No description available.

Thesis (Ph. D.)--University of Hong Kong, 1998. / Includes bibliographical references.

Improved actuator point-to-point positioning performance, as measured by settling time, has been demonstrated in the context of manufacturing automation applications such as circuit board assembly and other product-transfer operations. The control objective is to move a single mass in a single axis from a starting position to a target position following the fastest possible motion trajectory while meeting final-position accuracy requirements. The actuator's achievable force that is available for acceleration is the fundamental variable that determines optimal settling time. The actuator technology employed is the linear variable reluctance motor. Mathematical motor models and simulation programs have been developed to perform several tasks necessary for demonstrating improved actuator performance: (i) optimal commutation under force ripple constraints has been computed to determine ripple-specified force limits and to provide excitation waveforms necessary for force production, (ii) motion profiles for several positioning task scenarios have been generated based on computed ripple-specified force limits, (iii) state space integral position control simulations have been performed to evaluate the degree of success of the proposed relaxation of force ripple constraints in improving settling time and (iv) the computed settling times for positioning tasks have been examined in relation to the copper losses associated with them in order to assess the trade-off. It has been shown that higher force capability is achieved when force-ripple constraints, which have been customarily emphasized in positioning applications, are relaxed. The higher capability is exploited by adopting faster motion trajectories, which are then imposed under feedback control to achieve faster settling time. Improved force capability with relaxed ripple constraints is demonstrated by generating average force versus speed capability curves under ripple constraints ranging from minimal ripple to unconstrained ripple. Improved positioning performance, with relaxed ripple constraints and without violating the final-position accuracy specification, is demonstrated by computing and comparing settling time for multiple positioning tasks with trajectories based on both extremes of force capability, lowest (no-ripple) and highest (unconstrained-ripple) force limits. The results have been demonstrated for two LVR motor configurations: one motor configuration represents typical (switched) linear and rotary variable reluctance motors while the other exhibits features of both switched and synchronous varieties of variable reluctance motors.

No description available.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 58-59). Also available via the Internet.

Due to its cheap production costs, simple construction, and robustness, switched reluctance machines are viable candidates for traction motor drive applications in the electrification of transportation. However, high torque ripple and acoustic noise limit the performance of switched reluctance motors (SRM). This thesis considers control methods to reduce the electromagnetic torque ripple in SRM, while also analyzing the impact of these control methods on other aspect of machine performance, such as copper losses and radial force production. Traditionally, SRM is controlled using rectangular current profiles which are excited using discrete pulsations. Timing of these pulsations is quantified with conduction angles, and the performance of the machine at a given operating point can be optimized by carefully choosing these conduction angles. This thesis starts the analysis on controls of SRM using the conduction angle parameters to determine a baseline of torque ripple performance for comparison against advanced control techniques developed afterwards. Recently, current profiling techniques have been developed, and have been shown to have high performance for torque ripple reduction. In this thesis, one such technique is proposed in the form of an optimization problem where the solution of this problem yields an optimized current profile that both minimizes torque ripple while reducing copper losses. The proposed current profiling technique ensures good current tracking, which allow for optimal control performance over a wide speed range. Finally, this thesis shows the torque more generally as one component of the nodal forces in SRM. The other component of the nodal forces is the radial forces, which contributes to the noise, vibrations, and harshness of the machine. In this thesis, modeling of the radial forces has been conducted, and effects of the proposed current profiling technique on radial forces have been shown to comprehensively illustrate the performance of the current profiling technique. / Thesis / Master of Applied Science (MASc)

Doubly-Salient Reluctance Machines (DSRMs) sidestep many of the issues with permanent magnet and induction machines and embody the lowest cost and simplest manufacturing of the motor technologies. Major drawbacks to RMs have been (1) the need for failure-prone electrolytic capacitors, (2) large torque ripple, and (3) acoustic noise. Conventionally, these drawbacks have been addressed independently either through (1) excitation control or (2) machine design, but not as a holistic system or solution. This disseratation presents a design for high-efficiency low-cost RM while producing smooth output torque and avoiding pulsating inverter input current and the associated electrolytic capacitor. We propose a method for shaping the machine reluctance profile to reduce machine torque ripple to a desired level (here, <5%) without compromising on machine efficiency or power density, a Shaped Reluctance Machine (ShRM). Furthermore, a comprehensive approach which combines both phase excitation control and machine design to cooperatively address the excursions of input and output powers from their average values which results in less than 5% ripple for both electrical and mechanical net power — essentially a DC Reluctance Machine (DCRM). Compared to conventional practice in DSRMs, electrical power ripple is reduced by 85 times and torque ripple is reduced by almost 20 times, while overall efficiency, torque density, and power density are maintained. / Ph. D.

Lietuvos bendrojo lavinimo mokyklos bendrosiose programose pažymima, kad visas bendrasis ugdymas yra orientuotas į vaiką, jaunuolį, jaunuolę, jų poreikius ir gebėjimus. Todėl šiandieninės mokyklos tikslas — padėti asmeniui maksimaliai išskleisti individualias kūrybos galias ir gebėjimus, tenkinant jo įgimtas reikmes: savirealizacijos — savęs įprasminimo, laisvės, meilės, pagarbos, kūrybos, tvarkos ir darnos poreikius. Tačiau šiuolaikinėje visuomenėje mokyklos autoritetas mažėja, moksleivių lankomumas prastėja, o motyvacija mokytis taip pat turi neigiamą tendenciją. Siekiant atsakyti į šiuos klausimus autorė analizuoja vieną aktualiausių šiandienos mokyklos problemų- tai mokinių nenoras lankyti mokyklą. Mokinių nenoro lankyti mokyklą yra ne tik švietimo sistemos, bet ir visos Lietuvos valstybės nuostolis, todėl jau kurį laiką Lietuvoje sprendžiama nelankančiųjų mokyklos iki 16 metų apskaita ir sąlygų grįžti į švietimo sistemą sudarymas. Mokyklos nelankymo problema, mokinių požiūriu į mokyklą ir į mokymąsi, domėtasi visais laikais. Priežastys, kodėl mokiniai vengia lankyti mokyklos aktualios nuo pat mokslo atsiradimo iki šių dienų, o vaikų vengimas lankyti mokyklą yra aktualus ir tapęs socialine problema netik Lietuvoje, bet ir užsienyje, nes morališkai ir ekonomiškai susilpnėjo esminė vaiko saugumą garantuojanti institucija — šeima: tėvų abejingumas, nesidomėjimas vaiko mokymusi; nenoras mokytis, motyvacijos stoka; sunki mokymo programa; prastas mikroklimatas ir t.t. Būtent... [toliau žr. visą tekstą] / General education programs of Lithuania state, that all general education is oriented to children, young people, their needs and abilities. Therefore, the goal of modern school is to help a person to develop the maximum power of individual creativity and capacity to meet the needs of his or her innate needs such as self - expression, freedom, love, respect, creativity, trim and harmony. However, in modern society, the standing of schools is decreasing, school attendance is falling and the learning motivation has a negative tendency as well. To answer these questions, the author examines one of the most urgent problems - students' reluctance to attend school. Reluctance of students to attend school is the loss not only in the education system, but also in general context of Lithuania as a state. The accounting and the return of the education system of students under the age of 16 who do not attend school in Lithuania has already been in solving process for some time. The school attendance problem s well as the attitude of students towards school and learning has always been under consideration. The reasons why students avoid going to school have been relevant since the origination of science. Nowadays it has become a social problem in Lithuania and abroad because the family as an essential institution for ensuring the safety weakened morally and economically. Parents became indifferent to children‘s success and progress at school. Lack of motivation, stiff school curriculum... [to full text]

This master’s thesis is focuses on the reluctance motor, especially on the design of the rotor. It shows the development of the construction of rotors of reluctance motors. Furthermore, it shows the principle of reluctance machine and its basic mathematical description and the principle of improving the machine parameters by inserting permanent magnets into the rotor. It offers an overview of patents available from 2000 to present. Also it deals with the design of the rotor with permanent magnets for stator of induction motor.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy