Relation between Test Coverage and Timed Automata Model Structure
Krejčí L.; Sobotka J.; Novák J.
2021 - English This paper deals with problematics of structure of Timed Automata models suitable for Model-Based Testing of automotive systems. Previous ex-periments, primarily focused on the environmental models, have shown that their structure does not significantly affect the coverage speed of testing process. How-ever, similar questions regarding the observer part of the system model remained open. This paper analyzes those remaining questions and focuses on uncovering possible relation between an observer model structure and the quality of gener-ated test sequences according to multiple criteria. Goal of presented experiments is to compare multiple modeling approaches and discover which one is most suit-able for automotive systems. Keywords: Timed Automata; Model-Based; Testing; Structure; Coverage; Automotive Available in digital repository of ČVUT. Relation between Test Coverage and Timed Automata Model Structure

This paper deals with problematics of structure of Timed Automata models suitable for Model-Based Testing of automotive systems. Previous ex-periments, primarily focused on the environmental models, ...

Krejčí L.; Sobotka J.; Novák J.
České vysoké učení technické v Praze, 2021

Simple and Commutative Semirings
Korbelář, Miroslav
2021 - English Available in digital repository of ČVUT. Simple and Commutative Semirings

Korbelář, Miroslav
České vysoké učení technické v Praze, 2021

Postprocessor for Verification of Robot Movements with Additional Axis after Toolpath Optimization
Kratěna T.; Vavruška P.; Švéda J.; Valášek M.
2021 - English This paper discusses a postprocessor for milling robots connected to additional linear machine axes where toolpath is optimized with respect to variable properties of the robot in its workspace. A toolpath optimization method is proposed based on an experimentally verifiedrobot stiffness model. After postprocessor distribution of the movements between the robot and the linear axes, the collision states during machiningcannot be verified in common CAM. Therefore, a solution enabling simulation of movements after optimization is proposed. The tool center point coordinates are used to control the robot and additional machine axes, while the joint coordinates calculated by inverse kinematic transformation are used to verify the movements. Keywords: Robot; Tool path; Simulation; Milling; Computer aided manufacturing; Postprocessor; Robot stiffness Available in digital repository of ČVUT. Postprocessor for Verification of Robot Movements with Additional Axis after Toolpath Optimization

This paper discusses a postprocessor for milling robots connected to additional linear machine axes where toolpath is optimized with respect to variable properties of the robot in its workspace. A ...

Kratěna T.; Vavruška P.; Švéda J.; Valášek M.
České vysoké učení technické v Praze, 2021

Power device solutions for highly efficient power supplies
Siemieniec, Ralf; Mente, René; Kutschak, Matteo; Pulsinelli, Francesco
2021 - English Switched mode power supplies (SMPS) for target applications covering a wide range from telecom rectifiers through servers to solar inverters or electric vehicle chargers share the need for high efficiencies in order to minimize the overall energy consumption and the total cost of ownership. With the appearance of wide bandgap semiconductors designers cannot only choose between different devices but also may benefit from using advanced topologies. This work compares important properties of a CoolSiC™ Silicon-Carbide MOSFET, a CoolGaN™ E-mode GaN power transistor, a TRENCHSTOP 5™ IGBT accompanied by a SiC Schottky diode and a CoolMOS™ Superjunction (SJ) device, and discusses an approach to avoid the limitations of SJ devices with respect to hard commutation of the body diode and evaluates the achievable efficiency in the AC-DC conversion stage of a power supply. Available in digital repository of ČVUT. Power device solutions for highly efficient power supplies

Switched mode power supplies (SMPS) for target applications covering a wide range from telecom rectifiers through servers to solar inverters or electric vehicle chargers share ...

Siemieniec, Ralf; Mente, René; Kutschak, Matteo; Pulsinelli, Francesco
České vysoké učení technické v Praze, 2021

The influence of electrical stress on the distribution of electrically active defects in IGBT
Drobný, J.; Marek, J.; Chvála, A.; Faraga, J.; Jagelka, M.; Stuchlíková, L.
2021 - English This paper highlights electrically active defects investigation of the sixth generation 1200 V trench stop silicon-based Insulated Gate Bipolar Transistors by Deep Level Transient Fourier Spectroscopy. The focus is on the impact of electrical stress on defects distribution in the studied structures. Five electron- like deep energy levels ET1 (0.126 eV), ET2 (0.188 eV), ET3 (0.322 eV), ET4 (0.405 eV), and ET5 (0.514 eV), and nine hole-like deep energy levels HT1 (0.187 eV), HT2 (0.231 eV), HT3 (0.246 eV), HT4 (0.301 eV), HT5 (0.319 eV), HT6 (0.327 eV), HT7 (0.529 eV), HT8 (0.534 eV), and HT9 (0.750 eV) were identified. The presence of unintentional impurities like zinc, platinum, gold, etc. and emissions from structural imperfections was confirmed. A significant increase of the defect concentration after electrical stress in the temperature range of 120 to 225 K has been detected. Electrical stress did not affect the defect concentration above temperature 300 K. Available in digital repository of ČVUT. The influence of electrical stress on the distribution of electrically active defects in IGBT

This paper highlights electrically active defects investigation of the sixth generation 1200 V trench stop silicon-based Insulated Gate Bipolar Transistors by Deep Level Transient Fourier ...

Drobný, J.; Marek, J.; Chvála, A.; Faraga, J.; Jagelka, M.; Stuchlíková, L.
České vysoké učení technické v Praze, 2021

Scalable Vertical GaN FETs (SV- GaN FETs) for Low Voltage Applications
Hongyang Yan; Sankara Narayanan, E.M.
2021 - English This is the first report on a novel multi-polarization channel applied to realize normally-off and high- performance vertical GaN device devices for low voltage applications. This structure is made with 2DHG introduced to realize the enhancement mode channel instead of p-GaN as in conventional vertical GaN MOSFETs. As the 2DHG depends upon growth conditions, p-type doping activation issues can be overcome. The Mg-doped layer is only used to reduce the short-channel effects, as the 2DHG layer is too thin. Two more 2DEG layers are formed through AlGaN/GaN/AlGaN/GaN polarization structure, which minimizes the on-state resistance. Simulation analysis shows that this proposed structure can provide a large drain current at ~ 500 𝑚𝐴/𝑚𝑚 level. The calculation results show this novel vertical GaN MOSFET – termed as SV GaN FET - has the potential of breaking the GaN material limit in the trade- off between area-specific on-resistance (𝑅(𝑜𝑛,𝑠𝑝)) and breakdown voltage at low voltages. Available in digital repository of ČVUT. Scalable Vertical GaN FETs (SV- GaN FETs) for Low Voltage Applications

This is the first report on a novel multi-polarization channel applied to realize normally-off and high- performance vertical GaN device devices for low voltage applications. This structure is ...

Hongyang Yan; Sankara Narayanan, E.M.
České vysoké učení technické v Praze, 2021

Generalized Relay Shifting Method for System Identification
Hofreiter M.
2021 - English The paper describes an improved relay identification method, which enables the estimation of the parameters of a transfer function with various structures (stable, unstable, non-minimum phase, integrating, time delay systems, etc.) from a single relay feedback test. This identification approach follows the original shifting method and offers new possibilities. The proposed identification is demonstrated on a very versatile second-order time-delayed model and on systems with different structures. The proposed approach can be used for the tuning of PID controllers. The shifting method was implemented into a PLC Tecomat Foxtrot and used to control the laboratory apparatuses called “Air Aggregate”, “Water Levitation” and “Air Levitation” Keywords: System identification; relay control; parameter estimation; frequency characteristic; auto-tuning; PID control Available in digital repository of ČVUT. Generalized Relay Shifting Method for System Identification

The paper describes an improved relay identification method, which enables the estimation of the parameters of a transfer function with various structures (stable, unstable, non-minimum phase, ...

Hofreiter M.
České vysoké učení technické v Praze, 2021

Assessment of current state, past experiences and potential for CCS deployment in the CEE region
Bartovic, Vladimír; Hrubý, Michal; Visnerová, Alexandra
2021 - English Available in digital repository of ČVUT. Assessment of current state, past experiences and potential for CCS deployment in the CEE region

Bartovic, Vladimír; Hrubý, Michal; Visnerová, Alexandra
České vysoké učení technické v Praze, 2021

Integrated force interaction simulation model for milling strategy optimization of thin-walled Blisk blade machining
Sulitka M.; Falta J.; Stejskal M.; Hauptfleischová B.
2021 - English Complex shaped thin-walled blades that are extensively used in jet engines or stream turbines are very difficult to machine due to low rigidity of the blades, typically limited space between the blades and strict requirements on the surface quality and accuracy. The paper focuses on multi-axis machining of thin-walled and complex shaped Blisk blades made of aluminium alloys. The resulting surface quality and accuracy is mainly affected by the risk of elevated vibration occurrence, both forced and self-excited, and static deflections between the compliant tool and workpiece. An innovative integration of the transformed FE model of the blade into virtual machining simulation has been proposed, allowing to effectively solve the complex optimization task considering both the criterion of stable machining condition and static deflections as well. When choosing a machining strategy and cutting conditions, there are many variables that fundamentally affect the process. These variables are not easy to choose correctly the first time, so it is advisable to choose to use a simulation model in production preparation. The proposed simulation model allowed to effectively optimize the process parameters to keep the machining process stable and the static deformation of tool and workpiece under a defined level. The proposed model and optimization strategy was validated on a thin-walled blade machining. At the top part of the blade, the surface roughness decreased from 1.6 Ra to 0.84 Ra, and the maximum deviations from the reference model were reduced from 0.18 mm to 0.08 mm. Keywords: Digital Twin; Virtual machining; Stability; Milling Static deformation; Thin-walled blade Available in digital repository of ČVUT. Integrated force interaction simulation model for milling strategy optimization of thin-walled Blisk blade machining

Complex shaped thin-walled blades that are extensively used in jet engines or stream turbines are very difficult to machine due to low rigidity of the blades, typically limited space between the ...

Sulitka M.; Falta J.; Stejskal M.; Hauptfleischová B.
České vysoké učení technické v Praze, 2021

4th order tensors for multi-fiber resolution and segmentation in white matter
Tsegey T.; Kaushik S.; Bansal A.; Slovak S.
2021 - English Since its inception, DTI modality has become an essential tool in the clinical scenario. In principle, it is rooted in the emergence of symmetric positive definite (SPD) second-order tensors modelling the difusion. The inability of DTI to model regions of white matter with fibers crossing/merging leads to the emergence of higher order tensors. In this work, we compare various approaches how to use 4th order tensors to model such regions. There are three different projections of these 3D 4th order tensors to the 2nd order tensors of dimensions either three or six. Two of these projections are consistent in terms of preserving mean diffusivity and isometry. The images of all three projections are SPD, so they belong to a Riemannian symmetric space. Following previous work of the authors, we use the standard k-means segmentation method after dimension reduction with affinity matrix based on reasonable similarity measures, with the goal to compare the various projections to 2nd order tensors. We are using the natural affine and log-Euclidean (LogE) metrics. The segmentation of curved structures and fiber crossing regions is performed under the presence of several levels of Rician noise. The experiments provide evidence that 3D 2nd order reduction works much better than the 6D one, while diagonal components (DC) projections are able to reveal the maximum diffusion direction. Keywords: fiber crossing; 4th order tensor; HARDI Available in digital repository of ČVUT. 4th order tensors for multi-fiber resolution and segmentation in white matter

Since its inception, DTI modality has become an essential tool in the clinical scenario. In principle, it is rooted in the emergence of symmetric positive definite (SPD) second-order tensors modelling ...

Tsegey T.; Kaushik S.; Bansal A.; Slovak S.
České vysoké učení technické v Praze, 2021