This paper considers the problem of obtaining good attitude estimates from measurements obtained from typical low cost inertial measurement units. The outputs of such systems are characterized by high noise levels and time varying additive biases. We formulate the filtering problem as deterministic observer kinematics posed directly on the special orthogonal group SO (3) driven by reconstructed attitude and angular velocity measurements. Lyapunov analysis results for the proposed observers are derived that ensure almost global stability of the observer error. The approach taken leads to an observer that we term the direct complementary filter. By exploiting the geometry of the special orthogonal group a related observer, termed the passive complementary filter, is derived that decouples the gyro measurements from the reconstructed attitude in the observer inputs. Both the direct and passive filters can be extended to estimate gyro bias online. The passive filter is further developed to provide a formulation in terms of the measurement error that avoids any algebraic reconstruction of the attitude. This leads to an observer on SO(3), termed the explicit complementary filter, that requires only accelerometer and gyro outputs; is suitable for implementation on embedded hardware; and provides good attitude estimates as well as estimating the gyro biases online. The performance of the observers are demonstrated with a set of experiments performed on a robotic test-bed and a radio controlled unmanned aerial vehicle.

/pdf/nonlinear-complementary-filters-on-the-special-orthogonal-ysp0zzaoar.pdf

Nonlinear Complementary Filters on the Special Orthogonal Group

random data analysis and measurement procedures is available in our digital library an online access to it is set as public so you can get it instantly. Our book servers spans in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Merely said, the random data analysis and measurement procedures is universally compatible with any devices to read.

Random Data Analysis And Measurement Procedures

To obtain higher resolution acoustic source plots from microphone array measurements, deconvolution techniques are becoming increasingly popular. Deconvolution algorithms aim at identifying Point Spread Functions (PSF) in source plots, and may therefore fall short when actual beam patterns of measured noise sources are not similar to synthetically obtained PSF's. To overcome this, a new version of the classical deconvolution method CLEAN is proposed here: CLEAN-SC. By this new method, which is based on spatial source coherence, side lobes can be removed of actually measured beam patterns. Essentially, CLEAN-SC iteratively removes the part of the source plot which is spatially coherent with the peak source. A feature of CLEAN-SC is its ability to extract absolute sound power levels from the source plots. The merits of CLEAN-SC were demonstrated using array measurements of airframe noise on a scale model of the Airbus A340 in the 8×6 m2 closed test section of DNW-LLF.

/pdf/clean-based-on-spatial-source-coherence-1z42qt0ee7.pdf

CLEAN Based on Spatial Source Coherence

Several new numerical methods for compressible shear-layer simulations

This paper reviews the development of energy harvesting for low-power embedded structural health monitoring (SHM) sensing systems. A statistical pattern recognition paradigm for SHM is first presented and the concept of energy harvesting for embedded sensing systems is addressed with respect to the data acquisition portion of this paradigm. Next, various existing and emerging sensing modalities used for SHM and their respective power requirements are summarized followed by a discussion of SHM sensor network paradigms, power requirements for these networks, and power optimization strategies. Various approaches to energy harvesting and energy storage are discussed and limitations associated with the current technology are addressed. The paper concludes by defining some future research directions that are aimed at transitioning the concept of energy harvesting for embedded SHM sensing systems from laboratory research to field-deployed engineering prototypes. Finally, it is noted that many of the technologies discussed herein are applicable to powering any type of low-power embedded sensing system regardless of the application.

/pdf/energy-harvesting-for-structural-health-monitoring-sensor-40xb7fid8o.pdf

Energy Harvesting for Structural Health Monitoring Sensor Networks

A valuable new resource being developed for today’s soldier are small ducted fan VTOL UAVs. Although beneficial in many ways, a major operational problem of ducted fan vehicles is precise control when flying in crosswinds and turbulent conditions in general. There are two significant, inherent issues associated with ducted fan control in crosswinds; 1) lateral momentum drag and 2) a duct stabilizing torque which resist tipping into the wind. For vehicles designed for flight over large ranges in angle of attack (i.e. “transition to high-speed cruise”), trim over the flight envelope is strongly affected by the duct moment characteristics. Poor CG placement can lead to control saturation at intermediate flight speeds. These are characteristics of all ducted fan vehicles designed to hover as well as transition to horizontal flight. Techsburg, in collaboration with AVID LLC. and Honeywell Labs, has recently completed a research program to investigate and test new aerodynamic control devices to improve the handling of small ducted fan UAVs in crosswinds. This project consisted of both computational analysis and modeling of the vehicle aerodynamics and control system, as well as wind tunnel experiments using a powered ducted fan VTOL UAV model. This work leveraged methodologies and testing resources developed as part of a larger DARPAfunded VTOL UAV program. The research focused on a better understanding of the baseline vehicle and control vane aerodynamics, and selection and aerodynamic modeling and testing of new VTOL UAV auxiliary control device concepts. The analytical results are then used as input into an existing control system modeling framework, which in turn can be used to predict the vehicle’s dynamic response to turbulence. In addition to an improved flight control system, insights into establishing disturbance rejection criteria for VTOL UAVs are sought for use in future vehicle development efforts. This paper focuses on describing the baseline vehicle aerodynamics in a crosswind, as well as characteristics and design considerations for traditional control vanes used for this type of vehicle. Some limited, initial results from analysis of auxiliary control devices are presented as well.

Improving Control System Effectiveness for Ducted Fan VTOL UAVs Operating in Crosswinds

A 3‐mm‐diam, dual hot‐wire aspiring probe is described which can simultaneously measure total temperature and total pressure in an unsteady high‐speed gas flow. The probe consists of two coplanar constant temperature hot wires at different overheat ratios operated in a 1.5‐mm‐diam channel with a choked exit. Thus, the constant Mach number flow by the wires is influenced only by free‐stream total temperature and pressure. The probe design is a compromise between the conflicting requirements of spatial resolution, frequency response, and angular sensitivity. The dc temperature accuracy of the probe is about 1% while the resolution is 0.3%. Frequency response of the present design is dc to 20 kHz.

Wing Ng

Papers

Improving Control System Effectiveness for Ducted Fan VTOL UAVs Operating in Crosswinds

High‐frequency temperature and pressure probe for unsteady compressible flows

Improving Ducted Fan UAV Aerodynamics in Forward Flight

Wind Tunnel Aeroacoustic Measurements of a 26%-scale 777 Main Landing Gear

Reduction of unsteady stator–rotor interaction using trailing edge blowing