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Additive Manufacturing (AM) is intensifying the digitalization of the manufacturing and generating disruptive changes and the paradigm shift in the industry. To boost the productivity in AM, the improvement in parts qualification is required. Qualifying the parts implies the capability to ensure constant and repeatable part properties meeting the engineering design requirements. It implies to certify not only the structure, properties and global performance of a part but also its manufacturing process. Modelling and simulation techniques can target them separately, but linking models describing those characteristics is quite challenging since they have the different level of details and sometimes different purposes. Presenting those models in the form of causal graph will enable us to combine models with different level of details. The current research utilizes functional analysis and dimensional analysis to present the models in the form of the causal graph between associated parameters. The DACM Framework integrating fundamental required methods and theories is briefly explained in this article. The current research will then aim at developing a surrogate model capable of integrating the different models such as microstructure models, layer by layer melting/solidification and part models. The final comprehensive model can simulate to AM system to fulfill multi-criteria performances. publishedVersion

Calculations on the global energy consumption due to friction and wear in the mineral mining industry are presented. For the first time, the impact of wear is also included in more detailed calculations in order to show its enormous tribological and economic impacts on this industry. A large variety of mining equipment used for the extraction, haulage and beneficiation of underground mining, surface mining and mineral processing were analysed. Coefficients of friction and wear rates of moving mechanical assemblies were estimated based on available information in literature in four general cases: (1) a global average mine in use today, (2) a mine with today's best commercial technology, (3) a mine with today's most advanced technology based upon the adaptation of the latest R&D achievements, and (4) a mine with best futuristic technology forecasted in the next 10 years. The following conclusions were reached: • Total energy consumption of global mining activities, including both mineral and rock mining, is estimated to be 6.2% of the total global energy consumption. About 40% of the consumed energy in mineral mining (equalling to 4.6 EJ annually on global scale) is used for overcoming friction. In addition, 2 EJ is used to remanufacture and replace worn out parts and reserve and stock up spare parts and equipment needed due to wear failures. The largest energy consuming mining actions are grinding (32%), haulage (24%), ventilation (9%) and digging (8%). • Friction and wear is annually resulting in 970 million tonnes of CO2 emissions worldwide in mineral mining (accounting for 2.7% of world CO2 emissions). • The total estimated economic losses resulting from friction and wear in mineral mining are in total 210,000 million Euros annually distributed as 40% for overcoming friction, 27% for production of replacement parts and spare equipment, 26% for maintenance work, and 7% for lost production. • By taking advantage of new technology for friction reduction and wear protection in mineral mining equipment, friction and wear losses could potentially be reduced by 15% in the short term (10 years) and by 30% in the long term (20 years). In the short term this would annually equal worldwide savings of 31,100 million euros, 280 TWh energy consumption and a CO2 emission reduction of 145 million tonnes. In the long term, the annual benefit would be 62,200 million euros, 550 TWh less energy consumption, and a CO2 emission reduction of 290 million tonnes. Potential new remedies to reduce friction and wear in mining include the development and uses of new materials, especially materials with improved strength and hardness properties, more effective surface treatments, high-performance surface coatings, new lubricants and lubricant additives, and new designs of moving parts and surfaces of e.g. liners, blades, plates, shields, shovels, jaws, chambers, tires, seals, bearings, gearboxes, engines, conveyor belts, pumps, fans, hoppers and feeders. acceptedVersion

Highly corrosion- and wear-resistant thermally sprayed chromium carbide (Cr3C2)-based cermet coatings are nowadays a potential highly durable solution to allow traditional fluidized bed combustors (FBC) to be operated with ecological waste and biomass fuels. However, the heat input of thermal spray causes carbide dissolution in the metal binder. This results in the formation of carbon saturated metastable phases, which can affect the behavior of the materials during exposure. This study analyses the effect of carbide dissolution in the metal matrix of Cr3C2-50NiCrMoNb coatings and its effect on chlorine-induced high-temperature corrosion. Four coatings were thermally sprayed with HVAF and HVOF techniques in order to obtain microstructures with increasing amount of carbide dissolution in the metal matrix. The coatings were heat-treated in an inert argon atmosphere to induce secondary carbide precipitation. As-sprayed and heat-treated self-standing coatings were covered with KCl, and their corrosion resistance was investigated with thermogravimetric analysis (TGA) and ordinary high-temperature corrosion test at 550 °C for 4 and 72 h, respectively. High carbon dissolution in the metal matrix appeared to be detrimental against chlorine-induced high-temperature corrosion. The microstructural changes induced by the heat treatment hindered the corrosion onset in the coatings. acceptedVersion

Localized deformation and cracking in a system of thermally sprayed hard metal coating overlaid on a low alloy steel is studied by means of bend testing. In-situ digital image correlation measurements are used to characterize material strain field near the coating/substrate interface. The studied substrate undergoes softening upon yielding which manifests itself as narrow bands of localized shear deformation. The measurements show that the coating cracks and the substrate shear bands interact. When the coating starts cracking during the elastic loading of the substrate, the formed cracks function as nucleation points for the shear bands. In contrast, if the coating resists cracking until the yielding of the substrate, the coating cracks and substrate shear bands form simultaneously. Based on the experiments, continuum-scale finite element model of the system is developed, validated and then used for a systematic numerical analysis of the effects of substrate shear banding on the measurement of coating properties. Based on the results of this work, three main effects can be identified. Firstly, the flow localization in the substrate can increase the measured apparent (macroscopic) surface strain of the coating, if not accounted for by using microscopic techniques. Secondly, substrate shear bands increase the interfacial loading, which may cause unexpected delamination of the coating and thus affect the evaluation of the interfacial strength. Finally, substrate shear bands affect the stress state within the coating and may thus affect the cracking morphology in the coating. Therefore, based on the results of this study, if the coating and interfacial strengths are of similar magnitude with the substrate yield strength, the possible tendency of the substrate towards flow localization should be taken into account in the analysis of the coating behavior. acceptedVersion

There is direct link between non-idealities in fretting wear, friction and fretting fatigue, especially in the case of adhesion spots. Friction is not a constant and varies as a function of load cycles and non-Coulomb friction may occur. Fretting wear may lead to material transfer, resulting in tangential fretting scar interactions, and in the long run, wear debris is entrapped and cumulated in the interface. Fatigue failure can occur at low nominal stress amplitudes due to non-Coulomb effects. Novel tools are required in component design to fully capture these non-ideal phenomena. publishedVersion

Increasing penetration of intermittent renewable energy production in power systems will remarkably increase the need of flexible and controllable power generation. Subsidised renewable generation has revolutionized energy markets and brought down electricity prices leading to lack of investments to new controllable generation plants. As numerous existing thermal power generation units have been closed down, there is no doubt that all the possible flexibility available in power systems should be harnessed to stabilize the power systems. Combined heat and power (CHP) generation is widely used in district heating (DH) systems. As total heat production into the DH network needs to be balanced with the total heat consumption, this sets significant limitations to the long term power production. However, the coupling between the heat load and electric production can be decoupled temporarily by using the heat storage capacity of DH network consisting of network volume and optional heat accumulators. This paper presents the results of research work dealing with the analysis of dynamic operability of interconnected CHP plants and district heating networks. The flexibility of generation capacity was compared with the requirements set to power producers to be able to participate the Automatic Frequency Restoration Reserve (FRR-A) market. For that, two case studies were presented that include FRR-A tests in two municipal CHP plants that utilize a heat only boiler and a DH accumulator to balance the heat production variations that are caused by changes in power production. The results indicate that both cases fulfil the requirements and that the DH network operation is affected only slightly. However, the rapid power level change is a disturbance to CHP boilers and DH networks that the process components and automation systems must adapt to. Therefore these aspects must be considered carefully when applying such new operation practises in existing CHP plants. publishedVersion

This paper presents an investigation into the effect of unexpected overloading on scuffing initiation with a twin-disc test device. An existing twin-disc test device was modified to be suitable for applying overloading dynamically to the disc contact. Three test series including three pairs of discs in each series were subjected to combined normal force and rolling/sliding loading. First a base level for scuffing initiation was defined by increasing the normal load stepwise until failure, while keeping the rolling and sliding between the discs constant. In the subsequent test series, the overload cycles were applied at a significantly lower level in two different patterns leading to scuffing at both an earlier and later stage than was observed for the base level. acceptedVersion

Dielectric elastomers are materials often utilized for the fabrication of electroactive actuators. Acrylic rubber (ACM) is very widely used in dielectric elastomer actuators (DEAs). However, its overall good performance is limited by the high operating electric field required. In the present work, we compare the effect of different types of conventionally used carbon black (CB) as well as other carbon-based fillers on the dielectric and actuation properties of ACM in order to show that performance of DEAs can be improved by the development of ACM composites. Indeed, addition of CB, carbon nanotubes (CNTs), and synthetic graphite leads to an increase in the relative dielectric permittivity of elastomeric material. Moreover, incorporation of nanodiamonds results in reduction of dielectric losses. Finally, actuation stress is remarkably improved by CNTs and different grades of CB. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

In mobile machines, as well as in manufacturing, the overall productivity is essential for business competitiveness. As the operation of a modern mobile machine is affected by various parameters, they need to be tuned to reach an optimal performance – however, due to machine complexity, parameter optimisation is difficult for a typical operator. To enable parameter optimisation locally in machines, this article presents a system architecture to generate information and knowledge from machine fleet data and to utilise them in machine operations in the field. Measurement data is collected and analysed to discover the associations between machine performance and parameter values. While some results are plain statistical distributions, any resulting more sophisticated domain knowledge is stored as rules. Rule-based reasoning enables a zone of interoperation between the information system and domain experts. Once information and knowledge have been generated, they are made available to machines that run the actual parameter assessment application. Results made with forestry data indicate that the system has a considerable potential to improve machine productivity. acceptedVersion

Impedance-based analysis plays important role in assessing the stability and dynamics of grid-connected inverters and related systems. Measuring the inverter impedance is, however, not straightforward due to the load effect caused by the power grid. The power grid interacts with the inverter and produces additional (mirrored) frequency harmonics thus distorting the impedance measurements when applying conventional measurement techniques. This paper proposes an active-power filtering method to minimize the undesired load effect caused by the power grid in the measured impedance. Applying the method, the inverter output impedance can be reliably measured under non-ideal grid conditions. acceptedVersion

In the past years human-robot collaboration has gained interest among industry and production environments. While there is interest towards the topic, there is a lack of industrially relevant cases utilizing novel methods and technologies. The feasibility of the implementation, worker safety and production efficiency are the key questions in the field. The aim of the proposed work is to provide a conceptual safety system for context-dependent, multi-modal communication in human-robot collaborative assembly, which will contribute to safety and efficiency of the collaboration. The approach we propose offers an addition to traditional interfaces like push buttons installed at fixed locations. We demonstrate an approach and corresponding technical implementation of the system with projected safety zones based on the dynamically updated depth map and a graphical user interface (GUI). The proposed interaction is a simplified two-way communication between human and the robot to allow both parties to notify each other, and for the human to coordinate the operations. acceptedVersion

As the amount of renewable energy increases rapidly, power systems will face novel challenges to maintain power quality. Power quality issues, which usually arise from the grid connection through power-electronic devices, can be reduced by proper control strategies. Grid-connected devices are conventionally optimized into a single operating point, but real performance is affected by the interfaced grid conditions. As the grid conditions change over time, the control performance varies, as does the quality of the power produced. To tackle this issue, the adaptive grid-voltage feedforward is introduced to the control system. The adaptive method, applying a perturb-and-observe algorithm, improves the produced power quality in real time by taking the control system characteristics and the grid conditions into account. The results show the improved power quality in various grid conditions when comparing the adaptive grid-voltage feedforward and the conventional implementations. acceptedVersion

ITER Divertor maintenance equipment operates in the vacuum vessel in elevated temperature and under considerable radiation load. The heavy Divertor assemblies are lifted and transported using servo valve systems, such as Cassette Multi-functional Mover (CMM). Systems are powered with water hydraulics, using demineralized water as a pressure medium. Operations have not been tested in ITER-relevant environmental conditions and over projected duty cycles. As the hydraulic medium is rather aggressive and there are no servo valves designed for demineralized water, the greater than 2000-h operational time was considered a potential issue. Hence, a project was undertaken to ascertain the component compatibility with the environment and pressure medium, and their robustness over the required operational period. Irradiation of components was not considered at this phase of technology validation. A heated test chamber was constructed to emulate the projected maximum ambient temperature of 50 °C in the Divertor area. Test routines and measurements were specifically tailored to monitor the operational parameters of the servo valve. After the 2188-h test the servo valve parameters remained within the limits promised by the manufacturer. Pressure gain decreased and hysteresis increased but remained within the allowable limits. These changes did not have significant effect on the joint angle tracking error. acceptedVersion

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High-velocity impact wear can have a significant effect on the lifetime of thermally sprayed coatings in multiple applications, e.g., in the process and paper industries. Plasma-sprayed oxide coatings, such as Cr2O3- and TiO2-based coatings, are often used in these industries in wear and corrosion applications. An experimental impact study was performed on thermally sprayed ceramic coatings using the High-Velocity Particle Impactor (HVPI) at oblique angles to investigate the damage, failure, and deformation of the coated structures. The impact site was characterized by profilometry, optical microscopy, and scanning electron microscopy (SEM). Furthermore, the connection between the microstructural details and impact behavior was studied in order to reveal the damage and failure characteristics at a more comprehensive level. Differences in the fracture behavior were found between the thermally sprayed Cr2O3 and TiO2 coatings, and a concept of critical impact energy is presented here. The superior cohesion of the TiO2 coating inhibited interlamellar cracking while the Cr2O3 coating suffered greater damage at high impact energies. The HVPI experiment has proven to be able to produce valuable information about the deformation behavior of coatings under high strain rates and could be utilized further in the development of wear-resistant coatings.

A two-step masterbatch mixing technique was studied for preparation of carbon nanotube-filled ethylene–propylene diene elastomer compounds, and compared to conventional one-step mixing process. In the two-step process, a masterbatch compound with carbon nanotube content of 50 parts per hundred was prepared by melt-mixing ethylene–propylene diene elastomer. This material was then compounded with pristine ethylene–propylene diene elastomer and composites with different carbon nanotube concentrations were compared. The aim of this study is to compare the efficiency of two different mixing processes on the dispersion of carbon nanotubes and to facilitate the handling of carbon nanotubes, as the masterbatch can be prepared in a controlled way and used for further dilution without the problems related to carbon nanotube processing. The compound properties were studied with emphasis on mechanical characterization and dynamic mechanical thermal analysis. Masterbatch mixing resulted in the similar mechanical properties of the composites compared to the direct mixing method. At the relatively low loadings of carbon nanotubes, the considerable improvements of the mechanical properties were observed. The aspect ratio of the carbon nanotubes determined by transmission electron microscope was found to be similar to the one calculated from the Guth equation. It showed a considerable reduction in aspect ratio independent of the used mixing method. acceptedVersion

Carbide free bainitic (CFB) steels have been tested in two heat treated conditions and compared with currently used quenched and tempered (QT) steel in an industrial mining application subjected to erosive-abrasive wear. A conventional sliding abrasion and a new application oriented high-stress erosion wear tests were performed in laboratory. The results of the erosion and the field tests were compared. The microstructural changes were investigated by optical and scanning electron microscopy. The hardness and hardness profiles of the steels were measured. The results showed that in the laboratory tests, the abrasion and erosion wear rates of the CFB steels were 35 and 45 % lower respectively in comparison to the QT steel. In the field test, the mass losses of the CFB steels were about 80 % lower in comparison with the QT steel. The improved wear resistance of the CFB steel can be explained by its higher hardness and higher work hardening. The erosion wear test was able to simulate the work hardening effect and the wear mechanisms observed in the field test samples. acceptedVersion submittedVersion

Three commercially available quenched wear resistant steel grades were compared with a structural steel and four elastomer materials to reveal the differences in their behavior in slurry erosion conditions and to find the best solutions for demanding applications. A slurry-pot tester, allowing simulation of various wear conditions with different minerals, particle sizes (up to 10 mm), abrasive concentrations, and sample angles were used to simulate different industrial slurry applications. In this study, granite and quartz with concentrations of 9 and 33 wt% were used as abrasives in tests conducted at 45° and 90° sample angles. The performance of the studied steels was evaluated with respect to their material properties such as hardness and microstructure. Furthermore, the cross-sections and wear surfaces of the test samples were analyzed to reveal the possible differences in the mechanical behavior of the materials during slurry erosion. The wear surface analyses show that abrasion is the dominating wear mechanism already for the smallest particle size of 0.1/0.6 mm. In low-stress abrasive slurry erosion with the smallest particles, the elastomers showed better wear resistance than the steels, whereas in demanding high-stress abrasive slurry erosion conditions the quenched wear resistant steels can well compete with elastomers in wear resistance. The relative wear performance of the steels increased with increasing abrasive size, while for the elastomers it decreased. acceptedVersion

A phase fluorimetric sensor targeted for the monitoring of dissolved oxygen concentration in microfluidic in vitro cell models is presented. The sensing surface of the sensor consists of oxygen sensitive fluorescent dyes (PtOEPK) embedded in a thin polystyrene film. The simulated fluorescence emission characteristics show highly anisotropic distribution, and an efficient optical read-out based on a parabolic lens is presented. Experimental results show that the applied sensing scheme allows one to use thin films (

Modeling and simulation for additive manufacturing (AM) is commonly used in industry. Nevertheless, a central issue remaining is the integration of different models focusing on different objectives and targeting different levels of details. The objective of this work is to increase the prediction capability of characteristics and performances of additively manufactured parts and to co-design parts and processes. The paper contributes to this field of research by integrating part's performance model and additive technology process model into a single early integrated model. The paper uses the dimensional analysis conceptual modeling (DACM) framework in an AM perspective to generate causal graphs integrating the AM equipment and the part to be printed. DACM offers the possibility of integrating existing knowledge in the model. The framework supported by a computer tool produces a set of governing equations representing the relationships among the influencing variables of the integrated model. The systematic identification of the weaknesses and contradictions in the system and qualitative simulation of the system are some of the potential uses of the model. Ultimately, it is a way to create better designs of machines and parts, to control and qualify the manufacturing process, and to control three-dimensional (3D) printing processes. The DACM framework is tested on two cases of a 3D printer using the fused filament fabrication (FFF) powder bed fusion. The analysis, applied to the global system formed of the 3D printer and the part, illustrates the existence of contradictions. The analysis supports the early redesign of both parts and AM process (equipment) and later optimization of the control parameters.

The continuous demand for higher power density leads to a very challenging operational environment for sliding bearings regarding pressures and deformations. Understanding of the deformation behavior of heavily loaded bearings becomes even more pronounced when modern hybrid multilayer designs are considered. The aim of this study is to develop a numerical, multi-physical model for the evaluation of journal bearing performance. Hydrodynamics were based on the Reynolds equation and deformations were calculated using the integrated finite element method. Elastic and thermal deformations have a significant effect on bearing performance and those deformations can be adjusted with properties of polymer layer. The design of hybrid bearings is delicate and their properties must be tailored according to the operating conditions. acceptedVersion

We study in this paper nonlinear control of a rotary DC servo motor application. To be more specific, we design a reduced-order two-degree-of-freedom (2DOF) composite nonlinear feedback (CNF) controller for a Quanser QUBE-Servo 2 unit with a disc attachment. We compare our results with a carefully tuned proportional-derivative (PD) controller with set point weighting. Our simulation and experimental results show that the closed-loop system using 2DOF CNF controller yields much better set point tracking performance compared with the system using conventional PD-controller in terms of settling time. acceptedVersion

Heavy steel plates are used in demanding applications that require both high strength and hardness. An important step in the production of such components is cutting the plates with a cost-effective thermal cutting method such as flame cutting. Flame cutting is performed with a controlled flame and oxygen jet, which burns the steel and forms a cutting edge. However, the thermal cutting of heavy steel plates causes several problems. A heat-affected zone (HAZ) is generated at the cut edge due to the steep temperature gradient. Consequently, volume changes, hardness variations, and microstructural changes occur in the HAZ. In addition, residual stresses are formed at the cut edge during the process. In the worst case, unsuitable flame cutting practices generate cracks at the cut edge. The flame cutting of thick steel plate was modeled using the commercial finite element software ABAQUS. The results of modeling were verified by X-ray diffraction-based residual stress measurements and microstructural analysis. The model provides several outcomes, such as obtaining more information related to the formation of residual stresses and the temperature history during the flame cutting process. In addition, an extensive series of flame cut samples was designed with the assistance of the model. acceptedVersion

Thermally sprayed tungsten-carbide (WC) coatings have proven to be one of the most wear resistant coatings available and a respectable replacement for hard-chromium coatings. They are used in paper machine parts such as calender rolls. However, improved lifetime and performance are continuing considerations, as well as finding more economical alternatives. This study researched the wear phenomena of tungsten-carbide coatings in a paper machine environment. To achieve this, five different feedstock materials and coatings manufactured from these were compared by electron microscopy as well as dry abrasion-, high-speed slurry abrasion- and cavitation erosion tests. Improvements in ductility by changing the matrix material were found, while changing the particle strength had no effect on the behavior of the coatings. The findings suggest further research on altering the matrix of the feedstock could lead to overall improvements in coating quality and component lifetime. publishedVersion

We propose a deterministic recursive algorithm for approximate Bayesian filtering. The proposed filter uses a function referred to as the approximate Gaussian flow transformation that transforms a Gaussian prior random variable into an approximate posterior random variable. Given a Gaussian filter prediction distribution, the succeeding filter prediction is approximated as Gaussian by applying sigma point moment-matching to the composition of the Gaussian flow transformation and the state transition function. This requires linearising the measurement model at each sigma point, solving the linearised models analytically, and introducing the measurement information gradually to improve the linearisation points progressively. Computer simulations show that the proposed method can provide higher accuracy and better posterior covariance matrix approximation than some state-of-the art computationally light approximative filters when the measurement model function is nonlinear but differentiable and the noises are additive and Gaussian. We also present a highly nonlinear scenario where the proposed filter occasionally diverges. In the accuracy-computational complexity axis the proposed algorithm is between Kalman filter extensions and Monte Carlo methods. acceptedVersion

It is a well known fact that increasing temperature increases noise in all kind of electronics, which applies also to cell and tissue measurements by microelectrode arrays (MEAs). We show that ambient temperature may have a surprisingly big role in the noise level of MEA measurements. To study that we measured the baseline noise when the MEA amplifier was subject to temperature variations, either in a temperature chamber or by preventing amplifier unit’s normal heat exchange. Around room temperature (+24°C) the RMS value of the baseline noise was found to increase approximately 0.14 µV/°C, which is a huge variation as the default RMS noise at that temperature with our setup was only around 5.5 µV. Additional cooling of the MEA amplifier could thus be a clever way to decrease the noise level at very sensitive measurements and on the other hand, one should not interfere the amplifier’s normal heat exchange to the ambient air in order to avoid additional warming and thus increasing the noise level. acceptedVersion

Fluctuating power production in combined heat and power (CHP) plants may cause unwanted disturbances in district heating (DH) systems, which leads to the situation that the best efficiency in CHP production is not achieved. DH -systems are often automated, however, supply temperature is still primarily chosen manually by the operator. This is because of the uncertain heat demand in near future and uncertain behaviour of delay from heat supplier to consumers, which make the temperature scheduling problematic. In this work, future heat demand and return water temperature are predicted based on outdoor temperature forecast and process data history using neural network estimators. Consumers in network are presumed to be similar, but their distances from production site vary thus creating a distribution function of range. Delay is modelled as a distribution function based on the distances between heat consumers and the suppliers, which weights the supply temperatures from last few hours calculating the average supply temperature received by the consumers. The derived function models how the temperatures develop along the network, finally covering the entire network. A brute force optimizer was developed to minimize both pumping costs and heat losses as well as to smooth temperature gradient originated thermal stresses. System delays are fixed during an optimization cycle, and after each cycle the delays are updated according to new system flowing rates and the optimization is recalculated. The resulting supply temperature curve is a discrete curve that cuts the heat load peaks by charging and discharging the energy content of the District heating network (DHN). Optimization keeps the supply water temperature and flow rates in control and stabilizes the network smoothly and efficiently after disturbances. Optimization is demonstrated by using case data of one year from a district heating system in Finland. publishedVersion

This paper addresses the energy-inefficiency problem of four-degrees-of-freedom (4-DOF) hydraulic manipulators through redundancy resolution in robotic closed-loop controlled applications. Because conventional methods typically are local and have poor performance for resolving redundancy with respect to minimum hydraulic energy consumption, global energy-optimal redundancy resolution is proposed at the valve-controlled actuator and hydraulic power system interaction level. The energy consumption of the widely popular valve-controlled load-sensing (LS) and constant-pressure (CP) systems is effectively minimised through cost functions formulated in a discrete-time dynamic programming (DP) approach with minimum state representation. A prescribed end-effector path and important actuator constraints at the position, velocity and acceleration levels are also satisfied in the solution. Extensive field experiments performed on a forestry hydraulic manipulator demonstrate the performance of the proposed solution. Approximately 15–30% greater hydraulic energy consumption was observed with the conventional methods in the LS and CP systems. These results encourage energy-optimal redundancy resolution in future robotic applications of hydraulic manipulators. publishedVersion

Knowledge of deployed transmitters’ (Tx) locations in a wireless network improves many aspects of network management. Operators and building administrators are interested in locating unknown Txs for optimizing new Tx placement, detecting and removing unauthorized Txs, selecting the nearest Tx to offload traffic onto it, and constructing radio maps for indoor and outdoor navigation. This survey provides a comprehensive review of existing algorithms that estimate the location of a wireless Tx given a set of observations with the received signal strength indication. Algorithms that require the observations to be location-tagged are suitable for outdoor mapping or small-scale indoor mapping, while algorithms that allow most observations to be unlocated trade off some accuracy to enable large-scale crowdsourcing. This article presents empirical evaluation of the algorithms using numerical simulations and real-world Bluetooth Low Energy data. publishedVersion

This paper addresses the problem of redundancy resolution in closed-loop controlled hydraulic manipulators. The problem is treated at the hydraulic level using proposed cost functions formulated into a dynamic programming approach of minimum-state representation. Bounds on joint range, actuator velocity and acceleration were enforced. This approach minimises the hydraulic energy consumption of the widely popular load-sensing and constant-supply pressure systems. The presented approach can resolve the redundancy more effectively from the hydraulic side than do actuator velocity or energy optimisation approaches, point-wise optimal approaches or some standard direct optimisation tools that may lead to inferior solutions, as shown in simulation results where up to 15–30% greater energy use is seen with some competing approaches. The results obtained motivate joint trajectory optimisation at the hydraulic level in prospective applications at construction sites where frequently driven work cycles of hydraulic construction cranes are automated. acceptedVersion

Thermally sprayed tungsten carbide (WC) and chromium carbide (Cr3C2) based hard metal coatings are commonly applied on component surfaces as corrosion and wear resistant layers. Typically, WC-Co/Ni with optional Cr addition and Cr3C2-25NiCr powders are sprayed with high velocity oxy-fuel (HVOF) or high velocity air-fuel (HVAF) processes. Due to the poor oxidation resistance of the WC particles, Cr3C2-25NiCr composition is typically selected for high temperature environments, up to 800-900°C. In this study, two distinct Cr3C2-based compositions of Cr3C2-50NiCrMoNb and Cr3C2-37WC-18NiCoCr were selected as interesting alternatives to conventional Cr3C2-25NiCr. Sliding wear behavior of the coatings sprayed with HVOF and HVAF processes were tested with a ball-on-disk configuration against an Al2O3 ball at room temperature and at 700°C. It was found that both alternative materials had comparable coefficients of friction with the Cr3C2-25NiCr coatings. The Cr3C2-37WC-18NiCoCr coatings provided improved wear resistance at room temperature conditions, but at 700°C the wear rate was increased to the level of the Cr3C2-50NiCrMoNb coatings. Cr3C2-25NiCr coatings experienced the lowest wear rates at elevated temperatures, which was even lower than at room temperature. acceptedVersion

In this work, the dynamic response of Ti6Al4V alloy at high temperature was studied using the Split Hopkinson Pressure Bar –SHPB- apparatus with two different heating systems. The first device uses direct electric current to heat the sample to the testing temperature in a fraction of a second, whereas the second device uses a furnace to heat the sample and as a consequence, short sections of the bars, in few minutes. Tension tests were carried out at strain rates up to 1500 s-1 and at temperatures ranging from room temperature up to 700 °C. The conventional strain gauge measurements from the pressure bars were used to obtain the stress–strain curves and the Johnson-Cook material model was used to fit the results of the tests. High speed photography and digital image correlation were used to quantify the total strain during the test. The plasticity of the titanium alloy clearly increases as the temperature is increased. The maximum strains, obtained from the stress-strain curves, also increase when the temperature is increased from room temperature. DIC results, however, show clear differences in the maximum strain before failure with respect to the values obtained from strain gauges measurements. The maximum strain in the gauge section of the sample prior to failure increases steadily as the testing temperature is increased. At 60 °C, the strains within the gauge section reach values almost 50% just before failure. At 300 °C, the maximum strains are close to 65%, and at 700 °C the maximum strains extend close to 80%. publishedVersion

Wear resistant steels are commonly categorized by their hardness, and in the case of quenched wear resistant steels, their Brinell hardness grades are widely considered almost as standards. In this study, the abrasive wear performance of 15 commercially available 400 HB grade quenched wear resistant steels from all over the world were tested with granite gravel in high stress conditions. The aim was to evaluate the real wear performance of nominally similar steels. Also properties such as hardness, hardness profiles, microstructures and chemical compositions of the steels were studied and reasons for the differences in their wear performance further discussed. In terms of mass loss, over 50% differences were recorded in the abrasive wear performance of the studied steels. Variations in the chemical compositions were linked to the auto-tempered microstructures of the steels, and the microstructural characteristics were further linked to their ultimate wear behavior. © 2014 Elsevier B.V. acceptedVersion

Cavitation and cavitation erosion are sometimes unavoidable phenomena in hydro machine operation. For example, operating hydro turbines as regulating power leads to situations in which the risk of cavitation is accepted to some extent. Cavitation-resistant materials are therefore required to reduce machine damage and maintenance. This study characterizes the microstructure of two martensitic stainless steels from Francis turbines. They were already studied for cavitation erosion resistance in a previous study, and this study reveals the reasons behind the other steel having a significantly better resistance, while they had similar chemical compositions. The electron backscatter diffraction (EBSD) method is effective in defining the martensitic microstructure, specifically the block, packet, and prior austenite grain level. In addition, the retained austenite is effectively detected with the method. A fine prior austenite grain size and small packet and block sizes were found to be among the defining factors in cavitation erosion resistance of these steels. In addition, the transformation of retained austenite to martensite was detected in the edge region where cavitation had taken place. This transformation further increases cavitation erosion resistance. The better resistance of Steel 1 against cavitation was attributed to these microstructural differences. According to these findings, the microstructure in Steel 1 would be highly beneficial in building cavitation erosion resistant hydro machines and would be of interest to manufacturers of martensitic stainless steel components. acceptedVersion

The Annual SMACC Research Seminar is a new forum for researchers from VTT Technical Research Centre of Finland Ltd, Tampere University of Technology (TUT) and industry to present their research on the area of smart machines and manufacturing. The 1st seminar is held on 10th of October 2016 in Tampere, Finland. The objective of the seminar is to publish results of the research to wider audiences and to offer researchers a new forum for discussing methods, outcomes and research challenges of current research projects on SMACC themes and to find common research interests and new research ideas. Smart Machines and Manufacturing Competence Centre - SMACC is joint strategic alliance of VTT Ltd and TUT in the area of intelligent machines and manufacturing. SMACC offers unique services for SME`s in the field of machinery and manufacturing – key features are rapid solutions, cutting-edge research expertise and extensive partnership networks. SMACC is promoting digitalization in mechanical engineering and making scientific research with domestic and international partners in several different topics (www.smacc.fi). publishedVersion

Virtualization has become a supportive approach for simulating system behaviour efficiently thanks to the revolution of computer and smart devices. In fact, the employment of running virtual tools that mimic the real physical world is nowadays a requirement in some fields as in e.g. industrial automation. This research work presents a virtual tool that simulates a real assembly line. The main features of this simulator are listed as; web application that can be accessed with any devices that supports html web pages, animated application that provides a UI for the user, discovery mechanism that allows web applications to interact with the simulator automatically and RESTful-based services, which increases the flexibility and versatility in terms of deployment. FASTory simulator has been developed and deployed during the eScop project. In addition, presented simulator has been employed by C2NET (Cloud Collaborative Manufacturing Networks) project for development some of its tools. Furthermore, the exploitation of the FASTory simulator is extended to cover as well the education of next generation of engineers for design and implementation of modern CPS. As Tampere University of Technology provides a M.Sc. degree in automation engineering, students use the simulator for their experiments, ensuring that mistakes are recoverable and harmless. acceptedVersion

Capacitive sensors can be used to monitor changes in materials by monitoring complex permittivity. Inductively coupled passive resonance sensors provide means to make short range wireless permittivity measurements if the sensors are embedded in the tested material. In this study, inductively coupled sensors were embedded in biodegradable polymers, which are important materials in regenerative medicine. However, it is challenging to observe their decay especially in vivo. After preparing the samples by compression moulding, the encapsulated sensors and a reference series were immersed in buffer solution. The signals from the passive resonance sensors were measured for eight weeks. In addition, mechanical and chemical testing was periodically carried out to monitor the state of the reference series. The wirelessly measured signals are compared with water absorption, flexural modulus, glass transition temperature and viscosity. publishedVersion

We present a two-parameter Solar Radiation Pressure model for GNSS autonomous orbit prediction, in which the parameters vary with the daily and seasonal variations in the angle between the Sun and the satellite’s orbital plane. The estimator for this model’s parameters is described. We present the test results of orbit prediction with this model for GPS satellites using initial orbit states based on broadcast ephemeris data. acceptedVersion

A laboratory sized jaw crusher with uniform movement of the jaws, the Dual Pivoted Jaw Crusher (DPJC), was used to determine the relationship between wear and work. Wear was concentrated on the jaw plates opposing each other and was measured as mass loss of the specimens. Work was measured directly from the force and the displacement of the instrumented jaw, which allowed work to accumulate only from the actual crushing events. The tests were conducted with several jaw geometries and with two motional settings, where the relation of compressive and sliding motion between the jaws was varied. The comminution of rock is presumed to be irreversible, meaning that the energy used for crack formation in the rock particles eventually results in the fracture of the particles. Therefore, the amount of energy needed to comminute rock particles should be roughly constant and not dependent on the loading conditions, if the speed of the loading contact is not changed. The DPJC test method allows the separation of work components into comminution specific work and sliding specific work. The results can be used to compare the crushability of minerals without the influence of the used test geometry or the selected jaw plate materials. The sliding work can be used for the comparison of the wear of the jaw plate materials publishedVersion

The term fingerprint-based (FP) positioning includes a wide variety of methods for determining a receiver’s position using a database of radio signal strength measurements that were collected earlier at known locations. Nonparametric methods such as the weighted k-nearest neighbor (WKNN) method are infeasible for large-scale mobile device services because of the large data storage and transmission requirements. In this work we present an overview of parametric FP methods that use model-based representations of the survey data. We look at three different groups of parametric methods: methods that use coverage areas, methods that use path loss models, and methods that use Gaussian mixtures. Within each group we study different approaches and discuss their pros and cons. Furthermore, we test the positioning performance of several of the analyzed approaches in different scenarios using real-world WLAN indoor data and compare the results to those of the WKNN method. publishedVersion

Localization accuracy of trilateration methods in Long Term Evolution (LTE) cellular networks, which are based on time-of-arrival (ToA), may be highly degraded due to multipath and non-line of sight (NLoS) conditions in urban and indoor environments. Multipath mitigation techniques usually involve a high computational burden and require wideband signals to be effective, which limit their adoption in certain low-cost and low-power mobile applications using narrow-band signals. As an alternative to these conventional techniques, this paper analyzes an Expectation Maximization (EM) localization algorithm that considers the skewness introduced by multipath in the LTE ranging error distribution. The EM algorithm is extensively studied with realistic emulated LTE signals of 1.4 MHz bandwidth. The EM method is compared to a standard Nonlinear Least Squares (NLS) algorithm under ideal simulated conditions and using realistic outdoor measurements from a laboratory testbed. The EM method outperforms the NLS method when the ranging errors in the training and test stages have similar distributions. acceptedVersion

Manufacturing execution systems play an important role of bridging high-level enterprise functions and production or manufacturing operations. The embedded systems are usually in charge of controlling execution of the operations. Modern embedded systems have become capable of simultaneous and deterministic execution of control algorithms and IP-based communication, making it possible to create complex cyber–physical systems (CPSs), where the computational and communication resources of a device can be used directly for various control, supervisory, or monitoring functions. The complexity for defining open-knowledge-driven manufacturing execution system (OKD-MES) is in maintaining awareness of overall system state to avoid disruptive actions as various functions may be requested from a system. The problem is that obtaining such information on system state may necessitate collecting data from a number of devices, as there may not be a single data point for state information. This paper describes and illustrates an approach for designing OKD-MES on top of CPSs that controls robot workstations and conveyor-based transportation system of a pallet-based production system. publishedVersion

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We present a novel floor-plan and PDR (pedestrian dead reckoning) based proposal distribution for indoor positioning particle filtering. Including floor-plan information in the proposal distribution makes the particle filtering more efficient than using the map only in the measurement model, because the proposal distribution becomes more accurate and the measurement model less accurate. The method uses offline- computed distances from each point of a regular grid to the closest wall in each direction. Our simulations show that the novel proposal distribution combined with a floor-plan and PDR based motion model improves the positioning accuracy with small numbers of particles and noisy PDR compared to the particle filters that use the floor-plan only for particle weighting. acceptedVersion

Currently, technology-enhanced learning environments are a research hotspot in engineering education. Universities invest in modern environments equipped with the newest audiovisual hardware, computers and web-technologies. These environments support learner-centred model of education, which highlights active role of learners, learning-by-doing, and collaborative learner autonomy in a democratic atmosphere. Therefore, traditional teacher-led classrooms can be transformed to more diverse and more creative environments in which teachers and learners have relatively different roles compared with the traditional classroom. In this paper, we present layout, construction and hardware of our newly developed technology-mediated, configurable, and cell-oriented PC-classroom, which play a key role in our teaching development. We exemplify how the classroom has helped us to improve our automation science and control engineering education. To be more specific, we have adopted the well-known concept of computer-supported collaborative learning (CSCL), which concerns how students can learn together with the help of computers. We also demonstrate how redefining and redesigning the nature of activities occurring in modern learning environments can improve the effectiveness of contact teaching, and hence, allow learning episodes to be more impactful compared with the traditional teacher-led classroom. We would like to pinpoint that redefinition and redesign have allowed us, as teachers, to take the position of a facilitating guide, or mentor, which work in close cooperation with students, and thereby, is able to strengthen the knowledge level of students through intellectual face-to-face discussion as well as through technology-supported communication. Furthermore, our new classroom has enabled hands-on, competitive, cyber-physical attack-defence events to be conducted, which improve our automation security training. The events have invited participants from industry and academia, but most importantly, they have involved students. During the events, we have offered opportunities for students to make demonstration-of-skills to the participants from business. As a consequence, the new environment has enabled acts of openings for university-business cooperation in terms of education and recruit, free of charge. To our experience and according to student feedback, our redefined ways of conducting teaching has improved student motivation as well as increased their timely investment towards learning activities, which has eventually translated to better grades and overall satisfaction. publishedVersion

Zinc oxide (ZnO) is an important semiconductive material due to its potential applications, such as conductive gas sensors, transparent conductive electrodes, solar cells, and photocatalysts. Photocatalytic activity can be exploited in the decomposition of hazardous pollutants from environment. In this study, we produced zinc oxide thin films on stainless steel plates by hydrothermal method varying the precursor concentration (from 0.029 M to 0.16 M) and the synthesis temperature (from 70 °C to 90 °C). Morphology of the synthesized films was examined using field-emission scanning electron microscopy (FESEM) and photocatalytic activity of the films was characterized using methylene blue decomposition tests. It was found that the morphology of the nanostructures was strongly affected by the precursor concentration and the temperature of the synthesis. At lower concentrations zinc oxide grew as thin needlelike nanorods of uniform length and shape and aligned perpendicular to the stainless steel substrate surface. At higher concentrations the shape of the rods transformed towards hexagon shaped units and further on towards flaky platelets. Temperature changes caused variations in the coating thickness and the orientation of the crystal units. It was also observed, that the photocatalytic activity of the prepared films was clearly dependent on the morphology of the surfaces. publishedVersion

This article presents a probabilistic motion model that is based on an economical graph-based indoor map representation, such that the motion of the user is constrained according to the floor plan of a building. The floor plan is modeled as a combination of links and open space polygons that are connected by nodes. In the authors’ earlier work the link transition probabilities in this graph are proportional to the total link lengths that are the total lengths of the subgraphs accessible by choosing the considered link option, and this article extends this model to include open space polygons as well. A particle filter using the extended motion model in which all particles are constrained according to the map structure is presented. Furthermore, wireless local area network and Bluetooth Low Energy positioning tests show that the proposed algorithm outperforms comparison methods especially if the measurement rate is low. acceptedVersion

A prototype for eye-in-hand manipulation in the context of remote handling in the International Thermonuclear Experimental Reactor (ITER)1 is presented in this paper. The setup consists of an industrial robot manipulator with a modified open control architecture and equipped with a pair of stereoscopic cameras, a force/torque sensor, and pneumatic tools. It is controlled through a haptic device in a mock-up environment. The industrial robot controller has been replaced by a single industrial PC running Xenomai that has a real-time connection to both the robot controller and another Linux PC running as the controller for the haptic device. The new remote handling control environment enables further development of advanced control schemes for autonomous and semi-autonomous manipulation tasks. This setup benefits from a stereovision system for accurate tracking of the target objects with irregular shapes. The overall environmental setup successfully demonstrates the required robustness and precision that remote handling tasks need.

This paper presents an improved experimental setup for high strain rate testing based on the modified Tensile Hopkinson Split Bar device developed previously at TUT. The test setup can be used to study the effects of a sudden large change in the strain rate on the stress flow of the material. The setup allows deforming the sample at a low rate and at isothermal conditions before the high rate loading. During the strain rate jump, the deformation rate is rapidly increased by approximately six orders of magnitude. In this work, the low and high rate deformation of the specimen was recorded with a combination of low and high-speed digital cameras and analyzed using the Digital Image Correlation technique. The measurement provides information about the effects of the strain rate jump on the macroscopic response of the material and allows accurate observation of the deformation of the sample just before, during, and immediately after the strain rate jump, when the conditions change from isothermal to adiabatic. In this paper, we present the results for a metastable austenitic stainless steel and discuss the effects of the strain rate jump on the strain-hardening rate, compare the experimental results with numerical results from a thermomechanical model, and evaluate the effects of the preceding deformation at a low strain rate on the strain localization. We conclude that the strain rate jump results in a clear decrease in the strain-hardening rate, the deformation following the jump is uniform along the gauge section, and that the strain localization is not significantly affected by the strain rate or the amount of pre-strain in the studied conditions.

Synthesis of graphene oxide by the modified Hummers method and measuring the synthesis yield were investigated. Based on the results, a comprehensive method to measure graphene oxide synthesis yield was proposed, which will allow comparison of future literature results. In addition, changes are proposed to the exfoliation procedure to improve the yield of the modified Hummers synthesis. With the proposed method, systematic error of the concentration measurement was calculated to be ±0.08 × 10-3 g mL-1. In addition, changes proposed to the graphene oxide exfoliation process can improve the synthesis yield by up to 70%. acceptedVersion