A Model-based Tightly Coupled Architecture for Low-Cost Unmanned Aerial Vehicles for Real-Time Applications

This paper investigates the navigation performance of a vehicle dynamic model-based (VDM-based) tightly coupled architecture for a fixed-wing Unmanned Aerial Vehicle (UAV) during a global navigation satellite system (GNSS) outage for real-time applications. Unlike an Inertial Navigation System (INS) which uses inertial sensor measurements to propagate the navigation solution, the VDM uses control inputs from either the autopilot system or direct pilot commands to propagate the navigation states. The proposed architecture is tested using both raw GNSS observables (Pseudorange and Doppler frequency) and Micro-Electro-Mechanical Systems-grade (MEMS) Inertial Measurement Unit (IMU) measurements fused using an extended Kalman filter (EKF) to aid the navigation solution. Other than the navigation states, the state vector also includes IMU errors, wind velocity, VDM parameters, and receiver clock bias and drift. Simulation results revealed significant performance improvements with a decreasing number of satellites in view during 140 seconds of a GNSS outage. With two satellites visible during the GNSS outage, the position error improved by one order of magnitude as opposed to a tightly coupled INS/GNSS scheme. Real flight tests on a small fixed-wing UAV show the benefits of the approach with position error being an order of magnitude better as opposed to a tightly coupled INS/GNSS scheme with two satellites in view during 100 seconds of a GNSS outage

Error characteristics of a model-based integration approach for fixed-wing unmanned aerial vehicles

The paper presents the error characteristics of a vehicle dynamic model (VDM)-based integration architecture for fixed-wing unmanned aerial vehicles. Global navigation satellite system (GNSS) and inertial measurement unit measurements are fused in an extended Kalman filter (EKF) which uses the VDM as the main process model. Control inputs from the autopilot system are used to drive the navigation solution. Using a predefined trajectory with segments of both high and low dynamics and a variable wind profile, Monte Carlo simulations reveal a degrading performance in varying periods of GNSS outage lasting 10 s, 20 s, 30 s, 60 s and 90 s, respectively. These are followed by periods of re-acquisition where the navigation solution recovers. With a GNSS outage lasting less than 60 s, the position error gradually grows to a maximum of 8⋅4 m while attitude errors in roll and pitch remain bounded, as opposed to an inertial navigation system (INS)/GNSS approach in which the navigation solution degrades rapidly. The model-based approach shows improved navigation performance even with parameter uncertainties over a conventional INS/GNSS integration approach

Numerical study of nanocomposite phase change material-based heat sink for the passive cooling of electronic components

University of Nottingham Faculty of Engineering Research Excellence PhD Scholarshi

Active flow control systems architectures for civil transport aircraft

Copyright @ 2010 American Institute of Aeronautics and AstronauticsThis paper considers the effect of choice of actuator technology and associated power systems architecture on the mass cost and power consumption of implementing active flow control systems on civil transport aircraft. The research method is based on the use of a mass model that includes a mass due to systems hardware and a mass due to the system energy usage. An Airbus A320 aircraft wing is used as a case-study application. The mass model parameters are based on first-principle physical analysis of electric and pneumatic power systems combined with empirical data on system hardware from existing equipment suppliers. Flow control methods include direct fluidic, electromechanical-fluidic, and electrofluidic actuator technologies. The mass cost of electrical power distribution is shown to be considerably less than that for pneumatic systems; however, this advantage is reduced by the requirement for relatively heavy electrical power management and conversion systems. A tradeoff exists between system power efficiency and the system hardware mass required to achieve this efficiency. For short-duration operation the flow control solution is driven toward lighter but less power-efficient systems, whereas for long-duration operation there is benefit in considering heavier but more efficient systems. It is estimated that a practical electromechanical-fluidic system for flow separation control may have a mass up to 40% of the slat mass for a leading-edge application and 5% of flap mass for a trailing-edge application.This work is funded by the Sixth European Union Framework Programme as part of the AVERT project (Contract No. AST5-CT-2006-030914

Is Gly16Arg β₂ Receptor Polymorphism Related to Impulse Oscillometry in a Real-Life Asthma Clinic Setting?

PURPOSE: We evaluated whether Gly16Arg beta2-receptor genotype relates to impulse oscillometry (IOS) in a real-life clinic setting. METHODS: Patients with persistent asthma taking inhaled corticosteroid ± long-acting beta-agonist (ICS ± LABA) were evaluated. We compared genotype groups comprising either no Arg copies (i.e. GlyGly) versus one or two Arg copies (i.e. ArgArg or ArgGly). IOS outcomes included total airway resistance at 5 Hz (R5), central airway resistance at 20 Hz (R20), peripheral airway resistance (R5–R20), reactance at 5 Hz, area under reactance curve (AX) and resonant frequency (RF). In addition, we recorded ACQ-5 and salbutamol use. RESULTS: One hundred and twelve ICS-treated asthmatic patients (mean ICS dose 1238 µg/day), mean age 43 years, ACQ 2.34, FEV1 82 %, R5 177 % were identified—89 were also taking LABA. 61 patients were GlyGly, while 14 were ArgArg and 37 were ArgGly. There were no significant differences in IOS outcomes, ACQ or salbutamol use between the genotypes. The allelic risk (as odds ratio) for less well-controlled asthma (as ACQ > 1.5) was 1.1 (95 % CI 0.72–1.68) in relation to each Arg copy with a corresponding odds ratio for abnormal R5–R20 > 0.07kPA/l.s being 0.91 (95 % CI 0.57–1.44). 71 % of patients had an ACQ > 1.5 in the GlyGly group, versus 67 % in GlyArg/ArgArg group, with corresponding figures for abnormal R5–R20 > 0.07 kPa/l.s being 69 versus 73 %. CONCLUSION: In a real-life clinic setting for patients with poorly controlled persistent asthma taking ICS ± LABA, we found no evidence of any relationship of Gly16Arg to IOS, ACQ or salbutamol use

Interactive flow behaviour and heat transfer enhancement in a microchannel with cross flow synthetic jet

This paper examines the effectiveness in combining a pulsating fluid jet for thermal enhancement in microchannel heat sinks. The proposed arrangement utilises an oscillating diaphragm to induce a high-frequency periodic fluid jet with zero net mass output at the jet orifice hence, termed "synthetic jet". The pulsed jet interacts with the fluid flow through microchannel passages altering their flow characteristics. The present study develops a 2-dimensional finite volume numerical simulation based on unsteady Reynolds-averaged Navier-Stokes equations for examining the microchannel-synthetic jet flow interaction. For a range of parametric conditions, the behaviour of this periodic flow with its special features is identified and the associated convective heat transfer rates are predicted. The results indicate that the pulsating jet leads to outstanding thermal performance in microchannel flow increasing its heat dissipation rate by about 4.3 times compared to a microchannel without jet interaction within the tested parametric range. The degree of thermal enhancement is seen to grow continuously to reach a steady value in the absence of fluid compressibility. The proposed strategy has an intrinsic ability for outstanding thermal characteristics without causing pressure drop increases in microchannel fluid passages, which is identified as a unique feature of the technique.The study also examines and presents the effects of fluid compressibility on the heat removal capacity of this arrangement. The technique is envisaged to have application potential in miniature electronic devices where localised cooling is desired over a base heat dissipation load