力,必须加强中低产田改造,提高耕地质量;培育和推广超级稻,形成以广适应性超级稻品种为主导的品种结构;优化栽培技术,构建以轻简技术为核心的节本高效生产技术体系;强化技术推广,缩小产量差异,切实提高科技对水稻生产能力提升的支撑能力。     

A controller area network based electric vehicle drive system design

To solve the key problems of the electric drive system, a controller area network(CAN) based electric drive system for electric vehicles was designed. The system was composed of two parts: a CAN communication module and a motor control module. The newest transceiver (TJA1040) and a stand alone CAN controller were used during the design of the CAN communication module, and anti jamming measures were employed to guarantee communication stability. The fuzzy vector control method and direct speed control were applied to realize highly robust control functions. This system has high compatibility. It can be installed in electric vehicles as an independent module and be extended through CAN Bus.      

国家农业科技园区连片带动乡村振兴技术支撑服务体系探析——以C国家农业科技园区为例

国家农业科技园区工作是党中央、国务院提出的一项重要任务,是新时期推动农业结构调整、解决农民就业增收的重要途径,是发展现代农业的必然选择和客观要求。其中连片带动乡村振兴技术支撑服务体系建设是关键一环。自试点建设以来,国家农业科技园区在连片带动乡村振兴技术支撑服务方面取得了积极成效,但也存在一些不足。南开大学研究团队对此进行了详细的调研,通过走访多地的国家农业科技园区,并以具有代表性的C国家农业科技园区为例,重点围绕农业科技园区在促进传统农业的改造与升级、在连片带动乡村振兴中的定位等方面剖析问题并提出针对性对策,为促进地方经济发展和提高区域科技创新能力,实现中国特色社会主义乡村振兴的目标助力。     

电控发动机喷油驱动电路的波形分析及其在故障诊断中的应用

通过对喷油驱动电路的波形测试来介绍波形分析的一般方法,并通过故障诊断实例来反映波形分析法诊断汽车故障的优越性。     

甘肃兰州市耕地动态变化与驱动力关系定量研究

利用1990～2004年兰州市耕地统计资料,对该地区耕地资源利用与变化的基本特征和主要驱动机制进行了分析。运用主成分分析法对耕地变化及其影响因子的关系进行了定量研究,将其概括为人口经济因素和农业科技因素。在此基础上,建立了耕地动态变化与社会驱动因子之间的回归模型。     

Recognition Algorithm of Motorway Curl Road

Road detection is a sub-system of vehicle intelligent auxiliary drive system, which includes such sub-projects as road segmentation and road recognition. The image from CCD camera is processed, and road line is abstracted from it through image process. Then the direction of the road, such as left or right, can be identified according to the road line. Because of the special requirement, i.e. the rigid real-time requirement, the algorithm adopted must have the very low time cost. Through many experiments, a kind of recognition algorithm is proposed based on region-growing process and curve fitting, which was verified to have good effect.     

数控车床工的必备知识和操作技术

论述了数控车床工必须要掌握的数控车床"特点、组成、坐标、面板、模式"五个方面的知识和操作技术。     

ON THE PROBLEM OF SWITCHING CONDITIONS FOR A KIND OF MINIMUM-TIME CONTROL SYSTEMS

The paper provides a detailed study of switching conditions of minimum-time control systems based on application in engineering. By analysis in theory and experiment, the authors deduce a set of switching conditions with state and control variabes inequality constraints, the variations of system parameters and the time-delay of computer in real time control. As an example, a DC motor speed control system is considered. By digital simulation and physical experiments,these conditions proved to be correct. The method in this paper is also suitable for other control systems using compound control algorithm.