Tech Briefs

Experimental Confirmation of an Aquatic Swimming Motion Theoretically of Very Low Drag and High Efficiency

Researchers used an anguilliform swimming robot to replicate an idealized “wakeless” swimming motion.

It has been established theoretically that self-propulsion of deformable bodies in ideal fluid can occur with a careful specification of the deformation mode shape. With the fluid assumed ideal, vortex shedding, rotational wake, and induced drag would not occur. The implication is that for a real fluid, provided the existence of a thin boundary layer, similarly configured bodies with the same deformation mode shape self-propel without vortex shedding, rotational wake, and induced drag. Only viscous drag effects, due to the existence of the thin boundary layer, are present and unavoidable. The motion mode in question is the little-exploited anguilliform mode exhibited in some aquatic animal swimming. The Anguilla includes the snake, eel, lamprey, and leach, among others.

Posted in: Briefs, Aerospace

Gesture-Based Controls for Robots: Overview and Implications for Use by Soldiers

Developing a more effective means to communicate with robotic devices.

Afuture vision of the use of autonomous and intelligent robots in dismounted military operations is for soldiers to interact with robots as teammates, much like soldiers interact with other soldiers. Soldiers will no longer be operators in full control of every movement, as the autonomous intelligent systems will have the capability to act without continual human input. However, soldiers will need to use the information available from, or provided by, the robot. One of the critical needs to achieve this vision is the ability of soldiers and robots to communicate with each other. One way to do that is to use human gestures to instruct and command robots.

Posted in: Briefs, Aerospace

A Guide for Developing Human-Robot Interaction Experiments in the Robotic Interactive Visualization and Experimentation Technology (RIVET) Simulation

Using computer gaming technology to improve the interaction between humans and unmanned ground vehicles.

ARL's Intelligent Systems Enterprise vision is to enable the teaming of autonomous intelligent systems with soldiers in dynamic, unstructured combat environments, as well as in non-combat military installations and base operations. To accomplish this vision for interdependent soldier-robot teaming, there has been a paradigm shift in robotic research conducted by ARL from the current instantiation of fielded remote-controlled or teleoperated robots to systems with increased intelligence, decision-making capability, and autonomy. This type of teaming is needed for future joint, interdependent, network-enabled operations.

Posted in: Briefs, Aerospace

Identifying the Flow Physics and Modeling Transient Forces on Two-Dimensional Wings

Using mathematics and modeling to understand the flow physics of aircraft wings undergoing highly unsteady maneuvers.

The main objective of this research was to better understand the flow physics of aircraft wings undergoing highly unsteady maneuvers. Reduced-order models play a central role in this study, both to elucidate the overall dynamical mechanisms behind various flow phenomena (such as dynamic stall and vortex shedding), and ultimately to guide flight control design for vehicles for which these unsteady phenomena are important.

Posted in: Briefs, Aerospace

The Scaling of Loss Pathways and Heat Transfer in Small Scale Internal Combustion Engines

Understanding the performance parameters of small remotely piloted aircraft powerplants.

The rapid expansion of the remotely piloted aircraft market includes an interest in 10 kg to 25 kg vehicles (Group 2) for monitoring, surveillance, and reconnaissance. Power plant options for those aircraft are often 10 cm3 to 100 cm3 displacement internal combustion engines. Both power and fuel conversion efficiency decrease increasingly rapidly in the aforementioned size range, with fuel conversion efficiency falling from approximately 30% for automotive and larger scale engines (greater than 100 cm3 displacement) to less than 5% for micro glow fuel engines (less than 10 cm3 displacement).

Posted in: Briefs, Aerospace

Luminescence Materials as Nanoparticle Thermal Sensors

Particles could be used to record critical temperature history data during agent-defeat weapons testing.

The purpose of this research program was to create and study novel luminescence particles (phosphors} capable of sensing and retaining the time-temperature information to which they were exposed, therefore acting as nano- and microsized thermosensors. The thermometric property is the latent thermoluminescence (TL) signal associated with electron/hole pairs trapped at defect energy levels, which are differently affected by the environmental temperature.

Posted in: Briefs, Data Acquisition, Defense, Nanotechnology, Photonics, Architecture, Sensors and actuators, Research and development, Nanomaterials, Thermal testing

Using Dempster-Shafer Fusion for Personnel Intrusion Detection

New technique enables the use of ultrasonic micro-doppler and PIR sensors for improved security.

The Dempster-Shafer (D-S) mass function is used in effect as a common representation of heterogeneous sensor data. In order to cast each data source in this form, first the raw data is reduced to points in a multi-dimensional feature space specific to each sensor. From there, an approach is outlined that uses a distance metric in the feature space to assign mass to each state in the class hierarchy. This hierarchy begins with the full frame of discernment which represents complete uncertainty. From there it proceeds as an n-array tree broken down into further subclasses until the finest granularity of classification for the specific sensor is reached.

Posted in: Briefs, Defense, Detectors, Sensors, Mathematical models, Sensors and actuators, Data management, Reliability

Using Fisher Information Criteria for Chemical Sensor Selection via Convex Optimization Methods

Technique developed for simple linear sensor systems can be applied to broader array scenarios.

The design of chemical sensor arrays from the standpoint of chemical sensor selection and error quantification has historically proceeded as an ad hoc process. Frequently, chemical sensors are developed not as general purpose sensing devices, but as analyte or chemical class specific detectors. When such single purpose devices are integrated together as a chemical sensor array, it is unclear a priori how well they will function in concert with each other to provide expanded capabilities, an observation that is true of the integration of analytical instruments as well.

Posted in: Briefs, Aerospace, Optimization, Neural networks, Sensors and actuators, Identification, Chemicals

Development of an Optically Modulated Scatterer Probe for a Near-Field Measurement System

Using near-field radiation patterns to diagnose antenna array defects.

Near-field radiation patterns are useful in diagnosing antenna array defects, measuring far-field antenna patterns where the far-field is prohibitively far, and locating field concentrations in high power microwave applications, which could lead to material breakdown. There are two categories of near-field measurements: direct and indirect. In a direct measurement, the field from the antenna-under-test (AUT) is directly measured by a probe whereas, in an indirect measurement, the field is inferred from the scattering off of a probe that is placed in the near-field.

Posted in: Briefs, Aerospace, Finite element analysis, Measurements, Antennas, Radiation

Angular Random Walk Estimation of a Time-Domain Switching Micromachined Gyroscope

Achieving near navigation-grade performance without the need to produce resonators with very high quality factors.

The primary metrics that prohibit the use of microelectromechanical systems (MEMS) gyroscopes for navigation-grade inertial navigation units (IMUs) are angle random walk (ARW), bias instability, and scale factor instability. The need for MEMS gyroscopes is due to their decreased cost, size, weight, and power (CSWaP) constraints compared to current navigation-grade solutions. Note that to avoid confusion, while in a statistical context a random walk describes a particular type of random process, ARW is used herein to quantify the effects of white, or Gaussian, noise processes on the rate estimate of a gyroscope.

Posted in: Briefs, Aerospace, Mathematical analysis, Microelectromechanical devices, Navigation and guidance systems, Noise, Reliability