Adaptive Active Anti-vibration Control for a Three-dimensional Helicopter Flexible Slung-load System with Input Saturations and Backlash

This study investigates active anti-vibration control for a three-dimensional helicopter flexible slung-load system (HFSLS) subject to input saturations and backlash. The first target of the study is to establish a model for a three-dimensional HFSLS. The second target is to develop an adaptive control law for a HFSLS by analyzing its ability to compensate for the effects of input saturations, input backlash, and external disturbances, while achieving the goal of vibration reduction. Simulation results of the numerical show that the proposed adaptive active control technology is effective in solving the oscillation suppression problem for the three-dimensional HFSLS with input saturations and backlash.</p

Enhancing vibration control in cable-tip-mass systems using asymmetric peak detector boundary control

In this study, a boundary controller based on a peak detector system has been designed to reduce vibrations in the cable–tip–mass system. The control procedure is built upon a recent modification of the controller, incorporating a non-symmetric peak detector mechanism to enhance the robustness of the control design. The crucial element lies in the identification of peaks within the boundary input signal, which are then utilized to formulate the control law. Its mathematical representation relies on just two tunable parameters. Numerical experiments have been conducted to assess the performance of this novel approach, demonstrating superior efficacy compared to the boundary damper control, which has been included for comparative purposes"This work has been funded by the Generalitat de Catalunya through the research projects 2021-SGR-01044."Peer ReviewedPostprint (published version

Flatness-based Deformation Control of an Euler-Bernoulli Beam with In-domain Actuation

This paper addresses the problem of deformation control of an Euler-Bernoulli beam with in-domain actuation. The proposed control scheme consists in first relating the system model described by an inhomogeneous partial differential equation to a target system under a standard boundary control form. Then, a combination of closed-loop feedback control and flatness-based motion planning is used for stabilizing the closed-loop system around reference trajectories. The validity of the proposed method is assessed through well-posedness and stability analysis of the considered systems. The performance of the developed control scheme is demonstrated through numerical simulations of a representative micro-beam.Comment: Preprint of an original research wor

유격을 고려한 무미익 초소형 날갯짓 비행체 통합 설계: 기하분석 및 수치 해석을 통한 접근

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 협동과정 우주시스템 전공, 2021. 2. 신상준.Unlike birds, an insect type tailless flapping wing does not possess tail wings. Therefore, insect type flapping wing may be fabricated in small size and of decreased weight. Because of the taillessness, however, stable flight of an insect type flapping wing depends only on main wings. Thus, a number of researches were conducted regarding its control mechanisms. In this thesis, the trailing edge control, one of the methods developed to produce control moments, is adopted. Such method requires additional shafts that connect the root of the main wing and control mechanism, and the shafts are rotated to deform the wing shape. In this manner, asymmetric aerodynamic forces are produced. The control mechanism uses micro actuators for compact design. However, small size of the micro actuator gearbox causes relatively large backlash and the resulting free play of the main wings that generates undesirable aerodynamic forces. Under such circumstance, design improvement of the control mechanism is conducted to minimize the effects of the free play. First, geometry analysis is performed to investigate the factors that cause the free play. Control mechanism design for the minimized free play is obtained. Then, three-dimensional computer aided design (CAD) of modified configuration is drawn, and kinematic simulations are conducted by RecurDyn to determine the prevention of interference. Finally, the feasibility of modified design is examined by the numerical simulation. The main wings are modeled by the displacement-based geometrically exact beam model combined with cross-sectional analysis. To mimic the free play appropriately, the spring elements are attached to the joints. At the same time, two-dimensional unsteady aerodynamic model is used for aerodynamic forces. Consequently, the reasonable control moments are gathered in terms of the maneuverability.곤충 모방형 날갯짓 비행체는 꼬리날개가 없기 때문에 새 모방형 날갯짓 비행체와 비교하여 가볍고 작게 설계될 수 있다. 그러나, 곤충 모방형 날갯짓 비행체는 꼬리날개가 없다는 특징으로 인하여, 오직 두 날개만을 이용하여 조종력을 발생시킨다. 따라서, 이에 대한 많은 연구가 수행되었고 개발된 여러 자세 제어 방법 중 본 학위 논문에선 날개 끝단 비틀림을 이용한 자세 제어 장치를 다룬다. 해당 방법은 주날개의 뿌리 부분을 자세 제어 장치와 연결하고 이를 회전시켜 날개 끝단에 변형을 발생시킨다. 자세 제어 장치에는 경량화를 위하여 가볍고 작은 장비들이 사용된다. 그러나, 자세 제어 장치 제작에 사용되는 초소형 구동기는 작은 크기로 인하여 내부 기어에 백래시를 갖고 있다. 따라서, 이는 주날개의 불필요한 유격을 발생시킬 수 있다. 이러한 유격은 주날개의 진동으로 이어져, 불필요한 비대칭적 공력을 발생시킬 수 있다. 이러한 상황 때문에 유격이 최소화된 자세 제어 장치 설계를 수행하였다. 첫째로, 기하학적 해석을 통하여 유격에 영향을 주는 요인을 파악하였다. 이를 통하여 유격을 최소화한 설계를 도출하였으며, 3차원 computer aided design (CAD) 형상과 RecurDyn을 이용하여 동역학적 해석을 수행하였다. 이를 통하여 자세 제어 장치의 구동 중 발생하는 간섭을 확인하였다. 최종적으로, 수치적 시뮬레이션을 이용하여 개선된 자세 제어 장치의 타당성을 확인하였다. 이때, 주날개는 변위 기반 기하학적 정밀 보로 모델링 되었으며, 2차원 단면 해석 결과를 사용하여 해석을 수행하였고 공력 모델은 2차원 비정상 모델을 사용하였다. 또한, 유격을 모사하기 위하여 스프링 요소를 관절에 삽입하여 해석을 수행하였다. 결과적으로, 본 연구에서 설계한 자세 제어 장치가 유효한 조종력을 발생시키는 것을 확인하였다.Abstract i Contents iii List of Tables vi List of Figures vii List of Symbols x Preface xi Chpater 1 Introduction 1 1.1 Background 1 1.2 Previous Researches 3 1.2.1 Review of Control Mechanism Design Regarding the Insect-Type Flapping Wing 3 1.2.2 Review of Numerical Simulation Studies Regarding the Insect-type Flapping Wing 6 1.3 Research Objectives and Thesis Outline 8 Chpater 2 Control Mechanism Design with Free play 9 2.1 Overview of Control Mechanism Design with Free play 9 2.2 Control Mechanism: Trailing Edge Control 11 2.3 Components of the Control Mechanism 14 2.4 Control Mechanism Design with Minimize free play effect 17 Chpater 3 Numerical Simulations of FWMAV 25 3.1 Overview of Numerical Simulation based on Flexible Multibody Dynamics 25 3.2 Simulation Setup 26 3.2.1 Simulation Methodology 31 3.2.2 Aerodynamics 34 3.3 Numerical Simulation 37 Chpater 4 Conclusions 47 4.1 Contirbutions 47 4.2 Future Works 48 Acknowledgments 50 References 50 국문초록 55Maste

FLAIM: A Multi-level Anonymization Framework for Computer and Network Logs

FLAIM (Framework for Log Anonymization and Information Management) addresses two important needs not well addressed by current log anonymizers. First, it is extremely modular and not tied to the specific log being anonymized. Second, it supports multi-level anonymization, allowing system administrators to make fine-grained trade-offs between information loss and privacy/security concerns. In this paper, we examine anonymization solutions to date and note the above limitations in each. We further describe how FLAIM addresses these problems, and we describe FLAIM's architecture and features in detail.Comment: 16 pages, 4 figures, in submission to USENIX Lis

Uncertainty and disturbance estimator-based control of a flapping-wing aerial vehicle withwith unknown backlash-like hysteresis

Robust and accurate control of a flapping-wing aerial vehicle (FWAV) system is a challenging problem due to the existence of backlash-like hysteresis nonlinearity. This paper proposes uncertainty and disturbance estimator (UDE)-based control with output feedback for FWAV systems. The approach enables the acquisition of the approximate plant model with only a partial knowledge of system parameters. For the design of the controller, only the bandwidth information of the unknown plant model is needed, which is available through the UDE filter. The stability analysis of the closed-loop system with the UDE-based controller is presented. It is shown that the proposed control scheme can ensure the boundedness of the control signals. A number of numerical simulations are carried out to demonstrate the satisfactory trajectory tracking performance of the proposed method