Implementing a Time Optimal Task Sequence For Robot Assembly Using Constraint Programming

Assembly lines in a lean production environment may persist for months or years, but due to the rapid change in demands on the consumer market they can be subject to quick changes. Robots have been proved to handle tasks that previously were limited to human workers: this is the goal of the flexible two armed robot developed by ABB. When installing a new robot into an assembly line there are several parameters which make it a difficult job for programmers, even experienced ones, to install the robot. These problems lead to long installation processes that can take weeks, and there are great benefits of automating the process of finding good solutions to the problem. In this thesis a constraint programming approach is presented as a way to solve the complex sequencing problem when installing a two armed robot into a new environment. When benchmarked against a reference case study, the implemented prototype  solutions showed an improvement of 17%, all within a time limit of 20 minutes instead of weeks. This shows that constraint programming can be a good tool for automating robot installations

Corrosion resistant alumina-forming alloys for lead-cooled reactors

Generation IV nuclear power technologies provide attractive solutions to the common issues related to conventional nuclear power plants currently in operation worldwide. Through a significant reduction of the long-term radiotoxicity of nuclear waste, a more efficient use of nuclear fuel resources, and implementation of inherent safety features, Generation IV will make nuclear power sustainable and thus increase the public acceptance of nuclear power. Due to its attractive safety features, the lead-cooled fast reactor (LFR) is one of the most studied Generation IV reactor concepts currently. It is well known that liquid lead is corrosive to steels at elevated temperatures, thus limiting the operation temperature of the LFR. The use of alumina-forming FeCrAl alloys has been proposed to mitigate oxidation and corrosion issues. Commercial FeCrAl alloys have Cr-concentrations typically about 20 wt. % and are thus prone to α-α’ phase separation and embrittlement at temperatures up to about 500 °C. Reducing the Cr-concentration to levels around 10 wt. % would theoretically resolve the said issue. However, the oxidation and corrosion resistance may be impaired. In the scientific literature, compositional limits indicating the formation of protective alumina layers at various temperatures have been presented. Long-term corrosion studies are however scarce. Moreover, in-depth studies on the compositional limits regarding α-α’ phase separation are lacking. In this thesis, the long-term (up to 10,000 h) corrosion resistance and phase stability of alumina-forming alloys are studied at temperatures up to 550 °C. In addition, the influence of reactive elements (RE), e.g. Ti, Zr, and Y, on the liquid lead corrosion resistance of Fe10CrAl alloys is evaluated. By balancing the reactive element and the carbon content, with respect to carbide formation, it is demonstrated in this thesis that it is possible to form protective alumina layers on Fe10Cr4Al alloys from 450 °C, despite the low Al and Cr concentrations. It was found that the RE/carbon ratio needed to form protective alumina layers on Fe10Cr4Al alloys must be larger than unity to mitigate the detrimental effect of Cr-carbide formation.  The underlying phenomena are discussed, and a mechanism is suggested based on the outcome of the long-term oxidation studies. The phase stability of Fe10CrAl alloys was studied through thermal aging experiments in the temperature interval of 450 to 550 °C. In addition, the results were well reproducible using a developed Kinetic Monte Carlo (KMC) model of the FeCrAl system. Furthermore, the model indicated that the Cr-concentration should be limited to about 11 wt. % in a FeCr4Al alloy to mitigate α-α’ phase separation at all temperatures of interest for an LFR. The liquid lead corrosion resistance of alumina-forming austenitic stainless steels was shown to be superior compared to regular stainless steels, albeit the effect of ferrite stabilizing elements needs to be further addressed. The results included in this thesis provide a valuable input on the key issues related to the development of corrosion resistant alumina-forming alloys of interest for liquid lead applications. Moreover, the superior oxidation properties of the studied alumina-forming alloys make them of interest for use in other energy applications, where corrosion issues limits the operation temperature and thus the efficiency.  QC 20141217</p

Kalkindustrin, en möjlig marknad för Kanthal

The subject of this M.Sc. thesis is to find out whether the lime industry is a possible business area for Kanthal AB. The lime industry is one of the biggest chemical industries in the world and it is very energy demanding. In the process of making quicklime, calcium oxide, a lot of energy is needed as the dissociation of limestone, which consists mainly of calcium carbonate, takes place in the temperature span between 900°C and 1300°C. The total production of quicklime was in 2009 about 280 million tonnes, and the selling price was about $100 per ton. Today, all limekilns are driven by fossil fuels, i.e. oil, coal and gas. The increasing demand on lowering the emissions of carbon dioxide strongly affects the industry, as it is responsible for about 2 % of the total emissions of carbon dioxide. The industry itself claims that the emissions may only be reduced about 10 %, although at very high costs. Kanthal AB produces electric heating solutions that may be suitable for lime production. However, the lime industry is conservative and the use of electricity for lime production is not economically feasible today. Most of the electricity comes from coal power plants and therefore the use of electricity would not be more environmentally friendly in most countries. New limekilns, which are more environmentally friendly, are on the way. These kilns do not necessarily have to use fossil fuels, provides a purer end product and the emission of carbon dioxide is minimized. The size of the production is also much lower, but the end products might be used in more demanding areas, e.g. the pharmaceutical industry, and be sold at a higher price. It is this area Kanthal has to focus on if going to enter the lime industry at this point

Kalkindustrin, en möjlig marknad för Kanthal

The subject of this M.Sc. thesis is to find out whether the lime industry is a possible business area for Kanthal AB. The lime industry is one of the biggest chemical industries in the world and it is very energy demanding. In the process of making quicklime, calcium oxide, a lot of energy is needed as the dissociation of limestone, which consists mainly of calcium carbonate, takes place in the temperature span between 900°C and 1300°C. The total production of quicklime was in 2009 about 280 million tonnes, and the selling price was about $100 per ton. Today, all limekilns are driven by fossil fuels, i.e. oil, coal and gas. The increasing demand on lowering the emissions of carbon dioxide strongly affects the industry, as it is responsible for about 2 % of the total emissions of carbon dioxide. The industry itself claims that the emissions may only be reduced about 10 %, although at very high costs. Kanthal AB produces electric heating solutions that may be suitable for lime production. However, the lime industry is conservative and the use of electricity for lime production is not economically feasible today. Most of the electricity comes from coal power plants and therefore the use of electricity would not be more environmentally friendly in most countries. New limekilns, which are more environmentally friendly, are on the way. These kilns do not necessarily have to use fossil fuels, provides a purer end product and the emission of carbon dioxide is minimized. The size of the production is also much lower, but the end products might be used in more demanding areas, e.g. the pharmaceutical industry, and be sold at a higher price. It is this area Kanthal has to focus on if going to enter the lime industry at this point

Hydrophobic and superhydrophobic coatings for corrosion protection of steel

Since metals in general, and steels in particular, are vital construction materials in our modern society, the corrosion protection of said materials is of great importance, both to ensure safety and to reduce costs associated to corrosion. Previously, chromium (VI) and other harmful substances were effectively used to provide corrosion protection to steel, but since their use was heavily regulated around year 2000, no coating has yet been developed that, in a fully satisfactory manner, replaces their corrosion protective properties.In this thesis, the use of hydrophobic and superhydrophobic surface coatings as part of corrosion protective coating systems has been studied. Since the corrosion mechanism relies on the presence of water to take place, the use of a superhydrophobic coating to retard the penetration of water to an underlying metal surface is intuitive. The evaluation of corrosion protective properties of the hydrophobic and superhydrophobic surfaces was performed using mainly contact angle measurements and electrochemical measurements in severely corrosive 3 wt% NaCl water solution.First, the differences in corrosion protection achieved when employing different hydrophobic wetting states were investigated using a model alkyl ketene dimer wax system. It was found that superhydrophobicity in the Lotus state is superior to the other states, when considering fairly short immersion times of less than ten days. This is due to the continuous air film that can form between such a superhydrophobic surface and the electrolyte, which can retard the transport of electrolyte containing corrosive ions to the metal surface to the point where the electrical circuit is broken. Since corrosion cannot occur unless an electrical current is flowing, this is a very efficient way of suppressing corrosion.An air layer on an immersed superhydrophobic surface is, however, not stable over long time, and to investigate long-term corrosion protection using hydrophobic coatings a polydimethylsiloxane formulation containing hydrophobic silica nanoparticles was developed. This system showed enhancement in corrosion protective properties with increasing particles loads, up until the point where the particle load instead causes the coating to crack (at 40 wt%). The conclusion is that the hydrophobicity of the matrix and filler, in combination with the elongatedivdiffusion path supplied by the addition of particles, enhanced the corrosion protection of the underlying substrate.To further understand how hydrophobicity and particle addition affect the corrosion protective properties of a coating a three layer composite coating system was developed. Using this coating system, consisting of a polyester acrylate base coating, covered by TiO2 particles (with diameter &lt; 100 nm) and finally coated with a thin hexamethyl disiloxane coating, it was found that both hydrophobicity and particles are needed to reach a great enhancement in corrosion protective properties also for this system.Eftersom metaller, och då särskilt stål, är viktigta konstruktionsmaterial i vårt moderna samhälle är korrosionsskydd av stor betydelse, både för att garantera säkerhet och för att minska kostnader som uppkommer i samband med korrosion. Tidigare har sexvärt krom och andra skadliga ämnen använts för att på ett effektivt sätt skydda stål från korrosion, men efter att deras användning kraftigt reglerades runt år 2000 har ännu ingen beläggning utvecklats som helt kan ersätta krombeläggningarna med avseende på funktion.I denna avhandling har hydrofoba och superhydrofoba ytbeläggningar och deras möjliga applikation som en del av ett korrosionsskyddande beläggningssystem studerats. Eftersom korrosionsmekanismen är beroende av närvaron av vatten, är användandet av en superhydrofob beläggning för att fördröja transporten av vatten till den underliggande metallytan intuitiv. De korrosionsskyddande egenskaperna hos superhydrofoba ytbeläggningar utvärderades här främst med hjälp av kontaktvinkelmätningar och elektrokemisk utvärdering i korrosiv lösning bestående av 3 vikts% NaCl i vatten.Först undersöktes skillnaden i korrosionsskydd som uppnås vid användandet av ytbeläggningar med olika hydrofoba vätningsregimer med hjälp av ett modellsystem bestående av ett alkylketendimer vax. Det konstaterades att superhydrofobicitet i Lotusregimen är överlägset bättre än de andra hydrofoba vätningsregimerna, i alla fall när man ser till relativt korta exponeringstider, typiskt mindre än tio dagar. Detta beror på att den kontinuerliga luftfilm som kan bildas på en sådan typ av superhydrofob yta kan minska transporten av elektrolyt (som innehåller korrosiva joner) till metallytan till den grad att den elektriska kretsen bryts. Eftersom korrosion inte kan ske utan en sluten elektrisk krets är detta ett mycket effektivt sätt att förhindra korrosion från att ske.Ett luftskikt på en superhydrofob yta nedsänkt i vatten är dock inte stabilt under lång tid. För att undersöka möjligheten till korrosionsskydd under längre tid med hjälp av hydrofoba beläggningar utvecklades en hydrofob ytbeläggning bestående av polydimetylsiloxan och hydrofoba nanopartiklar av kiseldioxid. Detta system visade en förbättring av korrosionsskyddet vid ökat partikelinnehåll upp till den koncentration (40 wt%) där i stället sprickbildning i ytbeläggningen observerades. Från detta system kunde slutsatsen dras att matrisens och partiklarnasvihydrofobicitet i kombination med den längre diffusionsvägen som partiklarna orsakade förbättrade korrosionsskyddet av den underliggande metallen.För att ytterligare förstå hur hydrofobicitet och partikeltillsatser påverkar en ytbeläggnings korrosionsskyddande egenskaper har dessutom ett treskikts kompositbeläggningssystem utvecklats. Genom att använda detta beläggningssystem, som består av en basbeläggning av polyesterakrylat, ett lager TiO2-partiklar (med en diameter på &lt;100 nm) slutligen belagt med ett tunt ytskikt bestående av hexametyldisiloxan så kunde slutsatsen dras att både en hydrofob matris och partiklar behövs för att nå en markant förbättring av ytbeläggningens korrosionsskyddande egenskaper.QC 20151015</p

Kalkindustrin, en möjlig marknad för Kanthal

The subject of this M.Sc. thesis is to find out whether the lime industry is a possible business area for Kanthal AB. The lime industry is one of the biggest chemical industries in the world and it is very energy demanding. In the process of making quicklime, calcium oxide, a lot of energy is needed as the dissociation of limestone, which consists mainly of calcium carbonate, takes place in the temperature span between 900°C and 1300°C. The total production of quicklime was in 2009 about 280 million tonnes, and the selling price was about $100 per ton. Today, all limekilns are driven by fossil fuels, i.e. oil, coal and gas. The increasing demand on lowering the emissions of carbon dioxide strongly affects the industry, as it is responsible for about 2 % of the total emissions of carbon dioxide. The industry itself claims that the emissions may only be reduced about 10 %, although at very high costs. Kanthal AB produces electric heating solutions that may be suitable for lime production. However, the lime industry is conservative and the use of electricity for lime production is not economically feasible today. Most of the electricity comes from coal power plants and therefore the use of electricity would not be more environmentally friendly in most countries. New limekilns, which are more environmentally friendly, are on the way. These kilns do not necessarily have to use fossil fuels, provides a purer end product and the emission of carbon dioxide is minimized. The size of the production is also much lower, but the end products might be used in more demanding areas, e.g. the pharmaceutical industry, and be sold at a higher price. It is this area Kanthal has to focus on if going to enter the lime industry at this point

Hur länge hoppar gasellen? : En kvalitativ studie om gasellföretags utmaningar

Detta arbete undersöker utmaningar företag ställs inför efter en tid av snabb tillväxt. Det görsgenom att undersöka företag som blivit tilldelade Dagens Industris Gasell-pris för snabbtillväxt men vars omsättning senare stagnerat eller minskat under en period. Fokus ligger påatt undersöka hur företagen hanterat utmaningarna. Teorier kring utvecklingsfaser inomföretag och beslutsprocesser har använts för att analysera företagens tillvägagångssätt.Arbetet använder kvalitativa metoder där fyra personer med ledande roller på fyra företag harintervjuats. Resultaten visar att beroende på utvecklingstakt och marknad så ser utvecklingenolika ut från företag till företag men gemensamt för företagen i denna studie är att samtligahar tagit ett steg tillbaka och hanterat utmaningen med hjälp av tidigare erfarenheter

Hur länge hoppar gasellen? : En kvalitativ studie om gasellföretags utmaningar

Detta arbete undersöker utmaningar företag ställs inför efter en tid av snabb tillväxt. Det görsgenom att undersöka företag som blivit tilldelade Dagens Industris Gasell-pris för snabbtillväxt men vars omsättning senare stagnerat eller minskat under en period. Fokus ligger påatt undersöka hur företagen hanterat utmaningarna. Teorier kring utvecklingsfaser inomföretag och beslutsprocesser har använts för att analysera företagens tillvägagångssätt.Arbetet använder kvalitativa metoder där fyra personer med ledande roller på fyra företag harintervjuats. Resultaten visar att beroende på utvecklingstakt och marknad så ser utvecklingenolika ut från företag till företag men gemensamt för företagen i denna studie är att samtligahar tagit ett steg tillbaka och hanterat utmaningen med hjälp av tidigare erfarenheter