Modelagem e controle de um microveículo aéreo: uma aplicação de estabilidade robusta com a técnica backstepping em uma estrutura hexarrotor

In this Thesis, the development of the dynamic model of multirotor unmanned aerial vehicle with vertical takeoff and landing characteristics, considering input nonlinearities and a full state robust backstepping controller are presented. The dynamic model is expressed using the Newton-Euler laws, aiming to obtain a better mathematical representation of the mechanical system for system analysis and control design, not only when it is hovering, but also when it is taking-off, or landing, or flying to perform a task. The input nonlinearities are the deadzone and saturation, where the gravitational effect and the inherent physical constrains of the rotors are related and addressed. The experimental multirotor aerial vehicle is equipped with an inertial measurement unit and a sonar sensor, which appropriately provides measurements of attitude and altitude. A real-time attitude estimation scheme based on the extended Kalman filter using quaternions was developed. Then, for robustness analysis, sensors were modeled as the ideal value with addition of an unknown bias and unknown white noise. The bounded robust attitude/altitude controller were derived based on globally uniformly practically asymptotically stable for real systems, that remains globally uniformly asymptotically stable if and only if their solutions are globally uniformly bounded, dealing with convergence and stability into a ball of the state space with non-null radius, under some assumptions. The Lyapunov analysis technique was used to prove the stability of the closed-loop system, compute bounds on control gains and guaranteeing desired bounds on attitude dynamics tracking errors in the presence of measurement disturbances. The controller laws were tested in numerical simulations and in an experimental hexarotor, developed at the UFRN Robotics Laboratory

Educação científica no contexto pós-ontológico: por uma concepção plural de conhecimento e educação

The development of this work arises from the research of sociological and philosophical characters contemplating also other approaches which aims to answer the followingquestions: what is the responsibility of science teaching for the image one has about science? ; which scientific education should be designed for nowadays? . After considering the assumptions brought along by rationalism and the criticisms to the illuminist model proposed by sociology and philosophy of science, as well by the biology of the knowing process, going through discussions concerning post-modernity issues, one is given to understand that the image of science has become the central point of discussion in the last hundred years, including what concerns the area of science teaching, and that practically none of those discussions really reached natural science classes indeed. We adopt the term postontological to characterize the recent proposals on philosophy and sociology, because we evaluate that this term allows a better identification of the scientific realism crisis, which supports the existence of an ontological domain which science, and only science, is able to understand. One notices that the general public is not aware of those discussions, mainly if they are science teachers and students. So we believe that discussing the logic in which science is structured, the new understandings concerning the scientific undertaking, especially those of an externalist character, and the relationship between science and society, all of this contributes to build up a science teaching which contemplates a reflective contribution, besides allowing the inclusion of the study of other epistemologies in the educational practice. We argue that a revisionist posture seems to be the most appropriate for the contemporary scientific education, contemplating, besides the teaching of the usual science contents, discussions on the issues involving that knowledge, as well as respecting epistemologies alternative to the modern Western scientific one, in order one can work on the perception of local knowledge generated from other epistemological bases. We describe here practical activities we did involving teachers (short-term courses) and high-school students in an inland school in the Rio Grande do Norte state, in Brazil, as a way to demonstrate the possibility of interventions which can take those conceptions, discussions and changes to the classroom

Terceiro setor em HIV/AIDS: mapeando o ativismo social na contemporaneidade

The struggle against AIDS is a kind of action in favor of life and the organized Brazilian civil society incorporated it in a meaningful dimension. This struggle matured the creation of non-governmental organizations (NGOs) and advanced with the discoveries about the disease. Since the very early 90 s, the consolidation of the partnership involving the movement anti-aids with State came up with a dilemma for the entities of civil society: are they just executors of governmental policies or do they take up the role of effective demands concerning public policies? Since then, activism against aids started to stand for execution of projects and one considers that the institutional way of anti-aids work has problems because it constructs a basic strategy to take off the political aspect of the third sector. The NGOs/aids consolidate the reconfiguration of capital and get far from street activities. This is important to be studied because the relationship between society and aids, contemporarily, can prevent them from accomplishing their agenda referring to political mobilization and collective resistance. This research started to be carried after some visits, previously arranged, to an institutional life support group called Grupo de Apoio à Vida-GAV, in Campina Grande. A semi-structured interview was applied to 31 users and to 6 technicians of the entity mentioned. One aimed at investigating the activist anti-aids practice, identifying the conceptions of activism and knowing how social actors assess those practices. Preliminary results indicate that one of the conceptions on activism among the interviewees refers to the execution of projects through partnership of NGOs and supporting institutions, governmental or non-governmental. Although this new conception on activism consolidates a non-political aspect, there are other ways of executing projects and participating actively, according to some users, such as: meetings, lectures and other sorts of events promoted by the group, which are also legitimate actions representing anti-aids activism at the present context