Tunnel Circuit Research Articles

Observer-Based Stabilization of Networked IT2 Fuzzy Semi-Markov Jump Models With Redundant Channels and Applications to Tunnel Circuit Model

Observer-Based Stabilization of Networked IT2 Fuzzy Semi-Markov Jump Models With Redundant Channels and Applications to Tunnel Circuit Model

The Honda Automotive Laboratories of Ohio Wind Tunnel

<div class="section abstract"><div class="htmlview paragraph">The Honda Automotive Laboratories of Ohio (HALO) includes a new aeroacoustic wind tunnel located near Marysville, Ohio that started operations in 2022. This facility provides world-class aerodynamic flow quality and acoustic testing capabilities for the development of both passenger and motorsports vehicles.</div><div class="htmlview paragraph">This closed-return ¾ open jet wind tunnel features a two-position flexible nozzle system with cross sections of 25 m<sup>2</sup> and 18 m<sup>2</sup>, providing wind speeds of up to 250 km/h and 310 km/h, respectively. There is a ±180 degree turntable with boundary layer control systems, and interchangeable single belt and 5-belt moving ground plane (MGP) modules. Extensive applications of acoustic treatment in the test section and throughout the wind tunnel circuit provide a hemi-anechoic test environment and low background noise levels. A temperature control system provides uniform and stable air temperature over an operating environment between 10 °C and 50 °C.</div><div class="htmlview paragraph">The primary instrumentation of the wind tunnel includes the wind speed, temperature, and humidity measurement systems, a 6-component force balance integrated within the turntable, and an acoustic test system (ATS). The ATS includes four planar microphone arrays for external measurements and a spherical microphone array and binaural heads for internal measurements. A flow survey traverse system equipped with a 4-D probe holder mechanism is capable of placing a probe anywhere within the test volume.</div><div class="htmlview paragraph">The HALO facility includes the wind tunnel control room, secure vehicle preparation bays and office spaces for segregated customers, and a vehicle frontal and side area measurement system.</div><div class="htmlview paragraph">This paper provides an introduction to the HALO wind tunnel testing capabilities, design features and development, and the results of the aeroacoustic commissioning program. The background noise level and flow quality characteristics are provided.</div></div>

The axial fan design and commissioning test with nonuniform inlet flow

According to the two-dimensional flow theory of the axial fan rotor blades and the aerodynamic characteristics of the low speed wind tunnel, combined with the fan aerodynamic efficiency and wind tunnel pressure loss coefficient, a new equation which points out the inherent relationship of the fan blade setting angle, fan rotating speed and flow rate in wind tunnel circuit is derived. So a new method for fan rotor blade setting angle adjustment to satisfy the fan performance at off-design point by getting the test results of fan operating parameters but without the fan total pressure rise in the low speed wind tunnel is developed. Following the new method, the fan rotor blade setting angle adjusting value was provided directly only with the fan rotating speed and flow velocity in the wind tunnel test section, the adjusting target was achieved successfully by the new blade setting angle, the cost of the wind tunnel commissioning test were saved. The test results show that, after increasing the fan rotor blade setting angle by 4.5 degrees, when the flow velocity in the wind tunnel test section reaches 60m/s, the fan rotating speed is 570rpm, the deviation from the predicted fan rotating speed value of 575rpm is 0.9%. For the same test section flow velocity, the predicted value and the real value of the fan rotating speed are in good agreement, it proves that this method is reliable and accurate in practical application.

Resilient and Modular Subterranean Exploration with a Team of Roving and Flying Robots

Subterranean robot exploration is difficult, with many mobility, communications, and navigation challenges that require an approach with a diverse set of systems, and reliable autonomy. While prior work has demonstrated partial successes in addressing the problem, here we convey a comprehensive approach to address the problem of subterranean exploration in a wide range of tunnel, urban, and cave environments. Our approach is driven by the themes of resiliency and modularity, and we show examples of how these themes influence the design of the different modules. In particular, we detail our approach to artifact detection, pose estimation, coordination, planning, control, and autonomy, and we discuss our performance in the tunnel, urban, and self-organized cave circuits of the DARPA Subterranean Challenge. Our approach led to a winning result in the tunnel circuit, and placing second in the urban circuit event. We convey lessons learned in designing and testing a resilient system for subterranean exploration that can generalize to a large range of operating conditions, and potential improvements for the future.

Heterogeneous Ground and Air Platforms, Homogeneous Sensing: Team CSIRO Data61’s Approach to the DARPA Subterranean Challenge

Heterogeneous teams of robots, leveraging a balance between autonomy and human interaction, bring powerful capabilities to the problem of exploring dangerous, unstructured subterranean environments. Here we describe the solution developed by Team CSIRO Data61, consisting of CSIRO, Emesent, and Georgia Tech, during the DARPA Subterranean Challenge. These presented systems were fielded in the Tunnel Circuit in August 2019, the Urban Circuit in February 2020, and in our own Cave event, conducted in September 2020. A unique capability of the fielded team is the homogeneous sensing of the platforms utilized, which is used to obtain a decentralized multi-agent SLAM solution on each platform (both ground agents and UAVs) using peer-to-peer communications. This approach enabled a shift in focus from constructing a pervasive communications network to relying on multi-agent autonomy, motivated by experiences in early circuit events. These experiences also showed the surprising capability of rugged tracked platforms for challenging terrain, which in turn led to the heterogeneous team structure based on a BIA5 OzBot Titan ground robot and an Emesent Hovermap UAV, supplemented by smaller tracked or legged ground robots. The ground agents use a common CatPack perception module, which allowed reuse of the perception and autonomy stack across all ground agents with minimal adaptation.

System for multi-robotic exploration of underground environments CTU-CRAS-NORLAB in the DARPA Subterranean Challenge

We present a field report of the CTU-CRAS-NORLAB team from the Subterranean Challenge (SubT) organized by the Defense Advanced Research Projects Agency (DARPA). The contest seeks to advance technologies that would improve the safety and efficiency of search-andrescue operations in GPS-denied environments. During the contest rounds, teams of mobile robots have to find specific objects while operating in environments with limited radio communication, e.g., mining tunnels, underground stations or natural caverns. We present a heterogeneous exploration robotic system of the CTU-CRAS-NORLAB team, which achieved the third rank at the SubT Tunnel and Urban Circuit rounds and surpassed the performance of all other non-DARPA-funded teams. The field report describes the team’s hardware, sensors, algorithms and strategies, and discusses the lessons learned by participating at the DARPA SubT contest.

CERBERUS: Autonomous Legged and Aerial Robotic Exploration in the Tunnel and Urban Circuits of the DARPA Subterranean Challenge

Autonomous exploration of subterranean environments constitutes a major frontier for robotic systems, as underground settings present key challenges that can render robot autonomy hard to achieve. This problem has motivated the DARPA Subterranean Challenge, where teams of robots search for objects of interest in various underground environments. In response, we present the CERBERUS system-of-systems, as a unified strategy for subterranean exploration using legged and flying robots. Our proposed approach relies on ANYmal quadraped as primary robots, exploiting their endurance and ability to traverse challenging terrain. For aerial robots, we use both conventional and collision-tolerant multirotors to explore spaces too narrow or otherwise unreachable by ground systems. Anticipating degraded sensing conditions, we developed a complementary multimodal sensor-fusion approach, utilizing camera, LiDAR, and inertial data for resilient robot pose estimation. Individual robot pose estimates are refined by a centralized multi-robot map-optimization approach to improve the reported location accuracy of detected objects of interest in the DARPA-defined coordinate frame. Furthermore, a unified exploration path-planning policy is presented to facilitate the autonomous operation of both legged and aerial robots in complex underground networks. Finally, to enable communication among team agents and the base station, CERBERUS utilizes a ground rover with a high-gain antenna and an optical fiber connection to the base station and wireless “breadcrumb” nodes deployed by the legged robots. We report results from the CERBERUS system-of-systems deployment at the DARPA Subterranean Challenge’s Tunnel and Urban Circuit events, along with the current limitations and the lessons learned for the benefit of the community.

Editorial: Special Issue on Advancements and Lessons Learned during Phases I and II of the DARPA Subterranean Challenge

Complex underground environments such as tunnels, underground urban settings, and natural caves present significant challenges for first responders in the event of an emergency. Each of these subdomains has unique hazards while sharing some common elements. Apart from challenging terrain features and aspects such as smoke and dust, communications in these environments are often severely degraded as well. Motivated by these difficulties, the Defense Advanced Research Projects Agency (DARPA) Subterranean Challenge (SubT) was set up to drive the global robotics community to develop novel approaches to rapidly map, navigate, and search underground environments under time pressure. The DARPA SubT,1 conducted from April 2019 to September 2021, was organized as two competition tracks. In the systems track, teams developed and demonstrated physical systems and competed live in real subterranean environments representative of the three subdomains. In the virtual track, teams developed software and algorithms using virtual models of systems and environments to compete in simulation-based events representative of the three subdomains. Phase I and Phase II of the systems track of this challenge consisted of the following events: 1. SubT Integration Exercise (STIX) at the Edgar Experimental Mine in Idaho Springs, Colorado, USA, in April 2019. 2. Tunnel Circuit event at the National Institute for Occupational Safety and Health (NIOSH) mine in Pittsburgh, Pennsylvania, USA, in August 2019. 3. Urban Circuit event at the Satsop Nuclear power plant in Elma, Washington, USA, in February 2020. The Cave Circuit event scheduled for August 2020 was canceled by DARPA due to the COVID-19 pandemic. As a result, a number of the competing teams held their local Cave events to evaluate their system performance in natural cave environments. In each of these events, the task was to deploy a fleet of robots into the subterranean course to locate and identify a set of predefined artifacts within the 60-minute run time. These artifacts included cell phones, backpacks, power drills, fire extinguishers, survivors (thermal mannequins), air vents, rooms with high carbon dioxide concentration, climbing rope, and helmets. A point was scored for each correctly identified artifact located within a 5-meter accuracy. Only one human supervisor was allowed to control and communicate with the robots once the run started. A pit crew of 10 personnel was allowed to set up the robots in the staging area outside the course entrance in the 30-minute period immediately prior to the run.

An adaptive torus‐event‐based controller design for networked T‐S fuzzy systems under deception attacks

AbstractThis article addresses the adaptive torus‐event‐based control problem for a class of networked Takagi‐Sugeno (T‐S) fuzzy systems under deception attacks. Due to the inherent openness of the network, the inevitable deception attacks in the networked T‐S fuzzy systems always appear randomly. The occurrence of deception attacks is successfully described by using a binary stochastic variable with known statistical characteristics. Under the considered adaptive torus‐event‐based communication mechanism, fuzzy controllers are constructed to guarantee the asymptotically mean‐square stability (AMSS) and the index of the networked T‐S fuzzy systems under deception attacks. To design the desired fuzzy controllers, a unified framework of the networked T‐S fuzzy systems is first established via the adaptive torus‐event‐based communication mechanism, the mathematical model of deception attacks, and the asynchronous premise technology. By utilizing the extended Lyapunov function, the sufficient conditions are simultaneously derived to address the AMSS and the disturbance suppression issues of closed‐loop control systems. Subsequently, the adaptive torus‐event‐based fuzzy controller gains are calculated via linear matrix inequalities. Finally, a simulation example concerning the tunnel circuit system is established to verify the availability and reliability of the proposed control mechanism.

Computational studies to determine the design of prototype heater for a hypersonic wind tunnel

During the modernization of the TsAGI hypersonic wind tunnel, which implies an increase in the limiting values of the flow stagnation parameters, and in the thermal load, consequently, computational studies were realized for the existing design of the electric arc heater and new geometry options for the central electrode and the cooling duct of the external electrode and nozzle. The distribution of the heat flux density to the surfaces of the main elements of the wind tunnel was obtained based on the calculations for the air duct of wind tunnel. The qualitative data of the flow formation both in the pre-heater and the pre-chamber served as the basis for changing the geometry of the central electrode. In this study, a numerical modelling approach was implemented for a through calculation of the flow and heat transfer in all areas of the wind tunnel circuit (heater, pre-chamber, nozzle, test section, diffuser). The ANSYS FLUENT software package was used to solve the axisymmetric Navier-Stokes equations for a five-component chemically reacting gas mixture: O2; N2; O; N; NO using the Spalart-Allmaras turbulence model. To study the hydrodynamics and thermal state of the structure of the external and central electrodes, the possibility of the ANSYS FLUENT complex for solving conjugate problems was used (the complete Navier-Stokes equations and the energy balance equation were solved in a fluid, and the heat conduction equation was solved in a solid). In this case, at the interface between the media, the conditions for the continuity of temperature and heat flux were satisfied.

Collision‐free local planner for unknown subterranean navigation

When operating in confined spaces or near obstacles, collision-free path planning is an essential requirement for autonomous exploration in unknown environments. This study presents an autonomous exploration technique using a carefully designed collision-free local planner. Using LiDAR range measurements, a local end-point selection method is designed, and the path is generated from the current position to the selected end-point. The generated path showed the consistent collision-free path in real-time by adopting the Euclidean signed distance field-based grid-search method. The results consistently demonstrated the safety and reliability of the proposed path-planning method. Real-world experiments are conducted in three different mines, demonstrating successful autonomous exploration flights in environment with various structural conditions. The results showed the high capability of the proposed flight autonomy framework for lightweight aerial robot systems. In addition, our drone performed an autonomous mission in the tunnel circuit competition (Phase 1) of the DARPA Subterranean Challenge.

Design and characterization of a multifunctional low-speed anechoic wind tunnel at HKUST

The Hong Kong University of Science and Technology (HKUST) has installed and commissioned an Ultra-quiet Noise Injection Test and Evaluation Device (UNITED). This facility is the first closed-circuit anechoic wind tunnel in Hong Kong. Calibrations and improvements have been made to improve the aerodynamic and aeroacoustic performance since its commissioning in 2016, and various experiments have been conducted in it. The test section is enclosed within a 3.2 m × 3.1 m × 2 m anechoic chamber, and it can be configured as either open-jet or closed test section. The exit plane of the contraction section has a dimension of 0.4 m × 0.4 m, and the flow speed of the test section can be varied from 10 m/s up to 70 m/s. In this paper, the major design constraints and design principles of key wind tunnel sections are described. To achieve low background noise, a silencer network is carefully designed, and a low-noise axial fan is specially designed and manufactured for the wind tunnel circuit. It is shown that the metrics of aerodynamic and aeroacoustic performances are comparable to similar facilities across the world. Representative research activities are also briefly summarized in this paper. Particularly, the measurement of trailing edge noise of a flat plate is demonstrated. The measured trailing edge noise collapses well under the classical fifth power-law scaling, suggesting the good performance of the entire measurement system.

Low-frequency fluctuations and their suppression in the 5.5 m × 4 m aeroacoustic wind tunnel at CARDC

This paper experimentally investigated characteristics of low-frequency pressure fluctuations in a large-scale open jet wind tunnel using pressure transducers and far-field microphones. Two distinct low-frequency pressure fluctuations have been detected at the range of wind speeds between 50 m/s and 75 m/s. The two peak frequencies vary with the change of wind speed. Analysis results show that both the low-frequency pressure fluctuations are driven by the resonances of the large scale instability waves in the jet shear layer at two different feedback loop paths. One loop is through the entire circuit of the wind tunnel, another exists between the nozzle and the collector, which is termed as edge-tone feedback. A formula for predicting the peak frequency was derived and the prediction agrees well with the measurement. In addition, an effective control strategy to suppress the wind tunnel circuit resonance and the edge-tone feedback resonance were also presented.

Газодинамическое проектирование и численное исследование сверхзвукового контура аэродинамической трубы

For an advanced trisonic wind tunnel of a straight-flow type with a test section size of 1.2 × 1.2, intended for ground tests of rocket-space and aviation aircraft models, we implemented a gas-dynamic design of the circuit and did numerical simulation of the flow for the main supersonic regimes (M = 2, M = 4). The gas-dynamic design of the wind tunnel circuit was carried out on the basis of techniques developed at TsAGI and operating experience of existing facilities. The study considers both traditional configurations of the duct with the bending of the walls of all elements, i.e., nozzle, test section and diffuser in the XY plane, and alternative design developments with the bending of the diffuser walls in the XZ plane. When carrying out numerical studies in all areas of the wind tunnel, the ANSYS Fluent software package was used to solve the Navier --- Stokes equations for viscous and heat-conducting air using the turbulence model, i.e., Spalart --- Allmaras, SST. The paper investigates the effect of the wall opening angle, compensating the increasing thickness of boundary-layer longwise displacement, on the flow characteristics; shows the possibilities of obtaining a sufficiently uniform flow with the Mach number accuracy ΔM = ± 0.005 in the area of the model, and analyzes the influence of geometric parameters and boundary conditions on the efficiency of the supersonic diffuser

A Robust UAV System for Operations in a Constrained Environment

In this letter we present an autonomous system intended for aerial monitoring, inspection and assistance in Search and Rescue (SAR) operations within a constrained workspace. The proposed system is designed for deployment in demanding real-world environments with extremely narrow passages only slightly wider than the aerial platform, and with limited visibility due to the absence of illumination and the presence of dust. The focus is on precise localization in an unknown environment, high robustness, safety and fast deployment without any need to install an external infrastructure such as an external computer and localization system. These are the main requirements of the targeted SAR scenarios. The performance of the proposed system was successfully evaluated in the Tunnel Circuit of the DARPA Subterranean Challenge, where the UAV cooperated with ground robots to precisely localize artifacts in a coal mine tunnel system. The challenge was unique due to the intention of the organizers to emulate the unpredictable conditions of a real SAR operation, in which there is no prior knowledge of the obstacles that will be encountered.

Measurement of nuclei seeding in hydrodynamic test facilities

Microbubble populations within the test section of a variable-pressure water tunnel have been characterised for various operating conditions. The tunnel was operated with demineralised water and artificially seeded with microbubbles from an array of generators located in a plenum upstream of the tunnel contraction. The generators produce a polydisperse population of microbubbles 10–200 $$\upmu \hbox {m}$$ in the diameter. The microbubbles are generated from supersaturated feed water within a confined turbulent cavitating microjet. The generator and tunnel operating parameters were systematically varied to map the range of nuclei concentrations and size ranges possible in the test section. Microbubbles were measured with Mie Scattering Imaging (MSI), an interferometric sizing technique. A new method was introduced to calibrate the detection volume and extend the dynamic range of the MSI. The acquisition and processing of microbubble measurements with MSI have a fast turn-around such that nuclei concentration measurements are approaching real time. Estimation of the total bubble concentration was within 5% of the sampled concentration after only 100 detections but 10$$^4$$ were necessary for full histogram convergence. The tunnel is operated with water at low dissolved gas content to ensure all injected microbubbles dissolve and do not complete the tunnel circuit. As a result of this, the injected population is altered by dissolution as well as pressure change during the short residence between plenum and test section. The transformation is shown to be complex, changing with tunnel operating conditions. The measured test section nuclei populations were found to follow a power law for the higher concentrations. Test section nuclei concentrations of 0–24 $$\hbox {mL}^{-1}$$ can be achieved through variation of generator and tunnel operating parameters. a A schematic of the experiment. b Sample image data. c Measured concentration of the seeded microbubble cavitation nuclei. d Distribution of bubble concentration by size.

Mine Tunnel Exploration Using Multiple Quadrupedal Robots

Robotic exploration of underground environments is a particularly challenging problem due to communication, endurance, and traversability constraints which necessitate high degrees of autonomy and agility. These challenges are further exacerbated by the need to minimize human intervention for practical applications. While legged robots have the ability to traverse extremely challenging terrain, they also engender new challenges for planning, estimation, and control. In this work, we describe a fully autonomous system for multi-robot mine exploration and mapping using legged quadrupeds, as well as a distributed database mesh networking system for reporting data. In addition, we show results from DARPA Subterranean Challenge (SubT) Tunnel Circuit demonstrating localization of artifacts after traversals of hundreds of meters. These experiments describe fully autonomous exploration of an unknown Global Navigation Satellite System (GNSS)-denied environment undertaken by legged robots.

Natural nuclei population dynamics in cavitation tunnels

Nuclei, or microbubble, populations control the inception and dynamics of cavitation. It is, therefore, important to quantify distributions in cavitation test facilities to rigorously model nucleation dynamics. Measurements of natural nuclei population dynamics were made in two test facilities in Australia and Japan via mechanical activation using a Cavitation Susceptibility Meter (CSM). A range of tunnel operating parameters, including pressure, velocity and dissolved oxygen (DO) content, were investigated. The DO saturation condition upstream of the test section is found to provide a threshold as to whether the population is affected by DO in the Australian test facility. Historical trends in the population are quantified, indicating that regular monitoring is required. Variation of the population around the Australian cavitation tunnel circuit was studied by varying the water sampling location. Provided the water remains undersaturated, as defined above, the natural nuclei population in the test section can be measured by sampling from the lower limb resorber. Comparisons are made between test facilities in Australia, Japan and other countries, as well as environmental waters, using different measurement techniques. Optical and acoustic methods show microbubbles in the size range of 10–100 $$\,{\upmu }\hbox {m}$$ typical of those used to model cavitation nucleation. CSM measurements show varying distributions of nuclei with equivalent bubble diameters in the range of 0.5–5 $$\,{\upmu }\hbox {m}$$ but global trends suggest a universal characteristic.

A New Method for Adjusting Setting Angle of Rotor Blade for Axial Fan in Wind Tunnel

Combining the fan aerodynamic efficiency with the wind tunnel pressure loss coefficient, a new equation which points out the inherent relationship of the fan blade setting angle, fan rotating speed and gas flow rate in wind tunnel circuit is derived according to the two-dimensional flow theory of the axial fan rotor blades and the aerodynamic characteristics of the low speed wind tunnel. So a new method for setting angle adjustment of fan rotor blade to satisfy the fan performance at off-design point by getting the test results of fan operation parameters but without the fan total pressure rise in the low speed wind tunnel is developed. Flowing the new method, the setting angle adjusting value of fan rotor blade was provided only with the fan rotating speed and flow velocity in the test section of a low speed wind tunnel directly before the fan setting angle altered, the adjusting target was achieved by the new blade setting angle successfully and the time and cost of the wind tunnel commissioning test were saved. The test results show that, after increasing the fan rotor blade setting angle by 4.5 degrees, when the flow velocity in the wind tunnel test section reaches 60 m/s, the fan rotating speed is 570 r/min, the deviation from the predicted fan rotating speed value of 575 r/min is 0.9%. For the same test section flow velocity, the predicted value of the fan rotating speed is in a good agreement with the real value, it proves that this method is reliable and accurate in practical application.

Effect of applying screen and honeycomb to the flow characteristic in wind tunnel based on CFD simulation

In the field of wind tunnel testing, flow quality is one of considerations which determine the accuracy of data measurement. There are several aspects that affect the flow quality, such as blade design, flow conditioner application and tunnel circuit configuration (i.e. design of the corner vane, corner duct, contraction duct and etc.). Applying flow conditioner like screen or mesh and honeycomb is commonly used to improve the flow quality in the tunnel. This paper discusses about the effect of applying screen and honeycomb to the flow characteristic in a simple tunnel model. The screen was applied on the several locations at the WAD (wide angle diffuser), i.e. at the inlet, middle section, and at the outlet of the WAD. Honeycomb was applied after the last screen in the tunnel duct. In the modelization, the applied screen or mesh and honeycomb were modeled using porous media computational model and using Darcy law as a mathematical model. The CFD simulation was performed using Numeca by separating the domain into fluid domain section (for the tunnel section) and porous media domain (for the screen and honeycomb section). Unstructured mesh type, generated by Hexpress, was used on the tunnel computational domain. The results indicate the reduction of flow separation, hence more uniform flow in the tunnel, by applying screen or mesh at the WAD and by applying honeycomb in the chamber.