Flight control of tethered kites in autonomous pumping cycles for airborne wind energy

Energy harvesting based on tethered kites benefits from exploiting higher wind speeds at higher altitudes. The setup considered in this paper is based on a pumping cycle. It generates energy by winching out at high tether forces, driving an electrical generator while flying crosswind. Then it winches in at a stationary neutral position, thus leaving a net amount of generated energy.The focus of this paper is put on the flight control design, which implements an accurate direction control towards target points and allows for a flight with an eight-down pattern. An extended overview on the control system approach, as well as details of each element of the flight controller, is presented. The control architecture is motivated by a simple, yet comprehensive model for the kite dynamics.In addition, winch strategies based on an optimization scheme are presented. In order to demonstrate the real world functionality of the presented algorithms, flight data from a fully automated pumping-cycle operation of a small-scale prototype are given. The setup is based on a 30 m² kite linked to a ground-based 50 kW electrical motor/generator by a single line.     

Structural optimization of the pumping kite wind generator

This paper focuses on structural optimization of the so-called pumping kite wind generator whose operating principle consists in mechanically driving a ground-based electric generator by means of tethered kites. The employed mathematical model of the kite wind generator is based on the refined crosswind motion law derived under the assumption of equilibrium motion of the kite. The resulting simple approximate analytical formula for the mean mechanical power generated by the deploying kite is used for the constrained structural optimization of the pumping kite wind generator maximizing its electrical power output by adjusting the key structural parameters of the kite wind generator.     

Electricity in the air: Insights from two decades of advanced control research and experimental flight testing of airborne wind energy systems

Airborne wind energy systems convert wind energy into electricity using tethered flying devices, typically flexible kites or aircraft. Replacing the tower and foundation of conventional wind turbines can substantially reduce the material use and, consequently, the cost of energy, while providing access to wind at higher altitudes. Because the flight operation of tethered devices can be adjusted to a varying wind resource, the energy availability increases in comparison to conventional wind turbines. Ultimately, this represents a rich topic for the study of real-time optimal control strategies that must function robustly in a spatiotemporally varying environment. With all of the opportunities that airborne wind energy systems bring, however, there are also a host of challenges, particularly those relating to robustness in extreme operating conditions and launching/landing the system (especially in the absence of wind). Thus, airborne wind energy systems can be viewed as a control system designer’s paradise or nightmare, depending on one’s perspective. This survey article explores insights from the development and experimental deployment of control systems for airborne wind energy platforms over approximately the past two decades, highlighting both the optimal control approaches that have been used to extract the maximal amount of power from tethered systems and the robust modal control approaches that have been used to achieve reliable launch, landing, and extreme wind operation. This survey will detail several of the many prototypes that have been deployed over the last decade and will discuss future directions of airborne wind energy technology as well as its nascent adoption in other domains, such as ocean energy.     

系留气球测控系统设计

系留气球是一种通用航空平台,测控系统是系留气球最重要的组成部分之一,其工程设计关系到系留气球运行的安全和性能.为了满足系留气球稳定可靠、能够长时间连续滞空工作的要求,对测控系统进行科学设计和有效配置,阐述了测控系统的功能、组成、关键技术等,给出了系留气球测控系统的设计方案.该方案可以直接应用于系留气球产品的工程设计中.     

高空风电系统的优化控制研究进展与挑战

为了实现“碳达峰,碳中和”的战略目标,我国将持续推动可再生能源的高比例发展,构建以新能源为主的新型电力系统.作为可再生的清洁源,风能的开发和利用已成为研究的重要方向.研究表明远离地面的高空中风速更加强劲并且更均匀,风向也更稳定,因此,风力发电的进一步突破可以通过用风筝捕获高空风能来实现.为了确保高空风能系统安全、经济、高效地运行,对其控制系统设计的要求极高.本文阐述了国际上几种主流高空风电技术的发电原理、发展进程以及现状.通过对典型的Yo-Yo式结构进行动力学建模,分析了各类非线性控制技术的原理和特点,具体描述了非线性模型预测控制原理和轨迹跟踪控制的仿真结果.总结了未来高空风能控制技术面临的控制算法计算量大,控制系统可靠性研究缺乏以及智能化水平不高等关键问题.     

A Directional Modifier-Adaptation Algorithm for Real-Time Optimization

The steady advances of computational methods make model-based optimization an increasingly attractive method for process improvement. Unfortunately, the available models are often inaccurate. The traditional remedy is to update the model parameters, but this generally leads to a difficult parameter estimation problem that must be solved on-line. In addition, the resulting model may not represent the plant well when there is structural mismatch between the two. The iterative optimization method called Modifier Adaptation overcomes these obstacles by directly incorporating plant measurements into the optimization framework, principally in the form of constraint values and cost and constraint gradients. However, the number of experiments required to estimate these gradients increases linearly with the number of process inputs, which tends to make the method intractable for processes with many inputs. This paper presents a new algorithm, called Directional Modifier Adaptation, that overcomes this limitation by only estimating the plant gradients in certain privileged input directions. It is proven that plant optimality with respect to these privileged directions can be guaranteed upon convergence. A novel, statistically optimal, gradient estimation technique is developed. The algorithm is illustrated through the simulation of a realistic airborne wind-energy system, a promising renewable energy technology that harnesses wind energy using large kites. It is shown that Directional Modifier Adaptation can optimize in real time the path followed by the kite.     

Integrated control/structure optimization by multilevel decomposition

A method for integrated control/structure optimization by multilevel decomposition is presented. It is shown that several previously reported methods were actually partial decompositions wherein only the control was decomposed into a subsystem design. One of these partially decomposed problems was selected as a benchmark example for comparison. The presented paper fully decomposes the system into structural and control subsystem designs and produces an improved design. Theory, implementation, and results for the method are presented and compared with the benchmark example.     

Automatic hover control of an unmanned tethered rotorplatform

A tethered rotor platform is a special type of a rotary wing drone. Its dynamical behaviour is mainly determined by the interaction of the rotor, fuselage and tether. Starting from a discussion of the control and stabilization problems involved, the paper presents dynamical models of the plant with special emphasis on tether dynamics. These models were developed for the analysis of the dynamical behaviour of the vehicle and in particular for the design of an automatic hover control system (AHCS). Two approaches for the design of an AHCS are discussed. One uses optimal linear control theory and the other classical control techniques, resulting in a cascaded controller-structure for the various stabilization and guidance tasks. A discussion of the hardware realization, the measurement problems involved and results of actual flight tests with the designed AHCS are presented.     

基于保辛算法的绳系卫星系统闭环反馈控制问题求解

应用非线性系统滚动时域控制的保辛算法求解绳系卫星系统子星释放和回收过程的闭环反馈控制问题.通过第二类Lagrange方程推导出二体绳系卫星系统的动力学方程;通过拟线性化方法将绳系卫星系统闭环反馈控制问题转化为线性非齐次Hamilton系统两端边值问题的迭代求解;通过保辛算法将线性非齐次Hamilton两端边值问题转化为线性方程组的求解;通过递进更新时间步的状态变量和控制变量,完成绳系卫星系统的闭环反馈控制.数值仿真表明:相对于Legendre伪谱方法,用保辛算法求解绳系卫星系统的闭环反馈控制问题的计算速度和收敛速度较快.绳系卫星系统的开环控制和闭环反馈控制问题数值仿真结果表明:在绳系卫星的初始状态存在偏差的情况下,使用开环控制会导致系统在终端无法达到稳定状态,而使用闭环反馈控制则能在一段时间内抵消初始状态向量偏差对系统产生的影响,最终达到稳定状态.     

Tethered mobile robot for automating highway maintenance operations

The use of a self-propelled mobile robot working in close proximity to a support vehicle for purposes of power, materials, etc. would be extremely valuable for highway maintenance and construction operations. This paper discusses the development of such a uniqe mobile robot system and emphasizes the robot's control system. The wheeled mobile robot is differentially steered and tethered to a support vehicle via a mechanical linkage which has position tracking capability. This mobile robot system has been termed the tethered mobile robot (TMR), and such an approach has the potential for use in a wide variety of highway maintenance operations. An optimal control system applicable to many highway maintenance operations is designed and implemented through the utilization of recently developed servo control technology. Experimental results presented show significant promise for the TMR system.     

Application of genetic algorithms to state estimation of tethered systems

The class of intelligent systems tools known as genetic algorithms is applied to the problem of state estimation, specifically, to predict the orbital dynamics of a tethered satellite system. Emphasis here is placed on cases of tethered motion in which only a short arc of observational data is available. For several example cases of tethered system motion, the performance of a genetic algorithm-based method is compared with that of a conventional differential corrections filtering technique. Measures of comparison include orbit determination accuracy, computational speed, and overall ease of use.     

空间绳系机器人目标抓捕鲁棒自适应控制器设计

针对空间绳系机器人（Tethered space robot,TSR）目标抓捕过程中的稳定控制问题,建立空间绳系机器人系统模型,根据阻抗控制原理,设计基于位置的阻抗控制方法;针对空间绳系机器人系统的模型不确定性问题,利用神经网络对不确定性进行估计补偿,设计鲁棒项对空间系绳干扰和神经网络估计误差的影响进行抑制,在此基础上设计空间绳系机器人目标抓捕鲁棒自适应稳定控制器,并进行稳定性证明.最后对设计的控制器进行仿真验证.作为对比,对无鲁棒项自适应的稳定控制器进行仿真.仿真结果表明,设计的基于阻抗控制的鲁棒自适应控制可以实现对空间绳系机器人目标抓捕过程中的稳定控制,与无鲁棒项自适应的稳定控制器仿真结果相比,本文采用的鲁棒自适应控制方法可以有效地对不确定性进行补偿,控制过程中超调量更小,收敛时间更短,并且控制精度更高.     

中国风筝装饰特征研究

文章首先总结论述中国风筝的装饰特征,进而又分析了这种装饰特征形成的原因。最后提出在具体设计过程中,设计师如何运用这些因素。     

单片机系统的优化设计与实现

讨论了单片机系统的优化设计目标和原则,并就最小系统优化设计、单片机系统的串行扩展、现场多机通信等技术问题提出了看法,最后介绍了一个以此观点构成的用于低压电机群控的单片机优化系统.     

带可控臂的绳系卫星短距释放实验研究

通过绳系卫星轨道面内运动的天-地动力学相似,利用地面物理仿真平台实验研究绳系卫星短距离释放的控制问题.首先建立带控制臂的绳系卫星系统非线性动力学方程,获得天-地动力学相似条件,采用比例-微分反馈控制方法,对受控绳系卫星的姿态运动进行数值仿真.其次,利用地面物理仿真平台实现绳系卫星的天-地动力学相似环境,通过单根刚性臂实现卫星姿态运动和系绳摆动的两自由度运动控制.实验和数值对比结果表明,借助控制臂可以有效的对绳系卫星的释放进行控制.     

Development and Deployment of an Intelligent Kite Aerial Photography Platform (iKAPP) for Site Surveying and Image Acquisition

Aerial photographs and images are used by a variety of industries, including farming, landscaping, surveying, and agriculture, as well as academic researchers including archaeologists and geologists. Aerial imagery can provide a valuable resource for analyzing sites of interest and gaining information about the structure, layout, and composition of large areas of land that would be unavailable otherwise. Current methods of acquiring aerial images rely on techniques such as satellite imagery, manned aircraft, or more recently unmanned aerial vehicles (UAVs) and micro‐UAV technologies. These solutions, while accurate and reliable, have several drawbacks. Using satellite imagery or UAVs can prove to be very expensive, costing tens of thousands for images. They can also prove to be time‐consuming and in some cases have constraints on use, such as no‐fly zones. In this paper, we present an alternative low‐cost, versatile solution to these methods, an intelligent kite aerial photography platform (iKAPP), for the purpose of acquiring aerial images and monitoring sites of interest. We show how this system provides flexibility in application, and we detail the system's design, mechanical operation, and initial flight experiments for a low‐cost, lightweight, intelligent platform capable of acquiring high‐resolution images. Finally, we demonstrate the system by acquiring images of a local site, showing how the system functions and the quality of images it can capture. The application of the system and its capabilities in terms of capture rates, image quality, and limitations are also presented. The system offers several improvements over traditional KAP systems, including onboard “intelligent” processing and communications. The intelligent aspect of this system stems from the use of self‐image stabilization of the camera, the advantage being that one is able to configure the system to capture large areas of a site automatically, and one can see the site acquisition in real time, all of which are not possible with previous methods of AP. © 2013 Wiley Periodicals, Inc.     

民间艺术的瑰宝——潍坊风筝

潍坊风筝历史悠久,以纯厚质朴著称于世。本文通过对潍坊风筝在题材、造型、扎工以及绘画等方面深入的探讨,阐述了其独有的艺术特色和魅力,发掘潍坊风筝的艺术生命力之所在,有利于更好的拓展当地的民间艺术文脉。     

Motion planning for control-affine systems satisfying low-order controllability conditions

This paper is devoted to the motion planning problem for control-affine systems by using trigonometric polynomials as control functions. The class of systems under consideration satisfies the controllability rank condition with the Lie brackets up to the second order. The approach proposed here allows to reduce a point-to-point control problem to solving a system of algebraic equations. The local solvability of that system is proved, and formulas for the parameters of control functions are presented. Our local and global control design schemes are illustrated by several examples.     

Singular perturbations and order reduction in control theory — An overview

Recent results on singular perturbations are surveyed as a tool for model order reduction and separation of time scales in control system design. Conceptual and computational simplifications of design procedures are examined by a discussion of their basic assumptions. Over 100 references are organized into several problem areas. The content of main theorems is presented in a tutorial form aimed at a broad audience of engineers and applied mathematicians interested in control, estimation and optimization of dynamic systems.     

实时多任务过程控制机软件设计

本文从实用角度论述了一种可用于分布式系统和用户控制任务相对独立环境的实时多任务过程控制软件的整体设计思想、软件结构和实现的一般方法。文中还分别给出了两级系统监控级和过程控制级软件的实例。