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Seismic Isolation of Bridges Using the Principle of Electromagnetic Attraction and Repulsion

Abstract

This paper presents a new type of seismic isolator that uses the principle of electromagnetic attraction and repulsion, to control the friction force between two electromagnets during earthquakes. The two electromagnets are used in conjunction with a secondary high friction dissipating and damping mechanism composed from a 10mm thick neoprene ring layer and two steel surfaces coated with Si3N4 that are used to dissipate the kinetic energy in the bridge deck at some maximum ground accelerations. The isolator utilizes tri-axial accelerometers embedded in the abutments, high current rechargeable batteries and an automated controlling unit. The presented isolator was developed specifically for a concrete bridge deck with a span of 36 meters and simple supported on two abutments, using time history electromagnetic and structural analyses. The paper presents the advantages of using this active seismic isolation system, compared to classical passive devices and the important results obtained in terms of decreasing internal forces on the substructure elements cross sections together with the reduction of relative displacements between the two electromagnets.

Open access
Significance of Fines in Hot Mix Asphalt Synthesis

Abstract

According to their size, aggregates are classified in coarse grained, fine grained, and fines. The determination of fines content in aggregate materials is very simple and is performed through the aggregate washing during the sieving procedure to define the gradation curve. The very fine material consists of grains having a size lower than 63 μm. The presence of fines directly influences the composition and performance of concrete and asphalt mixtures (e.g. asphalt content, elasticity, fracture). The strength and load carrying capacity of hot mix asphalt (HMA) results from the aggregate framework created through particle-particle contact and interlock. Fines or mineral filler have a role in HMA. The coarse aggregate framework is filled by the sand-sized material and finally by the mineral filler. At some point, the smallest particles lose contact becoming suspended in the binder not having the particle-particle contact that is created by the larger particles. The overall effect of mineral filler in hot mix asphalt specimens has been investigated through a series of laboratory tests. It is clear that a behaviour influenced by the adherence of fines to asphalt film has been developed. The optimum bitumen content requirement in case of stone filler is almost the same as that for fly ash. It has been found that the percentage of fly ash filler is crucial if it exceeds approximately a value of 4%.

Open access
The Time-Space Approach in the Analysis of Traffic Safety on Rural Road

Abstract

Analysis of the traffic safety factors in some region (road, section of road, road’s kilometer) is an important task in the field of traffic safety. It is necessary to constantly monitor, analyze, compare traffic safety situation in order to develop and improve measures for increasing the level of traffic safety. The first part of each analysis is finding of positions of traffic accidents and its casualties, in other words it is necessary to find its coordinates in the space-time coordinate system.

This paper shows results of the descriptive statistical analysis of traffic accidents frequency on the rural road for the period 2005-2011. It will be point out advantages and disadvantages of this approach and also it will be suggested a new individual approach for determinate the mean time between consecutive traffic accidents.

Open access
Analytical Redundancy in Control Systems for Unmanned Aircraft and Optionally Piloted Vehicles

Abstract

The article presents key properties of a module intended to estimate non-measurable state variables of an aircraft (a fixed-wing aircraft). Sample calculations are applicable to the MP-02A Czajka light Optionally Piloted Vehicle (OPV). The quality of flight parameter values’ estimation is illustrated by comparing flight parameters of the MP-02A Czajka aircraft recorded during actual flight with estimated values of respective parameters calculated during simulation of selected sensor faults. This experiment allows to evaluate the usefulness of the analytical redundancy mechanism that determines attitude parameters (roll, pitch and heading angles) and navigational variables (airspeed, altitude and geographic coordinates).

Open access
Eddy-Current Sensor for a Tachometer

Abstract

The speed of a rotor or rotors of a turbine engine is important information on its operation. Due to the specific conditions, in which the measurement is taken in a turbine engine, which in particular applies to small engines that are becoming increasingly popular in manned and unmanned aviation, the most universal detector is the detector using the phenomenon of eddy currents. This article presents the developed detector system solution. The correct operation of a detector is conditional upon the possibility to detect the presence of a blade in the detection field in a reliable manner, while maintaining the resistance to interference. The developed system is resistant to changes in parameters due to the use of a differential system consisting of two detector coils connected in a bridge circuit, a rectifier circuit with filters acting as a demodulator and a comparator. The system works with a microprocessor performing data processing functions. The executed functional model was tested in a laboratory, which enabled to determine its characteristics in several configurations and to confirm its correct operation.

Open access
Estimation of Strength Parameters of Aviation Products Made of Polymer Composites Based on Markov Chain Theory

Abstract

The study investigates the fatigue strength of a component made of a glass composite material with polyester matrix, manufactured using a contact method (I) and by vacuum bagging (II). Modeling was carried out only for composite material II, due to significant spread of the strength of the composite material manufactured by contact lamination I, which means that such a material does not guarantee repeatability of the test results. Estimation of the composite material fatigue strength and residual strength was performed using a mathematical model based on the Markov chain theory. The model assumed that the material failure occurs at certain critical microvolume of the components operating within the plastic range. Observed relationships between the probability values and the distribution parameters for the static strength of the composite components, as well as the load values allow for deriving a fatigue curve equation. Obtained results are presented in the tables.

Open access
Posturographic Tests of Candidates for Military Pilots

Abstract

One of the many elements of the process of qualifying the candidates for military aircraft pilots is the assessment of the correct functioning of their body balance system, responsible, inter alia, for spatial orientation during a flight. That system continuously controls the spatial position of the center of body mass. To measure that value directly is a complex metrological task. That is why an equivalent measure is used in tests of standing posture stability, i.e. the position of a projection of the center of mass on a supporting plane.

Quantitative information determining the characteristics of the body balance system may be obtained in posturographic tests, which include measurement, recording and assessment of the trajectory of a projection of the examined person’s center of body mass.

At the preliminary stage, examined were nineteen candidates for fighter pilots (one woman and 18 men), students of the Polish Air Force Academy in Dęblin.

Based on the conducted measurements of the body mass center position and the stabilographic tests, the correctness of their balance system performance was assessed. The article discusses the examination methodology, presents measurement results and conclusions.

Open access
Reconfiguration of Unmanned Aircraft Control System

Abstract

Reliability of unmanned aircraft is a decisive factor for conducting air tasks in controlled airspace. One of the means used to improve unmanned aircraft reliability is reconfiguration of the control system, which will allow to maintain control over the aircraft despite occurring failures. The control system is reconfigured by using operational control surfaces, to compensate for failure consequences and to control the damaged aircraft. Development of effective reconfiguration algorithms involves utilization of a non-linear model of unmanned aircraft dynamics, in which deflection of each control surface can be controlled independently.

The paper presents a method for an unmanned aircraft control system reconfiguration utilizing a linear and nonlinear model of aerodynamic loads due to control. It presents reconfiguration algorithms, which differ with used models and with optimization criteria for deflections of failure-free control surfaces. Additionally it presents results of a benchmark of the developed algorithms, for various types of control system failures and control input.

Open access
Selected Aspects of the Low Level Automatic Taxi Control System Concept

Abstract

Taxiing of manned and remotely piloted aircraft is still performed by pilots without using a system of automatic control of direction and speed. Several reasons have emerged in recent years that make the automation of taxiing an important design challenge. The reasons are: decreased airport capacity due to the growing number of aircraft, poor ground operation conditions during poor visibility conditions, an increase in workload of pilots and air traffic controllers and the integration of simultaneous ground operations of manned and remotely piloted air vehicles. This paper presents selected aspects of the concept of a Low Level Automatic Taxi Control System. In particular, it emphasizes the means of controlling an aircraft during taxiing, accuracy requirements of the system and proposes control techniques. The resulting controller of the system is adaptable for different aircrafts. The actuators and their mechanical connections to available controls are the aircraft specific part and are designed for the particular type – in this case – a general aviation light airplane.

Open access
Supporting the Process of Aircraft Maintenance with Mobile Devices

Abstract

Maintenance of aircraft is a complex process and therefore, in order to optimize the process, integrated information systems are increasingly used. Rapid development and wide availability of mobile devices equipped with powerful processors and with a wide range of modern communication connections suggests their high usability for enterprise IT systems. In the Department of Avionics and Air Armament of the Military University of Technology (WAT) an ERP-class (Enterprise Resource Planning) system, intended to support aircraft maintenance [4] has been designed and developed. The main concept of the system is to store the aircraft related and maintenance information in a central repository, i.e. in databases hosted on a central database server. This solution ensures concurrent availability of the data to a large group of authorized users. The key components of the system include the database server and client applications, which ensure access to centralized information resources, according to assigned user rights. The project involves development of client applications using three technologies: web, desktop and mobile one. Developed client applications have successfully passed integration tests perfomed using sample maintenance data. Currently works on user authorization security and wireless data security are under way.

Open access