Takeoff and landing on slopes via inclined hovering with a tethered aerial robot

In this paper we face the challenging problem of takeoff and landing on sloped surfaces for a VTOL aerial vehicle. We define the general conditions for a safe and robust maneuver and we analyze and compare two classes of methods to fulfill these conditions: free-flight vs. passivelytethered. Focusing on the less studied tethered method, we show its advantages w.r.t. the free-flight method thanks to the possibility of inclined hovering equilibria. We prove that the tether configuration and the inclination of the aerial vehicle w.r.t. the slope are flat outputs of the system and we design a hierarchical nonlinear controller based on this property. We then show how this controller can be used to land and takeoff in a robust way without the need of either a planner or a perfect tracking. The validity and applicability of the method in the real world is shown by experiments with a quadrotor that is able to perform a safe landing and takeoff on a sloped surface

Modeling and natural mode analysis of tethered multi-aircraft systems

Two complementary simulators aimed at the dynamic analysis of airborne wind energy systems based on multi-aircraft configurations are presented. The first model considers a train of stacked aircraft linked among them by two inelastic and massless tethers with no aerodynamic drag. The architecture of the mechanical system in the second simulator is configurable, as long as the system is made of a set of aircraft linked by an arbitrary number of elastic tethers. In both cases, the aircraft are modeled as rigid bodies and the controller is incorporated in the aerodynamic torque through the deflections of control surfaces. An analysis of the symmetric equilibrium state and the corresponding natural modes of a train (stacked configuration) of aircraft was carried out. It revealed that the higher the position of the aircraft in the train, the more they participate in the modes. Tether inertial and aerodynamic drag effects increase the equilibrium angles of attack of the aircraft and the tether tension at the attachment points. The potential applications and computational performance of the two codes are discussed.This work was supported by the Ministerio de Ciencia, Innovación y Universidades of Spain and the European Regional Development Fund under the GreenKite project ENE2015-69937-R (MINECO/FEDER, UE) and continued under the GreenKite-2 project funded by Agencia Estatal de Investigación (PID2019-110146RB-I00/ AEI / 10.13039/501100011033). GSA work is supported by the Ministerio de Ciencia, Innovación y Universidades of Spain under the Grant RYC-2014-15357

Design and Control of Omni-directional aerial robot

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2016. 2. 이동준.우리는 비대칭적인 분산된 멀티 로터 배치로 SE(3)에서 fully-actuated한 특성을 가지고 비행과 회전이 동시에 가능하여 일반적인 비행로봇이 가지고 있는 under-actuation한 문제를 극복 할 수 있는 전방향 비행 로봇이라는 새로운 디자인의 비행 로봇을 제안한다. 먼저 우리는 각 로터들 사이의 공기역학적인 간섭을 최소화함과 동시에 최대의 제어 렌치를 생수 할 수 있게 하기 위해 로터 배치의 최적화 작업을 수행한다. 우리는 SE(3)에서 ODAR 시스템의 동역학 모델링을 제시하고 병진운동과 회전운동의 제어 디자인을 진행한다. 우리는 또한 ODAR 시스템을 실제 제작하고 그것의 성능을 검증한다. 기존의 비행로봇과는 완전히 다른 시스템으로서 우리는 ODAR 시스템이 전방향 렌치 생성이 중요한 항공 매니퓰레이터나 가상현실 렌더링 3D 환경구축을 위한 전방향 구동에서의 촬영 성능을 지닐 수 있는 항공 촬영 역할을 수행 할 것으로 믿는다.We propose a novel aerial robot system, Omni-Directional Aerial Robot (ODAR), which is fully-actuated in SE(3) with asymmetrically distributed multiple rotors and can fly and rotate at the same time, thereby, overcoming the well-known under-actuation problem of conventional multi-rotor aerial robots (or simply drones). We first perform optimization of rotor distribution to maximize control wrench generation in SE(3) while minimizing aero-dynamic interference among the rotors. We present dynamics modeling of the ODAR system in SE(3) and simultaneous translation / orientation control design. We also implement a ODAR system and experimentally validate its performance. Being completely different from the conventional drone, we believe this ODAR system would be promising for such applications as aerial manipulation, where omni-directional wrench generation is important, and also as aerial photography, where an ability to taking photos in omni-direction is desired for 3D environment reconstruction for VR scene rendering.1 서론 1 1.1 연구 동기 및 목적 1 1.2 연구 성과 4 2 시스템 디자인 및 제어 설계 6 2.1 시스템 디자인 6 2.2 제어 설계 16 3 시뮬레이션 21 3.1 시뮬레이션 준비 21 3.2 시뮬레이션 결과 24 4 시스템 제작 27 4.1 시스템 제작 준비 27 4.2 시스템 제작 구성품 28 4.3 시스템 제작 통합 34 5 실험 36 5.1 실험 준비 36 5.2 실험 결과 38 5.2.1 원형 궤적 추적 39 5.2.2 3D 영상촬영 모션 42 5.2.3 수직 구동 작업 45 6 결론 49 6.1 결론 49 6.2 향후 과제 50 참고문헌 52 Abstract 57Maste

Nonlinear Observer for the Control of Bi-Tethered Multi Aerial Robots

International audienceWe consider the problem of state-observation and control for a bi-tethered aerial system composed by a physical chain of two underactuated aerial robots, also called UAVs. The controlled outputs are the Cartesian position of the last robot and the internal forces along the links. We aim at a minimal use of sensors in order to retrieve the full state. For this goal we propose an output transformation method whose applicability implies the system observability. When this is the case we prove that it is possible to design a nonlinear state estimator based on the high gain-and Luenberger-observers that is able to retrieve the state from any dynamic condition. We also demonstrate how this estimator can be employed with a nonlinear controller for the Cartesian position and the link stresses while ensuring the stability in closed-loop. We show the validity of the method for sensorial configurations composed only by two accelerometers (no gyros) and just two encoders, or two accelerometers (no gyros) and just two inclinometers. A realistic simulative validation concludes the paper