Sampling the atmospheric boundary layer with small unmanned aircraft is a difficult task requiring informed selection of sensors and algorithms that are suited to the particular platform and mission Many factors must be considered during the design process to ensure the desired measurement accuracy and resolution is achieved, as is demonstrated through an examination of previous and current efforts A taxonomy is developed from these approaches and is used to guide a review of the systems that have been employed to make in situ wind and thermodynamic measurements, along with the campaigns that have employed them Details about the airframe parameters, estimation algorithms, sensors, and calibration methods are given

Overview of Small Fixed-Wing Unmanned Aircraft for Meteorological Sampling

This paper presents a self-powered energy harvesting circuit based on synchronous charge extraction with a single shared inductor for power conversion from arrays of independent piezoelectric transducers. The number of handled elements can be easily increased at the expense of few additional components and without affecting performance. The energy harvesting circuit was characterized with three 0.5 × 12.7 × 31.8 mm3 piezoelectric cantilevers subject to different types of vibrations. Throughout all operating conditions, the circuit was able to extract the maximum power independently from every transducer. Compared to passive energy harvesting interfaces, the output power is significantly higher, with worst-case increases ranging from +75% to +184%. The circuit starts up passively and is based on ultralow power active control, which consumes during operation at 3 V a fraction of the extra harvested power as low as 10 μW per source. As part of the best tradeoff between harvested and intrinsic power, an overall energy efficiency up to 74% was achieved.

Micropower Design of a Fully Autonomous Energy Harvesting Circuit for Arrays of Piezoelectric Transducers

The authors acknowledge the generous support of King Abdullah University of Science and Technology (KAUST). The authors thank Kelly Rader for proofreading this manuscript.

Recent Progress on Flexible Capacitive Pressure Sensors: From Design and Materials to Applications

The paper presents a power converter for piezoelectric energy harvesting implementing a modified version of a synchronous electrical charge extraction with quiescent current as low as 160 nA. The input energy is increased of more than 200% for weak vibrations, by inverting the residual charge left on the capacitance of the transducer after each energy extraction. Moreover, a power management policy, named two-way energy storage, is introduced in order to improve significantly the efficiency of the energy harvesting system in battery-less systems during the startup phase, when the energy storage is fully depleted. The converter behaves as a buck–boost converter, and the measured peak efficiency is 85.3%. The IC has been designed in a 0.32-μm microelectronic technology from STMicroelectronics in an active area of 0.95 mm2.

A Nanopower Synchronous Charge Extractor IC for Low-Voltage Piezoelectric Energy Harvesting With Residual Charge Inversion

Fixed-wing MAV attitude stability in atmospheric turbulence—Part 2: Investigating biologically-inspired sensors

This paper presents a capacitive pressure sensor strip implemented in general purpose printed circuit board (PCB) technology based on a thin 3D structure composed of polyimide, woven glass reinforced epoxy resin (FR4) and metal layers. Multiphysics finite elements method (FEM) simulations have been performed over the proposed structure in order to develop a time-dependent electrical and mechanical model that can be easily used to tailor the characteristics to the application. The device targets a wide class of fluid dynamics applications, being non-invasive, comformable and smart for placement. The device simulations are herein validated by experimental wind tunnel measurements and compared with figures obtained on a wing profile by conventional electromechanical pressure transducers. This approach is one of the first example of fully embedding and electronically controlled fluid flow monitoring apparatus that could be used in replacement of state of the art mechanical systems.

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A non-invasive capacitive sensor strip for aerodynamic pressure measurement

Experiments on aircraft flight parameter detection by on-skin sensors

Air speed and flight attitude angles are fundamental parameters for manual of automatic control of flying bodies Conventional measurement methods rely on probes (eg Pitot tubes or vanes) having a one-to-one correspondence with the physical quantities of interest and requiring specific placements Here, a novel measurement approach is proposed, relying on indirect measurement and on a plurality of pressure readings made by thin capacitive sensors directly placed on the aircraft skin A redundant number of probes relaxes the accuracy requirements posed on the individual units and helps achieving fault detection or fault tolerance A strategy for efficiently processing/combining sensor data is herein presented together with an error propagation analysis, and experimental data

/pdf/experiments-on-aircraft-flight-parameter-detection-by-on-3el2bw10v4.pdf

Air speed and angle of attack are fundamental parameters in the control of flying bodies. Conventional detection techniques use sensors that may protrude outside the aircraft, be too bulky for installation on small UAVs, or be excessively intrusive. We propose a novel readout methodology where flight parameters are inferred from redundant pressure readings made by capacitive strip sensors directly applied on the airfoil skin. Redundancy helps lower the accuracy requirements on the individual sensors. A strategy for combining sensor data is presented with an error propagation analysis. The latter enables foreseeing the precision by which the flight parameters can be detected. The methodology has been validated by fluid dynamic simulation and a sample case is illustrated.

http://ieeexplore.ieee.org/iel5/9624/30805/01426479.pdf

Aircraft angle of attack and air speed detection by redundant strip pressure sensors

This paper introduces an electromechanical model suitable for most piezoelectric devices, including the piezoelectric bimorph beams. The model provides an improved approach to design and to analyze the performance of piezoelectric transducers, especially in the case where piezoelectric devices are embedded in compound electronic systems. The main objectives of this work are: (i) to develop a versatile and easy-to-use electromechanical model of a piezoelectric transducer. The proposed model is based on the physical properties of the device and can be easily adapted to different operating conditions using experimental data analysis; (ii) to introduce an approach based on scattering (S-)parameters for better characterizing the frequency response of systems that exhibit resonant phenomena. To our knowledge, this is the first time that this approach has been applied to electromechanical transducers; (iii) to show the functionality of the model on a specific application. Results prove that although the model does not take into account second order effects such as nonlinear behavior and hysteresis, it fairly fits experimental data so as to be used for proposing and precisely describing new applications of piezoelectric sensors and actuators.

Alessandro Golfarelli

Papers

A non-invasive capacitive sensor strip for aerodynamic pressure measurement

Experiments on aircraft flight parameter detection by on-skin sensors

Experiments on aircraft flight parameter detection by on-skin sensors

Aircraft angle of attack and air speed detection by redundant strip pressure sensors

Modeling and characterization of piezoelectric transducers by means of scattering parameters. Part I: Theory