En hydraulisk riktningsventil av "öppet-centrum"-typ med ett ventilhus och en i detta rörlig vetilslid för reglering av flöde av hydraulfluid genom ventilen har en tryckkompenseringsventil anordnad i minst en för anslutning till en driven anordning avsedd arbetport för att tryckkompensera flödet från arbetsporten till den drivna anordningen.

Det här föredraget behandlar olika systemprinciper för att styra en variabel pump i en mobil applikation. Variabla pumpar med elektrisk styrning ger möjlighet till nya intressanta systemprinciper.

This thesis focuses on how to improve design and development of complex engineering systems by employing simulation and optimization techniques. Within the thesis, methods are developed and applied to systems that combine mechanical, hydraulical and electrical subsystems, so-called multi-domain systems. Studied systems include a landing gear system for a civil aircraft, electrohydrostatic actuation systems for aircraft applications as well as hydraulic actuation systems.

The usage of simulation and optimization in engineering design is gaining wider acceptance in all fields of industry as the computational capabilities of computers increase. Therefore, the applications for numerical optimization have increased dramatically. A great part of the design process is and will always be intuitive. Analytical techniques as well as numerical optimization could however be of great value and can permit vast improvements in design.

Within the thesis, a framework is presented in which modeling and simulation are employed to predict the performance of a design. Additionally, non-gradient optimization techniques are coupled to the simulation models to automate the search for the best design.

Engineering design problems often consist of several conflicting objectives. In many cases, the multiple objectives are aggregated into one single objective function. Optimization is then conducted with one optimal design as the result. The result is then strongly dependent on how the objectives are aggregated. Here a method is presented in which the Design Structure Matrix and the relationship matrix from the House of Quality method are applied to support the formulation of the objective function.

Another approach to tackle multiobjective design problems is to employ the concept of Pareto optimality. Within this thesis a new multiobjective genetic algorithm is proposed and applied to support the design of a hydraulic actuation system. The outcome from such a multiobjective optimization is a set of Pareto optimal solutions that visualize the trade-off between the competing objectives. The proposed method is capable of handling a mix of continuous design variables and discrete selections of individual components from catalogs or databases.

In real-world situations, system parameters will always include variations to some extent, and this fact is likely to influence the performance of the system. Therefore we need to answer not only the question "What is best?", but also "What is sufficiently robust?" Within this thesis, several approaches to handle these two different questions are presented.

The work presented in this thesis deals with information sharing within mobile robot teams. Main focus is on information related to team positioning and localization. The goal of this research is to find models for how to best deploy a group of robots.

The motion platforms covered are well adapted. although very important for the results. Motion models are crucial when calculating the dead reckoning of each platform. Results in the appended work show that the motion model has heavy impact on the possibility to affect the uncertainty of a robot team as new ground is deployed.

The sensor models discussed may not necessarily be what is commonly used in the research field. Instead good approximations are used, that describe the main features of the sensor type. The focus is to present different sensor types and describe how the characteristics affect the uncertainty of the robot team, not to create new sensor models. A general model for sensors with polar measurement coordinates is derived. This can be used with different sensors with the same characteristics.

A framework for sharing information within the robot team is derived. This is based on earlier work presented as "The Stochastic Map". However, the framework is tailored to suite the purpose of this work. Different estimation methods are also discussed, with main focus is on Kalman filtering techniques.

The resulting part of this work present different ideas of what should be considered when deploying a group of robots. Results show how different dist ribution of sensors will affect the localization uncertainty of the group. It is also shown how different deployment formations affect the uncertainty within the team.

When dealing with robot localization and simultaneous map building one of the greates problem is to keep the created map consistent. Due to linearization, simplifications and other errors in models resent work has shown that the map created will, eventually, diverge. One way of dealing with these problems is to present the map in robot coordinates and thereby increase the consistency of the map. In the case many robots are used to create a map collectively this consistency problem often arises even sooner. This work propose a new method of dealing with the consistency problem when doing collaborative mapping by presenting the map in a groupcentric coordinate frame that continuously moves together with the robot team as new areas are explored.

A standard IRB (Industrial Robot) of today is not capable of positioning itsels to within better than 2-5mm relative to a given structure or object. In order to be able to perform high precision manufacturing, the requirement is less than 0,5mm. Existing solutions for 6DOF measurements to enhance the accuracy are not only expensive but also lacks flexibility. An affordable, accurate concept for IRB closed loop position feedback is presented here. This article proposes a method for using a camera together with fixed features to enhance the accuracy of an IRB in industrial manufacturing processes. The method is based on SLAM (Simultaneous Localization and Mapping), used to structure collected information about the features (mapping), and for the IRB to locate itself among the features (localization). The concept covers a scenario in which a set of features are placed within the working area. A camera is mounted on the IRB to observe (measure) the relative pose of the feature set. When the system is running observation of only one feature increases accuracy. However, in normal operation more features are observed which will increase accuracy further. The system setup is a standard IRB, ABB4400, on which a single camera with IR flash is mounted and used as sensor. The features are made out of reflectors that are placed in the production cell. The camera is also equipped with an IRfilter to improve the signal to noise ratio, simplifying image processing and accelerating execution. The execution time is critical since the goal is to sample at such rate that as to cover the dynamics of the robot. 

Assembly system design is an important task for a manufacturing company regardless of the nature of its existing assembly activities. However, unlike the product development process, the process of designing assembly systems has not been emphasised.

The research presented in this thesis aims at identifying and structuring the performance of assembly systems and their design processes, and proposing a framework for identifying important relationships between the results of specific design projects and influencing factors in the field of the design process. These objectives have been accomplished through theoretical and empirical studies. The empirical studies were carried out in the form of an interview study at 15 companies and three case studies at Swedish manufacturing companies both aimed at describing and analysing companies' assembly systems as well as their assembly system design processes.

A number of characteristics of successful assembly systems have been identified and classified according to the system theory. They have then been structured in a model where the mentioned characteristics have been classified into nine groups indicating the performance of the assembly system. Assembly system performance is represented from a higher level of abstraction by assembly strategy, to a lower level of abstraction by quality, lead time and delivery precision, flexibility, cost and productivity of the assembly system.

The assembly system design processes have also been investigated and analysed empirically, showing that structured methods are seldom used in the assembly system design process, but mainly experience and knowledge of system designers is utilised. Although larger companies worked more systematically, no specific method for the design of assembly system has been found. The performance of the assembly system design process has been identified and presented in a model with nine performance indicators into three levels, from a higher level of abstraction (design process strategy) to a lower level of abs traction (quality, lead time and delivery precision, flexibility, cost and productivity).

From the two performance models, an approach to a matrix linking design factors to the design project results has been developed. Examples of the design factors have been given based on research studies in the field of product development, and on the theoretical and empirical studies presented in this thesis. The matrix described is an approach to a tool for the support of production managers and system designers in order to design successful assembly systems.

Creation of a supply base is perhaps the most important task of the purchasing function. In this creation process, potential suppliers must be identified, analysed and decisions made. Decisions that, in most cases, have direct effects on the company's "bottom line". The tools to support and aid this process are often one-dimensional and assume to a high degree that, in all cases, there is a valid description of the best possible supplier. This research suggests that this is not the case. Which is the best possible supplier is situation specific. This is a fact acknowledged in the literature and by the empirical material. What is missing is a tool to support the supplier selection process from a starting point that each sourcing situation is unique. This research proposes such a process approach and, at the same time, a model for supplier selection.

The purpose of this study is to analyse and develop the process of, and the criteria for, supplier selection in a sub-tier, business to business context. The research has been initiated by, and had its starting point in, one company (Volvo Aero Corporation) acting in the specific and very demanding environment of the aero-engine industry. The main aim of this research is to give managerial implications for purchasing professionals.

To be able to ensure that the best possible supplier for a specific situation is selected, the situation has to be analysed. This research proposes a model and process that starts by defining the minimum requirement which a supplier has to fulfil for a purchaser to be convinced that the intended relationship will be successful for the intended period of time. This minimum requirement is called the supplier profile. The business environment, network and market conditions, the.purchasing company 's strategies and the characteristics of the product, service or function to be sourced are identified as influential factors when creating the supplier profile. The results also highlight the need to work cross-functionally when creating the supplier profile and the need to combine different theoretical bases to get a complete picture of the requirements to put on a potential supplier.

Generally aircraft conceptual design is defined as the starting point for concept sketcing and evaluation, but before that work can start an even earlier stage has to be covered.

This is the stage where different scenarios are being worked through in which the aircraft as a platform is supposed to work. The scenarios will differ between civil and military use of course. but will have to fit well inside both customers and manufacturers strategic plans for the future.

In planning for the future it's vital to think and plan in broader terms, i.e. not only creating single products but rather create families of aircraft. This way of thinking and planning is usual amongst civil manufacturers. Creating a family based product line means better economics, better market coverage and of course lesser risk taking if and when the market changes. On the military side this way of thinking and planning is still quite unusual, mainly because customers are governments which usually only ask for single products.

The manufacturer from his point of view must think differently, he needs to spread his risk taking, especially as orders from the govemment are becoming scarcer. Therefore a modular product line would be of economic interest and would probably interest more customers.

The basic idea behind Saab Gripen (three roles merged into one single platform), or the US Joint Strike Fighter (JSF) idea of a modular aircraft, could be seen as the start of some kind of new family planning, but family planning on the military side could reach further than that. Probably military manufacturers can learn a lot from their civil counterparts.

Conceptual design might be a one man job in the early stages, but will very soon develop into team work. This development is only natural since the conceptual designer can't be expected to have detailed knowledge or experience which will cover every item. Conceptual design introduces a holistic viewpoint into the aircraft design process and it's vital to keep this viewpoint as long as possible. This becomes even more important over time, since the more detailed the project gets, the overall goal tends to drown into details.

Conceptual design phase offers the only occasion when design changes still can be made quite easily. Design freeze is not only a simple freeze of aircraft layout and geometry, it also sets the fmal prize tag on the aircraft. So in a way it is what you did (and what you forgot to do) in the conceptual design phase which fmally decides the faith of the end product. Hence conceptual design needs all the time it takes to be able to develop successful future products.

Generally there are two sides to conceptual design: either you develop a brand new design or make changes to an already existing one. Either way has its own needs and can't be run in the same manner, since different tools are needed in both cases. A new design needs a good conceptual design program, while in the latter case only minor parts of it might be used. A new design starts off fresh; everything is possible and nothing is sacred, but changing on an existing design means working with hands tied, you do not change things that easily.

Aircraft Conceptual Design takes long time to learn. It requires more than just being able to run a conceptual design program. Previous experience in a number of different aircraft design disciplines is a must; so is the ability to be able to humbly listen to experienced people's knowledge and advice.

This paper describes methods for aircraft conceptual design at two basic levels. At the top level there's a method described for conceptual design of civil jet transport aircraft.

On the second level different methods for conceptual design of core aircraft systems such as landing gear, environmental control and hydraulic are presented.

A well-designed landing gear and a proper integration is of utmost importance for the success of any aircraft design. This should never be neglected but often is, especially in the conceptual design stage. This paper reflects the author''s own experience in landing gear design of the Saab Gripen aircraft as well as experience gained on aircraft conceptual designs of later dates. The aim of the paper is to underline the importance of spending more time on landing gear design and integration in conceptual design. The paper reflects the importance of proper interaction between landing gear design and other disciplines and above all underlines the fact that landing gear design should be treated as an equally important design parameter, just as any other, in the final choice of aircraft configuration.

A tool has been developed in order to design or evaluate a proposed landing gear layout and to determine its size and weight. The methodology has been developed primarily for landing gears of the telescopic suspension type.

The design task for last year students in Aircraft Design at Linköping University was to design a manned solar-powered aircraft. The mission was to survey the U.S./Mexican borderline in search for possible intruders. The Sunriser began as a sole paper project, but quite soon we felt a need to prove that solar-powered flight really was feasible. Thus the decision was made to design and build a solar powered demonstrator of our own design.

The demonstrator aircraft, a radio controlled model aircraft named "the Sunrazor," was designed, built and flown with good result.

This paper deals with the basic theory of sun-powered flight and describes the basic thoughts and design considerations which finally led to the configurations chosen.

 Closed-loop instability caused by excess phase lag has been studied widely in aviation. Here we develop and test a model of its counterpart in vehicle-driver-coupling, where participants were asked to recover from a skid on a slippery road. We model the damping effect of sucessful recovery as viscoelastic behavior. Oscillation number is the predictor variable; steering wheel angle is the response variable. 

This thesis discusses how the problem of parking a passenger car can be solved. There ane numerous obstacles when creating a fully or semi automated system for assisting the parking maneuver. The obstacles range from unobtrusive Man Machine Interface issues to robust algorithms for finding features in sensor data.

Such a system will also have to cope with ever changing environments, most of which will not be discovered during the design phase. Misuse will also be common, since the function is aimed at a mass market - the car buyers. These interesting problem areas is also coupled with the customer value. A car buying customer today aims at feature content and comfort. So for a parking system to survive it needs to be extremely intuitive; the customer value must be discovered during a short test drive with the vehicle. A learning period before the user can operate the system is not feasible.

The work presented here proposes an interesting algorithm for finding parking space features in sensor data collected using ultrasonics. The algorithm, which is based on the well known Hough transform have been proved to be robust in real world experiments.

Furthermore it is also investigated how critical the mount ing of the environment sensing subsystem is. Where should the sensors be placed and where should they be facing to maximize the performance.

Emphasis have also been put on designing a functional architecture that fits in the car development process of today. The implementation of a system in a car must fit in the platform and component reuse is critical to keep cost down.

To test theories developed during the work a prototype car has been used. The prototype is essential to analyze the robustness of algorithms in different parking scenarios. It has also been an invaluable tool when conducting customer surveys to find where the customer value of these kind of systems is.

This paper describes a system for supporting the driver of a passenger car in different parking situations. Todays cars are getting larger in size and the drivers view in both forward and rearward direction is becoming more limited. This fact calls for a system of sensors and algorithms capable of supporting the driver through the parking maneuvre in a safe and smooth way.

The paper presents the development of some of the subsystems in a fully automatic parallel parking system, utilizing ultrasonic ranging sensors for environment mapping. In contrast to existing passive parking aid systems, the ultrasonic range sensors need to have a narrower aperture to be able to map the surroundings properly. This can be accomplished by either increased sensor size or by a higher number of sensors.

The emphasis of the paper is the signal conditioning in the parking system. The Hough-transform along with a statistical CUSUM test are used to find the properties of the target parking space.

The system makes use of hardware components already available in modern cars and a small number of added components. The resulting system is automated, from finding a suitable parking space to maneuvering the car into the parking space, while keeping the driver in authority since the longitudinal control, i.e. throttle and brakes, are still the drivers responsibilities.

The prototype system is implemented in a Volvo S60 which has been modified with an electric power steering unit and an ultrasonic sensor array consisting of a total of six sensors spread out around the vehicle. The electric power steering unit is used for steering wheel angle control when the system is active by adding an external torque to the assist torque normally applied.

This project describes how the Active Pinion hydraulic steering system can be used to replace a electric power steering actuator in the Parking Pilot automatic parking system.

Customer demand for fully or semi automatic parking systems in passenger cars, are getting higher with increased cost of parking related body damage repair coupled with restricted rearward sight and the larger dimensions of modern cars. This, however, puts new demands on the steering actuator. An automatic parking system requires full control of the steering servo, which is not possible with current hydraulic actuators. Instead these systems have to rely on electric servos which allow for the needed controllability.

All current electric steering servos have the drawback that it is impossible to use them on anything but small or medium sized cars. Since a parking system can be seen as a premium accessory, which is more likely to attract customers who buy larger cars, this is a major hindrance for the success of automatic parking systems.

A solution to the problem is to construct a controllable variant of the hydraulic steering servo, the Active Pinion. In this concept a small electric pilot motor is added to the traditional hydraulic valve, which adds one additional degree of freedom to the servo, accomplishing full four-quadrant operations.

The project discusses how the Active Pinion concept is introduced in the Parking Pilot parking system and how different demands on the parking system relates to the performance of the actuator. The parking system is installed in a prototype car and simulation of the Active Pinion concept is accomplished with HWIL simulation in a load simulator.

Software testing is complex and time consuming. One way to reduce testing effort is to automatically generate test data. In the first part of this thesis we consider a framework by Gupta et al. for generating tests from programs. In short, their approach consists of a branch predicate collector, which derives a system of linear inequalities representing an approximation of the branch predicates for a given path in the program. This system is solved using their constraint solver called the Unified Numerical Approach (UNA). In this thesis we show that in contrast to traditional optimization methods the UNA is not bounded by the size of the solved system. Instead it depends on how input is composed. That is, even for very simple systems consisting of one variable we can easily get more than a thousand iterations. We will also give a formal proof that UNA does not always find a mixed integer solution when there is one. Finally, we suggest using some traditional optimization method instead, like the simplex method in combination with branch-and-bound and/or a cutting-plane algorithm as a constraint solver.

In the second part we study a specification-based approach for generation of software tests developed by Meudec. Briefly, tests are generated by an automatic partitioning strategy based on partition rules. An important step in the process is to reduce the number of generated subdomains and find a minimal partition. However, we have found that Meudec-s algorithm does not always produce a minimal partition. In this work we present an alternative solution to the minimal partition problem by formulating it as an integer programming problem. By doing so, we can use well known optimization methods to solve this problem.

A more efficient way to derive a minimal partition would be using Meudec's conjectured two-step reduction approach: vertex merging and minimal path coverage. Failing to find a general solution to either of the steps, Meudec abandoned this approach. How-ever, in this work we present an algorithm based on partial expansion of the partition graph for solving the first step. Furthermore, our work in partial expansion has led to new results: we have determined an upper bound on the size of a minimal partition. In turn, this has led to a stronger definition of our current minimal partition algorithm. In some special cases we can also determine lower bounds. 

Two main drawbacks with hydraulic systems are noise and vibrations, mainly created from flow pulsations in positive displacement pumps. The flow ripple can be divided in two parts; kinematic and compressible. Kinematic flow ripple is created due to the limited number of pumping elements. Compressible flow ripple is created due to cornpressibility effects in the pumping chambers and is the dominating effect at high pressures. There are well proven methods to decrease noise in specific operation conditions, but there is an urgent need for new techniques in machines working under varying operation conditions. There is also a need for improved measurement methods to be used in product development and to judge new inventions to decrease noise.

Simulation techniques are useful in the early stages of the development process. There are useful and accurate simulation models capable of predicting source flow ripple in hydrostatic pumps and thereby useful for optimisation purposes. Simulation results are, however, of less practical use before they are experimentally verified . The experimental methods must be simple and straightforward if they are to be accepted in industry.

This paper describes a new method to measure source flow. It is called the source admittance method. Compared to earlier methods such as the two-microphone method, the main benefit is that there is no need for a model of the outlet channel - the source flow is measured through an additional pressure transducer inside the pump. The method works very well with a tested fixed bent-axis pump with a rather simple outlet channel. Experiments have also been performed with a variable in-line pump with added complexity to the out let channel. Although the overall impression is positive, these experiments show that the method needs to be further to be used for such machines. In both cases, the new method is compared with earlier verified simulation models and with measurements based on the two-microphone method. Apart from the mentioned discrepancies in a narrow frequency range, agreement is very good.

 Den här presentationen behandlar en metod som effektivt reducerar flödespulsationer i variabla hydraulmaskiner, genom att förskjuta dödpunktens läge. Det realiseras genom att införa en fast inklinationsvinkel vinkelrätt mot den normala deplacementsvinkeln. Genom att förskjutningsvinkeln ändrar kolvarnas dödpunkt kommer förkompressionen och efterexpansionen att variera när deplacementet ändras. Tidigare arbeten visar, både teoretiskt och experimentellt, fördelarna med förskjutningsvinkeln för pumpar men inga utförligare utredningar för maskiner som arbetar både som motor och pump.

This paper examines the dynamic properties of the pilot stage in a poppet type two-stage flow control valve of the -Valvistor- type. The particular valve studied is a screw-in Valvistor valve of NG16 size. There are several benefits to this valve type: it has a high closed loop bandwidth and the design allows big flow capacities. An attractive feature of this two-stage valve is that the pilot flow contributes to the total flow giving higher steady state flow efficiency. The dynamic characteristics of the main stage were discussed in an earlier paper. In this paper the aim is to study the influence of the pilot stage of the valve. The bandwidth of this type of valve is often unexpected low. Due to the high bandwidth of the Valvistor element the pilot dynamics is often dominating. In this paper it is shown by measurements the influence of different parts in the pilot valve that limits its bandwidth. Flow forces are used in this valve to compensate the pressure dependency in the flow. It is a common way of design in so called pressure compensated valves. It is discussed in the paper how this flow forces influences the dynamic properties of the pilot valve. The mentioned flow forces interact together with the mechanical spring in the pilot valve. Although the studied valve is just one of many variants of the Valvistor principle, we will investigate it closely due to the interest for this valve among other researchers. One important conclusion is that the inductance of the pilot solenoid is often limiting the bandwidth of the valve as a whole. 

These days, energy efficient mobile fluid power systems are of great interest. A mobile system containing several different cylinder drives supplied with a single load sensing pump (LS-pump) has a number of advantages as well as disadvantages. One of the main advantages is the need of only one system pump. This makes the fluid power system compact and cost-effective. A challenge is to keep the hydraulic losses at low level, especially losses at smaller loads. This paper introduces a fail-safe proportional valve element that is based on the Valvistor poppet valve. Due to the demands of flexibility the poppet valve is bi-directional. The valve has an innovative hydro-mechanical layout that makes it fail-safe, unwanted lowering loads, for example, never occur. The new valve includes simple sensors that are suitable for identification of mode switches, e g between normal, differential and regenerative modes. It is also possible to maneuver the system with maintainted velocity control in the case of sensor failure. In a less complex system the concept has benefits as well. For example in systems where fail-safe-bi-directional on/off valves are needed, then without mode sensing capabilities.

A review of recent and current research on individual metering fluid power systems is presented. An overview of different systems and their pros and cons is given. General challenges related to independent metering fluid power systems are discussed. The major choices in the design of these systems are the hardware layout and the control strategy. The evolution of existing independent metering fluid power systems from the 1970s until the present day is also presented.

 Detta paper presenterar en modellering av den kända Valvistorventilen samt en ny utvidgning av denna ventil som ger den proportionalegenskaper i två flödesriktningar på ett fail-safe sätt.

This is one of the earliest publications of the proposed energy efficient individual metering system shown in chapter 5, section 5.3.3. This paper introduces the novel system design, which utilizes independent meter-in and meter-out valves. This system design has the potential to increase energy efficiency considerably in a system that consists of a pump  connected to more than one fluid power actuator. The system proposed here is not dependent on pressure transducers for either flow control or mode selection. The main difference between the work presented in this paper and earlier work is the control strategy. The output signal choices in the closed loops are new. Some functionality is kept in hardware to avoid  critical sensor dependency. The presented system uses pressure compensators to achieve desired flows.

The aim of this study was to develop a finite element model for simulation of the thermal characteristics of brain electrodes and to compare its performances with an in vitro experimental albumin model. Ten lesions were created in albumin using a monopolar electrode connected to a Leksell Neuro Generator and a computer-assisted video system was used to determine the size of the generated lesions. A finite element model was set up of the in vitro experiments using the same thermal properties. With a very simple heat source applied to the finite element model in the proximity of the upper part of the tip, a good agreement (no deviations in width and distance from tip but a deviation in length of −1.6 mm) with the in vitro experiments (width 4.6±0.1 mm and length 7.4±0.1 mm) was achieved when comparing the outline of the lesion. In addition, a gelatinous albumin-model was set up and compared to computer simulations resulting in deviations in width of −0.4 mm, length of −2.2 mm and distance from the tip of −0.1 mm. Hence, the utilisation of finite element model simulations may be a useful complement to in-vitro experiments.

Within the Volvo Group there exist long-ranging experiences regarding hybrid propulsions systems for heavy commercial vehicles of the brands Volvo Trucks, Renalt Trucks, Mack Trucks, Nissan Diesel and Volvo Bus. For commercial vehicles like these, hybrid technology is to be regarded seriously and a business case is often given. The search for energy efficient solutions goes on also for construction equipment, and hybrids are everyone's topic. Within Volvo Construction Equipment there is a tradition of researching and developing energy efficient solutions, an example of which was the presentation of a first prototype of a hybrid wheel loader in the beginning of 2008. In this paper the wheel loader will be used as an example for other types of construction machinery. Using a systematic design approach, several more principle design solutions can be found. Reduced fuel consumption by 50% while keeping the performance and productivity at the same level is only possible by considering the complete machine as one system using a holistic approach. 

Med allt högre bränslepriser och den tilltagande samhällsdebatten om växthusgaser och klimatförändringar förvånar det inte att även företag utanför personbilsbranschen undersöker alternativa systemlösningar för att minska avgasutsläppen och oljeberoendet. Detta föredrag presenterar Volvo CEs satsning på elhybrider med fokus på hjullastare.

The coupled phenomenon of heat and water transfer is essential in many scientific and industrial problems. This thesis focuses this phenomenon on two areas; lacquer drying and thermal signatures. Simulations of physical phenomena may in some cases replace extensive experimental investigations, which may be complicated and expensive. In other cases simulations may provide means to reduce the number of experiments necessary to perform. In the thesis models, as simple as possible, are used to simulate heat and water transfer. Experiments were made and are compared with the simulations in order to verify the validity of the simplified models.

In the first part of the thesis the drying of a waterborne lacquer coating used in wood manufacturing industry is investigated. Problems concerning upward water transfer resulting in a specified drying period, and downward water transfer resulting in fibre swelling are addressed. Experiments were made in a full-scale drying plant.

In the second part of this thesis heat and water transfer in solar radiated sand is investigated. The main purpose of these investigations is to improve the predictions of thermal signatures related to detection of buried objects, e.g. buried land mines. Among several factors, influencing the thermal signatures received by optical systems, water movement in the soil and water evaporation from the surface have been found to be of particular interest. Experiments were made in an indoor test landscape.

In two related papers two other methods for investigating problems connected to lacquer drying are presented. In the first paper two-way factorial design is used to optimise the drying process of waterborne lacquer coating in a full-scale drying oven. In the second paper the inverse heat conduction problem is used to predict the surface temperature of a particleboard based on measurements inside the board.

Design processes for complex safety-critical systems in the automotive industry need to evolve in order to address increasing demands for integration of car functions over common networked infrastructures. New processes must address cost and safety concerns, and at the same time maximize profit. Automation provides a possibility to address these problems in design of complex systems and should thus be utilised. Automation is possibly the only option for handling the increasing technological complexity while still preserving the iterative design procedure that both reduces cost and gives room for design innovations. This thesis proposes a design process supported by novel techniques for semi-automatic safety and reliability analysis. System models are combined with multi-objective optimisation techniques to assist the gradual development of designs that can meet reliability and safety requirements as well as maximise profit within pragmatic development cost constraints. The proposed process relies on tools to automate some aspects of the design that can be automated and thus simplified without loss of the creative input brought to the process by designers. This thesis also presents the background and the necessity for this technical evolution towards network-embedded systems using open distributed architectures for future cars.

This paper presents a method to support designers and product planners in determining the functionalities that should be implemented in a product and those that should not. The proposed method identifies the set of customer functions and technical implementations that maximise the potential product profit. The customer functions represent the functionality of the product, and the technical implementations are the hardware and software components needed to realise these functions. For industrial applications, the numbers of possible combinations of customer functions and technical implementations are extremely large. We present a mathematical framework that handles this problem. Furthermore, optimisation is employed to find the set of customer functions that will maximise profit when subjected to a restricted development budget in order to find the best possible business case. The method was evaluated on an industrial case study of active safety systems performed at Volvo Cars. Based on this case study, the proposed method shows a substantial potential compared to the methods presently used.

For products with long life cycles, operational and support costs represent a significant part of the total cost for the product. Moreover, such products frequently tend to be complex and contain a mixture of both mature. stable technology with bng life cycles and new technology with short life cycles. lt is therefore of great interest to industry to determine how to take these factors into consideration in an efficient way during product development.

Another factor that affects product development for these and other kinds of products with shorter life cycles is interest in taking a wider view of the end-user or customer scenario, for instance by offering support and after sales services for the products. All these interests drive the demand to consider life cycle related issues in product development, not just life cycle cost. This also makes a life cycle perspective interesting for fums that produce products with shorter life cycles than the ones studied here through the opportunity for after market sales and services.

This research has been explorative, aiming to understand how firms manage to take life cycle related demands into consideration during product development. The aim was to expand from a cost oriented focus to a wider focus, a value oriented focus, here called life cycle value. The dominant question has been "how" life cycle related demands are considered, focusing on barriers to and enablers for this. Equally important has been to determine the implication of life cycle value for different firms and industries and to find out where value is added in product development. A combination of a quantitative and qualitative research approach has been used to collect empirical data.

One important finding was that there is an interest to deliver a solution to the customer rather than just a product, to consider customer revenue. This adds a new perspective to the implication of life cycle value, moving from a life cycle cost scenario to a life cycle cost versus revenue scenario. The results fom cases were categorized into six main attributes. These attributes were considered to be very influential and important for the ability to take life cycle perspective into account during product development.

• Holistic Perspective
• Requirements & Metrics
• Leadership & Management/Knowledge management
• Tools & Methods
• Organizational Factors
• Enterprise Relationships

Within each of these attributes, several practices and lessons learned were identified. Some of the results are also worth investigating further in continued research:

• Requirements formulation and management is considered to be critical. Well defined and clearly stated demands are key to taking life cycle issues into account due to the difficulty of incorporating life cycle related demands into the product. Nonetheless, balancing these demands against others is perceived to be difficult, and there is a clear need for tools, methods or models to support decision-making in this context.
• The incorporation of new technology and services is another field of interest to industry. Organizational support and planning for technology insertion and new innovations and services into existing products and product lines are needed.
• The organizational support to balance specialization and integration in a product development context, with a long-term focus
• The effect of a transfer from delivering a product to delivering product and support services to the organization.

Several factors prevent enterprises from having a holistic perspective during product development. Important aspects include increased product complexity and significant uncertainty with regard to technology. For products with a long life cycle this is extremely important since development and life cycle costs are high. The combination of complexity of system design and the limits of individual human comprehension typically make it difficult to envision a best value solution.

In an attempt to encircle a more holistic perspective of value, the concept of Life Cycle Value has evolved within the Lean Aerospace Initiative, LAI. The implication of this is development of products incorporating life cycle and long-term focus including cost and performance and reliability factors. A similar perspective has evolved within the Lean Aircraft Research Program, LARP, in Sweden.

This paper contributes a new study of how life cycle aspects are taken into consideration in a large corporation in the transportation industry. The purpose of the research was to examine relative contributions to product development and determine factors that significantly promote the ability to consider the life cycle perspective. The results will be discussed with respect to tools, methods, requirements, metrics, leadership and other organizational factors, innovation, and enterprise relationships.

Mobile machines of today often contain hydraulic valve controlled actuator loads in an open loop circuit. For the purpose of saving energy, the constant pressure pumps have in the past often been replaced by load sensing pumps and valves. In mobile applications, they have significantly reduced the energy consumption. Stricter environmental demands and rapidly increased fuel cost require an even lower consumption. By analyzing a typical working cycle of a construction machine, the possibility of energy recovery has been identified. The analyse confirms the importance of minimizing the metering losses. In a load-sensing valve solution these losses arise as a result of the unequal drive pressure levels. By adopting a displacement controlled regenerative solution, a significantly higher level of efficiancy can be obtained. 

Noise reduction in hydmulic systems has been an important research topic for several decades. In recent years, industry's interest in the area has grown dramatically. The reason is new national and international requirements and legislation governing working conditions. As a consequence of this, considerable reduction of noise from machinery in general has been achieved. The reduction of noise in hydraulic systems, however, has not gained from the same considerable progress, which implies that hydraulic noise has become perceptible through the surrounding machinery noise. Not only has noise reduction of hydraulic systems become increasingly important, it has also become more difficult because of the ever-increasing working pressure level, which is highly correlated to noise and vibration.

Noise in hydraulic systems is created mainly by the hydrostatic pump and motor, working with large pressure differences in the suction and delivery ports. Being exclusively of displacement type, the hydrostatic machine creates substantial flow pulsations in both the discharge and suction ports. The flow pulsations give rise to system pressure pulsations, which in turn transform into vibration and audible noise. Excessive pulsating piston forces and bending moments due to the large pressure difference between the machine's discharge and suction ports also contribute to noise and vibration.

To obtain satisfactory noise reduction, there is a need for effective and reliable design tools and design methods. This thesis concerns simulation, optimisation and experimental verification of axial piston pump design for noise reduction. Much of the work relates to the different origins of noise and how to formulate objective functions that simultaneously reflects different aspects of noise reduction. New and conventional design features are examined both theoretically and experimentally. One novel and promising design feature thoroughly investigated in this thesis is the so-called crossangle that aims to provide low noise in variable displacement machines. Different measurement approaches are employed for experimental verification. It is shown that conventional methods are often inadequate for measuring source flow in variable displacement units due to the complex outlet channel. A new method, referred to as the Source admittance method, is proposed.

AS A CONSEQUENCE OF increased requirements concerning pleasant working conditions, the system designer of today is facing challenges besides the traditional performance related ones. Subjects such as cleanliness, low sound and vibration levels etc. play important roles in modern system development. The requirements have resulted in considerable improvements on machineries in general, but still the noise often reaches unacceptable levels. In many applications of today, the noise emitted by the hydraulics can be identified through the totally emitted noise, and the trend towards increasing working pressure, which is directly correlated to noise and vibrations, seems to last. Therefore, studies regarding noise from hydraulic systems are still highly relevant.

The primary noise source in a hydraulic system is the hydrostatic machine, working with large pressure differences. Being exclusively of displacement type, the hydrostatic machine divides the flow into separate volumes, which are pressureized or de-pressurized. This working principle will cause phenomena such as pressure peaks, flow ripple and internal force and torque ripple, all contributing to noise and vibrations. However, when considering the complete system it becomes evident that noise is normally created by joint effort from different origins and their interaction with external hydraulic and mechanical systems. It is therefore difficult to point out one origin solely.

This thesis aims to survey and summarize work accomplished in the area of noise and vibrations in hydraulic systems. In the work, effort has been concentrated to the internal workings of the axial piston machine, mainly the pump. To map the couplings between geometric design and dynamic behaviour, simulation technique is frequently used. The most common design features are de­ scribed and discussed. A rating system, grading the different noise reducing devices mutually, which gives the designer the ability to chose the most beneficial design feature regarding to high reduction of flow ripple in relation to implementation cost, is presented.

Computational system design is as an area within engineering design that to a large extent is based on simulation models together with tools and methods for analysis and design. This area is becoming increasingly important for providing information to designers and decision makers early in the design process, and enabling qualitative decisions to be made.

Engineering design in general is today carried out in a collaborative, distributed, and at the same time competitive fashion where complex products are to a large extent assemblies of subsystems developed by several suppliers. It is important that models and computational design methods can be managed efficiently in such design projects, where models can be exchanged and integrated, design data managed, and proprietary information protected.

In this thesis, a framework is presented which facilitates management of simulation models, design data, and computational processes. The framework emphasizes a model-centric view, which means that models are represented on a high level of abstraction, without tool-specific information.

By defining models using the extensible Markup Language, XML, it is a straightforward matter to apply generic operators to the model and transform the model to several tool-specific implementations.

The framework also enables integration of distributed computational resources. By implementing standards for so-called web service technology, simulation modules are published as remote model services, enabling partners in a project to deploy and invoke simulation models as black boxes. By publishing an interface to the model in a standardized format, and keeping the model at its original location, the model can be accessed and integrated without revealing proprietary information about the model. This approach also facilitates integration of existing so-called legacy tools and models.

A data management approach is also presented where design data and the computational processes are handled. Variability measures for the design data are included, enabling probabilistic methodologies and design optimization to be applied in a straight-forward way. The computational

design process is formalized by representing the process as an executable process description enabling direct implementation, modification, and exchange of processes.

In the last part of the thesis, a number of evaluation examples are presented where some of the tools and concepts of this thesis are illustrated. These examples are mainly from the area of aircraft system design.