Análise e proposição de estratégias de estimação e controle de velocidade para motores de indução trifásicos

This study presents a proposal of speed servomechanisms without the use of mechanical sensors (sensorless) using induction motors. A comparison is performed and propose techniques for pet rotor speed, analyzing performance in different conditions of speed and load. For the determination of control technique, initially, is performed an analysis of the technical literature of the main control and speed estimation used, with their characteristics and limitations. The proposed technique for servo sensorless speed induction motor uses indirect field-oriented control (IFOC), composed of four controllers of the proportional-integral type (PI): rotor flux controller, speed controller and current controllers in the direct and quadrature shaft. As the main focus of the work is in the speed control loop was implemented in Matlab the recursive least squares algorithm (RLS) for identification of mechanical parameters, such as moment of inertia and friction coefficient. Thus, the speed of outer loop controller gains can be self adjusted to compensate for any changes in the mechanical parameters. For speed estimation techniques are analyzed: MRAS by rotóricos fluxes MRAS by counter EMF, MRAS by instantaneous reactive power, slip, locked loop phase (PLL) and sliding mode. A proposition of estimation in sliding mode based on speed, which is performed a change in rotor flux observer structure is displayed. To evaluate the techniques are performed theoretical analyzes in Matlab simulation environment and experimental platform in electrical machinery drives. The DSP TMS320F28069 was used for experimental implementation of speed estimation techniques and check the performance of the same in a wide speed range, including load insertion. From this analysis is carried out to implement closed-loop control of sensorless speed IFOC structure. The results demonstrated the real possibility of replacing mechanical sensors for estimation techniques proposed and analyzed. Among these, the estimator based on PLL demonstrated the best performance in various conditions, while the technique based on sliding mode has good capacity estimation in steady state and robustness to parametric variations.

A narrativa histórica de Alexandre Wollner sobre o design brasileiro em sua relação com arte, indústria e tecnologia

This work aims to investigate the historical narratives in which the graphic designer Alexandre Wollner assembled about the development of its own profession in Brazil, focusing the ways in which his discourse points relations among design (with greater emphasis in graphic design) and visual arts, the industrial development and notions about technology. Firstly, the theoretical setup searched for dialogues with design historians, with Mikhail Bakhtin, specially his concepts about “ideology” and “discourse’, and the theory of Field Autonomy by Pierre Bourdieu applied in the artistic practice. Following, the relation between Wollner’s own journey and the Brazilian industrial development is shown, and, at last, three of his historical texts are studied, which are written in different moments (1964; 1983; 1998), being those in which the analyzed author wished to point out the origens, events and names that are more remarkable. Throughout the work, it is pointed the importance of Wollner’s contact with the modernist european ideologies that share an abstract and rationalist matrix found at Hochschule für Gestaltung Ulm (HfG Ulm), the german design school from the city of Ulm, in the 1950s. Such modernist discourse understood the practice of design as a method with scientific character, being then different of some other more recurring artistic professional practices in some productive sectors. Wollner aimed to apply such ideals in his professional practice, being the foundation of the paulista office forminform, in 1958, one of his first expressions of such posture, and in his academic practice, helping the foundation of the Escola Superior de Desenho Industrial (ESDI), in Rio de Janeiro, in 1963. Such modernist ideals went along with moments of the Brazilian industrial development during the government of Juscelino Kubitschek (1956–1961) and the “Economical Miracle” from the military government (1968–1973). Wollner argued about the need for the development of national design as a technological and productive differential that would help the growth of national industry, based on Ulm’s project model concept. It is defended that Wollner’s professional and intelectual path, in his efforts of thinking a history of Brazilian design through the choice of pioneers in the area, was founded on an “ideal model” of design, leaving aside the modernist experiences from the 1950s. Such posture would indicate a search for validation of his own profession that was beginning to become more evident in Brazilian productive means, aiming the creation of a differential space in comparison with pre-established practices, usually link to graphic artists from the time.