On Modelling, System Identification and Control of Servo-Systems with a Flexible Load

The present study was done with two different servo-systems. In the first system, a servo-hydraulic system was identified and then controlled by a fuzzy gainscheduling controller. The second servo-system, an electro-magnetic linear motor in suppressing the mechanical vibration and position tracking of a reference model are studied by using a neural network and an adaptive backstepping controller respectively. Followings are some descriptions of research methods. Electro Hydraulic Servo Systems (EHSS) are commonly used in industry. These kinds of systems are nonlinearin nature and their dynamic equations have several unknown parameters.System identification is a prerequisite to analysis of a dynamic system. One of the most promising novel evolutionary algorithms is the Differential Evolution (DE) for solving global optimization problems. In the study, the DE algorithm is proposed for handling nonlinear constraint functionswith boundary limits of variables to find the best parameters of a servo-hydraulic system with flexible load. The DE guarantees fast speed convergence and accurate solutions regardless the initial conditions of parameters. The control of hydraulic servo-systems has been the focus ofintense research over the past decades. These kinds of systems are nonlinear in nature and generally difficult to control. Since changing system parameters using the same gains will cause overshoot or even loss of system stability. The highly non-linear behaviour of these devices makes them ideal subjects for applying different types of sophisticated controllers. The study is concerned with a second order model reference to positioning control of a flexible load servo-hydraulic system using fuzzy gainscheduling. In the present research, to compensate the lack of dampingin a hydraulic system, an acceleration feedback was used. To compare the results, a pcontroller with feed-forward acceleration and different gains in extension and retraction is used. The design procedure for the controller and experimental results are discussed. The results suggest that using the fuzzy gain-scheduling controller decrease the error of position reference tracking. The second part of research was done on a PermanentMagnet Linear Synchronous Motor (PMLSM). In this study, a recurrent neural network compensator for suppressing mechanical vibration in PMLSM with a flexible load is studied. The linear motor is controlled by a conventional PI velocity controller, and the vibration of the flexible mechanism is suppressed by using a hybrid recurrent neural network. The differential evolution strategy and Kalman filter method are used to avoid the local minimum problem, and estimate the states of system respectively. The proposed control method is firstly designed by using non-linear simulation model built in Matlab Simulink and then implemented in practical test rig. The proposed method works satisfactorily and suppresses the vibration successfully. In the last part of research, a nonlinear load control method is developed and implemented for a PMLSM with a flexible load. The purpose of the controller is to track a flexible load to the desired position reference as fast as possible and without awkward oscillation. The control method is based on an adaptive backstepping algorithm whose stability is ensured by the Lyapunov stability theorem. The states of the system needed in the controller are estimated by using the Kalman filter. The proposed controller is implemented and tested in a linear motor test drive and responses are presented.

Moral Hazard in Repeated Procurement of Services

This paper analyzes repeated procurement of services as a four-stage game divided into two periods. In each period there is (1) a contest stage à la Tullock in which the principal selects an agent and (2) a service stage in which the selected agent provides a service. Since this service effort is non-verifiable, the principal faces a moral hazard problem at the service stages. This work considers how the principal should design the period-two contest to mitigate the moral hazard problem in the period-one service stage and to maximize total service and contest efforts. It is shown that the principal must take account of the agent's past service effort in the period-two contest success function. The results indicate that the optimal way to introduce this `bias' is to choose a certain degree of complementarity between past service and current contest efforts. This result shows that contests with `additive bias' (`multiplicative bias') are optimal in incentive problems when effort cost is low (high). Furthermore, it is shown that the severity of the moral hazard problem increases with the cost of service effort (compared to the cost of contest effort) and the number of agents. Finally, the results are extended to more general contest success functions. JEL classification: C72; D82 Key words: Biased contests; Moral Hazard; Repeated Game; Incentives.

Normaalijakaumaan perustuva mutaatio-operaatio differentiaalievoluutioalgoritmiin

Evoluutioalgoritmit ovat viime vuosina osoittautuneet tehokkaiksi menetelmiksi globaalien optimointitehtävien ratkaisuun. Niiden vahvuutena on etenkin yleiskäyttöisyys ja kyky löytää globaali ratkaisu juuttumatta optimoitavan tavoitefunktion paikallisiin optimikohtiin. Tässä työssä on tavoitteena kehittää uusi, normaalijakaumaan perustuva mutaatio-operaatio differentiaalievoluutioalgoritmiin, joka on eräs uusimmista evoluutiopohjaisista optimointialgoritmeista. Menetelmän oletetaan vähentävän entisestään sekä populaation ennenaikaisen suppenemisen, että algoritmin tilojen juuttumisen riskiä ja se on teoreettisesti osoitettavissa suppenevaksi. Tämä ei päde alkuperäisen differentiaalievoluution tapauksessa, koska on voitu osoittaa, että sen tilanmuutokset voivat pienellä todennäköisyydellä juuttua. Työssä uuden menetelmän toimintaa tarkastellaan kokeellisesti käyttäen testiongelmina monirajoiteongelmia. Rajoitefunktioiden käsittelyyn käytetään Jouni Lampisen kehittämää, Pareto-optimaalisuuden periaatteeseen perustuvaa menetelmää. Samalla saadaan kerättyä lisää kokeellista näyttöä myös tämän menetelmän toiminnasta. Kaikki käytetyt testiongelmat kyettiin ratkaisemaan sekä alkuperäisellä differentiaalievoluutiolla, että uutta mutaatio-operaatiota käyttävällä versiolla. Uusi menetelmä osoittautui kuitenkin luotettavammaksi sellaisissa tapauksissa, joissa alkuperäisellä algoritmilla oli vaikeuksia. Lisäksi useimmat ongelmat kyettiin ratkaisemaan luotettavasti pienemmällä populaation koolla kuin alkuperäistä differentiaalievoluutiota käytettäessä. Uuden menetelmän käyttö myös mahdollistaa paremmin sellaisten kontrolliparametrien käytön, joilla hausta saadaan rotaatioinvariantti. Laskennallisesti uusi menetelmä on hieman alkuperäistä differentiaalievoluutiota raskaampi ja se tarvitsee yhden kontrolliparametrin enemmän. Uusille kontrolliparametreille määritettiin kuitenkin mahdollisimman yleiskäyttöiset arvot, joita käyttämällä on mahdollista ratkaista suuri joukko erilaisia ongelmia.

Diskreetin optimoinnin käyttö mekatronisen koneen virtuaalisuunnittelussa

Työn tavoitteena oli selvittää konetekniikan osastolla valmistetun optimointiohjelman soveltuvuutta virtuaaliprototyyppisen optimointiin. Lisäksi työn tavoitteena oli selvittää virtuaaliprototyyppien avulla tapahtuvan optimoinnin rajoitteet ja mahdollisuudet todellisilla optimointitehtävillä. Optimaze-ohjelma yhdistettiin simulointiohjelmistoon käyttäen apuna merkkitiedostoja ja simulointiohjelmiston sisäisiä makroja. Saadun optimointiympäristön toimivuus testattiin kahdella todellista puomia optimoivalla optimointitehtävällä. Simulointiohjelmistona käytettiin ADAMS:ia ja optimointialgoritmina differentiaalievoluutiota. Tuloksista havaittiin optimointiohjelman soveltuvan virtuaaliprototyyppien optimointiin. Raskaiden mallien optimoinnin huomattiin kuitenkin olevan liian hidas prosessi. Tutkimuksessa todettiinkin asian vaativan lisää tutkimista ja kehitystyötä.

Retentiojärjestelmän optimointi kartonkikoneella

Diplomityössä tutkittiin kartonkikoneen retentiojärjestelmää ja eri mahdollisuuksia retention ja vedenpoiston tehostamiseen. Tavoitteena oli parantaa etenkin runkokerroksen retentiota ja vedenpoistoa. Työssä testattiin kilpailevan kemikaalitoimittajan mikropartikkelia kartonkikoneella. Lisäksi runkokerroksessa testattiin retentiotärkkelyksen vaikutus kartongin palstaumislujuuteen, suoritettiin käytössä olevan mikropartikkelin annostuksen optimointi sekä testattiin alunan käyttöä retentioainesysteemin tehoaineena. Kirjallisuusosassa tarkasteltiin pinta- ja kolloidikemian perusteita, retentioainejärjestelmiä ja niissä käytettäviä kemikaaleja sekä retentioaineilla tehtävään flokkaukseen vaikuttavia tekijöitä. Laboratoriokokeilla tutkittiin kokeellisessa osassa eri mikropartikkelijärjestelmien toimivuutta kartonkikoneen eri kerroksien massoilla. Toimivimmaksi osoittautuneella mikropartikkelilla suoritettiin pilot-koeajo runkokerroksen massalla. Lisäksi suoritettiin toinen pilot-koeajo, jossa tutkittiin mikropartikkelin vaikutuksia saostuman aiheuttajana. Pilot-koeajoissa saavutettiin samat retentiotasot kuin referenssisysteemillä lähes puolet pienemmällä kemikaalin kulutuksella. Kartongin laatuominaisuuksista huokoisuus, formaatio ja AKD-liiman retentio muuttuivat viiraretention mukaan. Saostumakoeajossa ei todettu retentioaineen vaikuttavan saostumien syntyyn. Täyden mittakaavan koeajossa tarkoituksena oli testata kilpailevan mikropartikkelin toimivuus kartonkikoneella. Koeajossa etsittiin optimaalinen mikropartikkelin annostus eri kerroksiin. Pintakerroksen tuhkaretentio nousi hiukan ja vedenpoisto parani. Runko- ja taustakerroksessa saavutettiin samat retentiotasot sekä vedenpoistot. Samat retentiotasot saavutettiin n. 25 % pienemmällä mikropartikkelin kulutuksella. Kartongin laatuominaisuuksista seurattiin palstautumislujuutta, formaatiota ja AKD-liiman retentoitumista. Kartongin palstautumislujuus heikkeni. Vastaavasti runko- ja taustakerroksen AKD-liiman retentio oli hiukan korkeampi koeajetulla mikropartikkelilla. Formaatiossa ei tapahtunut merkittäviä muutoksia. Jatkokokeet tehtiin kartonkikoneen runkokerroksessa. Kokeissa todettiin retentiotärkkelyksen vaikuttavan kartongin palstautumislujuuteen. Käytössä olevan mikropartikkelin annostelun optimointikokeissa ei saavutettu parannusta retentioon eikä vedenpoistoon. Mikropartikkelilla saavutetaan tietty retentiotaso, jonka jälkeen sillä ei ole enää vaikutusta retentiotasoon. Alunan annostelukokeissa ei alle yksi kg/t annosmäärällä ole vaikutusta retentioon ja vedenpoistoon.

Populaation monimuotoisuuden mittaaminen liukulukukoodatuissa evoluutioalgoritmeissa

Diplomityössä esitetään menetelmä populaation monimuotoisuuden mittaamiseen liukulukukoodatuissa evoluutioalgoritmeissa, ja tarkastellaan kokeellisesti sen toimintaa. Evoluutioalgoritmit ovat populaatiopohjaisia menetelmiä, joilla pyritään ratkaisemaan optimointiongelmia. Evoluutioalgoritmeissa populaation monimuotoisuuden hallinta on välttämätöntä, jotta suoritettu haku olisi riittävän luotettavaa ja toisaalta riittävän nopeaa. Monimuotoisuuden mittaaminen on erityisen tarpeellista tutkittaessa evoluutioalgoritmien dynaamista käyttäytymistä. Työssä tarkastellaan haku- ja tavoitefunktioavaruuden monimuotoisuuden mittaamista. Toistaiseksi ei ole ollut olemassa täysin tyydyttäviä monimuotoisuuden mittareita, ja työn tavoitteena on kehittää yleiskäyttöinen menetelmä liukulukukoodattujen evoluutioalgoritmien suhteellisen ja absoluuttisen monimuotoisuuden mittaamiseen hakuavaruudessa. Kehitettyjen mittareiden toimintaa ja käyttökelpoisuutta tarkastellaan kokeellisesti ratkaisemalla optimointiongelmia differentiaalievoluutioalgoritmilla. Toteutettujen mittareiden toiminta perustuu keskihajontojen laskemiseen populaatiosta. Keskihajonnoille suoritetaan skaalaus, joko alkupopulaation tai nykyisen populaation suhteen, riippuen lasketaanko absoluuttista vai suhteellista monimuotoisuutta. Kokeellisessa tarkastelussa havaittiin kehitetyt mittarit toimiviksi ja käyttökelpoisiksi. Tavoitefunktion venyttäminen koordinaattiakseleiden suunnassa ei vaikuta mittarin toimintaan. Myöskään tavoitefunktion kiertäminen koordinaatistossa ei vaikuta mittareiden tuloksiin. Esitetyn menetelmän aikakompleksisuus riippuu lineaarisesti populaation koosta, ja mittarin toiminta on siten nopeaa suuriakin populaatioita käytettäessä. Suhteellinen monimuotoisuus antaa vertailukelpoisia tuloksia riippumatta parametrien lukumäärästä tai populaation koosta.

Estudo do estado fundamental de aglomerados de silício via redes neurais

We introduce a global optimization method based on the cooperation between an Artificial Neural Net (ANN) and Genetic Algorithm (GA). We have used ANN to select the initial population for the GA. We have tested the new method to predict the ground-state geometry of silicon clusters. We have described the clusters as a piling of plane structures. We have trained three ANN architectures and compared their results with those of pure GA. ANN strongly reduces the total computational time. For Si10, it gained a factor of 5 in search speed. This method can be easily extended to other optimization problems.

Bioaccumulation of metals in aquatic insects of streams located in areas with sugar cane cultivation

Streams located in areas of sugar cane cultivation receive elevated concentrations of metal ions from soils of adjacent areas. The accumulation of metals in the sediments results in environmental problems and leads to bioaccumulation of metal ions by the aquatic organisms. In the present study, bioaccumulation of the metals ions Al, Cd, Cr, Cu, Fe, Mg, Mn and Zn in aquatic insects in streams impacted by the sugar cane was evaluated. The results pointed out that the insects were contaminated by the sediment and that the collector organisms as Chironomus species accumulated higher concentration of metals than the predator organisms.

Methane combustion kinetic rate constants determination: an ill-posed inverse problem analysis

Methane combustion was studied by the Westbrook and Dryer model. This well-established simplified mechanism is very useful in combustion science, for computational effort can be notably reduced. In the inversion procedure to be studied, rate constants are obtained from [CO] concentration data. However, when inherent experimental errors in chemical concentrations are considered, an ill-conditioned inverse problem must be solved for which appropriate mathematical algorithms are needed. A recurrent neural network was chosen due to its numerical stability and robustness. The proposed methodology was compared against Simplex and Levenberg-Marquardt, the most used methods for optimization problems.

Utilization of Automatic Meter Reading in the Improvement of a District Heating System

A district heating system comprises production facilities, a distribution network, and heat consumers. The utilization of new energy metering and reading system (AMR) is increasing constantly in district heating systems. This heuristic study shows how the AMR system can be exploited in finding optimization opportunities in district heating system. In this study, the district heating system is mainly considered from the viewpoint of operational optimization. The focus is on the core processes, heat production and distribution. Three objectives were set to this study. The first one was to examine general optimization opportunities in district heating systems. Second, to figure out the benefits of AMR for general optimization opportunities. Finally, to define a methodology for process improvement endeavors. This study shows, through a case study, the usefulness of AMR in specifying current deficiencies in a district heating system. Based on a literature review, the methodology for the improvement of business processes is presented. Additionally, some issues related to future competitiveness of district heating are concerned. As a conclusion, some optimization objectives are considered more desirable than others. Study shows that AMR is useful in the specification of optimization targets in the district heating system. Further steps in optimization process were not examined in detail. That would seem to be interesting topic for further studies.

Evaluation of sediment production and siltation in a small earth dam in Fernandópolis, SP

The siltation is a natural process, but can be accelerated by human actions and results in major problems for the reservoirs, reducing its useful volume for irrigation. An example of this problem was the reduction of the area of mirror water of Fernandópolis municipal dam in 48.3% during 20 years. Therefore, this study aimed to evaluate the production of sediments and siltation of Fernandópolis municipal dam from a methodology that can be applied to small earth dams for agricultural purposes. For this, it was monitored, monthly throughout the year, the volume of sediment deposited in the reservoir. The percentage of retention sediment in Fernandópolis municipal dam ranged from 53.9 to 94.5%, that associated with a high specific sediment yield, will cause its full silting in at most 57 years. It is recommended to minimize this process the restoration of permanent preservation areas and the removal of 17,500 m³ of sediment from the riverbed of the dam.

Measuring the performance of corporate events : an empirical study of measuring practices in Finnish companies

Corporate events as an effective part of marketing communications strategy seem to be underestimated in Finnish companies. In the rest of the Europe and the USA, investments in events are increasing, and their share of the marketing budget is significant. The growth of the industry may be explained by the numerous advantages and opportunities that events provide for attendees, such as face-to-face marketing, enhancing corporate image, building relationships, increasing sales, and gathering information. In order to maximize these benefits and return on investment, specific measurement strategies are required, yet there seems to exist a lack of understanding of how event performance should be perceived or evaluated. To address this research gap, this research attempts to describe the perceptions of and strategies for evaluating corporate event performance in the Finnish events industry. First, corporate events are discussed in terms of definitions and characteristics, typologies, and their role in marketing communications. Second, different theories on evaluating corporate event performance are presented and analyzed. Third, a conceptual model is presented based on the literature review, which serves as a basis for the empirical research conducted as an online questionnaire. The empirical findings are to a great extent in line with the existing literature, suggesting that there remains a lack of understanding corporate event performance evaluation, and challenges arise in determining appropriate measurement procedures for it. Setting clear objectives for events is a significant aspect of the evaluation process, since the outcomes of events are usually evaluated against the preset objectives. The respondent companies utilize many of the individual techniques that were recognized in theory, such as calculating the number of sales leads and delegates. However, some of the measurement tools may require further investments and resources, thus restricting their application especially in smaller companies. In addition, there seems to be a lack of knowledge of the most appropriate methods in different contexts, which take into account the characteristics of the organizing party as well as the size and nature of the event. The lack of inhouse expertise enhances the need for third-party service-providers in solving problems of corporate event measurement.

A new approach to evaluate imperfection sensitivity in asymmetric bifurcation buckling analysis

A direct procedure for the evaluation of imperfection sensitivity in bifurcation problems is presented. The problems arise in the context of the general theory of elastic stability for discrete structural systems, in which the energy criterion of stability of structures and the total potential energy formulation are employed. In cases of bifurcation buckling the sensitivity of the critical load with respect to an imperfection parameter e is singular at the state given by epsilon =0, so that, a regular perturbation expansion of the solution is not possible. In this work we describe a direct procedure to obtain the relations between the critical loads, the generalized coordinates at the critical state, the eigenvector, and the amplitude of the imperfection, using singular perturbation analysis. The expansions are assumed in terms of arbitrary powers of the imperfection parameter, so that both exponents and coefficients of the expansion are unknown. The solution of the series exponents is obtained by searching the least degenerate solution. The formulation is here applied to asymmetric bifurcations, for which explicit expressions of the coefficients are obtained. The use of the method is illustrated by a simple example, which allows consideration of the main features of the formulation.

The Salmon Algorithm - A New Population Based Search Metaheuristic

This thesis introduces the Salmon Algorithm, a search meta-heuristic which can be used for a variety of combinatorial optimization problems. This algorithm is loosely based on the path finding behaviour of salmon swimming upstream to spawn. There are a number of tunable parameters in the algorithm, so experiments were conducted to find the optimum parameter settings for different search spaces. The algorithm was tested on one instance of the Traveling Salesman Problem and found to have superior performance to an Ant Colony Algorithm and a Genetic Algorithm. It was then tested on three coding theory problems - optimal edit codes, optimal Hamming distance codes, and optimal covering codes. The algorithm produced improvements on the best known values for five of six of the test cases using edit codes. It matched the best known results on four out of seven of the Hamming codes as well as three out of three of the covering codes. The results suggest the Salmon Algorithm is competitive with established guided random search techniques, and may be superior in some search spaces.

« Resolution Search » et problèmes d’optimisation discrète

Thèse réalisée en cotutelle avec l'Université d'Avignon.