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Simulated Environment in Robot Soccer

In fluid power system simulation, orifice flow is, in the main, clearly in the turbulent area. Only when a valve is closed or an actuator driven against an end stopper does the flow become laminar as pressure drop over the orifice approaches zero. So, in terms of accuracy, the description of laminar flow is hardly necessary. Unfortunately, when a purely turbulent description of the orifice is used, numerical problems occur when pressure drop becomes close to zero since the first derivative of flow with respect of pressure drop approaches infinity when pressure drop approaches zero. Furthermore, the second derivative becomes discontinuous, which causes numerical noise and an infinitely small integration step when a variable step integrator is used. In this paper, a numerically efficient model for the orifice flow is proposed using a cubic spline function to describe the flow in the laminar and transition areas. Parameters for the cubic spline are selected such that its first derivative is equal to the first derivative of the pure turbulent orifice flow model in the boundary condition. The key advantage of this model comes from the fact that no geometrical data is needed in calculation of flow from the pressure drop. In real-time simulation of fluid power circuits, a trade-off exists between accuracy and calculation speed. This investigation is made for the two-regime flow orifice model. The effect of selection of transition pressure drop and integration time step on the accuracy and speed of solution is investigated.

Current and expected developments in space transportation have led to growing interest in new space vehicles. These new vehicles require essential improvements over current vehicles in order to ensure economic viability and to fullfill mission and safety constraints. The size and complexity of this problem has led to growing importance of numerical methods for design and optimization involving all disciplines as well as the optimal use of all technical potentialities is necessary. The material presented here reviews the growth and advances achieved at DLR in the last years. The Status of the physical modeling, code development issues such as algorithms, grid generation and validation strategy is provided. Viscous, high speed unsteady flows are still restricted to simple problems due to a strong demand in Computer resources. The short coming to obtain adequate data for code validation in high speed flow problems is discussed. It tums out that little progress has been realized in numerical modeling since past major difficulties to obtain reliable experimental data in the high enthalpy flow environments still remain. On the other side, CFD based multidisciplinary analysis is emerging as a key discipline in aerospace design. Supported by a continuous, almost linear, grows in computer capacity and performance, this new procedure to conduct configuration analysis is paying off its way. A number of selected applications of multidisciplinary problems with complex physics are presented.

The paper presents the simulation of transient stability of one of 56.25 MVA generator and two of 22.5 MVA generators in combined steam-gas power plant "TE-TO" Osijek synchronized with 110 kV transmission network. This power plant is electrically very close to recently reconstructed substation 400/110 kV Ernestinovo. Three phase and single-line-to-ground faults were simulated at the 400 kV and 110 kV transmission lines. DIgSILENT software for electromagnetic transients (EMT) was used to simulate transient stability during the fault and switching process. All input data for transmission lines, transformers, synchronous machines and switching devices are obtained from available databases from the HEP group. Several cases are considered: 1. Analysis of dynamic behavior of generators during the single-line-to-ground faults and three phase faults on the closest associated 110 kV line to the power plant. 2. Analysis of dynamic behavior of generators during the single-line-to-ground faults and three phase faults on the associated 400 kV line on TS 400/110 kV Operational variables such as generator speed, electrical and mechanical power, excitation voltage, frequency, currents and voltages in transmission lines were observed. Transient behavior of generators was simulated both in the case when the protection system works properly and clears the faults on transmission lines and in the case when the protection system or breakers malfunctioned. Comparison of the results was performed in order to observe the effects of the control system. Modeling of the system components by considering a very large number of relevant parameters and constants, as well as using real operational values for each model has enabled the relative accuracy in representing of all the states. Furthermore, the control system together with the protection system protects the plant from hazardous states and allowing therefore safe, good and long-life operation of all the plant components. During the simulations, the 56.25 MVA block exhibited very good transient stability to possible operational states, disturbances and faults to which the generator was exposed during the operation. Even in the worst case of a three phase line to ground fault on the closest transmission line, there were no electric and mechanical effects on the components of power plant. Waveforms of transients on the 400 kV and 110 kV transmission lines, generators frequencies, rotor speeds and rotor angles deviation caused by faults have also been presented

Complex system dynamic, structure and behaviour performances asks wide range of methods, algorithms and tools to reach model capable for searching optimal performing parameters. In the modelling process, it is up to analyst to select appropriate combination of methods, algorithms and tools to express significant system performances. Such methodology for designing complex systems should be based upon conceptual modelling to perform sensitive analyse of different system levels and views, allowing system representations for developing computer models. Complex systems, such as business systems with continuous-discrete production process are demanding well organised supply chain highly reactive to production assortment changes. Aligning two different production components, distinctive in their behaviour, is especially sensitive in production parameters transition point. Such system performances request distinctive designing methods that could follow double behaviour nature of production process according to their entities dynamics, caused by assortment changes. Consequently, such systems need different conceptual presentations to realise its purpose from different views and aspects. Paper is based on results derived from project of parameters optimalisation in glass industry. Simulation modelling principles, methods and tools are solid environment for wide range of conceptual models developing to improve system performances. They offer qualitative and valuable results based upon large quantity of processed and verified data, as well as on the large number processed and checked possible problem solution variants. Upon those facts, choosing optimal processing parameters is done more qualitatively, and following implementation of new solution take benefits and leads to expected business results.

This paper describes the basic function of power system simulation software package PowerWorld Simulator 11.0. It was used to obtain power flows in Croatian electric power system. Time step simulation options in PowerWorld were used to simulate power flows during every hour in 2005. Completely Croatian electric power system is plotted in the PowerWorld oneline diagram. Then it is entered loads for every hour during 2005. (8760 time points). All input data for transmission lines, transformers, generators and loads are obtained from the HEP group. Oneline diagram is divided into five control areas: control area 1 (Croatia), control area 2 (Hungary), control area 3 (Slovenia), control area 4 (BiH) and control area 5 (Serbia). It was accomplished two cases of power flows. First single solutions of power flows were simulated when system is at its peak load. Second case was time step simulation of power flows for every hour in 2005. Results of simulation are saved as table in *.tsb file and in the paper they are presented as charts for relevant elements of the Croatian electric power system. Consumed electric energy, peak load, losses in the simulation are comparable with those on the official web page of Croatian electric company HEP. PowerWorld oneline diagram created in this paper can be used for further research as fault analysis in Croatian power system, energy interchange etc.

This paper describes the modelling language GPSS++. One of the main purposes of the language is its use in education. It extends the well-known discrete-event modelling language GPSS in several aspects, among which an object-oriented modelling is one of the most important. Other extensions of GPSS++ are: support for modular and hierarchical modelling, support for hybrid modelling (discrete and continuous), and significantly enhanced features for description of model behaviour (by using features of a general purpose programming languages). Syntax of the language is also modernized. In the same time, GPSS++ tries to retain the basic GPSS concept of modelling that uses transactions and blocks. The paper describes the main features of the GPSS++ mentioned above. Results of comparison of models written in GPSS and GPSS++ are given. The main advantages of GPSS++ over old versions of the language are better organization of the model and improved readability and writeability. Also, the language is better adapted to the programmers with the background in modern and widely used object-oriented languages. In addition, GPSS++ is better suited for larger models due to its modular and hierarchical organization. GPSS++ is currently under development and here we describe its first version and we also give directions for future improvements and research.

Melanocytic nevi (moles) are common, and can be found anywhere on the skin. Their number has been shown to be associated with a greater risk of cutaneous melanoma. Also, the knowledge of their natural evolution is important in the understanding of the development of melanoma. The aim of this study was to incorporate available knowledge about melanocytic proliferation and the role of immune system and to create a simulation model which will be able to explain the changes in number of melanocytic nevi during lifetime and to elucidate the importance of the immune system in their formation and regression (i.e. eruptive benign melanocytic nevi). The results were presented graphically and visually analyzed. Because of the great number of possible numerical solutions only approximately results that satisfy some basic criteria were take into account. A created system dynamics model proved to be able to simulate the appearance and disappearance of melanocytic nevi during lifetime and the eruption of nevi after immunosuppression in a way that mimics their changes reported in epidemiological studies. There are limitations in model assumptions due to many uncertainties regarding model parameters and thus much more detailed epidemiological data would be required for the creation of a more reliable model.

Neurogenesis (NG), as generation of neurons of the cortical plate (CP), includes processes of proliferation, migration and programmed cell death, which have been thoroughly studied on murine model through the series of experiments by Takahashi, Nowakowski, Caviness et al. Simple 11 cell cycle mathematical model of NG within pseudostratified ventricular epithelia (PVE) has been proposed and magnitude of the programmed cell death in CP during early postnatal life has been estimated. We developed system dynamics model of the NG in mouse neocortex that integrates available experimental data. Simulation experiments were run in order to establish its stability, validity and dependence on initial parameters. Following experimental data were used for PVE and CP at future area 1 of the murine neocortex: 1) cell cycle duration ; 2) q factor (proportion of the ongoing mitosis giving birth to young postmitotic neurons (PN)) during neurogenetic interval (NI) ; 3) growth fraction ; 4) duration of migration ; 5) distribution of young postmitotic neurons within CP as function of their time of birth ; and 6) proportion of cells that undergoes programmed cell death within CP in early postnatal life. Model was developed and tested with system dynamics software Stella 8.0 for Windows XP operating system. Duration of the cell cycle, cortical distribution of young postmitotic neurons and proportion of dying cells were implemented as table-vice-linear function with linear interpolation. Growth fraction and duration of migration were constant. Q factor was estimated by polynomial fit that was obtained by Microsoft Excel 2003 software. Simulation experiments were conducted with starting population of 1*103 cells, equally distributed throughout cell cycle, for the time frame from 11th embryonal (E11) to 22nd postnatal (P22) day. Euler’ s integration method was used ; with integration time (DT) equaled 1/10 hours. NI lasted for 150 hours (E11+4, 9h – E17+10, 9h). Each cell of the starting population of the PVE at the beginning of NI gave rise to ~145 postmitotic neurons. Population of the PVE was largest at E14+13, 5h. Distribution by layers (in %) was as follows: VI-23, 1 ; V-9, 0 ; IV-26, 4 ; III/II-41 ; I-0, 6. During NI, cells of the PVE executed 11 cell cycles if they just entered G1 phase at the onset of neurogenetic interval, but only 10 cycles if they were anywhere in the cell cycle at least 1.6 hours away from the start of G1 phase. Overall reduction PN number within CP in the early postnatal life (P0-P14) was 28, 0%. Reduction by layers (in %) was as follows: VI – 16, 6 ; V-11, 5 ; IV-24, 5 ; III/II-40, 3 ; I-20, 7. Final number of PN linearly depends on the size of the founder population within PVE, but polynomial (2nd order) on the length of the cell cycle. Alteration of q-factor considerably influenced final neuron number. Model was shown to be stable for given parameters providing repeatable results in each performed experiment. Results of simulation experiments were in accordance to experimentally observed facts for onset of NI, its duration, time of maximal size of PVE, and persistent migration of PN during early postnatal life. Cortical distribution of PN and postnatal cell death within CP showed differences when compared with previously published data that might be attributed to the numerical estimation methods used and populations of neurons that were not included in the model (SPP, GE, ML, SP). System dynamics was found suitable for simulation modeling of quantitative developmental cellular processes enabling integration of available experimental data into single model.

In this paper we present a methodology for modeling and simulation of dynamical discrete event systems (DDES), predominantly flexible manufacturing systems (FMS). Proposed technique is based on the matrix representation of a manufacturing system. Although prerequisites that are required for an event to start are given by static model of DES, we are not able to tell in which particular moment these prerequisites are met, i.e. we do not know when the event actually starts. In real applications on actual manufacturing processes, we will be sensing the completion of prerequisite jobs by either using sensors (e.g., proximity, tactile, etc.) or via notification from the machines or resources. On the other hand, for the purpose of computer simulation, we must find a way to keep track of time lapsed in the processing of jobs. To keep track of jobs time durations, we incorporated the system dynamics into the matrix model in a form of an extended lifetime. That is, a real number di, called a lifetime, is associated with each task in an MS. Problem that we analyze in the paper is that when described as a bill-of-material (BOM), or in some other engineering form, the job sequence does not disclose potential difficulties that might develop when the structure of an MS, which executes this particular sequence, is determined. In the paper we show how two of these potential difficulties, conflict and deadlock, can be exposed by using static and dynamic simulations of an MS. Based on the matrix model, these simulations provide a complete insight in the system performance.

The paper deals with dynamic analysis of automatic ship steering gear systems utilising com-plex controls that function according to the principle of proportional, integral and derivation regulators. The analysis involves a system dynamic simulation modelling methodology as one of the most suitable and effective means of dynamic modelling of complex non-linear, natu-ral, organisational and technical systems. The paper discusses system dynamics simulation models being used in qualitative (mental-verbal, structural) and quantitative (mathematical and computer) simulation models on ships equipped with trailing steering systems and PID regulator. Authors suggest using the presented models for designing and constructing new steering sys-tems, for diagnosing existing constructions and for education in Universities.

Food safety is not only an issue concerning human helth and business profit, but it is a political issue as well. Classical retroactive approach to food safety based on control of final product and govermental inspection survey is being changed to producers and distributors' self-control approach. In this respect, there are number of new tools that are in force: ISO, HACCP, IFS, BRC, Hygieneomic. The aim of research was to develop a mathematical model which would contribute to better understanding of technology process in ought to decrease risks present in it. The subject of research was fresh cheese. Variables measured during the cheese production are first analyzed to detect the most relevant components in technology process. Then the process is modelled by decision tree which classifies final products into two classes according to their quality. The ultimate goal of research was the recosideration of existing standards in cheese production.