Multi-robot team formation control in the GUARDIANS project

Purpose The GUARDIANS multi-robot team is to be deployed in a large warehouse in smoke. The team is to assist firefighters search the warehouse in the event or danger of a fire. The large dimensions of the environment together with development of smoke which drastically reduces visibility, represent major challenges for search and rescue operations. The GUARDIANS robots guide and accompany the firefighters on site whilst indicating possible obstacles and the locations of danger and maintaining communications links. Design/methodology/approach In order to fulfill the aforementioned tasks the robots need to exhibit certain behaviours. Among the basic behaviours are capabilities to stay together as a group, that is, generate a formation and navigate while keeping this formation. The control model used to generate these behaviours is based on the so-called social potential field framework, which we adapt to the specific tasks required for the GUARDIANS scenario. All tasks can be achieved without central control, and some of the behaviours can be performed without explicit communication between the robots. Findings The GUARDIANS environment requires flexible formations of the robot team: the formation has to adapt itself to the circumstances. Thus the application has forced us to redefine the concept of a formation. Using the graph-theoretic terminology, we can say that a formation may be stretched out as a path or be compact as a star or wheel. We have implemented the developed behaviours in simulation environments as well as on real ERA-MOBI robots commonly referred to as Erratics. We discuss advantages and shortcomings of our model, based on the simulations as well as on the implementation with a team of Erratics.</p

University Student Services Center

The building was found to be generally compliant with the requirements set forth in the codes and standards, any discrepancies are addressed within the report in their respective sections. The prescriptive-based analysis was performed using the appropriate NFPA standards, the Life Safety Code (LSC) and the International Building Code (IBC). The building is three storied and has an overall gross floor area of 101,579 sq ft. It is classified as a mixed occupancy use with a calculated total occupant load of 2,866 occupants and is being evaluated as a Type II-B structure as defined in the IBC. It is protected throughout by an automatic fire sprinkler system and a fire alarm system. The installed fire protection and life safety (egress) systems in this building are evaluated according to NFPA 13, NFPA 72, and NFPA 101. Hydraulic calculations on the sprinkler system show that the water supply is sufficient for the sprinkler system’s remote area. The standpipes in the stairwells appear to be maintained and are available and accessible to emergency responders in the event of an emergency. The fire alarm system provides adequate coverage for a fully-sprinklered facility. Initiating devices placed along the means of egress and at each building exit. Smoke detectors are provided for elevator control functions, releasing of smoke control barriers and releasing automatic closing doors. Duct smoke detectors are placed to shutdown air handling units upon detection of smoke in air supply plenums. The atrium on the north end of the building connects all three floors. As such, the atrium, requires a smoke control system. The smoke control system was designed in accordance with the smoke management calculations in NFPA 92, Standard for Smoke Control Systems – 2015 edition. A beam smoke detector is located in the atrium for control of three smoke exhaust fans and fire vent latch release. This smoke control system was further analyzed in the performance- based design analysis and found to be insufficient for the scenarios chosen. Based off the results of this building evaluation and walk-through of the building, the following deficiencies were noted and recommendations proposed: 1) The building has two stairwells that are provided 2-hour fire rated walls, large landings, and labeled as “Area of Refuge”. These areas are not provided with two-way communication as required by code. Since the buildings is fully sprinklered and areas of refuge are not required, it’s recommended that the university remove the signs labeling the stairwells as areas of refuge. 2) The third-floor banquet hall is capable of being configured for a large variety of events. It was noted that textile draperies were regularly mounted on the walls and ceilings for aesthetic purposes. A university representative mentioned that the practice was deemed allowable by the local jurisdiction and that the draperies were treated with fire-retardant chemicals. The chemicals, listing or test method used on these draperies was not able to be determined at the time of the walk-through. However, it is recommended that the exit markings are not covered when using the decorative draperies. 3) Overflow storage issues in the banquet halls storage room impede on the path of egress from the penthouse mechanical room. It is recommended that the proper housekeeping is performed, and the path kept clear. For performance-based analysis purposes, notification of building occupants was assumed to occur upon audible or visual signals from the building fire alarm system based of detection time of the fire alarm system. Evacuation modeling estimated the time to evacuate a fully populated building was approximately 180 seconds. Occupant characteristics and pre-movement time were addressed when doing occupant evacuation simulations for the chosen fire scenarios. The results of occupant evacuation and fire simulations were compared to ensure that tenability performance criteria within the building was maintained and that the available safe egress time (ASET) is greater than the required safe egress time (RSET). This comparison showed that the ASET of 503 seconds only marginally exceeded the RSET of 500 seconds for scenario #2. Scenario #1 included a scotch pine Christmas tree at the base of the atrium which overpowered the smoke control system in 77 seconds. This time is well before the required egress time of 500 seconds shown in the simulation. From these results, the University was deemed to not provide an adequate level of protection for building occupants in the event of a fire scenario. The following recommendations are proposed based off the results: 1) Discontinue the use of Christmas tree at the base of the atrium for decoration during the holidays. 2) Add secondary smoke detection devices in the atrium out coves for earlier detection and notification in the event a fire was to initiate from the out cove. 3) Consider replacing exhaust fans with larger capacity fans

Transport-Based Neural Style Transfer for Smoke Simulations

Artistically controlling fluids has always been a challenging task. Optimization techniques rely on approximating simulation states towards target velocity or density field configurations, which are often handcrafted by artists to indirectly control smoke dynamics. Patch synthesis techniques transfer image textures or simulation features to a target flow field. However, these are either limited to adding structural patterns or augmenting coarse flows with turbulent structures, and hence cannot capture the full spectrum of different styles and semantically complex structures. In this paper, we propose the first Transport-based Neural Style Transfer (TNST) algorithm for volumetric smoke data. Our method is able to transfer features from natural images to smoke simulations, enabling general content-aware manipulations ranging from simple patterns to intricate motifs. The proposed algorithm is physically inspired, since it computes the density transport from a source input smoke to a desired target configuration. Our transport-based approach allows direct control over the divergence of the stylization velocity field by optimizing incompressible and irrotational potentials that transport smoke towards stylization. Temporal consistency is ensured by transporting and aligning subsequent stylized velocities, and 3D reconstructions are computed by seamlessly merging stylizations from different camera viewpoints.Comment: ACM Transaction on Graphics (SIGGRAPH ASIA 2019), additional materials: http://www.byungsoo.me/project/neural-flow-styl

Computational Fluid Dynamic Studies of Vortex Amplifier Design for the Nuclear Industry—I. Steady-State Conditions

In this study the effects of changes to the geometry of a vortex amplifier are investigated using computational fluid dynamics (CFD) techniques, in the context of glovebox operations for the nuclear industry. These investigations were required because of anomalous behavior identified when, for operational reasons, a long-established vortex amplifier design was reduced in scale. The aims were (i) to simulate both the anomalous back-flow into the glovebox through the vortex amplifier supply ports, and the precessing vortex core in the amplifier outlet, then (ii) to determine which of the various simulated geometries would best alleviate the supply port back-flow anomaly. Various changes to the geometry of the vortex amplifier were proposed; smoke and air tests were then used to identify a subset of these geometries for subsequent simulation using CFD techniques. Having verified the mesh resolution was sufficient to reproduce the required effects, the code was then validated by comparing the results of the steady-state simulations with the experimental data. The problem is challenging in terms of the range of geometrical and dynamic scales encountered, with consequent impact on mesh quality and turbulence modeling. The anomalous nonaxisymmetric reverse flow in the supply ports of the vortex amplifier has been captured and the mixing in both the chamber and the precessing vortex core has also been successfully reproduced. Finally, by simulating changes to the supply ports that could not be reproduced experimentally at an equivalent cost, the geometry most likely to alleviate the back-flow anomaly has been identified

A robot swarm assisting a human fire-fighter

Emergencies in industrial warehouses are a major concern for fire-fighters. The large dimensions, together with the development of dense smoke that drastically reduces visibility, represent major challenges. The GUARDIANS robot swarm is designed to assist fire-fighters in searching a large warehouse. In this paper we discuss the technology developed for a swarm of robots assisting fire-fighters. We explain the swarming algorithms that provide the functionality by which the robots react to and follow humans while no communication is required. Next we discuss the wireless communication system, which is a so-called mobile ad-hoc network. The communication network provides also the means to locate the robots and humans. Thus, the robot swarm is able to provide guidance information to the humans. Together with the fire-fighters we explored how the robot swarm should feed information back to the human fire-fighter. We have designed and experimented with interfaces for presenting swarm-based information to human beings

Wake dynamics and rotor-fuselage aerodynamic interactions

The unsteady loads experienced by a helicopter are known to be strongly influenced by aerodynamic interactions between the rotor and fuselage; these unsteady loads can lead to deficiencies in handling qualities and unacceptable vibratory characteristics of the rotorcraft. This work uses a vorticity-based computational model to study the governing processes that underpin this aerodynamic interaction and aims to provide greater understanding of the wake dynamics in the presence of a fuselage, as well as an appreciation of how the geometry of the wake affects the loading on the fuselage. The well-known experiments using NASA's ROBIN fuselage are used to assess the accuracy of the computations. Comparisons of calculations against results from smoke visualization experiments are used to demonstrate the ability of the model to reproduce accurately the geometry of the rotor wake, and comparisons with inflow data from the experiments show the method to capture well the velocity field near to the rotor. The fuselage model is able to predict accurately the unsteady fuselage loading that is induced by blade passage and also by the inviscid interaction between the main rotor wake and fuselage

Deep Fluids: A Generative Network for Parameterized Fluid Simulations

This paper presents a novel generative model to synthesize fluid simulations from a set of reduced parameters. A convolutional neural network is trained on a collection of discrete, parameterizable fluid simulation velocity fields. Due to the capability of deep learning architectures to learn representative features of the data, our generative model is able to accurately approximate the training data set, while providing plausible interpolated in-betweens. The proposed generative model is optimized for fluids by a novel loss function that guarantees divergence-free velocity fields at all times. In addition, we demonstrate that we can handle complex parameterizations in reduced spaces, and advance simulations in time by integrating in the latent space with a second network. Our method models a wide variety of fluid behaviors, thus enabling applications such as fast construction of simulations, interpolation of fluids with different parameters, time re-sampling, latent space simulations, and compression of fluid simulation data. Reconstructed velocity fields are generated up to 700x faster than re-simulating the data with the underlying CPU solver, while achieving compression rates of up to 1300x.Comment: Computer Graphics Forum (Proceedings of EUROGRAPHICS 2019), additional materials: http://www.byungsoo.me/project/deep-fluids

Multidisciplinary design and flight testing of a remote gas/particle airborne sensor system

The main objective of this paper is to describe the development of a remote sensing airborne air sampling system for Unmanned Aerial Systems (UAS) and provide the capability for the detection of particle and gas concentrations in real time over remote locations. The design of the air sampling methodology started by defining system architecture, and then by selecting and integrating each subsystem. A multifunctional air sampling instrument, with capability for simultaneous measurement of particle and gas concentrations was modified and integrated with ARCAA’s Flamingo UAS platform and communications protocols. As result of the integration process, a system capable of both real time geo-location monitoring and indexed-link sampling was obtained. Wind tunnel tests were conducted in order to evaluate the performance of the air sampling instrument in controlled nonstationary conditions at the typical operational velocities of the UAS platform. Once the remote fully operative air sampling system was obtained, the problem of mission design was analyzed through the simulation of different scenarios. Furthermore, flight tests of the complete air sampling system were then conducted to check the dynamic characteristics of the UAS with the air sampling system and to prove its capability to perform an air sampling mission following a specific flight path