Control of Towing Kites for Seagoing Vessels

In this paper we present the basic features of the flight control of the SkySails towing kite system. After introduction of coordinate definitions and basic system dynamics we introduce a novel model used for controller design and justify its main dynamics with results from system identification based on numerous sea trials. We then present the controller design which we successfully use for operational flights for several years. Finally we explain the generation of dynamical flight patterns.Comment: 12 pages, 18 figures; submitted to IEEE Trans. on Control Systems Technology; revision: Fig. 15 corrected, minor text change

Intelligent and High-Performance Behavior Design of Autonomous Systems via Learning, Optimization and Control

Nowadays, great societal demands have rapidly boosted the development of autonomous systems that densely interact with humans in many application domains, from manufacturing to transportation and from workplaces to daily lives. The shift from isolated working environments to human-dominated space requires autonomous systems to be empowered to handle not only environmental uncertainties such as external vibrations but also interaction uncertainties arising from human behavior which is in nature probabilistic, causal but not strictly rational, internally hierarchical and socially compliant.This dissertation is concerned with the design of intelligent and high-performance behavior of such autonomous systems, leveraging the strength from control, optimization, learning, and cognitive science. The work consists of two parts. In Part I, the problem of high-level hybrid human-machine behavior design is addressed. The goal is to achieve safe, efficient and human-like interaction with people. A framework based on the theory of mind, utility theories and imitation learning is proposed to efficiently represent and learn the complicated behavior of humans. Built upon that, machine behaviors at three different levels - the perceptual level, the reasoning level, and the action level - are designed via imitation learning, optimization, and online adaptation, allowing the system to interpret, reason and behave as human, particularly when a variety of uncertainties exist. Applications to autonomous driving are considered throughout Part I. Part II is concerned with the design of high-performance low-level individual machine behavior in the presence of model uncertainties and external disturbances. Advanced control laws based on adaptation, iterative learning and the internal structures of uncertainties/disturbances are developed to assure that the high-level interactive behaviors can be reliably executed. Applications on robot manipulators and high-precision motion systems are discussed in this part

Nonlinear suboptimal and adaptive pectoral fin control of autonomous underwater vehicle

Autonomous underwater vehicles (AUVs) are used for numerous applications in the deep sea, such as hydrographic survey, sea bed mining and oceanographic mapping, etc. Presently, significant amount of effort, is being made in developing biorobotic AUVs (BAUVs) with biologically inspired control surfaces. However, the dynamics of AUVs and BAUVs are highly nonlinear and the hydrodynamic coefficients are not precisely known. As such the development of nonlinear and adaptive control systems is of considerable importance; We consider the suboptimal dive plane control of AUVs using the state-dependent Riccati equation (SDRE) technique. This method provides effective means of designing nonlinear control systems for minimum as well as nonminimum phase AUV models. Moreover, hard control constraints are included in the design process; We also attempt to design adaptive control systems for BAUVs using biologically-inspired pectoral-like fins. The fins are assumed to be oscillating harmonically with a combined linear (sway) and angular (yaw) motion. The bias (mean) angle of the angular motion of the fin is used as a control input. Using discrete-time state variable representation of the BAUV, adaptive sampled-data control systems for the trajectory control are derived using state feedback as well as output feedback. We develop direct as well as indirect adaptive control systems for BAUVs. The advantage of the indirect adaptive law lies in its applicability to minimum as well as nonminimum phase systems. Simulation results are presented to evaluate the performance of each control system

Low-thrust trajectories design for the European Student Moon Orbiter mission

The following paper presents the mission analysis studies performed for the phase A of the solar electric propulsion option of the European Student Moon Orbiter (ESMO) mission. ESMO is scheduled to be launched in 2011, as an auxiliary payload on board of Ariane 5. Hence the launch date will be imposed by the primary payload. A method to efficiently assess wide launch windows for the Earth-Moon transfer is presented here. Sets of spirals starting from the GTO were propagated forward with a continuous tangential thrust until reaching an apogee of 280,000 km. Concurrently, sets of potential Moon spirals were propagated backwards from the lunar orbit injection. The method consists of ranking all the admissible lunar spiral-down orbits that arrive to the target orbit with a simple tangential thrust profile after a capture through the L1 Lagrange point. The 'best' lunar spiral is selected for each Earth spiral. Finally,comparing the value of the ranking function for each launch date, the favourable and unfavourable launch windows are identified

해밀턴 구조와 외란 관측기 기법을 이용한 라그랑주 점 궤도 주변에서의 경계 상대 운동 및 궤도유지

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 기계항공공학부, 2020. 8. 김유단.In this dissertation, a novel strategy for station-keeping and formation flight of spacecraft in the vicinity of unstable libration point orbits is presented, and its performance and stability are analyzed. The presented control strategy leverages the Hamiltonian nature of the equations of motion, rather than simply applying the control theory from the perspective of ``signal processing". A filtered extended high-gain observer, a kind of disturbance observer, is designed to mitigate the performance degradation of the control strategy due to model uncertainties and external disturbances. Canonical coordinates are adopted to design a controller that exploits the mathematical structure of Hamiltonian system inherent in orbital mechanics, and then the equations of motion of spacecraft are represented in the form of Hamilton's equation with generalized coordinates and momenta. The baseline controller, utilizing the canonical form of the Hamiltonian system, is divided into two parts: i) a Hamiltonian structure-preserving control, and ii) an energy dissipation control. Hamiltonian structure-preserving control can be designed in accordance with the Lagrange-Dirichlet criterion, i.e., a sufficient condition for the nonlinear stability of Hamiltonian system. Because the Hamiltonian structure-preserving control makes the system marginally stable instead of asymptotically stable, the resultant motion of the Hamiltonian structure-preserving control yields a bounded trajectory. Through the frequency analysis of bounded relative motion, a circular motion can be achieved for particular initial conditions. By appropriately switching the gain of the Hamiltonian structure-preserving control, the radius of bounded motion can be adjusted systematically, which is envisioned that this approach can be applied to spacecraft formation flight. Furthermore, the energy dissipation control can be activated to make the spacecraft's bounded relative motion converge to the nominal orbit. On the other hand, a filtered extended high-gain observer is designed for the robust station-keeping and formation flight even under highly uncertain deep-space environment. The filtered extended high-gain observer estimates the velocity state of the spacecraft and disturbance acting on the spacecraft by measuring only the position of the spacecraft. The filtered extended high-gain observer includes an integral state feedback to attenuate navigation error amplification due to the high gain of the observer. The global convergence of the observer is shown, and it is also shown that the tracking error is ultimately bounded to the nominal libration point orbit by applying the Hamiltonian structure-based controller. Numerical simulations demonstrate the performance of the designed control strategy. Halo orbit around the L2 point of the Earth-Moon system is considered as an illustrative example, and various perturbations are taken into account.본 논문에서는 불안정한 동적특성을 갖는 라그랑주 점 궤도 주변에서 위성의 궤도유지 및 편대비행을 위한 제어기와 관측기를 설계하였으며, 설계된 제어기와 관측기의 안정성 그리고 전체 시스템의 안정성을 분석하였다. 설계한 기준 제어 전략은 신호처리 관점의 제어이론을 기반으로 하지 않고, 라그랑주 점 궤도의 자연적인 수학적 구조를 활용하였다. 모델 불확실성과 외부 외란으로 인한 기준 제어 전략의 성능저하를 완화하기 위해 외란관측기의 일종인 확장 고이득 관측기를 설계하였다. 본 논문에서는 궤도역학에 내재되어 있는 해밀턴 시스템의 구조를 활용하는 제어기를 설계하기 위해 정준좌표를 도입하였으며, 좌표변환을 통해 위성의 운동방정식을 해밀턴 시스템의 정준형식으로 나타내었다. 해밀턴 시스템의 정준형식으로 표현된 운동방정식을 이용해 설계한 기준 제어기는 해밀턴-구조 보존제어와 에너지 소산제어로 분리 설계된다. Lagrange-Dirichlet 기준은 정준형식으로 나타낸 해밀턴 시스템의 비선형 안정성을 판별하는 충분조건으로, 해밀턴-구조 보존제어 설계의 기준이 된다. 기준 라그랑주 점 궤도 주위에서 해밀턴-구조 보존 제어를 적용한 결과, 위성은 기준궤도로 수렴하지 않고 기준궤도와 유한한 거리를 유지하는 경계운동을 하였다. 경계운동의 주파수 분석을 통하여 특정한 초기조건 하에서는 원형 경계운동이 가능하였으며, 더 나아가 해밀턴-구조 보존제어의 제어이득 값을 적절히 설정함으로 원형 경계운동의 크기를 체계적으로 조절할 수 있고 이를 위성 편대비행에 응용할 수 있음을 보였다. 추가적으로 에너지 소산제어 입력을 설계하여 위성이 기준 라그랑주 점 궤도로 점근 수렴하는 운동도 가능함을 수학적으로 증명하였다. 한편, 심우주상의 예측하기 어려운 섭동력 및 불확실성 하에서도 강건한 궤도유지와 편대비행을 수행하기 위해 확장 고이득 관측기를 설계하였다. 확장 고이득 관측기는 위성의 위치 정보만을 이용하여 위성의 속도와 위성에 작용하는 외란을 동시에 추정하며, 추정된 상태변수를 이용하여 기준이 되는 피드백 제어입력을 생성한다. 추정된 외란은 피드포워드 형태의 제어입력으로 구성되어 제어기의 성능을 강건하게 만든다. 심우주 공간상의 위성의 궤도결정 결과로 얻어지는 위치정보는 상대적으로 큰 오차를 갖는데, 확장 고이득 관측기는 위치 오차를 증폭시킨다는 단점이 있다. 본 연구에서는 이러한 단점을 완화하고자 적분 관측기 형태로 개선된 필터링된 확장 고이득 관측기를 설계하고 수렴성을 분석하였다. 그리고 필터링된 확장 고이득 관측기와 시스템의 해밀턴 구조를 활용하는 제어기를 적용한 전체 시스템의 안정성을 분석하였다. 불안정한 라그랑주 점 궤도 주변에서 위성의 궤도유지와 편대비행을 위해 설계된 제어기법의 성능을 확인하고자 수치 시뮬레이션을 수행하였다. 수치 시뮬레이션을 위해 지구-달 시스템의 L2 주변 헤일로 궤도를 기준궤도로 설정하였으며, 심우주 공간에서의 다양한 섭동력 및 모델 불확실성을 고려하였다. 궤도결정 오차로 인한 위성의 위치 및 속도 불확실성이 존재 하더라도 제안한 제어기법을 통해 위성이 궤도유지와 편대비행을 만족스럽게 수행함을 보였다.1 Introduction 1 1.1 Background and Motivation 1 1.2 Literature Review 3 1.2.1 Spacecraft Station-Keeping in the Vicinity of the Libration Point Orbits 3 1.2.2 Spacecraft Formation Flight in the Vicinity of the Libration Point Orbits 5 1.3 Contributions 7 1.4 Dissertation Outline 10 2 Background 13 2.1 Circular Restricted Three-Body Problem 14 2.1.1 Equilibrium Solutions and Periodic Orbits 16 2.1.2 Stability of Periodic Orbits 20 2.2 Hamiltonian Mechanics 21 2.2.1 Hamiltonian Approach to CR3BP 21 2.2.2 Hamiltonian Approach to LPO Tracking Problem 22 3 Hamiltonian Structure-Based Control 25 3.1 Classical Linear Hamiltonian Structure-Preserving Control 27 3.2 Switching Hamiltonian Structure-Preserving Control 29 3.2.1 Orbital Properties of Spacecraft 33 3.2.2 Switching Point 1: From a Circular Orbit to an Elliptical Orbit 34 3.2.3 Switching Point 2: From an Elliptical Orbit to a Circular Orbit 37 3.3 Hamiltonian Structure-Based Control 39 3.3.1 Potential Shaping Control 39 3.3.2 Energy Dissipation Control 45 4 Filtered Extended High-Gain Observer and Closed-Loop Stability 49 4.1 Filtered Extended High-Gain Observer and Its Convergence 51 4.2 Closed-Loop Stability Analysis 56 5 Numerical Simulations 67 5.1 Disturbance Model 67 5.2 Navigation Error Model 68 5.3 Simulation Results 69 5.3.1 Simulation 1 71 5.3.2 Simulation 2 77 5.3.3 Simulation 3 81 5.3.4 Simulation 4 93 5.3.5 Simulation 5 98 6 Conclusion 101 6.1 Concluding Remarks 101 6.2 Further Work 103 Bibliography 105 국문초록 127Docto

Nonlinear constrained and saturated control of power electronics and electromechanical systems

Power electronic converters are extensively adopted for the solution of timely issues, such as power quality improvement in industrial plants, energy management in hybrid electrical systems, and control of electrical generators for renewables. Beside nonlinearity, this systems are typically characterized by hard constraints on the control inputs, and sometimes the state variables. In this respect, control laws able to handle input saturation are crucial to formally characterize the systems stability and performance properties. From a practical viewpoint, a proper saturation management allows to extend the systems transient and steady-state operating ranges, improving their reliability and availability. The main topic of this thesis concern saturated control methodologies, based on modern approaches, applied to power electronics and electromechanical systems. The pursued objective is to provide formal results under any saturation scenario, overcoming the drawbacks of the classic solution commonly applied to cope with saturation of power converters, and enhancing performance. For this purpose two main approaches are exploited and extended to deal with power electronic applications: modern anti-windup strategies, providing formal results and systematic design rules for the anti-windup compensator, devoted to handle control saturation, and “one step” saturated feedback design techniques, relying on a suitable characterization of the saturation nonlinearity and less conservative extensions of standard absolute stability theory results. The first part of the thesis is devoted to present and develop a novel general anti-windup scheme, which is then specifically applied to a class of power converters adopted for power quality enhancement in industrial plants. In the second part a polytopic differential inclusion representation of saturation nonlinearity is presented and extended to deal with a class of multiple input power converters, used to manage hybrid electrical energy sources. The third part regards adaptive observers design for robust estimation of the parameters required for high performance control of power systems

Linear robust output−feedback control for permanent−magnet synchronous motors with unknown load

International audienceWe solve the problem of set-point (respectively, tracking) control of a permanent-magnet synchronous motor via linear time-invariant (respectively, time varying) control. Our control approach is based on the physical properties of the machine: inherent stability and robustness to external disturbances. Our analysis is carried out under mild conditions, using cascaded systems theory. For all cases: constant operating point, trajectory tracking, and with known and unknown load, we show uniform global asymptotic stability of the closed-loop system with a linear controller that uses only velocity measurements. Furthermore, we explore natural extensions of our results to improve robustness with respect to external disturbances and parametric uncertainties

Synthetic in vitro transcriptional oscillators

The construction of synthetic biochemical circuits from simple components illuminates how complex behaviors can arise in chemistry and builds a foundation for future biological technologies. A simplified analog of genetic regulatory networks, in vitro transcriptional circuits, provides a modular platform for the systematic construction of arbitrary circuits and requires only two essential enzymes, bacteriophage T7 RNA polymerase and Escherichia coli ribonuclease H, to produce and degrade RNA signals. In this study, we design and experimentally demonstrate three transcriptional oscillators in vitro. First, a negative feedback oscillator comprising two switches, regulated by excitatory and inhibitory RNA signals, showed up to five complete cycles. To demonstrate modularity and to explore the design space further, a positive-feedback loop was added that modulates and extends the oscillatory regime. Finally, a three-switch ring oscillator was constructed and analyzed. Mathematical modeling guided the design process, identified experimental conditions likely to yield oscillations, and explained the system's robust response to interference by short degradation products. Synthetic transcriptional oscillators could prove valuable for systematic exploration of biochemical circuit design principles and for controlling nanoscale devices and orchestrating processes within artificial cells