Extensional stress−strain measurements on a polyurea (PU) were carried out at strain rates up to 830 s−1, in combination with ex post facto small-angle X-ray scattering (SAXS) and temperature-dependent SAXS. The elastomer is of interest because its application as an impact-resistant coating. highest used herein fall within the softening, or transition, zone viscoelastic spectrum are thus relevant working hypothesis that performance impact coating related transition glassy state when strained...

We consider the combined problem of frontier exploration in a complex indoor environment while seeking radio source. To do this an efficient manner, we incorporate signal strength (RSS) information into algorithm by locally sampling RSS and estimating 2-D gradient. The exploits local motion to collect samples for gradient estimation seeks explore way that brings robot This strategy avoids random or exhaustive exploration. An experiment demonstrates uses dynamically prioritize candidate...

Autonomous teams of unmanned ground and air vehicles rely on networking distributed processing to collaborate as they jointly localize, explore, map, learn in sometimes difficult adverse conditions. Co-designed intelligent wireless networks are needed for these autonomous mobile agents applications including disaster response, logistics transportation, supplementing cellular networks, agricultural environmental monitoring. In this paper we describe recent progress systems using a low...

Many applications of autonomy are significantly complicated by the need for wireless networking, with challenges including scalability and robustness. Radio accomplishes this in a complex environment, but suffers from rapid signal strength variation attenuation typically much worse than free space loss. In paper, we propose test algorithms to autonomously discover connectivity area base station an unknown environment using average received (RSS) values RSS threshold delineate goodness...

Insects breathe using an extensive network of flexible air-filled tubes. In some species, the rapid collapse and reinflation these tubes is used to drive convective airflow, a system that may have bio-inspired engineering applications. The mechanical behavior tracheal critical understanding how they function in this deformation process. Here, we performed quasi-static tensile tests on ring sections main thoracic trunks from American cockroach (Periplaneta americana) determine properties...

A novel high-speed tensile test instrument is described, capable of measuring the mechanical response elastomers at strain rates ranging from 10 to 1600 s−1 for strains through failure. The device employs a drop weight that engages levers stretch sample on horizontal track. To improve dynamic equilibrium, common problem in high speed testing, equal and opposite loading was applied each end sample. Demonstrative results are reported two 588 with maximum 4.3. At higher rates, there substantial...

Radio signal strength (RSS) is a reasonable proxy for link quality, but its accurate estimation requires frequency and spatial diversity due to fluctuation caused by fading. We consider Rayleigh/Rician fading model, gather RSS measurements during motion in complex environment enable gradient estimation. Using the gradient, we develop control laws track active sources. These may be used establish preserve connectivity among collaborative autonomous agents, locate approach radio sources, as...

Direction of arrival (DoA) estimation has wide-ranging applications and is particularly challenging in complex propagation environments. Conventional approaches estimate the DoA based on phase impinging signal a sensor array. This approach several challenges: for example, it requires tight synchronization among array elements estimated sensitive to multipath correct specification geometry. In this paper, we develop principled Bayesian algorithm received strength gradient. We present...

Radio communication between ground robots at low VHF frequencies is generally more reliable in complex environments compared to conventional systems operating higher UHF frequencies. Unfortunately, high-gain directional antennas are impractically large for backpack sized robots. However, if a robot carrying small, antenna having an omni-directional radiation pattern positioned desired location close set of parasitic elements (i.e., not connected radios and their input short-circuited), the...

We consider the fundamental problem of direction arrival (DoA) estimation for autonomous agents in obstacle-rich, near-ground channels. Classical phase-based approaches to DoA rely on impingement direct path signal an antenna array; when line sight is rare or unobtainable such methods may yield meaningless estimates. In this paper, we present a Bayesian algorithm based received strength (RSS) spatial gradient, where RSS measurements are collected while maneuvering environment. develop...

Mobile communications in complex environments such as mega-cities is a challenging problem that limits the ability to deploy autonomous agents support of operations. Building on recent progress low frequency networking utilizes miniature antennas provide persistent connectivity among agents, we consider design and collaborative manipulation distributed robotic antenna array directional will enable enhanced networking, interference rejection, control. The use parasitic elements Yagi-Uda type...

We present a solution to the problem of autonomously identifying safe region in partially-known environment from which mobile robot will navigate and transmit mission-critical data an operator. This work is context humanitarian-assistance, disaster-relief missions where operator tasks large standoff distances through extreme, real-world environments robust operations are required ensure optimized information gathering. Our proposed approach, referred as informed recovery behavior, identifies...

Autonomous platforms are confronted by a diversity of challenges in unstructured environments, which make monitoring performance non-trivial task. Some these environments so complex that they preclude persistent, nearby operator oversight. This absence oversight motivates the need for an online system, specifically robots operating difficult environments. We develop test methodology and set metrics extending methods characterizing robotic-systems using offline metrics. implement this...

The radiation pattern of an antenna within array environment is modified by mutual coupling to neighboring elements, which can create unknown phase and amplitude variation on the order 10° 5 dB. This uncertainty in element patterns results beamforming errors, be particularly problematic for applications requiring precise control. A new approach reported compensate single-mode radiators using only measured S-parameters received signal from several far-field sources. technique relies fact that...

We present a minimalist model for estimating point-to-point wireless connectivity in robotic networks where every node the network is mobile, i.e., space of problem truly ℝ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> × . This built on idea that geometry an environment leads to region-based decomposition communication between pairs regions can be approximated accurately by simple stochastic models. develop estimation framework allows...

Abstract Master curves of the small strain and dynamic shear modulus are compared with transient mechanical response rubbers stretched at ambient temperature over a seven‐decade range rates (10 −4 to 10 3 s −1 ). The experiments were carried out on 1,4‐ 1,2‐polybutadienes styrene–butadiene copolymer. These have respective glass transition temperatures, T g , equal −93.0, 0.5, 4.1 °C, so that room measurements probed rubbery plateau, zone, onset glassy state. For 1,4‐polybutadiene, in accord...

Recent developments in low-VHF antenna design and parasitic array research show it is possible to form multi-robot arrays. These arrays have the potential extend communication range urban indoor environments. However, existing control formulations are not general enough support this new capability. We first propose a generalized version of disk model that describes array. This then integrated into Fiedler maximization approach for maintaining communication. Through simulation, we test our...

In this paper, we develop and evaluate a calibration procedure for multi-robot unmanned ground vehicle (UGV) beamforming arrays operating in challenging non-line-of-sight (NLOS) scenarios. The proposed approach is open-loop, uni-directional, location agnostic. It enables array to employ the help of an auxiliary agent perform calibration. Location agnosticism useful on-the-fly reconfiguration urban environments. uni-directional nature allows increased covertness operational simplicity by...

Ranging between military assets is particularly challenging in complex non-line-of-sight (NLOS) environments where adversaries may contest access to traditional localization technologies. Recent research shows that it possible use technology for Ultraviolet C-band (UV-C) communication ranging as well. Based on the channel model UV-C links, we formulate a calibration-free approach requires no prior knowledge of orientations transmitter (Tx) and receiver (Rx). Detailed sensitivity analysis...

Safety, security, and rescue missions typically occur in environments where unreliable wireless communication impedes cooperative human robot missions. A low-VHF band antenna array formed through the coordination of ground robots has potential to transmit receive signals more reliably at longer ranges these environments. We advance this idea here by developing methods for controlling a forming improve or maintain with other agents complex propose test orienting robotic increase received...