Hasil untuk "Motor vehicles. Aeronautics. Astronautics"

Amir Hossein Baradaran

Predictive maintenance is a key strategy for ensuring the reliability and efficiency of industrial systems. This study investigates the use of supervised learning models to diagnose the condition of electric motors, categorizing them as "Healthy," "Needs Preventive Maintenance (PM)," or "Broken." Key features of motor operation were employed to train various machine learning algorithms, including Naive Bayes, Support Vector Machines (SVM), Regression models, Random Forest, k-Nearest Neighbors (k-NN), and Gradient Boosting techniques. The performance of these models was evaluated to identify the most effective classifier for predicting motor health. Results showed notable differences in accuracy among the models, with one emerging as the best-performing solution. This study underscores the practicality of using supervised learning for electric motor diagnostics, providing a foundation for efficient maintenance scheduling and minimizing unplanned downtimes in industrial applications.

Shantanu Rahman, Nayeb Hasin, Mainul Islam et al.

Autonomous vehicles are becoming popular day by day not only for autonomous road traversal but also for industrial automation, farming and military. Most of the standard vehicles follow the Ackermann style steering mechanism. This has become to de facto standard for large and long faring vehicles. The local planner of an autonomous vehicle controls the low-level vehicle movement upon which the vehicle will perform its motor actuation. In our work, we focus on autonomous vehicles in road and perform experiments to analyze the effect of low-level controllers in the simulation and a real environment. To increase the precision and stability of trajectory tracking in autonomous cars, a novel method that combines lane identification with Model Predictive Control (MPC) is presented. The research focuses on camera-equipped autonomous vehicles and uses methods like edge recognition, sliding window-based straight-line identification for lane line extraction, and dynamic region of interest (ROI) extraction. Next, to follow the identified lane line, an MPC built on a bicycle vehicle dynamics model is created. A single-lane road simulation model is built using ROS Gazebo and tested in order to verify the controller's performance. The root mean square error between the optimal tracking trajectory and the target trajectory was reduced by 27.65% in the simulation results, demonstrating the high robustness and flexibility of the developed controller.

Gang Lei, He Wang, Shaopeng Li

To attack a stationary target with both impact time and angle constraints, a guidance method is proposed based on trajectory tracking. According to the constraints of each stage of missile flight, a polynomial missile trajectory satisfying the impact time and angle is introduced, and the discrete kinematics equation of the missile flight process is established. In order to improve the tracking efficiency of the linear quadratic regulator, curvature feedback term and error feedback term are introduced into the weight matrix. The Savitzky–Golay filter is added to the output end, which weakens the chattering of guidance commands. Numerical simulation proves the effectiveness of the proposed guidance method.

Junlei Sun, Ye Zhou, Zhou Zhou et al.

This study focuses on a high-altitude long-endurance (HALE) joined-wing configuration UAV and completes a preliminary structural design based on aircraft design indices and the fundamental principles of aircraft structure design. Based on the preliminary structural design scheme and aerodynamic shape, a structural finite element model and a vortex lattice aerodynamic analysis model of the UAV are established, and the aerodynamic loads in typical states are obtained. The aerodynamic loads of the UAV are applied to a finite element model using the multipoint row method, and the structural static characteristics are obtained. The study further explores typical structural dynamic characteristics, including natural mode, static aeroelastic, flutter, and gust response characteristics. A comparison with the structural characteristics of a conventional configuration UAV with the same structural weight reveals that the HALE joined-wing configuration UAV exhibits significant advantages in structural stiffness, mode characteristics, flutter characteristics, and static aeroelastic characteristics, whereas the gust response characteristics are essentially equivalent to those of the conventional configuration. This superiority can be attributed to the reduced wingspan while providing the same lift and effective support effect of the rear wing on the front (Frt) wings, which enhances the structural stiffness of high-aspect-ratio HALE UAVs. This configuration is particularly suitable for deployment in high-subsonic HALE configurations that require close coordination with conventional tactical aircraft. By comparing with the structural characteristics of the conventional configuration UAV with equal structural weight, the paper comprehensively analyzes the structural characteristics of the HALE joined-wing configuration and obtains the advantages and disadvantages of applying the joined-wing configuration in HALE aircraft and defines the design direction, which lays a solid foundation for the engineering application in the next stage.

Peng Qiao, Jifei Wu, Hui Huang et al.

Pressure-sensitive paint (PSP) is an important wind tunnel testing technology. Compared with conventional PSP, the performance and test accuracy of cryogenic PSP are still immature. Therefore, investigating how to improve the pressure sensitivity of cryogenic PSP and reduce the interference of temperature effect is of great significance. By studying the PSP luminescence characteristics at different time points, temperatures, and pressures, some interesting phenomena have been discovered. When the temperature reaches 323 K, PSP can accelerate aging, leading to significant and irreversible changes in coating performance. Additionally, the effect of temperature on the luminescence characteristics of PSP shows significant differences over time. This unusual phenomenon may be related to the microstructure change in PTMSP (PtTFPP) coatings over time. In the beginning, PTMSP coating has high activity and spacing between PtTFPP luminescence centers, which change significantly with the microstructure as the temperature decreases. This might result in a stronger concentration quenching of PtTFPP, which counteracts the expected enhancement of luminescence efficiency typically caused by the temperature decrease. After 72 h, the microstructure of the coating tends to be stable, and the effect of temperature on the fluorescence characteristics of PSP becomes a thermal quenching law similar to that of traditional PSP. This discovery can provide a more precise basis for correcting the temperature effect for cryogenic PSP coatings with varying service lives.

Tian Bin, An Bingchen, Xie Kan, Yang Sulan

Electric propulsion technology has garnered significant attention due to its much higher specific impulse compared to traditional chemical propulsion. Currently, many mature on-orbit electric propulsion products have been developed worldwide. However, with the increasing demands of space missions, research in this field continues to advance. In recent years, the rapid development of artificial intelligence algorithms, such as machine learning and deep learning, has provided new approaches for the study of electric propulsion. These algorithms can not only train models based on data to optimize the performance of electric thrusters, but also analyze and solve the mathematical and physical models of plasmas within electric thrusters. By integrating machine learning and deep learning techniques, the accuracy and efficiency of solving related partial differential equations can be significantly improved, and optimal solutions for equation solving can be achieved. This paper summarizes the applications of artificial intelligence algorithms in the physical mechanism, equation solving, and model design of electric propulsion, with a particular focus on the research progress in ion thrusters, Hall thrusters, pulsed plasma thrusters, and helicon plasma thrusters. These studies not only demonstrate the great potential of artificial intelligence algorithms in enhancing the performance of electric propulsion systems, optimizing design, and reducing computational costs, but also provide new directions for the future development of electric propulsion technologies.

ZHANG Dengcheng, HE Yuting, LI Zhe et al.

The aerodynamic integrity of aircraft can comprehensively characterize the aerodynamic mass characteristics of aircraft during service（combat）use. However，there is currently no index that can comprehensively characterize the aerodynamic mass characteristics of aircraft. Therefore，the concept of aerodynamic integrity of military aircraft is first proposed and studied：during the operational use of military aircraft，the aerodynamic shape can be maintained intact，and the flight performance，quality，and control can meet and maintain the required attributes. The process and definition of the concept of aerodynamic integrity are introduced，and the basic connotation and basic characteristics are discussed. It is believed that the aerodynamic integrity of military aircraft is the basis of the combat effectiveness of aircraft. The characterization method of aircraft aerodynamic integrity is introduced，and the main influencing factors of military aircraft aerodynamic integrity are analyzed. The new concept of aerodynamic integrity of military aircraft is introduced aims to provide reference for the development of military aircraft design，manufacturing，testing and support in China.

Anton Novoshytskyi, Svitlana Bodu, Dmytro Fabritsyiev et al.

The improvement of heat exchange equipment is one of the key directions for increasing energy efficiency in industrial and energy systems. Technologies for manufacturing thin-walled heat exchange elements with a relief surface, which provides heat transfer intensification, are becoming particularly relevant. One of the promising solutions is the use of flat parts with spherical protrusions, the formation of which requires high accuracy and stability of geometric parameters. This study considers the technology of profiling such parts using the bending process with longitudinal tension. Unlike traditional forming methods, particularly stamping and drawing, the proposed approach reduces energy consumption, avoids residual deformations, and increases the repeatability of the profile geometry. The controlled tensile force imposed on the workpiece during the passage of the profiling rollers is a key technological factor. It has been experimentally established that the optimal result is achieved at a stress level of 85–95% of the yield strength of the material. It is in this range that a high-quality relief is formed without waviness in the zones of formation of spherical protrusions and on the edges, and the longitudinal curvature corresponds to the values 85–95% predicted by the tension correction. The design and principle of operation of the experimental equipment – the profiling unit is described, along with its technical characteristics and general appearance. The production of experimental batches of profiles on the experimental unit confirmed the possibility of manufacturing profiles with spherical protrusions by sequential local deformation under the action of longitudinal tension and clarified the technical requirements for the design of an experimental and industrial profiling unit. The proposed technology is confirmed by practical results and has the potential to be implemented in the serial production of heat exchange elements. It can be adapted to the manufacture of parts with various types of relief and used in related mechanical engineering industries, such as aviation, energy, and shipbuilding.

Fatemeh Delavari, Seyyed Mohammad Reza Hashemi Golpayegani, Mohammad Ali Ahmadi-Pajouh

Motor Imagery (MI) is gaining traction in both rehabilitation and sports settings, but its immediate influence on human postural control is not yet clearly understood. The focus of this study is to examine the effects of MI on the dynamics of the Center of Pressure (COP), a crucial metric for evaluating postural stability. In the experiment, thirty healthy young adults participated in four different scenarios: normal standing with both open and closed eyes, and kinesthetic motor imagery focused on mediolateral (ML) and anteroposterior (AP) sway movements. A mathematical model was developed to characterize the nonlinear dynamics of the COP and to assess the impact of MI on these dynamics. Our results show a statistically significant increase (p-value<0.05) in variables such as COP path length and Long-Range Correlation (LRC) during MI compared to the closed-eye and normal standing conditions. These observations align well with psycho-neuromuscular theory, which suggests that imagining a specific movement activates neural pathways, consequently affecting postural control. This study presents compelling evidence that motor imagery not only has a quantifiable impact on COP dynamics but also that changes in the Center of Pressure (COP) are directionally consistent with the imagined movements. This finding holds significant implications for the field of rehabilitation science, suggesting that motor imagery could be strategically utilized to induce targeted postural adjustments. Nonetheless, additional research is required to fully understand the complex mechanisms that underlie this relationship and to corroborate these results across a more diverse set of populations.

Nuno M. B. Matos, André C. Marta

Acquiring knowledge of aircraft flight dynamics is crucial for simulation, control, mission performance and safety assurance analysis. In the fast-paced UAV market, long flight testing campaigns are hard to achieve, leaving limited controlled flight data and a significant amount of unplanned flight data. This work delves into the application of system identification techniques on unplanned flight data when faced with a shortage of dedicated flight test data. Based on a medium-sized, fixed-wing UAV, it focuses on the system identification of longitudinal dynamics using structural routine flight test data of pitch down and pitch up manoeuvres with no specific guidelines for the control inputs given. The proposed solution uses first- and second-order parameter-based models to build a non-linear dynamic model which, using a least square error optimisation algorithm in a time domain formulation, has its parameters tuned to converge the model behaviour with the real aircraft dynamics. The optimisation uses a combination of pitch, altitude, airspeed and pitch rate responses as a measure of model accuracy. Very significant improvements regarding the UAV model response are found when trimmed flight manoeuvres are used, resulting in proper estimation of important aerodynamic and control derivatives. Pitching moment and control derivatives are shown to be the crucial parameters. However, difficulties in estimation are shown for untrimmed flight manoeuvres. Better results were obtained when using multiple manoeuvres simultaneously in the optimisation error metric, as opposed to single manoeuvres that led to system bias. The proposed system identification procedure can be applied to any fixed-wing UAV without the need for specific flight testing campaigns.

Gerard Derosiere

In this Habilitation Thesis, I synthesize 10 years of work on the role of the motor system in sensorimotor decision-making. First, a large part of the work we initially performed (2014-2020) questioned the functional role of the motor system in the integration of so-called decision variables such as the reward associated with different actions, the sensory evidence in favor of each action or the level of urgency in a given context. To this end, although the exact methodology may have varied, the approach exploited has been to study either the impact of a perturbation of the primary motor cortex (M1) on the integration of such decision variables in decision behavior, or the influence of these variables on changes in M1 activity during the decision. More recently (2020 - present), we have been investigating the neural origin of some of the changes in M1 activity observed during decision-making. To answer this question, a "perturbation-and-measurement" approach is exploited: the activity of a structure at a distance from M1 is perturbed, and the impact on the changes in M1 activity during decision-making is measured. The thesis ends up with a personal reflection on this paradigmatic evolution and discusses some key questions to be addressed in our field of research.

Fanxing Meng, Jing Xiao

This paper presents an innovative method for humanoid robots to acquire a comprehensive set of motor skills through reinforcement learning. The approach utilizes an achievement-triggered multi-path reward function rooted in developmental robotics principles, facilitating the robot to learn gross motor skills typically mastered by human infants within a single training phase. The proposed method outperforms standard reinforcement learning techniques in success rates and learning speed within a simulation environment. By leveraging the principles of self-discovery and exploration integral to infant learning, this method holds the potential to significantly advance humanoid robot motor skill acquisition.

Li Jin, Qinzhi Fang, Xingwei Yan et al.

The purpose of this work is to study the effects of different loading rate ratios and loading speeds on the biaxial tension of hydroxyl-terminated polybutadiene (HTPB) solid propellant. A proper kind of biaxial tensile specimen with which the stresses in its central part can be obtained with the loads acted on each loading direction is designed and used in the study, and the strains in its central parts are obtained with the digital image correlation (DIC) method. The stress and strain relationship at each direction can be obtained by experiments. The uniaxial stress vs. strain curves and the biaxial stress vs. strain curves were obtained, and it was found that the loading speed remarkably influenced the biaxial tensile behaviors of HTPB propellant. The Mises equivalent stress and strain could be used to describe the biaxial tension stress and strain state, and the exponential constitutive model obtained in the study could be used to predict the stress vs. strain curve under different test conditions.

Jian Liu, Mengyao Xu, Wenxiong Xi

To protect turbine endwall from heat damage of hot exhaust gas, film cooling is the most significant method. The complex vortex structures on the endwall, such as the development of horseshoe vortices and transverse flow, affects cooling coverage on the endwall. In this study, the effects of gas thermophysical properties on full-range endwall film cooling of a turbine vane are investigated. Three kinds of gas thermophysical properties models are considered, i.e., the constant property gas model, ideal gas model, and real gas model, with six full-range endwall film cooling holes patterns based on different distribution principles. From the results, when gas thermophysical properties are considered, the coolant coverage in the pressure side (PS)-vane junction region is improved in Pattern B, Pattern D, Pattern E, and Pattern F, which are respectively designed based on the passage middle gap, limiting streamlines, heat transfer coefficients (HTCs), and four-holes pattern. Endwall <i>η</i> distribution is mainly determined by relative ratio of ejecting velocity and density of the hot gas and the coolant. For the cooling holes on the endwall with an injection angle of 30°, the density ratio is more dominant in determining the coolant coverage. At the injection angle of 45°, i.e., the slot region, the ejecting velocity is more dominant in determining the coolant coverage. When the ejecting velocity Is large enough from the slot, the coolant coverage on the downstream endwall region is also improved.

Mubashar Sarfraz, Muhammad Farhan Sohail, Sheraz Alam et al.

Unmanned air vehicle communication (UAV) systems have recently emerged as a quick, low-cost, and adaptable solution to numerous challenges in the next-generation wireless network. In particular, UAV systems have shown to be very useful in wireless communication applications with sudden traffic demands, network recovery, aerial relays, and edge computing. Meanwhile, non-orthogonal multiple access (NOMA) has been able to maximize the number of served users with the highest traffic capacity for future aerial systems in the literature. However, the study of joint optimization of UAV altitude, user pairing, and power allocation for the problem of capacity maximization requires further investigation. Thus, a capacity optimization problem for the NOMA aerial system is evaluated in this paper, considering the combination of convex and heuristic optimization techniques. The proposed algorithm is evaluated by using multiple heuristic techniques and deployment scenarios. The results prove the efficiency of the proposed NOMA scheme in comparison to the benchmark technique of orthogonal multiple access (OMA). Moreover, a comparative analysis of heuristic techniques for capacity optimization is also presented.

Anne Steenbeek, Francesco Nex

Unmanned Aerial Vehicles (UAVs) for 3D indoor mapping applications are often equipped with bulky and expensive sensors, such as LIDAR (Light Detection and Ranging) or depth cameras. The same task could be also performed by inexpensive RGB cameras installed on light and small platforms that are more agile to move in confined spaces, such as during emergencies. However, this task is still challenging because of the absence of a GNSS (Global Navigation Satellite System) signal that limits the localization (and scaling) of the UAV. The reduced density of points in feature-based monocular SLAM (Simultaneous Localization and Mapping) then limits the completeness of the delivered maps. In this paper, the real-time capabilities of a commercial, inexpensive UAV (DJI Tello) for indoor mapping are investigated. The work aims to assess its suitability for quick mapping in emergency conditions to support First Responders (FR) during rescue operations in collapsed buildings. The proposed solution only uses images in input and integrates SLAM and CNN-based (Convolutional Neural Networks) Single Image Depth Estimation (SIDE) algorithms to densify and scale the data and to deliver a map of the environment suitable for real-time exploration. The implemented algorithms, the training strategy of the network, and the first tests on the main elements of the proposed methodology are reported in detail. The results achieved in real indoor environments are also presented, demonstrating performances that are compatible with FRs’ requirements to explore indoor volumes before entering the building.

Ryota Takaki, Mauro L. Mugnai, D. Thirumalai

Molecular motors belonging to the kinesin and myosin super family hydrolyze ATP by cycling through a sequence of chemical states. These cytoplasmic motors are dimers made up of two linked identical monomeric globular proteins. Fueled by the free energy generated by ATP hydrolysis, the motors walk on polar tracks (microtubule or filamentous actin) processively, which means that only one head detaches and executes a mechanical step while the other stays bound to the track. Thus, the one motor head must regulate chemical state of the other, referred to as "gating", a concept that is not fully understood. Inspired by experiments, showing that only a fraction of the energy from ATP hydrolysis is used to advance the kinesin motors against load, we demonstrate that additional energy is used for coordinating the chemical cycles of the two heads in the dimer - a feature that characterizes gating. To this end, we develop a general framework based on information theory and stochastic thermodynamics, and establish that gating could be quantified in terms of information flow between the motor heads. Applications of the theory to kinesin-1 and Myosin V show that information flow occurs, with positive cooperativity, at external resistive loads that are less than a critical value, $F_c$. When force exceeds $F_c$, effective information flow ceases. Interestingly, $F_c$, which is independent of the input energy generated through ATP hydrolysis, coincides with force at which the probability of backward steps starts to increase. Our findings suggest that transport efficiency is optimal only at forces less than $F_c$, which implies that these motors must operate at low loads under $\textit{in vivo}$ conditions.

Louis Annabi, Alexandre Pitti, Mathias Quoy

In this work, we build upon the Active Inference (AIF) and Predictive Coding (PC) frameworks to propose a neural architecture comprising a generative model for sensory prediction, and a distinct generative model for motor trajectories. We highlight how sequences of sensory predictions can act as rails guiding learning, control and online adaptation of motor trajectories. We furthermore inquire the effects of bidirectional interactions between the motor and the visual modules. The architecture is tested on the control of a simulated robotic arm learning to reproduce handwritten letters.

GONG Junjun, FU Wei, ZUO Yuanhao et al.

The similar scale model experiment can provide some reference for the research and development of naval gun weapons. This paper takes the naval gun bracket as an example to explain. Based on the dimensional analysis, equation analysis and finite element method, the modal parameter similarity relationship between the original model for bracket and the shrinkage ratio model is established. The results show that the error of predicting the natural frequency of the original model based on similarity relation is less than 2% comparing with the results of finite element numerical simulation, and the error is less than 10% comparing with the experimental results, and the mode of shrinkage model is close to that of the original model. It is proved that the theoretical method in this paper is feasible and practical in engineering. Therefore, the vibration characteristics of the original model can be estimated by analyzing the vibration characteristics of the carrier shrinkage ratio model, which provides a reference for ship gun designers.

MA Liqun, YANG Shibin, SHI Linxuan

The advanced fly-by-wire flight control system can greatly improve the maneuverability and stability of civil helicopters, but this novel design also brings huge challenges to safety assessment.Traditional airworthiness standards may not fully cover the design features of fly-by-wire flight control helicopters, and corresponding special conditions need to be formulated to determine whether the helicopter design meets the airworthiness requirements.T his article focuses on the five special conditions of civil helicopter fly-by-wire system:interaction of systems and structure, control authority perception, crew alerting system, integrity of command signal and flight envelope protection.First, the technical content of the conditions is given, and then the background and significance of the formulation of the terms are explained.The existing compliance methods and verification technology are given, and the key technical problems of helicopter fly by wire flight control in the process of model demonstration and design are put forward.T he results can provide a certain reference for the airworthiness design and certification of civil helicopters.