Current Issue : January - March Volume : 2021 Issue Number : 1 Articles : 5 Articles
The emergence of the novel coronavirus has led to a global pandemic which\nhas led to the airline industry facing severe losses. For air travel to recover,\nairlines need to ensure safe air travel. In this paper, the authors have modeled\ndroplet dispersion after a single breath from an index patient........................................
This paper presents a novel method for motion planning of aerial long-reach manipulators that considers the aerodynamic effects\ngenerated by close surfaces in the trajectory generation process. The aerial manipulation system consists of a multirotor equipped\nwith a robotic long-reach arm that enables multidirectional inspection and also increases considerably the safety distance between\nthe rotors and the inspected elements. Since these systems operate in the proximity of elements that can modify significantly the\nrotorsâ?? airflow, the inclusion of Aerodynamics Awareness within the motion planning process is required to ensure robust\nobstacle avoidance. To this end, a proper characterisation of the aerodynamic effects based on both theoretical and experimental\nconsiderations has been derived. This characterisation is taken into account in the trajectory generation process to discard states\nwhose associated aerodynamic phenomena are not well compensated by the system controller and to explore alternatives that\nlead to the most efficient trajectories within the area of safe operation. Moreover, the motion planner also stands out for three\nother relevant features: the joint consideration of the multirotor and the robotic long-reach arm, the generation of efficient\ntrajectories in terms of energy consumption, and the Dynamics Awareness of the strong coupling between the aerial platform\nand the robotic arm. The resulting motion planner has been successfully tested in a simulated environment that faithfully\nreflects an application scenario strongly affected by aerodynamic effects: the inspection of bridges to find potential cracks in the\nsurface of pillars....
The design of the control systems of the inertially stabilized platforms (ISPs) as part of airborne equipment for the majority of\naircraft has its peculiarity. The presence of rate gyros in the inertial measurement unit gives the possibility to measure the\nrotation rate of the ISP base, which is the main disturbance interfering with the ISP accuracy. Inclusion of the feedforward\ndisturbance gain in the control law with the simplest PI feedback significantly improves the accuracy of stabilization by the\ninvariance theory. A combination of feedback and feedforward controllers produces a synergetic effect, thus, improving ISP\naccuracy. This article deals with the design of the airborne ISP control systems consisting of two stages: the parametric\noptimization of the PI feedback control based on composite â??performance-robustnessâ? criterion and the augmentation of the\nobtained system with feedforward gain. To prove the efficiency of the proposed control laws, the simulation of the ISP was\nundertaken. We have used a simulation of the heading-hold system of the commuter aircraft Beaver and the yaw rate output of\nthis closed-loop system we have used as a source of the disturbance. The results of modeling proved the efficiency of the\nproposed design method....
LOX/GCH4 pintle injector is suitable for variable-thrust liquid rocket engines. In order to provide a reference for the later\ndesign and experiments, three-dimensional numerical simulations with the Euler-Lagrange method were performed to study\nthe effect of the initial particle diameter on the combustion characteristics of a LOX/GCH4 pintle rocket engine. Numerical\nresults show that, as the momentum......................
In this study, a CO2 laser ignition experimental system was built to study the ignition process and characteristics of the Nitrate Ester\nPlasticized Polyether (NEPE) propellant. The effect of the energy density, ingredients, and the grain size distribution of the\npropellant on the ignition process was investigated using a CO2 laser igniter, a high-speed camera, and a tungsten-rhenium\nthermocouple. Four types of NEPE propellants were tested under different laser heat fluxes, and the ignition delay time, the\nignition temperature, and the ignition energy were obtained. Experimental results show that the ignition process of the NEPE\npropellant can be divided into three stages, namely the first-gasification stage, the first-flame stage, and the ignition delay stage.\nWhen the energy density is lower than the ignition energy threshold, the ignition process cannot be achieved even under\ncontinuous energy loading. The increase of the energy density can lead to the decrease of the ignition delay time but has little\neffect on the ignition temperature. The ingredients and grain size distribution have great effects on both the ignition delay time\nand the ignition temperature. The grain size effect of aluminum is the largest compared with that of Ammonium Perchlorate\n(AP) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), while the grain size effect of AP is larger than that of HMX....
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