Browsing by Department "Department of Automation and Systems Technology"
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- A-Stack : a TDMA framework for reliable, real-time and high data-rate wireless sensor networks
School of Electrical Engineering | D4 Julkaistu kehittämis- tai tutkimusraportti tai -selvitys(2012) Cosar, Emre Ilke; Mahmood, Aamir; Björkbom, Mikael (editor)The reduced size, power consumption and cost of wireless sensors make them an excitingtechnology for many monitoring and control applications. However, developing reliable, realtimeand high data-rate applications is challenging due to time-variations and interference inwireless channels and the medium access delays. For high data-rate and real-time applications,time division multiple access (TDMA) based medium access approach performs better ascompared to carrier sense multiple access (CSMA) based approach. On the other hand,implementation of TDMA in resource constrained wireless nodes requires difficult designdecisions. This document presents A-Stack, a real-time protocol stack for time synchronized, multichanneland slotted communication in multi-hop wireless networks. The stack is developed tomeet the reliability and accuracy requirements of real-time applications such as wirelessautomation and wireless structural health monitoring. A-Stack provides a flexible developmentenvironment for such applications by ensuring deterministic reliability and latency. It includesMAC, routing and time-synchronization protocols as well as a node-joining algorithm. Thestack is further supplemented with PC tools for optimizing the network as per the targetapplication for easy prototyping. This document explains the design and operational aspects ofA-Stack. Various deployment scenarios as well as long term system and communicationreliability tests are presented in the document. - ActionPool : a novel dynamic task scheduling method for service robots
Aalto-yliopiston teknillinen korkeakoulu | Doctoral dissertation (monograph)(2010) Taipalus, TapioService robots require the seamless utlisation of several technical disciplines. Most of the required technologies are sufficiently advanced to provide feasible solutions to be used in the designing of service robots. For instance, mechanical engineering, control theory, electronics and electrical engineering aspects of the design have all matured well. On the other hand, it is the perception and artificial intelligence that provide the means for modelling the environment and the knowledge which are lagging behind. The latter two disciples in their current state, greatly limit the complexity of the tasks which can be performed by service robots. In this thesis, an ActionPool method for representing task knowledge and executing multiple tasks simultaneously with service robots is presented. The method is based on a concept in which the actions that are ready for execution are placed into a pool and from those most suitable for the situation are selected one by one. The number of actions in a pool and the number of tasks are limited only by the available computational resources. The actions can belong to different tasks, and thus the action pool allows the robot's indivisible resource to be dynamically dealt out for various tasks requiring the resources. In the ActionPool method, the functional parts of the service robot are divided into resources and an action pool is assigned to each one of them. This way, numerous tasks can be executed simultaneously. The ActionPool method allows a natural way of dynamically adding and removing tasks to and from the robot's active execution. The action selection method can direct the perception processes to observe the relevant parts of the environment. The ActionPool method has been implemented on two different service robot platforms to verify the generic nature of the method. Several tasks have been executed successfully to validate the claims about the qualities of the method. Compared to previous approaches, this work provides a fresh execution- and contingency-centric vantage point to the well studied robot control problem. - Active control of radial rotor vibrations : identification, feedback, feedforward, and repetitive control methods
Doctoral dissertation (monograph)(2007-05-04) Tammi, KariActive vibration control methods for rotors were studied in order to develop solutions to enhance machines' dynamic behaviour, durability, and operating range. The aim of the thesis was to develop identification and control methods for active vibration control of a rotor. The identification method developed in the thesis improved run-time rotor identification by compensating rotation-related disturbances before the actual identification procedure. The control system design comprised an inner feedback loop and an outer loop for compensation for harmonic excitations due to mass unbalance and other rotation-related excitations. The feedback loop was shown to be essential in terms of providing favourable conditions for the other compensation algorithm in the outer loop. For the outer loop, three algorithms were tested: two feedforward control methods and a repetitive control method. The algorithms were validated and compared using an experimental set-up. Concerning the feedforward methods, the Convergent Control algorithm was found to be a more effective and simpler algorithm for the purpose than the adaptive FIR filter with the LMS algorithm. The adaptive gradient-based repetitive control, developed in this thesis, was found to have a poorer performance than the feedforward control methods, but to provide benefits for applications where excitation frequencies are not as predictable as in the current application. - Active control of radial rotor vibrations in electric machines : identification, modeling and control design
Faculty of Electronics, Communications and Automation | A4 Artikkeli konferenssijulkaisussa(2008) Orivuori, Juha; Laiho, Antti; Sinervo, AnssiThis paper presents results related to modeling, identification, control design and simulation of an electric motor equipped with a new force actuator. The model consists of several partial models, thus separating certain physical phenomena into independent processes. The inputs and outputs of the models to be identified are strongly correlated. This makes the identification process significantly more complicated. Three different control algorithms are designed for the process. The performance of the control algorithms are tested against finite element models in extensive simulations. The paper concludes in description of preliminary test results with an actual test machine. - Adapting problem solving strategies in control software development to new standards : case examples IEC 61499 and ISOBUS
Doctoral dissertation (article-based)(2007-12-14) Sierla, SeppoNew standards in software development can significantly constrain teamwork, and practical success in applying a new standard in a pilot project is therefore more than a technical problem. This dissertation focuses on teamwork specifically from the aspect of problem solving. In two case examples in which the new standards IEC 61499 and ISOBUS were adopted, it is observed that preferred or familiar problem solving strategies can be unsuccessful when work is constrained by a new standard. Adaptations to problem solving strategies are required for successful control software development, yet these changes should permit a team to continue working in a way that has been successful in the past. A compromise is needed between familiar practices and new practices that would best support the use of the new standard. This dissertation studies the emergence of such practices in the context of two standards: IEC 61499 and ISOBUS. Case studies focus on projects, in which there was a requirement to adopt a new standard: either IEC 61499 or ISOBUS. It was presumed that the teams would make attempts to use problem solving strategies that would match the nature of the standard adoption problem. Such attempts were observed only in some situations; participants were inclined to use problem solving approaches that had been successful in the past, even though the nature of problem to be solved had changed due to the new standard. Hence, there are two disparate and possibly conflicting forces at work in a standard adoption project: firstly, there is an attempt to orient problem solving according to the new problem, and secondly there is a tendency to cling to familiar practices that have been successful in the past. Two theoretical frameworks, knowledge networking and technological frames, are used to analyze these two disparate aspects of standard adoption in a software development project. The frameworks are first applied separately and then some conclusions are drawn regarding how these analyses can complement each other to address the two aspects of standards adoption mentioned above. The results suggest how problem solving strategies can be assessed before a project, taking into consideration both the nature of the standard adoption problem and the capability and willingness of the team to follow a particular problem solving approach. - Adaptive autonomous navigation of mobile robots in unknown environments
Doctoral dissertation (monograph)(2002-12-12) Selkäinaho, JormaAutonomous navigation of a mobile robot is a challenging task. Much work has been done in indoor navigation in the last decade. Fewer results have been obtained in outdoor robotics. Since the early 90's, the Global Positioning System (GPS) has been the main navigation system for ships and aircrafts. In open fields, satellite navigation gives absolute position accuracy. The absolute heading information is also obtained by satellite navigation when the mobile robot is in motion. However, the use of GPS satellite navigation is mainly restricted to open areas where at least three satellites can be seen. For example, mobile robots working in underground or deep open mines cannot use satellite navigation at all, and in forest or city areas, there are serious limitations to its use. Laser range finder technology has evolved remarkably over the last decade, and offers a fast and accurate method for environment modeling. Furthermore, it can be used to define robot position and heading relative to the environment. It is obvious that the use of several alternative sensors according to the environment will make the navigation system more flexible. Laser range finder technology is particularly suitable for indoors or feature rich outdoor environments. The goal of this thesis is to develop a multi sensor navigation system for unknown outdoor environments, and to verify the system with a service robot. Navigation should be possible in unstructured outdoors as well as indoor environments. The system should use all available sensor information and emphasize those that best suit the particular environment. The sensors considered in this thesis include a scanning laser range finder, a GPS receiver, and a heading gyro. The main contribution of the thesis is a flexible navigation system developed and tested with a service robot performing versatile tasks in an outdoor environment. The used range matching method is novel and has not been verified earlier in outdoor environments. No unique solution can be guaranteed in the developed map matching algorithm, although it seems to work well in the practical tests. Position and heading errors grow without bound in successive map matchings, which could be referred to as laser odometry. Therefore, the position and heading have been corrected by means of global matching when the robot returns to a place it has previously visited. Alternatively, structured landmarks have been used for position and heading correction. In field tests, tree trunks and walls have been used as structured landmarks. When structured landmarks are not present, navigation has been based on counting the translation and rotation between two successive maps based on a scanning laser range finder. In featureless environments, the robot is able to switch automatically from laser based to satellite navigation. The biggest difference compared to other methods, such as iterative closest point, is that odometry is not needed since the matching is based on a global search. However, when included, mobile robot dynamics and odometry increase the reliability of the matching process. The flexibility of the navigation system presented here means that a mobile robot can enter different environments, and the system automatically selects an appropriate set of sensors for each particular environment. It additionally means that the system can work without landmarks, but if they exist, they will be used to improve navigation accuracy. This kind of flexibility in the navigation system is of the utmost importance when in the near future increasingly mobile robots will move out from structured indoor environments into unknown outdoor environments. - Advanced process monitoring and control methods in mineral processing applications
School of Electrical Engineering | Doctoral dissertation (article-based)(2012) Remes, AnttiIn minerals processing the high material volumes yield the fact that benefits of even small improvements in the process efficiency are remarkable. On a daily basis, the efficiency of a concentrating plant relies on the performance of the process control system, and secondly, on the adequate information of the process state provided for the plant operators. This thesis addresses the problems in the monitoring and control of the selected, widely applied mineral concentration unit processes and the processing circuits. The case studies cover operations in the ore grinding stages, including size separation units, followed subsequently by the concentration and the thickening stages in the downstream process. The developed methods and applications are all verified with industrial data, industrially identified models or by the practical implementations and tests on the industrial case plants. Advanced control systems - including a rule-based, a fuzzy and a model predictive control, with different combinations and setups - are studied with simulated grinding and flotation processes. A new model-based expert system for controlling of the ground ore particle size and the circulating load of the grinding process is proposed. The system was tested with a simulation model representing an industrial milling of apatite ore. In a plant-wide process monitoring, a data-based modeling approach is applied to predict the concentrate quality and the impact of the grinding stage parameters on that. The plant model, used for the monitoring, is updated adaptively; this enables timely information on the process. The monitoring system was set up based on the data of a chromite ore processing plant. Two unit operations, a hindered settling separator and a thickener, were modeled from a viewpoint of equipment monitoring and control purposes. The hindered settling separator incorporates both a mechanistic particle-settling model and a separation efficiency characterization curve in a novel manner. Separation characteristics in a pyrite concentrate case and in a ground apatite ore case were studied with the model. Operation of a thickener was modeled based on on-line mass-balance estimation. The monitoring application was implemented in an industrial apatite concentrate thickener. This thesis demonstrates the benefits of the above described monitoring and control methods. The metallurgical performance improvements are pointed out for each case. Also this thesis outlines the practical implementation and robustness issues for the methods. Thus the thesis promotes the advantages of more extensive use of plant models in process operation purposes. - Affordance-based task communication methods for astronaut-robot cooperation
Sähkötekniikan korkeakoulu | Doctoral dissertation (monograph)(2011) Heikkilä, Seppo SThe problem with current human-robot task communication is that robots cannot understand complex human speech utterances, while humans cannot efficiently use the fixed task request utterances required by robots. Nonetheless, future planetary exploration missions are expected to require astronauts on extra-vehicular activities to communicate task requests to robot assistants with speech- and gesture-type user interfaces that can be easily embedded in their space suits. The solution proposed in this thesis is indirect task communication based on the human-like ability to utilise object-action relationships in task communication. Conventional task communication methods, in which all task parameters need to be communicated explicitly, are evaluated against task communication methods where affordances, i.e. action possibilities, are used to complete task communication. These so-called affordance-based task communication methods are evaluated by means of four user experiments: two performed with a fully autonomous centauroid robot in a planetary exploration work context and two with a simulated robot in a lander assembly work context. The first two experiments are performed in unambiguous work environments, where each object is associated with only one action and vice versa, while the last two experiments are performed in ambiguous work environments, where each object and action is normally associated with several actions and objects, respectively. The user experiments show that affordance-based task communication methods can be used to decrease both the human workload and task communication times in a planetary exploration work context. Furthermore, affordance-based task communication methods are found to be preferred over conventional task communication methods. The affordance-based task communication methods derived can be applied to facilitate any human-robot task communication that includes a priori known or recurring task sequences. In this thesis, the feasibility of the approach was demonstrated for frame-based dialogue managers, which are widely used in robotics. - Application-driven data processing in wireless sensor networks
Sähkötekniikan korkeakoulu | Doctoral dissertation (article-based)(2011) Bocca, MaurizioWireless sensor networks (WSNs) are composed of spatially distributed, low-cost, low-power, resource-constrained devices using sensors and actuators to cooperatively monitor and operate into the environment. These systems are being used in a wide range of applications. The design and implementation of an effective WSN requires dealing with several challenges involving multiple disciplines, such as wireless communications and networking, software engineering, embedded systems and signal processing. Besides, the technical solutions found to these issues are closely interconnected and determine the capability of the system to successfully fulfill the requirements posed by each application domain. The large and heterogeneous amount of data collected in a WSN need to be efficiently processed in order to improve the end-user comprehension and control of the observed phenomena. The thesis focuses on a) the development of centralized and distributed data processing methods optimized for the requirements and characteristics of the considered application domains, and b) the design and implementation of suitable system architectures and protocols with respect to critical application-specific parameters. The thesis comprehends a summary and nine publications, equally divided over three different application domains, i.e. wireless automation, structural health monitoring (SHM) and indoor situation awareness (InSitA). In the first one, a wireless joystick control system for human adaptive mechatronics is developed. Also, the effect of packet losses on the performance of a wireless control system is analyzed and validated with an unstable process. A remotely reconfigurable, time synchronized wireless system for SHM enables a precise estimation of the modal properties of the monitored structure. Furthermore, structural damages are detected and localized through a distributed data processing method based on the Goertzel algorithm. In the context of InSitA, the short-time, low quality acoustic signals collected by the nodes composing the network are processed in order to estimate the number of people located in the monitored indoor environment. In a second phase, text- and language-independent speaker identification is performed. Finally, device-free localization and tracking of the movements of people inside the monitored indoor environment is achieved by means of distributed processing of the radio signal strength indicator (RSSI) signals. The results presented in the thesis demonstrate the adaptability of WSNs to different application domains and the importance of an optimal co-design of the system architecture and data processing methods. - Automated control of compliance with production standards in precision agriculture
School of Electrical Engineering | Doctoral dissertation (article-based)(2013) Nikkilä, RaimoSignificant manual effort is currently involved in monitoring the compliance of agricultural production with legislation. While this administrative effort has little actual benefit for farms, compliance with legislation, or more generally production standards, is tied to the payout of economically vital farm subsidies. Information technology, together with the data collected automatically in precision agriculture, could alleviate this problem by automatically determining compliance with a significant portion of agricultural production standards. This thesis identifies the technical requirements of automated compliance control, formulates a design that conforms with the requirements of the stakeholders in precision agriculture and evaluates this design. The primary research objective can be further subdivided into three information systems: a farm management information system (FMIS) for precision agriculture, an infrastructure of Web services for automated compliance control and finally, spatial computer inference. These research objectives are addressed with the methodology of design science, using the agricultural field operation of precise fertilisation as the principal use case for automated compliance control. The results consist of information system designs and evaluation of these designs for functionality and feasibility. This thesis contributes the designs for three information systems: a software architecture for an FMIS in precision agriculture, a service infrastructure for automated compliance control and spatial computer inference with an interchangeable rule format. Through their prototype implementations, these are evaluated to constitute the necessary framework for automated compliance control. While technically demanding, automated compliance control with pertinent agricultural legislation is attainable, given the functionality of precision agriculture and the information systems presented in this thesis. However, the feasibility of the process relies on a degree of data interchange, which due to the lack of established data formats is currently difficult in agriculture. On the other hand, parts of the proposed solution can be applicable on a shorter time frame in agriculture or other domains. - Automatic locomotion mode control of wheel-legged robots
Doctoral dissertation (monograph)(2007-09-07) Leppänen, IlkkaTraditional manipulator-type robots are mostly mounted in a fixed position and no locomotion is needed. During the past two decades, robots have slowly moved from factories to more open areas, such as metro stations, hospitals or mines. These mobile robots, called field and service robots, have to move and act on partly closed working sites or in ordinary environments, therefore the significance of their locomotion has increased. The main land locomotion principles, wheeled and legged locomotion, can be combined as hybrid to help find an optimal solution for greatly varying ground conditions. Hybrid locomotion can also be called rolking (rolling-walking). The wheel-legged robot can move using different locomotion modes; it can drive with wheels, rolk (use wheels and legs at the same time) or even walk. In this work, an automatic locomotion mode control for the wheel-legged robot has been developed. The developed locomotion mode control can utilize two locomotion modes, wheeled and rolking, depending on terrain properties. The developed generic solution is valid for wheeled locomotion systems with a 2-dof active suspension system for the wheel. The basis for the automatic locomotion mode control is to measure characteristics of vehicle-terrain interaction, such as energy consumption, slipping and drawbar force of a wheel and terrain parameters, such as terrain slope and roughness. Algorithms for sensing these in real time, utilizing the locomotion system as a sensing system, have been developed. The characteristics of vehicle-terrain interaction and terrain parameters are used as criteria for indicating the functioning of a wheel in wheeled mode and terrain trafficability in rolking mode. These criteria are used to determine if a mode change is required. The criteria are mainly based on sensing forces and energy consumption by utilizing the sensor system used for the locomotion control; a minimum number of additional sensors is needed. The automatic locomotion mode control was successfully implemented and verified in the wheel-legged service robot, WorkPartner. It can use rolking mode on soft terrain or in negotiating obstacles and use wheeled mode for moving faster on flat terrain automatically. In the future, the developed sensing methods can also be used in developing new locomotion modes, such as free gait-based moving in which the motion control switches a single wheel to a different mode, depending on terrain properties. - Building and sharing the cognition model of the environment with collaborative service robots
Sähkötekniikan korkeakoulu | Doctoral dissertation (monograph)(2011) Terho, SamiThis research presents a shared cognition concept for building a cognition model collaboratively by robot and human. The proposed concept is based on an object-oriented approach that abstracts robot's perception, cognition, and knowledge to separate but interconnected elements. The shared cognition concept allows the human and robot share information related to objects in the environment for effective task execution and information exchange. The concept enables building a model using sensors, as well as inputting data from the user. User can utilize also robot's sensor data for inputting information. This utilizes the robot's perception of the environment in conjunction with human's cognitive understanding. The proposed concept can be used for exchanging information on the objects, their classes, identities, appearances, locations, structures, and states. Representation of perceived entities is done through observed objects, robot's cognitive understanding of the objects is represented by real objects, and the knowledge of objects' classes by meta-objects. Observed objects are created with segmentation which can be autonomous or assisted by human. Real objects are used to transfer the actual object information between human and robot. Recognition of objects is done by matching real and observed objects. Uncertainties of recognition and localization are handled by probabilistic approach. The model enables learning from perceived information allowing the model to improve its performance as more data is gathered. The cognition model can be used for collaborative task execution. Several aspects of the model are validated with two different platforms, WorkPartner service robot and Avant machine based semi-autonomous robot. Based on the tests, the proposed model is an effective mechanism for collaboratively exchanging spatial information between a robot and a human. - A companion model approach to modelling and simulation of industrial processes
Doctoral dissertation (monograph)(2005-09-23) Juslin, KajModelling and simulation provides for huge possibilities if broadly taken up by engineers as a working method. However, when considering the launching of modelling and simulation tools in an engineering design project, they shall be easy to learn and use. Then, there is no time to write equations, to consult suppliers' experts, or to manually transfer data from one tool to another. The answer seems to be in the integration of easy to use and dependable simulation software with engineering tools. Accordingly, the modelling and simulation software shall accept as input such structured design information on industrial unit processes and their connections, as provided for by e.g. CAD software and product databases. The software technology, including required specification and communication standards, is already available. Internet based service repositories make it possible for equipment manufacturers to supply "extended products", including such design data as needed by engineers engaged in process and automation integration. There is a market niche evolving for simulation service centres, operating in co-operation with project consultants, equipment manufacturers, process integrators, automation designers, plant operating personnel, and maintenance centres. The companion model approach for specification and solution of process simulation models, as presented herein, is developed from the above premises. The focus is on how to tackle real world processes, which from the modelling point of view are heterogeneous, dynamic, very stiff, very nonlinear and only piece vice continuous, without extensive manual interventions of human experts. An additional challenge, to solve the arising equations fast and reliable, is dealt with, as well. - Computational models for microvia fill process control
Aalto-yliopiston teknillinen korkeakoulu | Doctoral dissertation (article-based)(2010) Pohjoranta, AnttiThe microvia fill process is an electrochemical copper deposition process applied in the manufacturing of multilayered printed circuit boards (PCBs). It is the process where the metallic interconnections between adjacent signal layers of the multilayered PCB are made. The process chemistry is complex, including the interactions of several additive chemicals in addition to the underlying basic electrochemical processes of copper electrodeposition. To this day, the microvia fill process equipment set-ups utilized in the industry have none or very little automatic online control of the process variables. This is mostly because direct online measuring of the microvia fill process is practically impossible due to the vast number of microscopic features on a PCB, as well as to the small size of the features. The electronics industry is continuously striving to produce cheaper, smaller and more complex devices for an immeasurable number of applications. In the core of every electronics-appliance there is a PCB, which forms the chassis for the electronic components of the device as well as the signal paths between the components. Considering the enormous size of the electronics industry, as well as the ubiquitous nature of electronics, it is clear why PCB manufacturers consider that improving the microvia fill process technology is a relevant object for development. This doctoral thesis presents novel means for improving the microvia fill process through process simulation and model-based process design. The main results of the thesis are distributed parameter models, which together form the main components necessary for modeling a practical microvia fill electrolysis apparatus and designing a model-based control system for the process. Though the models are primarily based on physical and chemical first principles, the development work of all models presented in this thesis relies on experimental data that is gathered to parameterize and to validate the models. The thesis consists of a summary and nine publications, which address the modeling of the microvia fill process, the computational methods necessary for these models and the modeling of copper electrolysis systems in general. - Current state of digital signal processing in myoelectric interfaces and related applications
School of Electrical Engineering | A2 Katsausartikkeli tieteellisessä aikakauslehdessä(2015) Hakonen, Maria; Piitulainen, Harri; Visala, ArtoThis review discusses the critical issues and recommended practices from the perspective of myoelectric interfaces. The major benefits and challenges of myoelectric interfaces are evaluated. The article aims to fill gaps left by previous reviews and identify avenues for future research. Recommendations are given, for example, for electrode placement, sampling rate, segmentation, and classifiers. Four groups of applications where myoelectric interfaces have been adopted are identified: assistive technology, rehabilitation technology, input devices, and silent speech interfaces. The state-of-the-art applications in each of these groups are presented. - Design of robust controllers for telecom power supplies
Doctoral dissertation (article-based)(2002-10-11) Gadoura, Idris, A.A Telecom power supply is studied and analyzed from control system viewpoint. It consists of three stages: AC/DC rectifier, a backup battery, and a Telecom load. The AC/DC rectifier stage can be composed of paralleled DC/DC converters preceded by paralleled AC/DC converters. However, paralleled DC/DC converters are only considered in this thesis because they constitute the main dynamics in practice. A system of paralleled DC/DC converters operating in continuous inductor current mode with either voltage mode control or peak current mode control are modeled and analyzed using state-space representation. The H∞ control design is used in order to guarantee the robust stability and robust performance of the system in spite of different uncertainties. Also the H∞ loop-shaping design is used to design robust controllers in the presence of uncertainties. μ-analysis is used to evaluate the robustness of the system. Simulation results are presented to demonstrate the control design procedure and to compare between the two approaches presented. A Telecom power system can be composed of voltage-loop and current-loop subsystems. The multi-input-multi-output proportional-integral-derivative (PID) controller is first designed achieving robust stability and robust performance of the voltage-loop. Then, the multi-input-multi-output proportional-integral (PI) controller for current-loop is designed to achieve robust stability and robust performance of the overall system. μ-analysis is used to evaluate the robustness of PID and PI controllers. Simulation results are also presented to demonstrate and validate the control design. The required output characteristic of a Telecom power system contains three modes of operation: constant-voltage, modified constant-power, and constant-current modes. This nonlinear operation can be achieved by using the fuzzy-logic approach. A fuzzy PID-like controller is implemented to achieve the robust output voltage in spite of load disturbances. A fuzzy PI-like controller is implemented to ensure the overload protection reaching the optimal output characteristic of a Telecom power system. Also the internal-model control (IMC) method is applied to basic DC/DC converters: buck, boost, and buck-boost converters. IMC scheme is used to improve the dynamic performance of basic converters by achieving a robust output voltage against line and load disturbances. Simulations show good dynamic performance of the IMC controller. - Development of a biocatalytic fuel cell system for low-power electronic applications
Doctoral dissertation (monograph)(2006-12-15) Appelqvist, AnjaThis thesis describes the development of a biocatalytic fuel cell which is intended for low-power electronic appliances. The operation of a biocatalytic fuel cell is based on the same principles as are metal catalyst fuel cells. The main difference between the two technologies is the catalyst material: in biological fuel cells the catalytic power is derived from a microorganism or an enzyme instead of the usual platinum-based transition metal catalysts. Activity in connection with biocatalytic fuel cells has been lively during the past decade, as has been the study of fuel cells in general. In principle, biocatalytic fuel cells offer inexpensive catalyst and component materials in contrast to metal catalyst fuel cells. However, so far the performance values of the metal catalyst fuel cells have been at least 10 times better. The essence of this study is the analysis of restrictions on electron transfer in the energy generation process of a biocatalytic fuel cell, with the emphasis being placed on the anodic process. Consequently, methods to improve functionality in respect of power and current density will be discussed. The novel Direct Methanol Biocatalytic Fuel Cell (DMBFC) that was developed was utilised as a case to study biocatalytic energy generation. The operating principle of the DMBFC is the enzymatic breakdown of methanol by methanol dehydrogenase (MDH) from Methylobacterium extorquens. A significant increase in performance was achieved by improving the stability of the mediator, which enhances the electron transfer rate, and by introducing potassium permanganate as the terminal electron acceptor. Additionally, a first prototype of a stack-structured DMBFC was constructed and tested. Further development is required to optimise the process technology of the stack. As a result of the research work and development of the DMBFC power source, knowledge of biological energy generation processes has deepened significantly. In addition, a novel method of fuel cell control was created. The power source that was developed, the DMBFC, is the basis for further research towards small disposable power sources based on biocatalytic energy generation. - Droplet self-alignment: High-precision robotic microassembly and self-assembly
School of Electrical Engineering | Doctoral dissertation (article-based)(2012) Sariola, VeikkoDroplet self-alignment is a microassembly process where the surface tension of liquid aligns microparts to a substrate. Traditionally, solder has been used, but using unconventional liquids, such as water or adhesives in air, has several attractive properties. Water is compatible with most materials and processes, it is easy to achieve good droplet confinement and it evaporates quickly. Adhesives have the ability to make irreversible bonding. Nevertheless, achieving adhesive droplet self-alignment is difficult, because adhesives generally have a small surface tension. Both liquids can be adapted to low temperature processes. This thesis describes water droplet self-alignment in high detail, by measuring yield, accuracy, capabilities to build complex structures, and speed of the process. Experiments have been done using an environment-controlled microassembly station and recorded using high-speed microscopy. The results show that droplet self-alignment can achieve industrially relevant performance, and the results may be used as a basis of future process design rules. A new, microfabricated silicon capillary gripper has been developed, which picks microparts using the surface tension of water. Pick-and-place experiments showed that microparts are self-aligned to the tool by droplet self-alignment. The developed gripper enables handling microparts accurately and delicately. Finally, new patterned oleophilic / oleophobic surfaces have been developed that enable self-alignment using oil-like liquids, including low-temperature curable adhesives. Self-alignment using an industrial adhesive on the patterns was demonstrated. While this surface was used for droplet self-alignment, a micropatterned oleophilic / oleophobic surface may well have other applications outside droplet self-alignment. - Automated Construction of Dynamic Bayesian Networks in Simulation Metamodeling
Sähkötekniikan korkeakoulu | Master's thesis(2013-05-20) Harju, MikkoTässä työssä esitellään uusi lähestymistapa dynaamisten Bayes-verkkojen (dynamic Bayesian networks, DBNs) automatisoituun konstruointiin simulaatiometamallinnuksessa. DBN-metamallien avulla tutkitaan diskreetillä tapahtumasimuloinnilla (discrete event simulation, DES) luotua simulointidataa. Lähestymistavan avulla kyetään konstruoimaan DBN-metamalleja helposti ja nopeasti tuntematta Bayes-verkkojen toimintaa lähemmin. Aiemmin konstruoitujen DBN-metamallien mahdollisia puutteita voidaan korjata vaivattomasti luomalla uusia paranneltuja metamalleja. Tämä menettely parantaa DBN-metamallien tarkkuutta ja käytettävyyttä. DES on stokastinen simulointimuoto, joka mahdollistaa mallin muuttujien arvojen aikakehityksen tarkastelun. Simulointimetamalleilla tutkitaan simulointimallien ominaisuuksia kuvaamalla niiden sisäänmenojen ja ulostulojen välistä yhteyttä. DBN-metamalleissa DBN kuvaa DES-mallin aikariippuvien muuttujien yhteisjakauman, minkä avulla voidaan tarkastella muuttujien reuna- ja ehdollisten todennäköisyysjakaumien aikakehitystä. Tämä mahdollistaa erilaiset mitä-jos -analyysit, joita ei voida toteuttaa pelkillä sisäänmeno-ulostulokuvauksilla. Tässä työssä esiteltävä lähestymistapa DBN-metamallien automatisoituun konstruointiin koostuu koesuunnittelusta, simulointidatan esikäsittelystä, muuttujakohtaisten ajanhetkien valinnasta DBN:ää varten, DBN:n luomisesta sekä metamallin validoinnista. Automatisoidun mallintamislähestymistavan lisäksi tässä työssä esitellään DBN:ien muuttujakohtaiset aikaskaalat, joiden avulla kyetään konstruoimaan tarkempia DBN:iä kasvattamatta niiden kokoa. Esitettyyn lähestymistapaan perustuen kehitetään DBN-metamallien konstruointityökalu. Työssä havainnollistetaan esitetyn lähestymistavan ja konstruointityökalun käyttökelpoisuutta kahdella esimerkkitapauksella, jotka liittyvät ilmataistelua ja ilmatukikohdan toimintaa kuvaaviin simulointimalleihin. - Dynamic Obstacle Overcoming Capability of Pendulum-driven Ball-Shaped Robots
School of Electrical Engineering | A4 Artikkeli konferenssijulkaisussa(2014) Ylikorpi, Tomi; Forsman, Pekka; Halme, AarneThis paper discusses dynamic step-crossing capability of pendulum-driven ball-shaped robots. We introduce an extended dynamic model that allows modeling of ballrobot rolling, bouncing and slipping. Based on the new model, our simulations predict the maximum over-passable step-height for the robot. The simulation results agree well with the result from a parallel simulation in Adamssoftware as well as with practical experiments. The new dynamic model can be applied for mobility analysis of robot-ball designs as well as for path planning.