Comprehensive review on controller for leader-follower robotic system

985-1007This paper presents a comprehensive review of the leader-follower robotics system. The aim of this paper is to find and elaborate on the current trends in the swarm robotic system, leader-follower, and multi-agent system. Another part of this review will focus on finding the trend of controller utilized by previous researchers in the leader-follower system. The controller that is commonly applied by the researchers is mostly adaptive and non-linear controllers. The paper also explores the subject of study or system used during the research which normally employs multi-robot, multi-agent, space flying, reconfigurable system, multi-legs system or unmanned system. Another aspect of this paper concentrates on the topology employed by the researchers when they conducted simulation or experimental studies

Advances in Spacecraft Systems and Orbit Determination

"Advances in Spacecraft Systems and Orbit Determinations", discusses the development of new technologies and the limitations of the present technology, used for interplanetary missions. Various experts have contributed to develop the bridge between present limitations and technology growth to overcome the limitations. Key features of this book inform us about the orbit determination techniques based on a smooth research based on astrophysics. The book also provides a detailed overview on Spacecraft Systems including reliability of low-cost AOCS, sliding mode controlling and a new view on attitude controller design based on sliding mode, with thrusters. It also provides a technological roadmap for HVAC optimization. The book also gives an excellent overview of resolving the difficulties for interplanetary missions with the comparison of present technologies and new advancements. Overall, this will be very much interesting book to explore the roadmap of technological growth in spacecraft systems

Concept and Feasibility Evaluation of Distributed Sensor-Based Measurement Systems Using Formation Flying Multicopters

Unmanned aerial vehicles (UAVs) have been used for increasing research applications in atmospheric measurements. However, most current solutions for these applications are based on a single UAV with limited payload capacity. In order to address the limitations of the single UAV-based approach, this paper proposes a new concept of measurements using tandem flying multicopters as a distributed sensor platform. Key challenges of the proposed concept are identified including the relative position estimation and control in wind-perturbed outdoor environment and the precise alignment of payloads. In the proposed concept, sliding mode control is chosen as the relative position controller and a gimbal stabilization system is introduced to achieve fine payload alignment. The characterization of the position estimation sensors (including global navigation satellite system and real-time kinematics) and flight controller is carried out using different UAVs (a DJI Matrice M600 Pro Hexacopter and Tarot X4 frame based Quadcopter) under different wind levels. Based on the experimental data, the performance of the sliding mode controller and the performance of the gimbal stabilization system are evaluated in a hardware-in-the-loop simulation environment (called ELISSA). Preliminary achievable control accuracies of the relative position and attitude of subsystems in the proposed concept are estimated based on experimental result

1999 Flight Mechanics Symposium

This conference publication includes papers and abstracts presented at the Flight Mechanics Symposium held on May 18-20, 1999. Sponsored by the Guidance, Navigation and Control Center of Goddard Space Flight Center, this symposium featured technical papers on a wide range of issues related to orbit-attitude prediction, determination, and control; attitude sensor calibration; attitude determination error analysis; attitude dynamics; and orbit decay and maneuver strategy. Government, industry, and the academic community participated in the preparation and presentation of these papers

AAS/GSFC 13th International Symposium on Space Flight Dynamics

This conference proceedings preprint includes papers and abstracts presented at the 13th International Symposium on Space Flight Dynamics. Cosponsored by American Astronautical Society and the Guidance, Navigation and Control Center of the Goddard Space Flight Center, this symposium featured technical papers on a wide range of issues related to orbit-attitude prediction, determination, and control; attitude sensor calibration; attitude dynamics; and mission design

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 control and synchronization of multiple Lagrangian systems with application to tethered formation flight spacecraft

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 217-228).This dissertation focuses on the synchronization of multiple dynamical systems using contraction theory, with applications to cooperative control of multi-agent systems and synchronization of interconnected dynamics such as tethered formation flight. Inspired by stable combinations of biological systems, contraction nonlinear stability theory provides a systematic method to reduce arbitrarily complex systems into simpler elements. One application of oscillation synchronization is a fully decentralized nonlinear control law, which eliminates the need for any inter-satellite communications. We use contraction theory to prove that a nonlinear control law stabilizing a single-tethered spacecraft can also stabilize arbitrarily large circular arrays of tethered spacecraft, as well as a three-spacecraft inline configuration. The convergence result is global and exponential due to the nature of contraction analysis. The proposed decentralized control strategy is further extended to robust adaptive control in order to account for model uncertainties. Numerical simulations and experimental results validate the exponential stability of the tethered formation arrays by implementing a tracking control law derived from the reduced dynamics.(cont.) This thesis also presents a new synchronization framework that can be directly applied to cooperative control of autonomous aerospace vehicles and oscillation synchronization in robotic manipulation and locomotion. We construct a dynamical network of multiple Lagrangian systems by adding diffusive couplings to otherwise freely moving or flying vehicles. The proposed tracking control law synchronizes an arbitrary number of robots into a common trajectory with global exponential convergence. The proposed control law is much simpler than earlier work in terms of both the computational load and the required signals. Furthermore, in contrast with earlier work which used simple double integrator models, the proposed method permits highly nonlinear systems and is further extended to adaptive synchronization, partial-joint coupling, and concurrent synchronization. Another contribution of the dissertation is a novel nonlinear control approach for underactuated tethered formation flight spacecraft. This is motivated by a controllability analysis that indicates that both array resizing and spin-up are fully controllable by the reaction wheels and the tether motor. This work reports the first propellant-free underactuated control results for tethered formation flight.(cont.) We also fulfill the potential of the proposed strategy by providing a new momentum dumping method. This dissertation work has evolved based on the research philosophy of balancing theoretical work with practicality, aiming at physically intuitive algorithms that can be directly implemented in real systems. In order to validate the effectiveness of the decentralized control and estimation framework, a new suite of hardware has been designed and added to the SPHERES (Synchronize Position Hold Engage and Reorient Experimental Satellite) testbed. Such recent improvements described in this dissertation include a new tether reel mechanism, a force-torque sensor and an air-bearing carriage with a reaction wheel. This thesis also introduces a novel relative attitude estimator, in which a series of Kalman filters incorporate the gyro, force-torque sensor and ultrasound ranging measurements. The closed-loop control experiments can be viewed at ...by Soon-Jo Chung.Sc.D

Dynamics and control of tethered satellite formations in low-Earth orbits

This thesis is focused on the study of dynamics and control of a multi-tethered satellite formation, where a multi-tethered formation is made up with several satellites (agents) connected by means of cables (tethers). The goal of the first part of the study is to evaluate the effect of tether mass on multi-tethered clusters. Due to the complexity of the formations analyzed, the stability of the formation is assessed through a numerical simulation. The behavior is evaluated in the ideal case of circular orbits, but also in non-ideal cases such as that of elliptical reference orbit or perturbed motion. For circular reference orbits, the dynamics of tethered satellite formation is studied, showing that tether mass affects formation dynamics for closed configurations featuring external tethers. This leads to significant instability effects affecting the position of deputies with respect to the parent body neglected by a more elementary modeling approach. When combined effect of orbit eccentricity and tether mass on tethered formations is analyzed, the most noticeable effect due to eccentricity is the increase in the variation of the local spin rate of the cluster between perigee and apogee passes of the reference elliptical orbit. This effect has consequences over the elongation of tethers, shape of tether oscillations and angular separation between adjacent tethers especially for open formations. When taking into account the J2 effect on massive tethered satellite formations, in the Earth¿facing scenario, the trajectory of the parent body presents oscillations of increasing amplitude in the direction perpendicular to the orbital plane. The second part of the study is focused on deriving a control law for position and attitude control of an Earth-facing double pyramid multi-tethered cluster. The control problem is decomposed in two levels: A first level to perform position and attitude coarse control of the formation as a whole, and a second level to achieve accurate position and control of each agent of the cluster. For the purpose of attitude control, and taking advantage again of the similarities between a tethered cluster and a rigid body, the virtual structure approach is chosen as the most suitable option. The formulation shown in this thesis augments the general virtual structure equations valid for a static formation by adding the kinematics of a spinning formation, since the original formulation is valid only to achieve a static final state. The controller is designed to modify the spin rate and the moment of inertia of the formation through a reeling mechanism, and therefore to be able to control the Likins-Pringle tilting angle of the cluster. For the derivation of the accurate positioning control law, the study initially discusses different alternatives based on the state of the art of the robotics control literature. After evaluating other alternatives, two control laws are chosen for this application: One based on a PID controller and one based on the sliding mode control technique. For the sliding mode based control, a proof of semi-global exponential stability is provided. Results of a representative simulation assess the viability of the control approach proposed leading to a submillimetric positioning accuracy.La tesi es centra en l'estudi de la dinàmica i control de formacions de satèl·lits connectats per tethers. Aquestes formacions estan compostes per diversos satèl·lits (agents) connectats per cables (tethers). L'objectiu de la primera part de l'estudi, és l'avaluació de l'efecte de la massa a clústers connectats per múltiples tethers. Degut a la complexitat de les formacions analitzades, l'estabilitat de la formació s'analitza a través de simulacions. S'estudia el comportament pel cas ideal d'orbites circulars, així com en casos no ideals tals com orbites de referència el·liptiques, o moviment sota l'efecte de pertorbacions. La tesi analitza la dinàmica de les formacions per òrbites circulars, mostrant que l'efecte de la massa dels tethers afecta la dinàmica de formacions de geometria tancada (on el perímetre extern esta definit per tethers) amb un satèl·lit central. Aquest efecte dóna lloc a una clara inestabilitat que afecta la posició dels agents respecte a l'objecte central. Aquest efecte no és apreciable en models simplificats on s'ignora l'efecte de la massa al model. Quan es combina una òrbita de referència el·liptica amb un model que incorpora la massa dels tethers, l'efecte més notori és la variació de la velocitat de rotació local del clúster entre el pas per l'apogeu i perigeu de l'òrbita de referència. Aquest efecte té conseqüències sobre l'elongació dels tethers, la forma de les oscil·lacions, i la separació entre tethers adjacents (especialment en el cas de formacions obertes). Quan es té en compte l'efecte de la pertorbació J2, en el cas de formacions orientades envers la Terra, la trajectòria de l'objecte central presenta oscil·lacions d'amplitud creixent en la direcció perpendicular al pla orbital. La segona part de l'estudi es centra en la definició d'una llei de control per regular la posició i orientació d'un clúster amb geometria de doble piràmide orientat envers la Terra. El problema de control es descompon en dos nivells. Un primer nivell per un control primari de posició i orientació del cluster, i un segon nivell per un control de posició precís per a cada agent del cluster. Per tal d'aconseguir el primer nivell de control, i aprofitant les similituds entre un cluster connectat per tethers i un sòlid rígid, s'utilitza la tècnica d'estructura virtual. La formulació utilitzada en aquest estudi amplia el model general d'estructura virtual utilitzat per formacions estàtiques, tot afegint les equacions necessàries per a una formació que gira sobre un eix propi. El controlador esta dissenyat per permetre el canvi de la velocitat de gir i el moment d'inèrcia de la formació a través d'un sistema que permet modificar la longitud dels tethers. D'aquesta forma es permet controlar l'angle d'inclinació de Likins-Pringle del clúster. Per a la definició del control de precisió, l'estudi avalua inicialment diferents alternatives basades en l'estat de l'art de sistemes de control aplicats a robòtica. Després de descartar altres alternatives, es proposen dues lleis de control : Una primera basada en un controlador PID, i una basada en control lliscant. Per l'opció de control lliscant es presenta una demostració d'estabilitat exponencial semiglobal. Els resultats de simulacions confirmen la viabilitat de la solució de control que permet posicionament amb precisió submil·limetric