Nonlinear flight control system with neural networks

In this study an adaptive critic based neural network controller is developed to obtain near optimal control laws for a nonlinear automatic flight control system. The adaptive critic approach consists of two neural networks. The first network, called the critic, captures the mapping between the states of a dynamical system and the co-states that arise in an optimal control problem. The second network, called the action network, maps the states of a system to the control. This study uses nonlinear aircraft models in the stall regions from a paper (Garrad and Jordan2 to develop optimal neural controllers for an aircraft; we then compare the results with singular perturbation based nonlinear controllers developed in the literature. The results show that with the neural controllers the aircraft can operate in a broader region of angles of attack beyond stall as compared to other linear and nonlinear controllers.University of Missouri-Roll

Development of an Emergency Radio Beacon for Small Unmanned Aerial Vehicles

Emergency locator transmitters (ELTs) used to locate manned aircrafts are not well suited to find and recover small crashed unmanned aerial vehicles (UAVs). ELTs utilize an international satellite system for search and rescue (Cospas-Sarsat System), which should leverage its expensive resources to save lives as a priority. Besides, ELTs are too big and heavy to be used within small UAVs. Some of the existing solutions for this problem are based on receivers that detect signal strength, which may be a long and tedious process not suitable for user needs. Others do not have enough range or require radio license and expensive amateur radio receivers. This paper presents an emergency radio beacon specifically designed to locate small UAVs. It is triggered automatically in the event of a crash and allows finding and recovering a crashed UAV in a fast and simple way. It meets not only the required specifications of user-friendliness, size and weight of this kind of application, but also it is a high precision and low cost device. Besides, it has enough range and endurance. The experiments carried out show the operation of the proposed system

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Nonlinear flight control using adaptive critic based neural networks

Ultimately the purpose of the nonlinear flight control system developed in this work is to pave the way for an adaptive reconfigurable nonlinear controller that would make aviation a safe way of transportation even in the presence of control failures and/or damaged aerodynamic surfaces. --Abstract, page iii

Three-time-scale nonlinear control of an autonomous helicopter on a platform

A three-time scale singular perturbation control is applied to an autonomous helicopter model on a platform to regulate its vertical position. Two singularly perturbation time-scale analysis approaches are presented, the Top-Down (TD), and the Bottom-Up (BU), which permit to analyze multi-time scale systems

Trajectory tracking for fixed-wing UAV using model predictive control and adaptive backstepping

This paper presents a two layer guidance and control system design for fixed-wing unmanned aerial vehicles (UAV). On the top level, the guidance system makes the airplane follows precomputed references using a novel iterative model predictive scheme, which can handle the nonlinear optimization problem by successive linearizations (starting the algorithm using a robust L1 navigation law which ensures the availability of the solution). The outputs of this algorithm are references in airspeed, flight path angle and bank angle, which are seek by the low level controller also presented in this paper. This controller uses an adaptive backstepping approach for the longitudinal dynamics, and a conventional integral-LQR controller for the lateral-directional dynamics. Simulations show good performances of the overall architecture

Development of GaN Technology-Based DC/DC Converter for Hybrid UAV

Wide band-gap (WBG) semiconductors technology represents a potential candidate to displace conventional silicon (Si) technology used in power electronics. Between Silicon Carbide (SiC) and Gallium Nitride (GaN) power semiconductors, the latter is the least mature of both technologies, with many open research problems, especially in the aerospace industry. In this paper, we address the design and implementation of a DC/DC converter for a hybrid small unmanned aerial vehicle (UAV) based on GaN technology. Both theoretical and simulation comparisons of Si, SiC and GaN transistors for the converter are presented. The conclusion is that GaN devices are the most appropriate to ful ll converter requirements for the size and weight limitations of the selected UAV. The paper presents a buck converter which handles an input voltage range of 32 V to 40 V and provides a 12 V regulated output and output power up to 60 W. The experimental results carried out on the prototype converter show how promising the GaN technology is for aerospace systems, not only regarding its volume and size, but also its ef ciency. Besides, practical implementation details are reported to contribute to the design of small, light and reliable GaN power converters for aeronautics.Ministerio de Ciencia, Innovación y Universidades RTI2018-101519-A-I0

Erratum to: Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition) (Autophagy, 12, 1, 1-222, 10.1080/15548627.2015.1100356

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