Safe Low-Altitude Navigation in Steep Terrain with Fixed-Wing Aerial Vehicles

Fixed-wing aerial vehicles provide an efficient way to navigate long distances or cover large areas for environmental monitoring applications. By design, they also require large open spaces due to limited maneuverability. However, strict regulatory and safety altitude limits constrain the available space. Especially in complex, confined, or steep terrain, ensuring the vehicle does not enter an inevitable collision state(ICS) can be challenging. In this work, we propose a strategy to find safe paths that do not enter an ICS while navigating within tight altitude constraints. The method uses periodic paths to efficiently classify ICSs. A sampling-based planner creates collision-free and kinematically feasible paths that begin and end in safe periodic (circular) paths. We show that, in realistic terrain, using circular periodic paths can simplify the goal selection process by making it yaw agnostic and constraining yaw. We demonstrate our approach by dynamically planning safe paths in real-time while navigating steep terrain on a flight test in complex alpine terrain.Comment: Accepted to IEEE Robotics and Automation Letters (RA-L

The Use of a Stringent Selection System Allows the Identification of DNA Elements that Augment Gene Expression

The use of high stringency selection systems often results in the induction of very few recombinant mammalian cell lines, which limits the ability to isolate a cell line with favorable characteristics. The employment of for instance STAR elements in DNA constructs elevates the induced number of colonies and also the protein expression levels in these colonies. Here, we describe a method to systematically identify genomic DNA elements that are able to induce many stably transfected mammalian cell lines. We isolated genomic DNA fragments upstream from the human Rb1 and p73 gene loci and cloned them around an expression cassette that contains a very stringent selection marker. Due to the stringency of the selection marker, hardly any colony survives without flanking DNA elements. We tested fourteen ~3500 bp DNA stretches from the Rb1 and p73 loci. Only two ~3500 bp long DNA fragments, called Rb1E and Rb1F, induced many colonies in the context of the stringent selection system and these colonies displayed high protein expression levels. Functional analysis showed that the Rb1 DNA fragments contained no enhancer, promoter, or STAR activity. Our data show the potential of a methodology to identify novel gene expression augmenting DNA elements in an unbiased manner

Safe Low-Altitude Navigation in Steep Terrain With Fixed-Wing Aerial Vehicles

ISSN:2377-376

Circling Back: Dubins set Classification Revisited

Dubins paths are commonly used in robot motion planning for generating minimal-length fixed-curvature motions between two states. Existing analytical approaches generate the Dubins set - the set of paths consisting of different sequences of arcs and straight lines that contains the optimal solution for travelling between a state pair. Typically, the length for each path in the set is evaluated and the shortest path is selected. Dubins set classification approaches use an additional pre-calculation phase to further reduce the Dubins set before evaluating path length. This can significantly reduce computational costs, especially for sampling based planners in the Dubins space that perform many path length evaluations during a search. This paper addresses the issue of degenerate solutions from the Dubins set classification method presented in~\cite{shkel_classication_2001} when solving for a shortest path using Dubins paths. The results show that a Dubins set classification approach can result in 58$\%$ reduced computation time for computing a Dubins path but still return the optimal path when compared to evaluating the full Dubins set

Fisher Information Based Active Planning for Aerial Photogrammetry

Small uncrewed aerial systems (sUASs) are useful tools for 3D reconstruction due to their speed, ease of use, and ability to access high-utility viewpoints. Today, most aerial survey approaches generate a preplanned coverage pattern assuming a planar target region. However, this is inefficient since it results in superfluous overlap and suboptimal viewing angles and does not utilize the entire flight envelope. In this work, we propose active path planning for photogrammetric reconstruction. Our main contribution is a view utility function based on Fisher information approximating the offline recon struction uncertainty. The metric enables online path planning to make in-flight decisions to collect geometrically informative image data in complex terrain. We evaluate our approach in a photorealistic simulation. A viewpoint selection study shows that our metric leads to faster and more precise reconstruction than state-of-the-art active planning metrics and adapts to different camera resolutions. Comparing our online planning approach to an ordinary fixed-wing aerial survey yields 3.2 × faster coverage of 16 ha undulated terrain without sacrificing precision

Flying Robotic Workers: High-precision Aerial Physical Interaction

We present our research in aerial robotics and 3D mapping at the Swiss Robotics Day 2022 in Lausanne, Switzerland. This includes a booth open to researchers and the general public and demos where we show contact-based inspection