In this study, overlapped biaxial and seamless twill carbon fiber pipes and vessels were manufactured. Steel pressure vessels were repaired with flexible twill and biaxial fabric. The pipes and vessels were subjected to hydrostatic pressure, ...

In situ resource utilization (ISRU) of lunar regolith is indispensable for the success of large-scale and long-term human lunar explosions at lower costs. Many new technologies must be developed to realize efficient ISRU. Because particle sorting ...

Control of the boundary layer upstream and in the region of the engine inlet is an important consideration for airplane designers. One important aspect of this problem can be seen in the performance analysis of submerged inlets for which the design is based on boundary layer ingestion. With a large offset between the flush entrance and the compressor face, these low drag concepts are suitable for stealth

Large eddy simulations (LES) were carried out to investigate the influence of surface roughness, which was applied to the inner walls of a cooling hole, on cooling performance and flow structures. The cooling hole was a 30-degree inclined, baseline 7-7-7 fan-shaped hole relative to a turbulent flat plate boundary layer of the mainstream. Numerical simulations were performed at two different blowing

In the commented paper, the authors considered a two-dimensional airfoil with nonlinear stiffness and damping, and derived the amplitude modulation equation (AME) of the system limit cycle oscillation around its bifurcation. Based on the variation equation of the AME, they conducted the stability analysis. Unfortunately, the obtained variation equation associated with the AME is incorrect.

Thanks to the recent advances in digital vision systems, a question might arise about where the full-field optical and contactless methods can bring modern design procedures. An answer lies on the methodologically detailed comparison of the results, processed from different full-field optical techniques, in exploring consistent and high-resolution maps of rotational and strain FRFs that is done through

The high functional performance exhibited by modern applications is very often established by an aggregation of various intricate mechanical mechanisms, providing the required motion dynamics to the overall system. Above all, the mechanism’s behavior should be reliable for a wide range of operating conditions to assure at all times appropriate functioning of the entire application. In particular, cam-follower

Many of today’s industrial applications are powered by electromechanical drives. Wind turbines, fuel based and hydroelectric generators or electric drivetrains are examples of these applications. Developing accurate models of these systems has attracted a significant interest in recent years, because it can help enormously to enhance their reliability and develop efficient maintenance strategies to

Bearing prognostics is an important aspect in condition-based maintenance (CBM), and a key step to successful prognostic methods is the ability to quantify the fault severity of the bearing. Previous studies have resulted in some severity assessment methods based on certain types of signals, such as vibration, acoustic emission (AE) and instantaneous angular speed (IAS), however, their performances

Abstract not available

External airborne installations of cylindrically-shaped objects, such as turrets, can lead to severe degradation of flight performance. This engineering challenge is mainly due to an unsteady and separated vortex flow field that evolves in the wake downstream of the turret. This study focuses on providing an engineering solution to attenuate the wake unsteadiness. Experiments were performed in the

Any space trajectories are subject to state uncertainty due to imperfect state knowledge, random disturbances, and partially known dynamical environments. Ideally, such uncertainty and associated risks must be properly quantified and taken into account in the process of trajectory design, ensuring a sufficiently low risk of causing hazardous events. To bridge the gap between the ideal goal and current

Journal of Guidance, Control, and Dynamics, Ahead of Print.

Electromagnetic formation flight (EMFF) uses the electromagnetic force to control the relative positions of multiple satellites without using conventional fuel-based propulsion. To compensate for the electromagnetic torque generated alongside the electromagnetic force, in most previous studies, all satellites were assumed to have reaction wheels (RWs) besides electromagnetic coils. However, the RW-loaded

Despite lacking scientific proof, thinking about extraterrestrials and extraterrestrial intelligence is part of our psychological reality. It is often stated that cultural and scientific reception and representation of these strange entities suffer from anthropocentric bias. To profoundly investigate such bias and the minds of extraterrestrials, we propose a revised definition for the psychological

The paper introduces a new method for ground-reaction forces (GRF) analysis for the evaluation of cosmonaut locomotor functions stability after a long-duration spaceflight (LDSF). The method is based on the analysis of GRF profiles obtained before and after LDSF by standard БД-2 treadmill reaction force data readings. Following probabilistic indicators were introduced: distributions of step and step-phase

For long-duration space missions to be successful, it is necessary to develop an understanding of the psychological factors that promote effective coping in isolated, confined, and extreme (ICE) environments. We evaluated relationships between Big Five personality traits and social functioning (liking one's teammates, social conflict, and social cohesion), anxiety and sad affect, well-being (health

A novel concept of a looped tether transportation system with multiple rungs (L-TTS-R) is proposed for highly efficient payload transfer in space. In addition to two huge platforms connected by two parallel tethers with multiple moving climbers, some rigid rungs are evenly distributed between the two tethers in L-TTS-R to suppress the libration movement of the system and to reduce or avoid the risk

One common sensor used for attitude determination in CubeSats is the cosine-type photodiode Sun sensor. By placing one on each of the six sides, it is possible to have full coverage of the surroundings and determine the direction to the Sun. One flaw is that it is not possible to discriminate between different light sources. As such the Earth's albedo can negatively influence the readings. After reviewing

The success of the launch mission depends on the dynamic characteristics of the rocket engine system, while the engine development process is based on the parameter sensitivity analysis. However, the dynamic characteristics and parameter sensitivity of the hydrogen-oxygen expansion cycle engine remain unclear. This research built the simulation model of basic components and overall system of the hydrogen-oxygen

The aerodynamic shape of the hypersonic forebody/inlet integrated vehicle is usually designed according to the inviscid flow. However, due to the effect of air viscosity, there is a boundary layer flow near the wall surface. In order to get the actual flow characteristics and performance parameters of the inviscid design vehicle close to the inviscid design values, the inviscid design surface must

The buzz, squeak, and rattle (BSR) problem is one of the most important issues affecting vehicle satisfaction related to unexpected noise and vibration and has been attracting increased attention because of the rise of electric and hybrid vehicles. However, until recently, the vehicle underbody BSR has not been studied as extensively as the upper-body or interior BSR owing to a number of complex issues

Honeycomb-core sandwich structures are commonly utilized as orbital debris shielding in unmanned satellites. This study investigated the effects of projectile shape on the ballistic performance of aluminum honeycomb-core sandwich panels subjected ...

In this paper, a passive fault tolerant attitude control is investigated for a nano-satellite with three magnetorquers and one reaction wheel in the presence of actuator constraints, external disturbances, and partial loss of actuator ...

Waverider is expected to break the lift-to-drag ratio constraint in the hypersonic flight condition and it is commonly been studied as the forebody of the cruise vehicle. In this paper, we developed an approach to make waverider as the airframe for the air-breathing cruise vehicle. The fuselage that designed based on the cone-derived waverider theory with a unique upper boundary curve generates the

This research article explores Urban Air Mobility (UAM) from a System of Systems (SoS) perspective in order to understand the impact of different fully electric UAM aircraft architectures on the overall SoS capability. For this purpose, a framework, combining aircraft design methods with an agent-based simulation, is developed. Thereby, not only different UAM aircraft architectures, but also fleet

For the purpose of improving the performance of trajectory tracking for quadrotors with the control input saturation, a novel model-free saturated prescribed performance reinforcement learning framework is proposed in the presence of the model uncertainties, nonlinearities and external disturbances. In this paper, saturation functions are employed to deal with input saturation, and the actuator's saturation

The ditching performance of a BWB aircraft is studied using the numerical method. The unsteady Reynolds-Averaged Navier-Stokes equations and the Realizable k−ε turbulence model are solved by the finite volume method, the implicit volume-of-fluid model is adopted to capture the water-air interface, the six-degree-of-freedom model is employed to couple fluid dynamics and aircraft rigid-body kinematics

This paper presents a Control Allocation formulation aimed at altering the dynamic transient response of an aircraft by exclusive means of the aerodynamic effectiveness of its control effectors. This is done, for a given Flight Control System architecture and, optionally, closed-loop performance, by exploiting the concept of Control Center of Pressure, i.e. the center of pressure due to only aerodynamic

The fuel injection system is a highly significant process in the design of the scramjet engine. In this paper, the presence of the upstream ramp edge on fuel distribution of jet flow at supersonic air stream of Mach = 4 is fully investigated. RANS equations are coupled with SST turbulence scheme to model the flow feature and diffusion of the fuel jet flow in attendance of angled ramp edge. The main

This paper proposes a numerical method to solve the two-target interception problem with a single impulse. Free impulse position and free interception position are considered. Both elliptic and hyperbolic transfers are analyzed. Under the two-body model, by using the Gibbs method for orbit determination from three position vectors, the problem is transformed into solving nonlinear equations of only

This paper presents two types of concatenated LDPC coding schemes which are viewed as generalized globally coupled ( GC ) LDPC coding schemes in which outer codes serve as the local codes for correcting local errors and inner codes serve as global coupling codes to correct global errors. The first type of concatenated LDPC coding scheme globally couples a finite geometry (FG) LDPC code as the local

Automated and coordinated vehicle platoon driving is challenging as the complexity of vehicle control and the presence of unreliable wireless inter-vehicle communication. This subject has an interdisciplinary nature, involving control theories, vehicle dynamics, and communication. Due to the constant interaction between control logic and communication topology, a co-design approach for the controller

Unmanned aerial vehicles (UAVs) have emerged as a promising candidate solution for data collection of large-scale wireless sensor networks (WSNs). In this paper, we investigate a UAV-aided WSN, where cluster heads (CHs) receive data from their member nodes, and a UAV is dispatched to collect data from CHs. We aim to minimize the total energy consumption of the UAV-WSN system in a complete round of

This paper describes a frequency-domain method for the identification of multi-input control equivalent turbulence input models. Such models can be identified from flight data gathered in specific turbulent environments, such as behind a ship or near a rooftop vertiport, and used to accurately simulate an aircraft’s response to turbulence. Identification of control equivalent turbulence input models

Considerable attention has been paid to the exploration of moon, especially the construction of lunar habitat. However, few studies are found working on the construction equipment being suitable for trans planetary transportation, assembly, and working in lunar environment. This paper proposed a novel cable-driven printer used to build lunar architecture. The pose measurement and control strategy of

Background Sustained high levels of astronaut cognitive performance are a prerequisite for mission success. A neuropsychological battery of 10 brief cognitive tests (Cognition) covering a range of cognitive domains was specifically developed for high performing astronauts to objectively assess cognitive performance. Extended mission durations require repeated cognitive testing and thus high acceptability

A surrogate-based optimization method is proposed in this paper to realize the optimization of the entire trajectory from launch to reentry. Different from traditional strategy of multiphase trajectory optimization that directly utilizes the original dynamical model, a surrogate model is substituted for the original time-consuming model to improve the iterative efficiency and decrease the computational

When lunar probes make a landing on the lunar surface, lunar-soil particles will be blown away by the engine plume with a significant collision phenomenon. The hard-sphere model, whose governing equations satisfy the momentum and kinetic-energy conservation equations, is used in research to study collision phenomena among particles having different diameters. The lunar-soil particles with different

Flow-induced vibration of the tube bundles in two-phase flow involves complicated interactions between the fluids and structures. Although a substantial number of studies have been devoted to investigating the flow-induced vibration and fluidelastic instability of the tube bundles subjected to two-phase cross-flow, the fatigue damage features of the tubes are not fully understood. In this paper, considering

We investigate the dynamics of the 3 DOF model of two self-excited pendula suspended on the oscillating beam. The research is focused on the analysis of possible multistability of the synchronous configurations. The regions of different behaviours (both unique, as well as the co-existing ones) are shown and the influence of the model’s parameters on their occurrence is studied. We exhibit, that the

Modeling uncertainty or modeling error has been widely recognized as one major challenge in structural model updating for structural identification and damage detection. It renders model updating inherently ineffective in converging to the real structural model because of the physical bias present in establishing the numerical model. This study aims to minimize the influence of modeling uncertainty

Active noise control (ANC) has been widely studied to eliminate low-frequency noise. However, efficiently controlling higher-order distortions of nonlinear primary and secondary path is still a major challenge. To address this, this paper proposes a novel nonlinear ANC algorithm based on the fast empirical wavelet transform and recursive Chebyshev nonlinear filter. In this method, the fast empirical

The vibration signal of the planetary gearbox shows complicated modulation sidebands no matter the gear is normal or fault. It leads to a challenge in the fault diagnosis, especially for the localized faults which stimulate resonance modulation phenomena. To reveal the resonance modulation mechanism of sun gear’s localized fault, the vibration signal model is built based on the convolution of transient

The classical random vibration theory has been well developed with broad applications, and the efficiency of analysis for random vibration has been improved by the pseudo-excitation method. However, random analysis for structural vibration under non-Gaussian excitation remains a substantial challenge. In this work, higher-order statistics for the response of the multiple-degree-of-freedom linear structure

Reducing rotor blade–vortex interaction (BVI) noise is a major challenge in rotorcraft research. This paper presents a high-resolution numerical study of the effects of blade surface blowing on BVI noise reduction. Using the improved fifth-order ...

Blade-vortex interaction (BVI) noise is a significant source of rotor noise. In recent years, active flap control (AFC) has been used successfully to control BVI by adding a trailing edge flap to the blade. However, due to the rotor’s complex ...

This paper investigates the safe coordination problem for a team of quadrotor unmanned air vehicles (UAVs) in the presence of model uncertainties and polygonal obstacles. Firstly, collision avoidance potential functions (PFs) related with both positions and velocities are utilized to construct the basic and bounded controller for achieving collision-free coordination. Then, in order to enhance the

Spacecraft attitude tracking control is a challenge for different space moving target observation tasks, especially when uncertainties exist. Traditional controllers have poor adaptability, and iterative learning controllers are time consuming. This paper focuses on the spacecraft attitude tracking control problem with uncertainties, including an unknown inertia matrix, desired attitude and desired

This study used large eddy simulation (LES) to investigate the control mechanism of a fluidic oscillator in the suppression of non-reattachment separation of a boundary layer from an ultra-high-lift, aft-loaded, low-pressure turbine under low Reynolds number. The internal flow characteristics of the fluidic oscillator were examined, with a focus on the influence mechanism of the pulse jet from the

Solar sails with the capability of generating a tangential radiation pressure at the sun-pointing attitude, such as refractive sails can provide more efficient methods for attitude and orbital control of sailcraft. This paper presents the concept of gradient-index sail as an advanced class of refractive sail, which operates by guiding the solar radiation through a structure made of graded refractive

Stable control of magnetically levitated rotors with a high gyroscopic effect is an important subject in the field of rotating machinery. This paper describes a method to address this problem using a cross-coupled control approach. In the low and middle speed range a constant diagonal controller and a speed dependent cross-coupled controller is used. In the high speed range the controller takes advantage

System quality requirements are typically formed by consideration of reliability and safety performance. Failures caused by system weakness, degradation or fatigue may cause undesired, and potentially dangerous, consequences. For various reasons, not all processes of system degradation are easily monitored in the lifecycle of a system. Degradation evolution leads to changes in both performance and

Large deformation analyses of structures are of great importance to the evaluation of structural performance under extreme environmental loads, but currently available methods are time-consuming because of the requirement of factorizing large-...

It is seemingly inevitable that one day humans will land on the surface of Mars. Between the Apollo lunar missions, International Space Station, and Martian rovers and landers, much of the technology required to transport astronauts to Mars ...

Plasma is considered as a potential method to promote the establishment of supersonic flame and has been investigated wildly. This paper provides the establishment process of flame with a plasma igniter (PI) in axisymmetric kerosene combustor under the conditions of Ma=3 and Tt=1680 K, and finds that proposes several typical modes of flameholding during the establishment process, as well as investigates

In this paper, we compare the characteristics of hovering stability for two insect-inspired flapping-wing micro air vehicles (FW-MAVs) with different strategies to generate control moments for the longitudinal and lateral attitude controls. The two robots were named according to their control mechanisms, i.e., the Stroke-Plane-Change (SPC), and the Trailing-Edge-Change (TEC). The forces and moments

Thermal Protection Materials (TPM) such as carbon/phenolic composites are used to protect spacecraft structures from extreme conditions. This protection is, in part, achieved by the decomposition via pyrolysis of the phenolic resin. Finite rate chemistry models are however still unable to predict the chemical production rates and composition of the pyrolysis products accurately. This is mostly due

Journal of Guidance, Control, and Dynamics, Ahead of Print.