Disturbance Attenuating Tracking Controller Design of a Quadrotor UAV via a T-S Fuzzy-model-based Disturbance Observer

In this thesis, The disturbance attenuating tracking controller design method of a quadrotor unmanned aerial vehicle (UAV) via the Takagi-Sugeno (T-S) fuzzy-model-based disturbance observer is proposed. The quadrotor UAV can perform vertical takeoff and landing (VTOL) propelled by four rotors. In addition, the control system of the quadrotor UAV can be decomposed into the attitude, altitude, and position models. However, since the dynamics of the quadrotor UAV is underactuated in which the number of degrees of freedom is higher than the number of actuators, its controller design is not easy. On the other hand, among the methods modeling the nonlinear system, the T-S fuzzy modeling approach has gained significant attention. The T-S fuzzy model control approach represents a nonlinear system as the IF-THEN rules based on the sector nonlinearity concept. The given nonlinear system is expressed as a convex sum of the linear subsystem and membership function that is the weight of each IF-THEN rule. Employing the T-S fuzzy modeling approach, in this thesis, each control system of the quadrotor UAV is represented by the T-S fuzzy model. Next, the external disturbance affecting the quadrotor UAV is estimated by the disturbance observer. Additionally, I derive the tracking error dynamics between each control system and predefined reference model and disturbance estimation error dynamics between the disturbance observer and exogenous system, respectively. The augmented system is obtained by combining the tracking error dynamics and disturbance estimation error dynamics. Based on this system configuration, this thesis proposes the disturbance attenuating tracking controller design method of the quadrotor UAV via the T-S fuzzy-model-based disturbance observer with uncertain control gain. The stabilization condition of the augmented system is derived in terms of the linear matrix inequality (LMI) by using the fuzzy Lyapunov function. Furthermore, I consider the perturbation of the control gain matrix generated by the aging of the actual controller. Finally, through the simulation example, The effectiveness of the H∞ tracking performance and disturbance attenuation performance of the proposed control design method is validated.|본 학위 논문에서는 Takagi-Sugeno (T-S) 퍼지 모델 기반의 외란 관측기를 통한 쿼드로터의 외란 감쇠 추종 제어기 설계 방법을 제안한다. 쿼드로터는 수직 이착륙이 가능하고 네 개의 로터로 추진력을 얻는 무인 항공기이다. 또한, 쿼드로터는 자세, 고도, 위치 모델로 제어 시스템을 세분화할 수 있다. 하지만, 자유도에 비해 제어 입력의 수가 적은 underactuated system 이기 때문에 제어기 설계가 어렵다. 한편, 비선형 시스템을 모델링하는 방법 중에서 T-S 퍼지 모델링 기법이 있다. T-S 퍼지 모델링 기법은 수학적 모델로 표현된 비선형 시스템을 IF-THEN 규칙들로 표현하고, sector nonlinearity 개념을 기반으로 부분 선형 시스템과 각 규칙의 가중치의 의미를 가진 소속도 함수를 볼록 합으로 나타낸다. 이를 이용하여 각각의 쿼드로터 제어 시스템을 IF-THEN 규칙으로 표현하고, T-S 퍼지 모델로 나타낸다. 외란 관측기를 설계하여 쿼드로터에 영향을 주는 외부 외란을 추정한다. 또한, 참조 모델을 설정하여 시스템과 참조 모델의 오차 동역학과 외란을 생성하는 외인성 시스템과 외란 관측기의 외란 추정 오차 동역학을 유도하며, 이들을 하나의 증가 시스템으로 나타낸다. 본 학위 논문에서는 H∞ 추종 성능과 외란 감쇠 성능을 만족하고 점근 안정화를 보장하는 안정화 조건을 유도한다. 이를 위해, 퍼지 리아푸노프 함수 (Lyapunov function)을 사용하고 선형 행렬 부등식 (linear matrix inequality) 형태로 안정화 조건을 유도한다. 또한, 실제 제어기의 노후화 때문에 발생하는 제어 이득 행렬의 섭동을 고려한다. 마지막으로 시뮬레이션 예제를 통해 제안된 방법의 추종 성능과 외란 추정 성능의 타당성을 검증한다.1 Introduction 1 2 Preliminaries 5 2.1 Attitude model 7 2.2 Altitude model 10 2.3 Position model 12 2.4 Reference model 15 2.5 Disturbance observer-based controller under the control gain uncertainty 15 2.6 Tracking error dynamics 16 2.7 Exogenous system 18 2.8 Disturbance observer 18 2.9 Augmented system 20 3 Controller design procedure 22 3.1 Design formulation 22 3.2 Stability condition 23 3.3 LMI-based stabilization condition 32 4 Simulation example 38 4.1 System configuration 38 4.2 Controller design 41 4.3 Simulation results 45 5 Conclusions 55Maste

Photosynthesis and formation of UV-absorbing substances in Antarctic macroalgae under different levels of UV-B radiation

Effects of artificial and solar UV--B radiation on five rhodophytes (Curdiearacovitzae, Gigartina skottsbergii, Mazzaella obovata, Myriogramme manginii, Palmaria decipiens) from Antarctica have been investigated using PAM fluorescence in laboratory and in the field. Laboratory studies showed that there were significant differences in the UV sensitivity between different species, and that the differencesappeared to be correlated with the depth of collection of the specimens. It was apparent from the observations that the samples such as M. manginii and P. decipiens collected from 20~30 m depths were more sensitive to UV--B radiation compared with those collected from shallower depths. The present study confirmed that an acclimation to the surrounding light regime could be an important factor to determine the UV--sensitivity of a species or individuals and that PAM measurements are rapid and non--destructive methods to evaluate UV influences. From field studies on M. manginii and P. decipiens it was observed that both plants exhibited changes in the effective quantum yield, with the minimum values at noon followed by a recovery in the evening. Photoinhibition occurred in these species could therefore be accounted for by so-- called dynamic photoinhibition. It seems likely that this protective mechanism may contribute to survival of the species in shallow water where they may encounter intense solar radiation. The presence or absence of the UV--B component under solar radiation differently affected the photosynthetic recovery process, and the rate of recovery was much slower in UV--present than in UV--absent conditions. Functional role of UV--B appears to delay the recovery of photosynthesis in the studied macroalgae. Differential sensitivity to UV--B recognised between M. manginii and P. decipiens seemed to correspond well with the amount of UV--absorbing substances (UVAS) contained in the respective species. Higher tolerance to solar radiation by the latter species22othe

EFFECTS OF UV-B RADIATION ON REPRODUCTION AND GERMINATION OF THE INTERTIDAL GREEN ALGA, ULVA PERTUSA KJELLMAN

In macroalgae, UV-B radiation affects severely photosynthesis, growth, pigmentation and enzyme activity. However, little is known about the effects of UV-B radiation on reproduction and germination although these processes are clearly of importance affecting the population recruitment. We have conducted investigations into UV-B effects on Ulva pertusa which is a common fast growing macroalga of the intertidal zone on most coasts of Korea where its population is often exposed to highirradiances of solar radiation and must possess efficient mechanisms to prevent or counteract the harmful effects of solar radiation. There was a significantly lower incidence of reproduction and germination in UV-irradiated samples with the degree of reduction being greater in those exposed to higher UV doses. When plants were incubated under different irradiances of PAR immediately after UV exposures percentage inhibition of sporulation was lesser at higher irradiances. After exposure to moderate levels of UV-B irradiation, subsequent exposure to visible light caused differential germination being significantly higher at higher photon irradiances and in blue light compared to white and red light. The action spectrum for photoreactivation of germination in UV-B irradiated U. pertusa spores shows a major peak at 435 nmwith a smaller peak at 385 nm. After 2 h exposure to December sunlight, there was complete inhibition of germination in PAR + UV-A + UV-B in contrast to 100% germination in PAR or PAR + UV-A. In addition to mat-forming characteristics which would act as a selective UV-B filter under the canopy, lightdriven repair of reproduction and germination following UV-B exposure could explain successfulcontinuation of U. pertusa in intertidal settings possibly affected by intense solar UV-B radiation.1