Team NimbRo at MBZIRC 2017: Fast landing on a moving target and treasure hunting with a team of micro aerial vehicles

The Mohamed Bin Zayed International Robotics Challenge (MBZIRC) 2017 has defined ambitious new benchmarks to advance the state‐of‐the‐art in autonomous operation of ground‐based and flying robots. This study covers our approaches to solve the two challenges that involved micro aerial vehicles (MAV). Challenge 1 required reliable target perception, fast trajectory planning, and stable control of an MAV to land on a moving vehicle. Challenge 3 demanded a team of MAVs to perform a search and transportation task, coined “Treasure Hunt,” which required mission planning and multirobot coordination as well as adaptive control to account for the additional object weight. We describe our base MAV setup and the challenge‐specific extensions, cover the camera‐based perception, explain control and trajectory‐planning in detail, and elaborate on mission planning and team coordination. We evaluated our systems in simulation as well as with real‐robot experiments during the competition in Abu Dhabi. With our system, we—as part of the larger team NimbRo—won the MBZIRC Grand Challenge and achieved a third place in both subchallenges involving flying robots.     

Thermal response to firefighting activities in residential structure fires: impact of job assignment and suppression tactic

Firefighters’ thermal burden is generally attributed to high heat loads from the fire and metabolic heat generation, which may vary between job assignments and suppression tactic employed. Utilising a full-sized residential structure, firefighters were deployed in six job assignments utilising two attack tactics (1. Water applied from the interior, or 2. Exterior water application before transitioning to the interior). Environmental temperatures decreased after water application, but more rapidly with transitional attack. Local ambient temperatures for inside operation firefighters were higher than other positions (average ~10–30 °C). Rapid elevations in skin temperature were found for all job assignments other than outside command. Neck skin temperatures for inside attack firefighters were ~0.5 °C lower when the transitional tactic was employed. Significantly higher core temperatures were measured for the outside ventilation and overhaul positions than the inside positions (~0.6–0.9 °C). Firefighters working at all fireground positions must be monitored and relieved based on intensity and duration.

Practitioner Summary: Testing was done to characterise the thermal burden experienced by firefighters in different job assignments who responded to controlled residential fires (with typical furnishings) using two tactics. Ambient, skin and core temperatures varied based on job assignment and tactic employed, with rapid elevations in core temperature in many roles.     

Investigation of Lipid Oxidation in High- and Low-Lipid-Containing Topical Skin Formulations

Lipid oxidation can impact the odour of skin care products during storage. A study was conducted to identify and monitor representative markers for lipid oxidation in skin care products over time. Four lip care formulations and three skin care formulations with different lipid contents were stored at various cosmetic industry‐relevant conditions for 84 days. The skin care products were analysed for lipid hydroperoxides and secondary volatile oxidation products. A trained sensory panel performed an odour difference (triangle) test and odour‐profiled the products to detect and describe odour changes during storage. Several potential markers for lipid oxidation were identified. In skin care formulations, peroxide value (PV) analysis was a useful marker for lipid oxidation if the product was exposed to light during storage, but no clear changes were observed for PV in samples stored under other conditions. Furthermore, concentrations of several secondary volatile oxidation products increased during storage, and the highest increase was observed for products exposed to light. Pentanal and heptanal were found to be reliable markers for secondary volatile oxidation products in the skin care formulations (especially during exposure to light), whereas in the lip care formulations the best candidates were pentanal (especially during exposure to light and iron), 2‐methyl furan and 3‐methyl‐3‐buten‐2‐one (especially during exposure to light, iron and high temperatures).     

Estimating the residual fatigue lifetimes of impact‐damaged composites using thermoelastic stress analysis

A new experimental method is presented for quantifying impact damage and estimating the remaining fatigue lifetime of impact damaged polymer matrix composite materials. The procedure is demonstrated using composites of glass fiber reinforced polyurethane produced by injection molding and structural reaction injection molding. Thermoelastic stress analysis (TSA) was used to quantify the stress concentration associated with impact‐damage in test samples of each composite. Following impact and TSA imaging, the samples were fatigued to failure over a range of stress amplitudes. The TSA‐derived stress concentration factors were used to determine a modified stress amplitude that collapsed the impact‐fatigue data onto a master stress‐life curve. This approach provides a quantitative measure of impact damage and a practical methodology for estimating the residual fatigue lifetime of impact; damaged composites.     

Use of femtosecond laser-induced breakdown spectroscopy (fs-LIBS) for micro-crack analysis on the surface

It is well-known that the initiation and propagation behaviour of small cracks is strongly influenced by the microstructure. In addition to the visible structure on the surface, in-depth information is essential for the evaluation of influencing factors. Investigations on micro-crack behaviour have been performed with intermetallic γ-based TiAl. Starter notches facilitate systematic studies as cracks initiate from notch tips. In this case artificial notches in the scale less than colony dimensions were prepared by femtosecond pulsed laser radiation, which causes no significant damage. After multistage tensile compression tests under increasing load, several small cracks were generated and analyzed in the SEM. Using femtosecond laser-induced breakdown spectroscopy (fs-LIBS) it was possible to analyze spectrochemically the surrounding microstructure of these micro-cracks and their propagation on the surface.     

Natural gas vehicles: An option for Europe

In Europe natural gas vehicles play a minor role. A decisive reason for this is the dependence of most European countries from gas imports. Except for Italy, there is no tradition to use natural gas as fuel. In addition, there is a lack of infrastructure (e.g. fuelling stations). In contrast to Europe, in Latin American and Asian countries natural gas vehicles are widespread. Some countries foster natural gas vehicles because they have own gas resources. Many countries must reduce the high air pollution in big cities. Environmental reasons are the main motive for the use of natural gas vehicles in Europe. In last years, high oil prices stimulated the use of natural gas as fuel. European governments have developed incentives (e.g. tax reductions) to foster natural gas vehicles. However, the focus is on hybrid technology and the electric car, which, however, need further technical improvement. In contrast, the use of natural gas in conventional engines is technically mature. Additional gas imports can be avoided by further improvements of energy efficiency and the use of renewable energy. In sum, the market penetration of natural gas as fuel should be promoted in Europe.