Search Results

Within the pre-development phase of a vehicle validation process, the role of computational simulation is becoming increasingly prominent in efforts to ensure thermal safety. This gain in popularity has resulted from the cost and time advantages that simulation has compared to experimental testing. Additionally many of these early concepts cannot be validated through experimental means due to the lack of hardware, and must be evaluated via numerical methods. The Race Track Simulation (RTS) can be considered as the final frontier for vehicle thermal management techniques, and to date no coherent method has been published which provides an efficient means of numerically modeling the temperature behavior of components without the dependency on statistical experimental data.

Contrails and aircraft-induced cirrus clouds are reputed being the largest components of aviation-induced global warming, even greater than carbon dioxide (CO2) exhaust emissions by aircraft. This article presents a contrail model algorithm specifically developed to be integrated within a multi-objective flight trajectory optimization software framework. The purpose of the algorithm is to supply to the optimizer a measure of the estimated radiative forcing from the contrails generated by the aircraft while flying a specific trajectory. In order to determine the precise measure, a comprehensive model is employed exploiting the Schmidt-Appleman criterion and ice-supersaturation regions. Additional parameters such as the solar zenith angle, contrail lifetime and spread are also considered.

When presented with new technology that removes past constraints, it is often beneficial to revisit old learning's to see if they still hold, and to understand how these can be best applied to the new technology. Brake-By-Wire (BBW) systems replace all the mechanical linkages of conventional hydraulic brake systems with ‘dry’ electrical components [2],[3]. The advent of this technology poses the possibility of revisiting conventional ABS control systems by utilizing the continuous nature that BBW offers. Presented is a BBW model based wheel slip controller using a generic continuous time Model Predictive Control (MPC) algorithm [15]. The result being the first of many steps taken in understanding the full potential that BBW systems offer.

This paper is the first of two papers that address the simulation and effects of turbulence on surface vehicle aerodynamics. This, the first paper, focuses on the characteristics of the turbulent flow field encountered by a road vehicle. The natural wind environment is usually unsteady but is almost universally replaced by a smooth flow in both wind tunnel and computational domains. In this paper, the characteristics of turbulence in the relative-velocity co-ordinate system of a moving ground vehicle are reviewed, drawing on work from Wind Engineering experience. Data are provided on typical turbulence levels, probability density functions and velocity spectra to which vehicles are exposed. The focus is on atmospheric turbulence, however the transient flow field from the wakes of other road vehicles and roadside objects are also considered.

This paper summarises the effects of turbulence on the aerodynamics of road vehicles, including effects on forces and aero-acoustics. Data are presented showing that a different design of some vehicles may result when turbulent flow is employed. Methods for generating turbulence, focusing on physical testing in full-size wind tunnels, are discussed. The paper is Part Two of a review of turbulence and road vehicles. Part One (Cooper and Watkins, 2007) summarised the sources and nature of the turbulence experienced by surface vehicles.

Noise and vibration have an important influence on a customer's perception of vehicle quality and cabin interior noise levels are a key criteria. The interior sound levels of automobiles have been significantly reduced over the years, with reductions in power train, tire and external wind noise. One of the highest in-cabin noise levels now arises from heating, ventilating and air conditioning systems, generated by the air-rush noise at various HVAC settings. Thus quieter climate control systems are desired by car manufacturers. A systematic benchmarking study was performed to investigate the in-cabin noise of vehicles. 21 passenger cars including compact, mid-size, full-size, and a truck were selected. Tests were conducted on relatively new production vehicles in various conditions. A binaural head system was used in front passenger seat to measure noise levels. The methodology used and the experimental results were presented in this paper.

Vortices formed around the A-pillar region dictates the pressure distribution on the side panels of a passenger vehicle and also can lead to aerodynamic noise generation. This paper compares the suitability of various turbulence models in simulating the flow behind a vehicle A-pillar region under laboratory operating conditions. Commercial software's (FLUENT and SWIFT) were used to compare the performance of various turbulence models. In FLUENT, a simplified vehicle model with slanted A-pillar geometry was generated using GAMBIT and in SWIFT, the simplified vehicle model was generated using Fame Hybrid. Computational Fluid Dynamics (CFD) simulations were carried out using FLUENT under steady state conditions using various turbulence models (k-, k- Realize, k- RNG, k- and Spalart Allamaras). In SWIFT, k-, A-RSM and HTM2 turbulence models were used for the steady state simulations. Investigations were carried out at velocities of 60, 100 and 140km/h and at 0-degree yaw angle.

The design of a longitudinal stability augmentation system (SAS) for an aircraft with reduced tail size in the preliminary design phase is presented. Reducing tail size will reduce drag and weight and result in better fuel consumption, but it will reduce the level of stability. A control law is designed to give the aircraft the same stability level as that with the initial tail size. The feedback gains of the control law is computed with the equivalent stability derivative criteria of and CmαCmq . The paper also gives an overview of classical root locus and pole placement method and demonstrates that equivalent stability derivative criteria is suitable for preliminary aircraft design applications. Moreover, the control laws are also synthesized using robust control LQG/LTR which can be elaborated more in the detail design phase.

An accurate aeroelastic assessment of powered HALE aircraft is of paramount importance considering that their behaviour contrasts the one of conventional aircraft mainly due to the use of high aspect-ratio wings with distributed propulsion systems. This particular configuration shows strong dependency of the wing natural frequencies to the propulsion distribution and operating conditions. Numerical and experimental investigations are carried out to better understand the behaviour of flexible wings, focusing on the effect of distributed electric propulsion systems. Several configurations are investigated, including a single propulsion system using an engine pod (a weight with embedded electric motor, a propeller, and the wing-attached structure) installed at selected spanwise positions, and configurations with two and three propellers.

Kinetic energy recovery systems (KERS) placed on one axle coupled to a traditional thermal engine on the other axle is possibly the best solution presently available to dramatically improve the fuel economy while providing better performances within strict budget constraints. Different KERS may be built purely electric, purely mechanic, or hybrid mechanic/electric differing for round trip efficiency, packaging, weights, costs and requirement of further research and development. The paper presents an experimental analysis of the energy flow to and from the battery of a latest Nissan Leaf covering the Urban Dynamometer Driving Schedule (UDDS). This analysis provides a state-of-the-art benchmark of the propulsion and regenerative braking efficiencies of electric vehicles with off-the-shelve technologies.

A KIA Soul was instrumented to measure the relative velocity (magnitude and yaw angle) at the front of the vehicle and in-cabin sound at a location close to the side glass near the A-pillar vortex impingement. Tests were conducted at a proving ground under a range of conditions from low wind conditions (~3 m/s) to moderate (7-8 m/s) wind speeds. For any given set of atmospheric conditions the velocity and sound data at any given position on the proving ground were noted to be very repeatable, indicating that the local wakes dominated the "turbulent" velocity field. Testing was also conducted in an aeroacoustic wind tunnel in smooth flow and with a number of novel turbulence generating methods. The resulting sounds were analyzed to study the modulation at frequencies likely to result in fluctuation strength type noise.

Wind noise sources are described including those from the A-pillar region, cavities and bluff bodies. Hydrodynamic pressure fluctuations results from flow separations (in such areas as the A-pillars and mirrors) that generate relatively broad band in-cabin noise. The influence on local radii of the A-pillar is outlined and shown to be a dominant factor in determining hydrodynamic pressure fluctuations in the side-glass regions. Small cavities (eg. styling or water management channels on the mirror casing) generate high-frequency acoustic tones that can also be heard in the cabin and an example of tones from a whistling mirror cavity is shown. A spectrogram of in-cabin noise obtained whilst driving in strong winds is used to illustrate the variability of noise that can be heard on-road and to consider the influence of the relative wind speed.

A small-scale aeroacoustic wind tunnel has been designed and built to investigate tonal cavity noise in the frequency range applicable to passenger vehicles; 1 - 16 kHz. The tunnel is required for testing associated with an investigation into tonal cavity noise on passenger-vehicle wing mirrors. It was designed to operate in the low subsonic speed range (60 - 140 km/h) with a nozzle exit cross-sectional area of 0.02 m2 and a 4:1 aspect ratio. The design was intended to achieve a smooth, quiet flow facility. In this paper the design process is summarised and the factors leading to particular design decisions are detailed. An initial evaluation has shown that only minimal changes are required to achieve very smooth, even flow at the nozzle exit at all required test speeds. The acoustic design needs further work as there is a significant amount of flow noise at the nozzle exit between 1 and 13 kHz.

This paper relates to the design and development of a multi-modal UAV capable of aerial flight and underwater propulsion. A novel hybrid propulsion system has been manufactured and tested. Consisting of folding blades, the propeller has been optimized for propulsion both in air and water. The critical water to air transition phase is achieved by an additional impulsive thruster powered by a C02 cartridge. To decrease the drag in underwater cruise and reduce the potential damage when the vehicle impacts the water, a morphing wing has been developed. This consists of foam-carbon fiber lay-up constructed wings in a variable sweep configuration. The actuation of the sweep is achieved by linear servos mounted on the sleeve shaped spar. An integrated prototype is constructed, using an unconventional, anhedral horizontal stabilizers to allow clearance for the morphing wing.

Accurate and robust tracking of objects is of growing interest amongst the computer vision scientific community. The ability of a multi-sensor system to detect and track objects, and accurately predict their future trajectory is critical in the context of mission- and safety-critical applications. Remotely Piloted Aircraft System (RPAS) are currently not equipped to routinely access all classes of airspace since certified Detect-and-Avoid (DAA) systems are yet to be developed. Such capabilities can be achieved by incorporating both cooperative and non-cooperative DAA functions, as well as providing enhanced communications, navigation and surveillance (CNS) services. DAA is highly dependent on the performance of CNS systems for Detection, Tacking and avoiding (DTA) tasks and maneuvers.

One of the primary hazards associated with the operation of Unmanned Aircraft (UA) is the controlled or uncontrolled impact of the UA with terrain or objects on the terrain (e.g., people or structures). National Aviation Authorities (NAAs) have the responsibility of ensuring that the risks associated with this hazard are managed to an acceptable level. The NAA can mandate a range of technical (e.g., design standards) and operational (e.g., restrictions on flight) regulatory requirements. However, work to develop these regulations for UA is ongoing. Underpinning this rule-making process is a safety case showing how the regulatory requirements put in place ensure that the UA operation is acceptably safe for the given application and environment.

A unified approach to cooperative and non-cooperative Detect-and-Avoid (DAA) is a key enabler for Remotely Piloted Aircraft System (RPAS) to safely and routinely access all classes of airspace. In this paper state-of-the-art cooperative and non-cooperative DAA sensor/system technologies for manned aircraft and RPAS are reviewed and the associated multi-sensor data fusion techniques are discussed. A DAA system architecture is presented based on Boolean Decision Logics (BDL) for selecting non-cooperative and cooperative sensors/systems including both passive and active Forward Looking Sensors (FLS), Traffic Collision Avoidance System (TCAS) and Automatic Dependent Surveillance - Broadcast (ADS-B). After elaborating the DAA system processes, the key mathematical models associated with both non-cooperative and cooperative DAA functions are presented.

Multi-Sensor Data Fusion (MSDF) techniques involving satellite and inertial-based sensors are widely adopted to improve the navigation solution of a number of mission- and safety-critical tasks. Such integrated Navigation and Guidance Systems (NGS) currently do not meet the required level of performance in all flight phases of small Remotely Piloted Aircraft Systems (RPAS). In this paper an innovative Square Root-Unscented Kalman Filter (SR-UKF) based NGS is presented and compared with a conventional UKF governed design. The presented system architectures adopt state-of-the-art information fusion approach based on a number of low-cost sensors including; Global Navigation Satellite Systems (GNSS), Micro-Electro-Mechanical System (MEMS) based Inertial Measurement Unit (IMU) and Vision Based Navigation (VBN) sensors.

Flow control over aerodynamic shapes in order to achieve performance enhancements has been a lively research area for last two decades. Synthetic Jet Actuators (SJAs) are devices able to interact actively with the flow around their hosting structure by providing ejection and suction of fluid from the enclosed cavity containing a piezo-electric oscillating membrane through dedicated orifices. The research presented in this paper concerns the implementation of zero-net-mass-flux SJAs airflow control system on a NACA0015, low aspect ratio wing section prototype. Two arrays with each 10 custom-made SJAs, installed at 10% and 65% of the chord length, make up the actuation system. The sensing system consists of eleven acoustic pressure transducers distributed in the wing upper surface and on the flap, an accelerometer placed in proximity of the wing c.g. and a six-axis force balance for integral load measurement.

Global Navigation Satellite Systems (GNSS) can support the development of low-cost and high performance navigation and guidance architectures for Unmanned Aircraft Systems (UAS) and, in conjunction with suitable data link technologies, the provision of Automated Dependent Surveillance (ADS) functionalities for cooperative Sense-and-Avoid (SAA). In non-cooperative SAA, the adoption of GNSS can also provide the key positioning and, in some cases, attitude data (using multiple antennas) required for automated collision avoidance. A key limitation of GNSS for both cooperative (ADS) and non-cooperative applications is represented by the achievable levels of integrity. Therefore, an Avionics Based Integrity Augmentation (ABIA) solution is proposed to support the development of an Integrity-Augmented SAA (IAS) architecture suitable for both cooperative and non-cooperative scenarios.