Acta Polytechnica 2004/2 - 3th International Conference on AED
Biological Systems Thinking for Control Engineering Design
D. J. Murray-Smith
Artificial neural networks and genetic algorithms are often quoted in discussions about the contribution of biological systems thinking to engineering design. This paper reviews work on the neuromuscular system, a field in which biological systems thinking could make specific contributions to the development and design of automatic control systems for mechatronics and robotics applications. The paper suggests some specific areas in which a better understanding of this biological control system could be expected to contribute to control engineering design methods in the future. Particular emphasis is given to the nonlinear nature of elements within the neuromuscular system and to processes of neural signal processing, sensing and system adaptivity. Aspects of the biological system that are of particular significance for engineering control systems include sensor fusion, sensor redundancy and parallelism, together with advanced forms of signal processing for adaptive and learning control.
Keywords: biology, control systems, design, neuro-muscular system
Computational Fluid Dynamic Simulation (CFD) and Experimental Study on Wing-external Store Aerodynamic Interference
Tholudin Mat Lazim, Shabudin Mat, Huong Yu Saint
The main objective of the present work is to study the effect of an external store to a subsonic fighter aircraft. Generally most modern fighter aircraft is designed with an external store installation. In this project a subsonic fighter aircraft model has been manufactured using a computer numerical control machine for the purpose of studying the effect of the external store aerodynamic interference on the flow around the aircraft wing. A computational fluid dynamic (CFD) and wind tunnel testing experiments have been carried out to ensure the aerodynamic characteristic of the model then certified the aircraft will not facing any difficulties in stability and controllability. In the CFD experiment, commercial CFD code is used to simulate the interference and aerodynamic characteristics of the model. Subsequently, the model together with an external store was tested in a low speed wind tunnel with test section sized 0.45 m×0.45 m. Result in the two-dimensional pressure distribution obtained by both experiments are comparable. There is only 12% deviation in pressure distribution found in wind tunnel testing compared to the result predicted by the CFD. The result shows that the effect of the external storage is only significant at the lower surface of the wing and almost negligible at the upper surface of the wing. Aerodynamic interference is due to the external storage were mostly evidence on a lower surface of the wing and almost negligible on the upper surface at low angle of attack. In addition, the area of influence on the wing surface by store interference increased as the airspeed increase.
Keywords: computational fluid dynamic (CFD), wind tunnel testing, validation, aerodynamic interference
Dynamics of Micro-Air-Vehicle with Flapping Wings
Small (approximately 6 inch long, or hand-held) reconnaissance micro air vehicles (MAVs) will fly inside buildings, and require hover for observation, and agility at low speeds to move in confined spaces. For this flight envelope insect-like flapping wings seem to be an optimal mode of flying. Investigation of the aerodynamics of flapping wing MAVs is very challenging. The problem involves complex unsteady, viscous flow (mainly laminar), with the moving wing generating vortices and interacting with them. At this early stage of research only a preliminary insight into the nature of the little known aerodynamics of MAVs has been obtained. This paper describes computational models for simulation of the controlled motion of a microelectromechanical flying insect – entomopter. The design of software simulation for entomopter flight (SSEF) is presented. In particular, we will estimate the flight control algorithms and performance for a Micromechanical Flying Insect (MFI), a 80–100 mm (wingtip-to-wingtip) device capable of sustained autonomous flight. The SSEF is an end-to-end tool composed of several modular blocks which model the wing aerodynamics and dynamics, the body dynamics, and in the future, the environment perception, control algorithms, the actuators dynamics, and the visual and inertial sensors. We present the current state of the art of its implementation, and preliminary results.
Keywords: micromechanical flying insect, entomopter aerodynamics, entomopter dynamics, insect flight, software simulator, insect aerodynamics, insect dynamics
The Role of CAD in Enterprise Integration Process
M. Ota, I. Jelínek
This article deals with the problem of the mutual influence between software systems used in enterprise environment and enterprise integration processes. The position of CAD data and CAx systems in the integrated environment of manufacturing enterprises is clarified. As a consequence, the key role of CAx systems used in those companies is emphasized. It is noted that the integration of CAD data is nowadays only on a secondary level, via primarily integrated PDM systems. This limitation is a reason why we are developing a unified communication model focused on product-oriented data. Our approach is based on Internet technologies, so we believe that is independent enough. The proposed system of communication is based on a simple request-replay dialogue. The structure of this model is open and extensible, but we assume supervision supported by an Internet portal.
Keywords: CAD, Enterprise Information Systems, Internet Portals, PDM
Development of a Technique and Method of Testing Aircraft Models with Turboprop Engine Simulators in a Small-scale Wind Tunnel - Results of Tests
A. V. Petrov, Y. G. Stepanov, M. V. Shmakov
This report presents the results of experimental investigations into the interaction between the propellers (Ps) and the airframe of a twin-engine, twin-boom light transport aircraft with a Ő-shaped tail. An analysis was performed of the forces and moments acting on the aircraft with rotating Ps. The main features of the methodology for windtunnel testing of an aircraft model with running Ps in TsAGI`s T-102 wind tunnel are outlined.The effect of 6-blade Ps slipstreams on the longitudinal and lateral aerodynamic characteristics as well as the effectiveness of the control surfaces was studied on the aircraft model in cruise and takeoff/landing configurations. The tests were conducted at flow velocities of VĄ= 20 to 50 m/s in the ranges of angles of attack a = -6 to 20 deg, sideslip angles of b = -16 to 16 deg and blade loading coefficient of B=0 to 2.8. For the aircraft of unusual layout studied, an increase in blowing intensity is shown to result in decreasing longitudinal static stability and significant asymmetry of the directional stability characteristics associated with the interaction between the Ps slipstreams of the same (left-hand) rotation and the empennage.
Keywords: windtunnel testing, propeller slipstream, engine failure, test methodology
Developing a Conceptual Design Engineering Toolbox and its Tools
R. W. Vroom, E. J. J. van Breemen, W. F. van der Vegte
In order to develop a successful product, a design engineer needs to pay attention to all relevant aspects of that product. Many tools are available, software, books, websites, and commercial services. To unlock these potentially useful sources of knowledge, we are developing C-DET, a toolbox for conceptual design engineering. The idea of C-DET is that designers are supported by a system that provides them with a knowledge portal on one hand, and a system to store their current work on the other. The knowledge portal is to help the designer to find the most appropriate sites, experts, tools etc. at a short notice. Such a toolbox offers opportunities to incorporate extra functionalities to support the design engineering work. One of these functionalities could be to help the designer to reach a balanced comprehension in his work. Furthermore C-DET enables researchers in the area of design engineering and design engineers themselves to find each other or their work earlier and more easily. Newly developed design tools that can be used by design engineers but have not yet been developed up to a commercial level could be linked to by C-DET. In this way these tools can be evaluated in an early stage by design engineers who would like to use them. This paper describes the first prototypes of C-DET, an example of the development of a design tool that enables designers to forecast the use process and an example of the future functionalities of C-DET such as balanced comprehension.
Keywords: toolbox, conceptual design engineering, development process, use process forecast, balanced comprehension
Knowledge Support of Simulation Model Reuse
M. Valášek, P. Steinbauer, Z. Šika, Z. Zdráhal
This describes the knowledge support for engineering design based on virtual modelling and simulation. These are the results of the EC Clockwork project. A typical and important step in the development of a simulation model is the phase of reusing. Virtual modelling and simulation often use the components of previous models. The usual problem is that the only remaining part of the previous simulation models is the model itself. However, a large amount of knowledge and intermediate models have been used, developed and then lost. A special methodology and special tools have therefore been developed on support of storing, retrieving and reusing the knowledge from previous simulation models. The knowledge support includes informal knowledge, formal knowledge and intermediate engineering models. This paper describes the overall methodology and tools, using the example of developing a simulation model of Trijoint, a new machine tool.
Keywords: Simulation model, reuse, knowledge management, machine tool
The Effect of Pedestrian Traffic on the Dynamic Behavior of Footbridges
The dynamic response of a footbridge depends namely on the natural frequencies of the structure in vertical, in horizontal and in torsion. If any of the frequencies in vertical is in the range 1.0 Hz to 3.0 Hz, the dynamic response from moving people can be significant. In this case it is necessary to calculate vibrations taking into account both serviceability and ultimate limit states. The same problem arises when any of the frequencies in horizontal (transversal) or in torsion are in the range 0.5 Hz to 1.5 Hz. Such frequencies haveare found namely in footbridges with larger spans or cable-stayed and suspension footbridges.A unique cable-stayed footbridge with prestressed concrete was dynamically analyzed and the dynamic response to simulated pedestrian loading was calculated. The calculated effects were compared with the pedestrian comfort criteria for serviceability limit states. These criteria are defined in terms of maximum acceptable acceleration of the bridge deck.
Keywords: vibrations, footbridge, dynamic actions due to pedestrians, acceptance criteria, response, serviceability
Control of Systems of Reservoirs with the Use of Risk Analysis
P. Fošumpaur, L. Satrapa
A system of reservoirs is usually defined as a system of water management elements, that are mutually linked by inner and outer connections in a purpose-built complex. Combined elements consist of reservoirs, river sections, dams, weirs, hydropower plants, water treatment plants and other hydraulic structures. These elements also include the rainfall system, the run-off system, the ground water system, etc. A system of reservoirs serves many purposes, which result from the basic functions of water reservoirs: storage, flood control and environmental functions. Most reservoirs serve several purposes at the same time. They are so called multi-purposes reservoirs. Optimum design and control of a system of reservoirs depends strongly on identifying the particular purposes. In order to assess these purposes and to evaluate the appropriate set of criteria, risk analysis can be used. Design and control of water reservoir functions is consequently solved with the use of multi-objective optimisation. This paper deals with the use of the risk analysis to determine criteria for controlling the system. This approach is tested on a case study of the Pastviny dam in the Czech Republic.
Keywords: risk analysis, system of reservoirs, multi-objective optimisation, water supply, hydropower plant, fuzzy logic
A coding and On-Line Transmitting System
V. Zagursky, I. Zarumba, A. Riekstinsh
A distributed data acquisition system is proposed. It provides parallel and simultaneous coding and on-line transmission of signals. This system has higher accuracy of measurements and performance in sampling and transmission than known analogs.
Speech Signal Recovery in Communication Networks
V. Zagursky, A. Riekstinsh
Interpolation approaches to the shape recovery of a speech signal in transmission over packet switched communications networks are proposed. The samples of signal fragments are mixed and transmitted in correspondence with standard procedure for packet-switched transmission. After reception a reverse permutation is made. In the case of packet losses missing samples are separated by several samples of the source signal. Correlation properties of the signal are used for the recovery samples due to first- and second-order non-adaptive and adaptive interpolation. For the loss of 25 % packets and second order adaptive interpolation a 2- 4 % error distribution range has been achieved.
Simulation of Scoliosis Treatment Using a Brace
Ivo Mařík M.D. has treated many child patients with scoliosis at the "Centre for Locomotor Defects", Olšanská 7, 130 00 Prague 3. The author has cooperated with him, and composed the computer program for the spine stress state under brace effects and for simulating scoliosis treatment. The program simulates the spinal curve remodelling in time for a specific child patients, and the algorithm for stress state calculation and treatment simulation is given.Orthopaedists in the Czech Republic use Cheneau-type or Cerny-type corrective braces. The brace exerts force effects on the skeleton of a child. The brace is made individually for each patient, in the following way: first, a negative plaster form of the child`s trunk is made, and then the positive plaster form is created. The orthopaedist determines the places where brace has to load the patient`s trunk, and the plaster form deepened in these places on the basis of his advice. The laminate brace made according to this plaster form constricts the child`s trunk (like a tight shoe).This paper shows how the stress state is determined in vertebrae and in inter-vertebral discs, and the solution of spinal curvature correction under brace force effects for a specific child patient. The project aims to find the dependence of the activation and velocity of spinal curvature correction in the spinal stress state for many patients. The paper shows the computing algorithms for spinal deformations and the stress state under brace force effects, and a simulation of spinal curvature correction.Spinal curvature is determined according to measured values on an X-ray of a patient before a brace is applied. The stress state in the spine and the spinal deformation are investigated by the finite element method as beam (spine) in an elastic ground (soft tissue). Two algorithms are used. The first algorithm deals with the spine above and below the soft tissues, and it is loaded by given displacements of the trunk surface. The second algorithm determines from the X-ray of a patient with and without a brace the spine deformation and the spine stress state, and the necessary trunk surface displacement is determined from this deformation.The calculation algorithm and parameters were compared with contest of treatment. The trunk surface load was checked by sensor that plates were placed into the braces to measure the load values between the brace and the surface of the child. The simulation program assesses the spinal curvature correction according to the spinal curvature type, the spinal stress state and the period of time for which the brace will be applied.
Keywords: biomechanics, simulation of treatment, scoliosis, spine stress state, spine remodelling
Image Analysis of Eccentric Photorefraction
J. Dušek, M. Dostálek
This article deals with image and data analysis of the recorded video-sequences of strabistic infants. It describes a unique noninvasive measuring system based on two measuring methods (position of I. Purkynje image with relation to the centre of the lens and eccentric photorefraction) for infants. The whole process is divided into three steps. The aim of the first step is to obtain video sequences on our special system (Eye Movement Analyser). Image analysis of the recorded sequences is performed in order to obtain curves of basic eye reactions (accommodation and convergence). The last step is to calibrate of these curves to corresponding units (diopter and degrees of movement).
Keywords: eccentric photorefraction, purkynje images, strabismus, image analysis
A Novel Approach to Power Circuit Breaker Design for Replacement of SF6
D. J. Telfer, J. W. Spencer, G. R. Jones, J. E. Humphries
This contribution explores the role of PTFE ablation in enhancing current interruption for various background gases in high voltage circuit breakers. An assessment of the current interruption capability has been made in terms of the arcing duration and the contact gap length at which critical arc extinction is achieved. These observations are supported by measurements of the magnitude of extinction and re-ignition voltage peaks. Most previous and other current experimental work on gas filled circuit breaker design follows conventional wisdom in investigating arcing behaviours at elevated gas pressures (usually up to 6 bar). But in this work we concentrate on the effects of using low gas pressures (less than 1 bar) in the presence of a close-fitting shield of ablatant polymer material (PTFE) that surrounds the electrode assembly of an experimental high power circuit breaker. We demonstrate that for several different gases, arc extinction capability compares well under these conditions with SF6, suggesting that SF6 could be replaced entirely in this novel system by more environmentally friendly gases. Moreover, the critical contact gap lengths at extinction are only slightly greater than when using SF6 at 6 bar. Weight loss measurements from the ablatant shield suggest that a chemical puffer action is the most likely mechanism for achieving the observed arc extinctions in this system.
Keywords: circuit breaker, power distribution, SF6 replacement, arc-induced ablation, anti-pollution
Numerical Analysis of the Temperature Field in Luminaires
J. Murín, M. Kropáč, R. Fric
This paper contains a calculation of the thermal field caused by electro-heat in lighting devices. After specifying the heat sources, a thermal analysis is make using the finite element method and the equivalent thermal scheme method. The calculated results have been verified experimentally.
Keywords: thermal analysis, luminaire, choke coil, heat loss, surface temperature, finite element method
Computer Aided Design of Transformer Station Grounding System Using CDEGS Software
S. Nikolovski, T. Barić
his paper presents a computer-aided design of a transformer station grounding system. Fault conditions in a transformer station can produce huge damage to transformer station equipment if the grounding system is not designed properly. A well designed grounding system is a very important part of the project for transformer station design as a whole. This paper analyses a procedure for transformer grounding system design and spatial distribution of touch and step voltage on the ground surface level, using the CDEGS (Current Distribution Electromagnetic Interference Grounding and Soil Structure Analysis) software. Spatial distribution is needed for checking and finding dangerous step and touch voltages above and around the transformer station. Apparent earth resistivity data is measured and analyzed using the RESAP module of the CDEGS software. Because of the very high current flow into the grounding system during a single line to ground fault or a three phase fault in the transformer station, very high and dangerous potentials can be induced on the metallic structures including the fence, which can cause dangerous situations for people and animals near the station and for the personnel inside the station. The PLOT module of CDEGS is used to view the results of the scalar potential, step and touch voltage on the surface. Graphic displays include equipotent contour lines and potential profiles (gradients) in 3D and 2D perspective and apparent soil resistivity (Wm) versus inter electrode spacing (m). The results of alternative grid designs may be displayed simultaneously for the purpose of comparison.
Keywords: computer-aided design, substation, grounding grid, soil, safety, touch and step voltage
Recycling and Networking
In recent years, the notion that for environmental and legislative reasons improvements The national environmental policies and practice, including recycling strategies, are desirable and in many cases might be economically beneficial has been gaining ground. Although according to recent surveys the state of the environment in Hungary is in line with average values of the European Union, the main challenge for the country is to achieve sustainability in economic, environmental and technological terms. With a view to accession to the European Union, a harmonisation strategy must be worked out and implemented. This harmonisation strategy includes not only legislative aspects, but also social, technological, financial and logistic considerations.Because of the high logistic costs of achieving closed loop recycling systems, the author focuses on logistic aspects and tasks of the improvement phases and concentrates on the possibilities of networking and co-operation. The paper describes some possible alternative solutions for co-operative recycling processes, to improve the following logistic parameters: delivery times, accuracy of supply, running times, utilization of capacities, stock quantities, flexibility, transparency of the system, high forwarding capability, quality of product. The logistic aspects of co-operation will be analysed from the viewpoint of a closed loop economy.
Keywords: co-operation, logistics, networking, optimisation, recycling
Response of a Light Aircraft Under Gust Loads
This project presents work performed by the Institute of Aerospace Engineering, Brno University of Technology. The primary purpose of this work was to estimate the aeroelastic response of a light aircraft under gust loads. In the past, the gust response has been investigated using the Pratt - Walker formula. This formula is derived from the response of a rigid airplane to a discrete gust. However, the Pratt-Walker formula does not capture either the stochastic nature of continuous turbulence or the effects of structural flexibility. The analysis described here was performed using the advanced FEM software package MSC Nastran.
Keywords: gust load, finite element, aeroelasticity, frequency response, continuous turbulence
Preliminary Determination of Propeller Aerodynamic Characteristics for Small Aeroplanes
This paper deals with preliminary determination of propeller thrust and power coefficients depending on the advance ratio by means of some representative geometric parameters of the blade at a specific radius: propeller blade chord and blade angle setting at 70 % of the top radius, airfoil thickness at the radius near the tip and the position of the maximum blade width. A rough estimation of the non-linear influence of propeller blades number is included.The published method is based on Lock`s model of the characteristic section and the Bull-Bennett lift and drag propeller blade curves. Lock`s integral decomposition factors and the loss factor were modified by the evolution of the experimental propeller characteristics. The numerical-obtained factors were smoothed and expressed in the form of analytical functions depending on the geometric propeller blade parameters and the advance ratio.
Keywords: propeller, propeller aerodynamics, thrust coefficient, power coefficient, propeller efficiency, propeller design