Search Results

Starting January 2015 the government of the United Kingdom will allow driverless cars on public roads. From a first glance this can and should be seen as a great step towards the adoption of autonomous vehicles. Yet as any new technology driverless vehicles carry with them many new risks and disadvantages that need to be understood and protected against in order for the introduction of said systems into the market place to be a long lasting and fruitful one. The present work will look at the possible safety and security risks posed by the use of Light Detection and Ranging (LiDAR) systems on the open road, motivated by the fact that many projected autonomous vehicle concept systems rely on them for object detection and avoidance.

Upon their arrival, Unmanned Autonomous Systems (UAS) brought with them many benefits for those involved in a military campaign. They can use such systems to reconnoiter dangerous areas, provide 24-hr aerial security surveillance for force protection purposes or even attack enemy targets all the while avoiding friendly human losses in the process. Unfortunately, these platforms also carry the inherent risk of being built on innately vulnerable cybernetic systems. From software which can be tampered with to either steal data, damage or even outright steal the aircraft, to the data networks used for communications which can be jammed or even eavesdropped on to gain access to sensible information. All this has the potential to turn the benefits of UAS into liabilities and although the last decade has seen great advances in the development of protection and countermeasures against the described threats and beyond the risk still endures.

Energy management system designs for road vehicle applications have for some time considered the use of road data geospatial attributes such as elevation, speed limits and GPS derived online information, like traffic and position, to forecast the amount of fuel that could be consumed by a given vehicle on a specific route. This approach is especially useful when dealing with electrified platforms as on-board energy storage devices (such as fuel cells or batteries) have a lower energy density ratio [kJ/g]. Unfortunately within the tactical mobility context such information might not be readily available, either by passive obstructions, like mountains, or active ones due to jamming, etc. This paper will elaborate on an energy management system meant to deal with the uncertainty created by navigating in terrain where only basic trip information is available, such as probable distance to be travelled.

The incorporation of hydrogen fuel cells into heavy duty tactical mobility vehicles can bring about great opportunities in reducing the pollutant emissions of this kind of platforms (GVW > 30,000 kg). Furthermore the transportation of fuel to operational areas has become a key aspect for any deployment therefore optimal use of this resource is of paramount importance. Finally, it is also quite common for such platforms to serve additional purposes, besides freight delivery, such as powering external equipment (i.e. field hospitals or mobile artillery pieces). This work will describe the intelligent energy management system for a PEM Fuel Cell-Battery-Ultracapacitor Hybrid 8×8 heavy truck of the aforementioned weight class which also contemplates an internal electric/traction power generation unit. It will describe how the system optimizes the use of battery and hydrogen fuel energy while keeping system efficiency and performance at a maximum.

This paper reports studies of jet-induced upwash fountains for twin-nozzle, short take-off and vertical landing (STOVL) aircraft. Experimental and 3-D computational fluid dynamics studies were carried out using twin circular jets at nozzle pressure ratios (NPR) between 1.05 and 3, impingement heights between 2.5 and 8.5 nozzle diameters and a nozzle separation of 7 diameters. This paper describes an extension to our previous work on jet-induced fountain unsteadiness, with the development of pressure-instrumented ground and suck-down plates and a vertically-moving ground landing simulator. The aims of the studies were to model and measure the average pressure and time-varying fluctuations present around the upwash fountain and to correlate this information with flow visualisation data and hence to understand better the flow mechanisms involved in upwash fountain flapping, with application to modern STOVL aircraft.

The effect of various wing parameters on the performance of a micro air vehicle using insect-like flapping wings is studied. A nonlinear aerodynamic model that was developed for modelling the flow associated with such wings in the hover is used to make a parametric study. The effects of both wing kinematics and wing shape on a flapping wing is investigated by considering their influence on lift and lift-to-torque ratio. A default set of parameters is defined and wing performance is measured with respect to this benchmark case. It is found that lift is greater for larger stroke amplitudes and higher flapping frequencies, varying almost as the square in both cases. The effect of advanced wing rotation is generally to improve the lift performance but lift-to-torque ratio begins to diminish beyond a lead of about 5% of the flapping cycle.

The motivation for investigating micro air vehicles (MAVs) is given, and the advantages of insect-like flapping-wing MAVs (FMAVs) over other possible solutions are shown to be manifold. The complex kinematics of an insect-like flapping wing, and the highly unsteady flow produced by this motion, are examined. The inability of conventional, steady, aerodynamics to explain the large forces produced by such mechanisms is shown. A review is made of some early techniques in unsteady aerodynamics, followed by an examination of some more recent attempts to analyse the problem. Finally, the scope of the current research is explained, and a research plan is outlined.

Laser Doppler anemometry (LDA) data and a 3D Fluent computational fluid dynamics (CFD) solution are presented from a 1044mm length Ahmed (1) reference model. LDA velocity measurements are taken from a transverse plane one model length downstream at a freestream speed of 25m/s with a moving ground plane, and are compared to the CFD model. Comparisons were also made between the current computation and a previous study employing a different turbulence model. In addition, 6 component force data was recorded during the experiment and comparisons are made between the current CFD model and current and previous experimental work. Comparisons show the CFD model to successfully capture the main flow structures in the wake although discrepancies in the predicted vortex positions were thought in part to be caused by a model misalignment error.

This paper presents the results of an investigation of the near wake of isolated, cambered and un-cambered, 40%-scale, non-deformable Champ Car wheels rotating in ground contact. Three-dimensional velocity measurements were made in their near wakes using Laser Doppler Anemometry. Inspection of the derived velocity contours, vectors and vorticity contours, suggested that several of the theoretical vortical structures are suppressed by ‘real’ wheel geometry and the presence of a support sting. Drag force measurements were made, revealing the cambered wheel to have 12% higher drag coefficient than the un-cambered equivalent.