Control Law Design for Perching an Agile MAV with Articulated Wings

This paper explores the use of variable wing dihedral and variable wing twist (in conjunction with a conventional horizontal elevator) to control an aircraft performing a perching maneuver. A choice of controller architecture wherein the dihedral is employed in the forward path and the elevator and twist are employed in the feedback path, is considered. The aircraft is modeled as a multivariable linear time-varying system. A specific perching trajectory is considered; and the open-loop aircraft is longitudinally unstable for a segment of this perching trajectory and lateral-directionally unstable for the entire perching trajectory. A multivariable time-varying controller is designed to efficiently stabilize the aircraft as well as reject longitudinal-lateral-directional wind disturbances, while closely tracking the reference perching trajectory

Tracking early lung cancer metastatic dissemination in TRACERx using ctDNA

Circulating tumour DNA (ctDNA) can be used to detect and profile residual tumour cells persisting after curative intent therapy1. The study of large patient cohorts incorporating longitudinal plasma sampling and extended follow-up is required to determine the role of ctDNA as a phylogenetic biomarker of relapse in early-stage non-small-cell lung cancer (NSCLC). Here we developed ctDNA methods tracking a median of 200 mutations identified in resected NSCLC tissue across 1,069 plasma samples collected from 197 patients enrolled in the TRACERx study2. A lack of preoperative ctDNA detection distinguished biologically indolent lung adenocarcinoma with good clinical outcome. Postoperative plasma analyses were interpreted within the context of standard-of-care radiological surveillance and administration of cytotoxic adjuvant therapy. Landmark analyses of plasma samples collected within 120 days after surgery revealed ctDNA detection in 25% of patients, including 49% of all patients who experienced clinical relapse; 3 to 6 monthly ctDNA surveillance identified impending disease relapse in an additional 20% of landmark-negative patients. We developed a bioinformatic tool (ECLIPSE) for non-invasive tracking of subclonal architecture at low ctDNA levels. ECLIPSE identified patients with polyclonal metastatic dissemination, which was associated with a poor clinical outcome. By measuring subclone cancer cell fractions in preoperative plasma, we found that subclones seeding future metastases were significantly more expanded compared with non-metastatic subclones. Our findings will support (neo)adjuvant trial advances and provide insights into the process of metastatic dissemination using low-ctDNA-level liquid biopsy

Numerical optimization of the UAS-S4 Éhecatl airfoil using a morphing wing approach

In this paper, we describe the new methodology and the results obtained for multiple flight conditions optimization of the airfoil of the S4 unmanned aerial system, using a morphing wing approach. The goal of reducing the airfoil drag coefficient over a broad range of speeds and angles of attack has been achieved using an in-house optimization tool based on the relatively new Artificial Bee Colony algorithm, coupled with the Broyden-Fletcher-Goldfarb-Shanno algorithm to provide a final refinement of the solution. The obtained results were validated with an advanced, multi-objective, commercially available optimizing tool. The aerodynamic calculations were performed using a 2D linear panel method, coupled with an incompressible boundary layer model and a transition estimation criterion, to provide accurate estimations of the airfoil drag coefficient. For very small displacements of the airfoil surface, less than 2.5 mm, drag reductions of up to 14% have been achieved for a wide range of different flight conditions

A review of morphing aircraft

Aircraft wings are a compromise that allows the aircraft to fly at a range of flight conditions, but the performance at each condition is sub-optimal. The ability of a wing surface to change its geometry during flight has interested researchers and designers over the years as this reduces the design compromises required. Morphing is short for metamorphose: however, there is neither an exact definition nor an agreement between the researchers about the type or the extent of the geometrical changes necessary to qualify an aircraft for the title “shape morphing”. Geometrical parameters that can be affected by morphing solutions can be categorized into: planform alteration (span, sweep and chord), out-of-plane transformation (twist, dihedral/gull, spanwise bending) and airfoil adjustment (camber and thickness).Changing the wing shape or geometry is not new. Historically, morphing solutions always led to penalties in terms of cost, complexity or weight, although in certain circumstances these were overcome by system level benefits. The current trend for highly efficient and “green” aircraft makes such compromises less acceptable, calling for innovative morphing designs able to provide more benefits and fewer drawbacks. Recent developments in “smart” materials may overcome the limitations and enhance the benefits from existing design solutions. The challenge is to design a structure that is capable of withstanding the prescribed loads, but is also able to change its shape: ideally there should be no distinction between the structure and the actuation system. The blending of morphing and smart structures in an integrated approach requires multi-disciplinary thinking from the early development, which significantly increases the overall complexity, even at the preliminary design stage. Morphing is a promising enabling technology for future, next generation aircraft. However, manufacturers and end users are still too skeptical of the benefits to adopt morphing in the near future. Many developed concepts have a technology readiness level that is still very low. The recent explosive growth of satellite services means that UAVs are the technology of choice for many investigations on wing morphing.This paper presents a review of the state of the art on morphing aircraft and focuses on structural, shape changing morphing concepts for both fixed and rotary wings, with particular reference to active systems. Inflatable solutions have been not considered, and skin issues and challenges are not discussed in detail. Although many interesting concepts have been synthesized, few have progressed to wing tunnel testing, and even fewer have flown. Furthermore, any successful wing morphing system must overcome the weight penalty due to the additional actuation systems.<br/