Clivaldo Oliveira

The current critical global climate situation, which is due to greenhouse gas emissions, has led society to look for ways to preserve the environment. One of these is the use of renewable energies, including wind power. This energy uses the wind to operate. Based on this, this work seeks to design and produce wind blades using polymeric materials in an additive manufacturing process, in this case, with a 3D printer. The materials used were ABS, PETG, PLA and Tritan. The shapes developed were straight, curved and curved tip for the Tritan polymeric material, while for the other materials, the shape designed was straight. Once manufactured, the blades were subjected to performance tests with a wind turbine coupled to an alternator consisting of a tripod turbine. During the experiments, the construction materials, the shapes and the angle of attack as a function of the linear wind speed generated by a wind tunnel were changed so that the analysis was consistent. The results obtained were compared to identify the best combinations of the parameters analyzed. In the end, it was concluded that the blades printed with the Tritan polymeric material could be applied to various wind speed conditions—low, medium and high—as well as having good mechanical properties and the best performance in their manufacturing process, making them the best of those studied.

Wind energy is recognized not only for its high generating capacity among renewable sources, but also for its growing popularity in recent years. However, conventional wind turbines, which rely on blades to capture wind energy, present significant challenges, including noise pollution, interference with bird migration and the frequent need for maintenance due to the complexity of their mechanical components. In an attempt to minimize these problems, current innovations include bladeless wind turbines (VBWT). These operate from wind-induced vibrations, mostly vortex-induced vibrations (VIV). Among the various designs that have been documented, those that exploit energy generation through electromagnetic induction and piezoelectric systems deserve to be highlighted, as they have gained increasing recognition in the academic sphere. In this context, this work focuses on carrying out a dynamic analysis of a vortex-induced vibration energy harvester (VIVEH), which will have its energy generated from a piezoelectric patch connected to a beam with non-linear stiffness due to a magnetic coupling. The system will have its equations of motion simulated using a Runge-Kutta integrator implemented in the Python programming language, where its responses will be analyzed in the time domain by studying the system's sensitivity to different wind speeds, and in the frequency domain using tools such as Fast Fourier Transforms (FFT) and Continuous Wavelet Transforms (CWT). The results focus on analyzing the influence of the beam's non-linearity and its response in the frequency and time domain for different wind speeds.

Understanding and researching the human body has been fundamental due to its importance for living beings. As one of the vital organs of the human body, the heart has always been of great academic relevance. One of the areas of study of the heart is the study of the electrical stimuli that provide blood pumping. These electrical stimuli come from the Sinoatrial Node (SA), known as the natural pacemaker, which transmits the stimuli to the other parts of the heart, thus allowing blood to be pumped. A model to represent the signals of a pacemaker has been developed using a relaxation oscillator, the Van der Pol oscillator, given by a second-order differential equation. In this particular study, a more comprehensive investigation is proposed by introducing fractional order differential equations. Varying the order of the system allows for a more refined analysis of the dynamic properties of the Van der Pol oscillator and, by extension, of the cardiac pacemaker modeled by it. This approach is especially relevant considering the complex and nonlinear nature of the cardiovascular system. The practical implementation of this model is carried out by means of numerical simulation, using algorithms developed in the Python programming language. This choice of platform allows for efficient and flexible analysis of the resulting signals under different conditions and system parameters. Signal analysis in the time domain is complemented by advanced signal processing techniques in the frequency domain. The Discrete Fourier Transform (DFT) and Continuous Wavelet Transform (CWT) are employed to investigate the system's response at different frequencies, providing an in-depth understanding of its stability and dynamic behavior. In addition, the graphical representation of the results using phase spaces and bifurcation diagrams provides a visual understanding of the complex interactions between the system components and their dependencies on the model parameters.

The present work proposes the use of a hybrid controller combining concepts of a PID controller with LQR and a feedforward gain to control the positioning of a 2 DOF robotic arm with flexible joints subject to non-ideal excitations. To characterize the performance of the controls, two cases were studied. The first case considered the positioning control of the two links in fixed positions, while the second case considered the situation in which the second link is in rotational movement and the first one stays in a fixed position, representing a system with a non-ideal excitation source. In addition to the second case, the sensitivity of the proposed controls for changes in the length and mass of the second link in the rotational movement was analyzed. The results of the simulations showed the effectiveness of the controls, demonstrating that the PID control combined with feedforward gain provides the lowest error for both cases studied; however, it is sensitive to variations in the mass of the second link, in the case of rotational movements. The numerical results also revealed the effectiveness of the PD control obtained by LQR, presenting results similar to the PID control combined with feedforward gain, demonstrating the importance of the optimal control design.