This thesis compares Model Predictive Control (MPC) and Proportional-Integral (PI) control in a pin-on-disc tribometer. The tribometer consists of a geared Direct Current (DC) motor driving a flywheel and a voice coil actuating a pin onto the surface of the flywheel. The contact surface of both pin and disc can be replaced with the desired material. The system is first modeled, and both conntrollers are derived from the models and Matlab and Simulink. A PI-cascade controller is used for the disc while a single PI controller is used for the pin. The PI controller is derived using the pole placement, the MPC is derived using the Simulink MPC-designer.  The control methods are evaluated using the Root Mean Sqaure Error (RMSE), percentage overshoot and rise time of step responses from two cases: The ideal case and the operational case. The ideal case contians minimal disturbance as only one actuator is operating at a time. The operational case intends to depict the future use case of the test rig where both actuators are operating simultaneously.  Statistical analysis is conducted as a three was Analysis of Variance (ANOVA) between controller (MPC/PI), case (ideal/operational) and actuator level (40/80 N or 100/200 rpm). In conclusion the MPC has a faster rise time but a higher RMSE than the PI controller in both the ideal and operational case when controlling the disc application of a tribometer. No significant difference in overshoot is established in the disc application of the tribometer. Considering the pin system of the tribometer, no conclusion can be drawn. The main factor being the large impact of the noise at the sampling frequency. This causes failure of the controllers in the operational case. / Denna avhandling jämför Model Predictive Control (MPC) och Propertionell-Integral (PI) kontroll i en stift-på-skiva tribometer. Tribometern består av en likströmsmotor med en växellåda som driver ett svänghjul, och en talspole som är kopplat till ett stift som i sin tur applicerar kraft på svänghjulets yta. Kontaktytan för både stift och skiva kan ersättas med önskat material. Systemet modelleras först, och de båda reglersystemen härleds från modellerna i Matlab och Simulink. En PI-kaskad kontroller används för skivan medan en enkel PI-kontroller används för stiftet. PI-kontrollern härleds med hjälp av polplacering MPC-kontrollern härleds med hjälp av MPC-designern i Simulink.  Reglermetoderna utvärderas med hjälp av kvadratroten ur medelkvadratavvikelsen (RMSE), procentuell översläng och stigtid för stegsvar från två fall: Det ideala fallet och de operativa fallet. Det ideala fallet innehåller minimala störningar eftersom endast ett ställdon åt gången är i drift. Det operativa fallet är avsett att representera det framtida användningsområdet för testriggen där båda ställdonen är i drift samtidigt.  Den statistiska analysen utförs som en trevägs Anlysis of Variance (ANOVA) mellan kontroll (MPC/PI), fall (idealt/operativt) och nivå (40/80 N eller 100/200 rpm). Slutsatsen är att MPC-kontrollern har en snabbare stigtid med en högre RMSE än PI-kontrollern i både idealfallet och driftfallet vid styrning av skivan i en tribometer. Ingen signifikant skillnad i översläng konstaterades i skivan. Ingen slutsats kan dras när det gäller drivning av tribometerns stift. Den huvudsakliga faktorn är den stora mängden störningar vid samplingsfrekvensen. Detta leder till att kontrollerna misslyckas in det operativa fallet.

Submitted by RENATO ARAUJO BARROS null (greensleeves@uol.com.br) on 2017-03-08T17:38:24Z No. of bitstreams: 1 Tese Renato Barros - Versão Final.pdf: 24319782 bytes, checksum: f4d58ce4ebe77961a2e94b04cf3515cc (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-03-13T17:07:44Z (GMT) No. of bitstreams: 1 barros_ra_dr_guara.pdf: 24319782 bytes, checksum: f4d58ce4ebe77961a2e94b04cf3515cc (MD5) / Made available in DSpace on 2017-03-13T17:07:44Z (GMT). No. of bitstreams: 1 barros_ra_dr_guara.pdf: 24319782 bytes, checksum: f4d58ce4ebe77961a2e94b04cf3515cc (MD5) Previous issue date: 2017-02-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os aços de ultra alta resistência como o aço 4340 tem sido amplamente utilizados pela indústria aeronáutica e aeroespacial em aplicações como trens de pouso de aeronaves e o veículo lançador de satélite brasileiro (VLS), além de um uso extensivo para diversos setores da indústria em geral. Isso se deve, em grande medida, às suas propriedades mecânicas. Este trabalho se propõe a avaliar as propriedades tribológicas do par aço 4340, inicialmente submetido ao tratamento térmico de têmpera e revenimento, e a liga bronze alumínio 630, utilizados em trens de pouso. Será estudado o comportamento destas estruturas após o aço ser submetido a tratamentos de superfície por nitretação a plasma e carbonetação a laser, como forma de melhorar seu desempenho com relação ao atrito e ao desgaste. Neste estudo foi escolhido o ensaio tipo pino-disco para simular a situação real de desgaste. Os discos foram confeccionados a partir do aço AISI/SAE 4340 e os pinos foram feitos da liga bronze-alumínio 630. Foram realizadas análises microestruturais das estruturas e das camadas de compostos formadas devido ao tratamento de superfície, Após os ensaios de desgaste foram feitas observações das superfícies através de microscopia e perfilometria óptica, microscopia eletrônica de varredura, difratometria de raios-X, testes de riscamento (scratching tests), dureza, observação de rugosidade e pesagem dos corpos de prova. Foram levantados os parâmetros do desgaste e alterações microestuturais devido à interação entre as superfícies de contato durante os ensaios de deslizamento. Foi analisada a perda de massa e levantadas as curvas de desgaste e dos parâmetros relacionados ao atrito em função da distância percorrida e/ou do tempo de ensaio. Nos ensaios foram utilizadas três velocidades de ensaio: 0,5; 1,0 e 1,5 m/s. Foi possível o cálculo da taxa de desgaste para cada par e velocidades estudadas. De uma maneira geral constatou-se que os mecanismos de desgaste detectados são semelhantes para todas as condições de superfície dos discos. As imagens mostram que partículas do pino são deformadas sobre o disco, em forma de camadas, evidenciando o mecanismo de adesão. A carbonetação a laser criou uma camada rica em carbono com a presença de grafite que contribuiu para reduzir o coeficiente de atrito e o desgaste do pino, principalmente, para as velocidades de 0,5 e 1,0 m/s. A nitretação a plasma reduziu a perda de massa do disco e do pino, com indicativos de pequena perda de massa para todas as velocidades estudadas; a rugosidade e o aumento do coeficiente de atrito no par pino-disco para as velocidades de 1,0 e 1,5 m/s podem ter sido induzidas por alteração no tipo de desgaste, de adesivo para uma abrasão a três corpos. / Ultra high strength steels as 4340 steel has been widely used by the aerospace industry in applications such as aircraft landing gears and the Brazilian satellite launch vehicle (VLS), plus an extensive use for various sectors of the industry in general. This is due largely to their mechanical properties. This work aims to evaluate the tribological properties of 4340 steel pair, initially submitted to heat treatment of quenching and tempering, and aluminum bronze 630 alloy, used in landing gear. The behavior of these structures after the steel be subjected to surface treatment by plasma nitriding and laser carbonetation will be studied, as a way to improve its performance with respect to friction and wear. For this study, pin-on-disc test was chosen in order to simulate the real situation of wear. The discs were made from 4340 steel and pins were made of aluminium bronze 630 alloy. Micro-structural analyses were undertaken of the structures and compound layers formed due to surface treatment. After the wear tests surface observations were made through microscopy and perfilometry optical, scanning electron microscopy, x-ray diffractometry, x-ray tests, scratching tests, hardness, roughness and weighing of the specimens. Parameters of wear and microestuturals changes were raised due to interaction between the contact surfaces during rehearsals. Loss of mass was analyzed and curves of wear and friction related parameters were plotted in function of the slided distance and/or time of test. In the tests three test velocities were used: 0.5; 1.0 and 1.5 m/s. It was possible to calculate the wear rate for each pair and studied velocities. In general it was noted that the mechanisms of wear detected are similar for all conditions of the surface of the discs. The images show that the particles are bent on the disc, in the form of layers, showing the mechanism of adhesion. The laser carbonetation created a carbon-rich layer with the presence of graphite, which contributed to reduce the friction coefficient and pin wear, mainly for the 0.5 and 1.0 m/s velocities. The plasma nitriding reduced the loss in mass of the disk and pin, with indicative of small mass loss for all velocities studied; the roughness and the increase of the coefficient of friction in the couple pin-disc for the velocities of 1.0 and 1.5 m/s may have been induced by changes in the type of wear, from adhesive wear to a three-body abrasion. / CAPES: 99999.002441/2014-04

A fairly new technology used to produce metallic components is powder metallurgy (PM). Among the advantages with this technique are decreased cost of production for complex-shaped parts, new alloys are made possible, reduced end processing, less material loss, and vibrational damping effects. The downside is the number of pores created which can alter the tribological properties of the material. The focus of this report is to investigate how lean PM steel behaves under tribological contacts.  Friction and wear will be investigated using a pin-on-disc setup to mimic the sliding part of a gear tooth mesh. Previous studies show that the amount of wear, and if the wear increases or decreases with increased density is dependent on the degree of porosity and the pore size. This means that the wear might be minimized by optimizing the number of pores in the material and their shape and size. The result of this study shows that the friction coefficient decreases with increasing density. The wear coefficient show signs of the same correlations but further tests are needed. The main wear comes from adhesive wear, with signs of abrasive wear. The amount of abrasive wear seems to increase with an increase in density, supporting previous studies claiming that pores can trap wear debris and decrease the number of abrasive particles in the contact.