Journal of Le Quy Don Technical University
DESIGN AN ADAPTIVE FINITE TIME CONTROLLER FOR INTEGRATED GUIDANCE CONTROL SYSTEMS BY USING FINITE DISTURBANCE OBSERVER AND BACKSTEPPING TECHNIQUE
A novel control synthesis approach for Integrated guidance and control (IGC) systems in aerial vehicle (AV), based on Finite-time backstepping (FTB) combined with a Finite-time disturbance observer (FTDO) is proposed. Comparing to the conventional backstepping methods ensuring asymptotic convergence, the proposed approach guarantees finite-time convergence and significantly improves disturbance rejection capability. The controller is designed in a strict-feedback structure containing layers employing nonlinear control laws to satisfy Lyapunov stability conditions. Individual FTDOs are constructed for each state equation to accurately estimate the lumped disturbances and enhance compensation performance. Simulation results show that the proposed method shortens transient response time, reduces control errors, and ensures accurate target tracking even under strong disturbance conditions.
AERODYNAMIC INTERFERENCE CHARACTERISTICS OF BUSEMANN BIPLANE AIRFOIL WITH SLAT AND FLAP IN LOW-SPEED FLOW
In this study, aerodynamic interference characteristics of a Busemann biplane incorporating both leading-edge slats and trailing-edge flaps are investigated, utilizing wind tunnel experiments and numerical simulations. The aerodynamic characteristics of the biplane configuration are assessed through a comparative analysis with the performances of its individual upper and lower wings when operating as single configurations. The deflections of the slat and flap are 15° and 30°, respectively. Stall occurred on both the upper and lower wings in the single configuration. The addition of the leading-edge slat enabled the single model to stall at a larger angle of attack, consequently leading to a higher maximum lift coefficient. In the biplane configuration with slat and flap, the lower wing did not experience stall, and its lift coefficient increased with the angle of attack, similar to the case with only trailing-edge flaps. The drag interference ratio was observed to exceed 1.0 at angles of attack below 5° for the biplane with only a trailing-edge flap and below 12° for the configuration including both a slat and a flap. This finding implies that, within these ranges, the biplane generated a higher total drag compared to the sum of the individual drag values of each element in a single-element configuration. The lift interference ratio exhibited a minimum value of 0.72 at 16° for the biplane with both slat and flap.
EFFECT OF VIBRATIONS ON THE DYNAMICS OF THE RING RESONATOR MICROMECHANICAL GYROSCOPE
This article examines the dynamics of a micromechanical gyroscope with a ring resonator, used in navigation and motion control systems. The gyroscope’s sensitive element consists of a thin elastic ring resonator supported by an elastic suspension, detecting small bending vibrations to measure angular motion. The study investigates the impact of external vibrations on the resonator’s mechanical design. A mathematical model is developed using the Hamilton-Ostrogradsky variational principle and the Bubnov-Galerkin projection method to analyze the system’s multimodal oscillations. Results show that vibrations mainly affect the first vibrational mode, with maximum deformation of the resonator is proportional to the magnitude of the peak impact acceleration and inversely proportional to the square of the lowest natural frequency in the first natural mode of oscillation. The second vibrational mode remains unaffected under normal conditions. Additionally, manufacturing errors can cause symmetry violations, impacting measurement accuracy. This study provides insights into improving ring resonator micromechanical gyroscope design for enhanced reliability under dynamic external vibrations.
ALGEBRAIC INTEGRAL BARRIER LYAPUNOV-BASED EVENT-TRIGGERED NONSMOOTH CONTROL FOR N-DOF ROBOTIC MANIPULATORS UNDER NON-LIPSCHITZ UNCERTAINTIES
This study aims to develop a robust control framework for robotic manipulators operating under non-Lipschitz uncertainties and strict state constraints. A novel Algebraic Integral Barrier Lyapunov-Based Event-Triggered Nonsmooth Control (AIBET-NSC) strategy is proposed to achieve fixed-time convergence while minimizing control effort. The method integrates four key components: (i) an algebraic integral observer for noise-resilient state estimation, (ii) a barrier Lyapunov function to strictly enforce joint constraints, (iii) a nonsmooth sliding-mode-based term for fixed-time stability, and (iv) an event-triggered mechanism to reduce control updates. Theoretical analysis proves global fixed-time stability and Zeno-free triggering. Simulation results on a 2-DOF robotic manipulator demonstrate that, compared with conventional sliding mode control, the proposed AIBET-NSC achieves 35-40% lower control torque oscillation, 28% faster settling time, and over 50% fewer control updates, while maintaining accurate trajectory tracking. These results verify the controller’s strong robustness, chattering suppression, and practical feasibility. The proposed framework provides both theoretical and practical contributions toward efficient and constraint-safe control of robotic manipulators under complex uncertain environments.
LONGITUDINAL FLYING QUALITY ANALYSIS FOR A SMALL FIXED-WING UAV MODEL
This article presents a detailed analysis of the longitudinal flying qualities of a small fixed-wing unmanned aerial vehicle (UAV). The UAV model is developed using MATLAB/Simulink, supported by the Aerospace Blockset for six-degree-of-freedom dynamic modeling. Aerodynamic coefficients are obtained from Digital DATCOM based on the UAV’s geometry and operating conditions. A trimmed flight state is determined, and the nonlinear model is linearized to extract longitudinal dynamics. The short-period and phugoid modes are analyzed according to MIL-STD-1797A criteria. Results indicate that the UAV meets Level 1 requirements for both modes, with the short-period damping ratio near the lower limit and the natural frequency well above the minimum threshold. These findings clarify the UAV’s inherent dynamic behavior and provide a foundation for future control system development and flight performance optimization.
ENHANCED SEPIC CONVERTER REDUCES CURRENT STRESS ON SWITCHING DEVICES AND DIODES WHILE MAINTAINING HIGH EFFICIENCY
This article presents an innovative DC buck-boost converter design that mitigates the excessive switching current stress inherent in SEPIC converters. The study highlights a significant reduction in current strain on switching devices and diodes during transitions. A thorough steady-state analysis has been conducted, encompassing voltage conversion ratios, power dissipation, and voltage stress on key switching components. Simulation and theoretical evaluations in buck and boost modes demonstrate that the proposed converter achieves exceptionally low source current overshoot across switches S1, S2, D1, and D2, even when the conversion ratio varies from 0.2 to 2. Compared to SEPIC and other analyzed topologies, this converter delivers superior efficiency with substantially lower power losses. Furthermore, experimental validation, considering the impact of parasitic resistances, confirms that this design outperforms existing solutions by maximizing efficiency, enhancing reliability, minimizing energy dissipation, and extending operational lifespan, making it an optimal choice for power electronics applications. Moreover, experiments with nonlinear load currents were conducted further to validate the superior performance of the proposed converter.
EXPERIMENTAL STUDY AND IMAGE PROCESSING-BASED MEASUREMENT OF SPRAY BREAKUP LENGTH IN MICROTURBINE VAPORIZER TUBES
Measuring spray breakup length is a critical requirement for optimizing vaporizer tube design in microturbines. High-speed photography is a widely used modern measurement technique; however, its application in vaporizer tubes requires accurate image processing algorithms to account for light refraction through quartz tube walls and noise from fuel density variations. This study develops an algorithm that combines adaptive thresholding with Sobel edge detection, optimized for the vaporizer tube environment. Experiments were conducted at injection pressures ranging from 1.38 to 4.14 bar, with more than 4000 images analyzed per condition to ensure statistical reliability. The results show that breakup length increases from 3.2 mm to 6.8 mm as injection pressure rises, with clear periodic oscillations observed. The algorithm achieves an accuracy of ±0.01 mm with full automation, providing an effective tool for research on vaporizer tube optimization in microturbines.
DEVELOPMENT OF A FORCE CONTROL SOLUTION FOR SINGLE-CHANNEL AERIAL VEHICLES WITH A LINEAR ACTUATOR
This paper presents the development of a mathematical foundation for synthesizing control commands and constructing the control force diagram for single-channel flying equipment (SCFV) equipped with linear actuators. A solution is proposed to enhance the control command gain for SCFV using linear actuators, along with a mathematical proof of its validity. The control force utilization coefficient can exceed 0.5 when the input control signal supplied to the actuator is shaped as a sinusoidal function with amplitude limitation. The research results extend existing domestic academic works and provide a foundational basis for the synthesis of autonomous flight control systems.
PROPOSE A HYBRID TRAINING METHOD FOR SPIKING NEURAL NETWORKS TO IMPROVE THE ACCURACY IN IDENTIFYING THE AERODYNAMIC COEFFICIENTS OF AN AIRCRAFT
This paper proposes a hybrid training method for spiking neural networks to identify the aerodynamic coefficients of an aircraft in the attitude channel using a nonlinear model. The proposed training method combines the backpropagation algorithm with adaptive decay time and the normalized spiking error backpropagation algorithm. This combination leverages the strengths of both algorithms in updating decay times and synaptic weights. As a result, it reduces training time and enhances stability during error reduction, thereby improving the accuracy and reliability of the identified aerodynamic parameters. Simulation results show that the aerodynamic coefficients in the aircraft’s pitch channel identified using the proposed method are more accurate than those obtained with traditional methods, and the network achieves faster convergence compared to using each training method individually. Additionally, the bootstrapping technique is used to determine the confidence interval for the aerodynamic parameters. The confidence interval indicates that the proposed method yields more reliable results compared to the algorithm before the combination.
EXTENDING THE CBSL ALGORITHM FOR DIRECTION OF ARRIVAL ESTIMATION WITH A NESTED ARRAY IN PASSIVE SONAR
This paper investigates the application of the CBSL (Combine Filter - Broadband - Simultaneous Orthogonal Matching Pursuit - Least Squares) algorithm for Direction of Arrival (DOA) estimation in passive sonar using a Nested Array. The algorithm integrates sparse representation and adaptive comb filtering, which was previously proposed by the authors. The paper focuses on analyzing the signal model for the Nested Array and evaluating the performance of the proposed method through simulations. The results demonstrate that this approach improves spectral resolution, reduces the number of sidelobes, and enhances DOA accuracy compared to the Uniform Linear Array (ULA).
INVESTIGATION OF THE EFFECT OF SAMPLE HEIGHT AND SURFACE CURVATURE ON THE ANTI-REFLECTION PROPERTIES OF DLC COATINGS ON Si SUBSTRATES USING PECVD TECHNOLOGY
In the field of security, thermal imaging devices are increasingly employed in surveillance systems and often operate under harsh environmental conditions. To ensure their durability and performance, protective diamond-like carbon (DLC) coatings are often deposited on the outer lens or protective lens. DLC films are highly attractive owing to their excellent wear resistance, high hardness, environmental stability, and infrared transparency within the spectral range of thermal imaging systems. In this study, DLC coatings were deposited using plasma-enhanced chemical vapor deposition (PECVD) with the Aegis DLC-PECVD system (Intlvac, Canada). A challenge in coating large optical components is that variations in plasma distribution can lead to film non-uniformity. We report experimental results on the deposition of anti-reflective DLC coatings on Si substrates for the mid-wave infrared spectral region (3-5 µm). The uniformity of the DLC layers was assessed through transmission spectroscopy of samples placed at different positions inside the deposition chamber. The results indicate that varying the sample height from 0 to 40 mm relative to the plasma electrode caused negligible changes in spectral shape, while the transmission intensity exhibited only a slight variation of ~1.6% for single-side DLC-coated samples. For samples placed at different tilt angles, the transmission peak shifted toward longer wavelengths, from 3.4 to 4 µm, corresponding to incident angles between 0° and 50°. These findings provide useful insights for optimizing sample holder design to improve the thickness uniformity and optical performance of DLC coatings on large thermal imaging lenses.
EXPLORING THE MUTUAL INFLUENCE BETWEEN THE DISCHARGE CURRENT AND NICKEL POWDER ON THE SURFACE PROPERTIES OF 30CrNi2MoVA STEEL MANUFACTURED BY POWDER MIXED ELECTRICAL DISCHARGE MACHINING
To date, a lot of studies have been conducted to investigate the surface layer characteristics resulting from Electrical Discharge Machining (EDM). However, research utilizing nickel powder in Powder Mixed Electrical Discharge Machining (PMEDM) and examining its effects on surface properties remains relatively limited. In this study, the influence of key process parameters, including discharge current (Ip) and Ni powder, on the material removal rate (MRR) and surface properties such as average surface roughness (Sa) and the microstructure of the surface layer of 30CrNi2MoVA steel machined by PMEDM with nickel powder was investigated. The results indicate that discharge current (Ip) has the most significant impact on both the material removal rate and surface roughness. Specifically, when increasing Ip from 5A to 9A, MRR increased by 128% and 83%, respectively for PMEDM and EDM modes, Sa increased by 31.8% and 30.5%, respectively for PMEDM and EDM modes. Besides, the presence of Ni powder improved the surface roughness and MRR.
DEVELOPMENT OF A POWER CONTROL ALGORITHM BASED ON THROUGHPUT WINDOW FOR WIRELESS BODY AREA NETWORKS
Sensors in Wireless Body Area Networks (WBANs) require low power consumption to ensure continuous long-term operation while maintaining accurate and stable data transmission. This article proposes a novel power control algorithm that significantly improves energy efficiency for WBAN sensors compared to existing schemes. The proposed “Throughput Window-based Power Control” (TWC) algorithm ensures that the sensor’s throughput remains within a predefined range, aligning with system requirements. Simulation results demonstrate that TWC not only significantly reduces energy consumption but also maintains stable communication performance with high reliability under the unique transmission conditions of WBANs. In particular, TWC achieves the highest average energy efficiency, which is 1.5 times higher than the Max-Min Power Control (MMC) algorithm and 7.5 times higher than the No Power Control (NPC) scenario. Moreover, TWC yields the lowest average power consumption, reaching 0.75 times that of MMC and only 0.3 times that of NPC. Compared to MMC and NPC, TWC offers superior energy-saving capability while ensuring quality of service. These findings support the development of energy-autonomous WBAN models that meet the requirements of advanced health monitoring applications.
A NEW BUCK-BOOST CONVERTER WITH HIGH VOLTAGE CONVERSION RATIO AND REDUCED VOLTAGE AND CURRENT STRESS ON SWITCHES AND DIODES
This article presents an improved buck-boost converter configuration capable of achieving a high voltage conversion ratio while significantly reducing voltage and current stresses on key components such as MOSFETs and diodes. The proposed design not only enhances operational efficiency but also optimizes system reliability. To provide an objective evaluation, experimental tests were conducted to compare voltage overshoot across switching components, including switches and diodes, relative to the output voltage and to analyze the current overshoot ratio of switches and diodes concerning the input current. Additionally, the overall efficiency of the proposed converter was assessed against existing designs, considering the impact of parasitic resistances in the components. Simulation and experimental results validate the theoretical analysis and demonstrate that the proposed topology outperforms conventional two-switch buck-boost converters in mitigating voltage and current stresses on critical elements. With these advantages, the proposed design holds strong potential for applications demanding high efficiency and long-term stability.
DYNAMICS AND STATISTICAL VIBRATION CHARACTERISTICS OF A BASE VEHICLE OF MOBILE WATER PURIFICATION STATION MOVING ON RANDOM ROAD SURFACES
The vehicle-mounted VFS-2.5 water filtration station is one of the devices used to provide clean water during rescue and relief missions; therefore, it often operates on complex terrains. This article studies the dynamic model of the mobile water filtration station VFS-2.5 of a base vehicle during movement, taking into account random road surface roughness. Based on the dynamic model of the base vehicle, the Lagrange's Equation II is used to establish a set of differential equations describing the system motion. The article employs the inverse Fourier transform method, statistical techniques, and simulations available in MATLAB to evaluate the probability density distribution, value range, and statistical characteristics of vibration acceleration for road classes C, D, and E, as well as the dynamic parameters when the vehicle moves on the class-C road within a speed of 25 km/h which is the maximum permitted speed on unpaved roads. The obtained results can serve as a basis for assessing stability, vibration effects on operators during movement, and as input parameters for experiments to evaluate the degradation of technical conditions and the reliability of the equipment on the filtration station.
HIGHLY EFFECTIVE SIMULATION MODELS IN ANALYZING AERODYNAMICS OF AIRFOILS AT LOW REYNOLDS NUMBER
Recently, much work has been conducted for airfoils at low Reynolds and high velocity for further improving design airplanes those can fly on Mars and on stratosphere of the Earth. In this study, the aerodynamic characteristics of a typical airfoil shape named Ishii are studied by numerical approach for understanding the aerodynamic forces and flow fields at different angle of attack and Mach number. To reduce the numerical time, the Reynolds averaged Navier-Stokes equations are used for the simulation. The numerical results are compared with previous experimental data at the same flow conditions. This study found that the turbulent model should be changed from k-ω SST for angles of attack below 8° to k-ε model for higher angles of attack to obtain the accurate results. The maximum difference between simulation and experimental results is less than 9%. To extend the results, the aerodynamic characteristics were investigated for angles of attack from 0° to 20° and the Mach number between 0.2 and 0.8. The effect of serration at the leading edge on aerodynamic characteristics was also investigated. The results of the current study show that the angle of attack with maximum lift coefficient is around 8° at M = 0.2 and it increases for increasing Mach number. At high angle of attack, the lift decreases but large stall does not occur. The reason is from the generation of a separation bubble at leading edge of airfoil, which shows different characteristics from normal airfoil model. The serration at leading edge increases lift and aerodynamic performance for angles of attack above 8°. The results of the proper orthogonal decomposition indicates that the unsymmetric flow with a large wake structure is the most dominant flow at high angles of attack. The flow pattern of those modes, velocity and pressure distributions around the model are discussed.
DEVELOPMENT OF AN AUTOMATIC PROGRAM FOR DYNAMICS ANALYSIS OF 3D CONCRETE PRINTER FRAME WITH FLEXIBLE LINKS
This article presents the development of an automated program for calculating the dynamics of a large-scale concrete 3D printer frame with flexible links. The calculation program was developed by integrating three modules: Ansys© Parametric Design Language (APDL) code, MSC Adams© code, and MATLAB© code. The Ansys APDL code is used to establish the model of flexible links. The MSC Adams code is utilized to analyze the dynamics of the printer frame. The MATLAB code connects the modules, enabling automatic modification of structural parameters and motion rules of the printer axis. The developed program allows for automated dynamic calculations of the system with flexible links across various design parameters conveniently. Based on this, the effects of some structural parameters of the flexible links (beam cross-sectional dimensions) and kinematic parameters (frequency of motion variation, velocity) on the positional error of the print nozzle trajectory have been calculated, analyzed, and compared to systems with rigid links. Particularly, the simulation time for each set of design parameters has been significantly shortened, from 30-40 minutes (in case manually) to just 3-4 minutes. The research results provide a foundation for optimizing the printer frame design according to structural and dynamic criteria.
A HYBRID METHOD IN DETERMINING SKIN FRICTION FIELDS ON THE SURFACE OF FLYING OBJECTS
The study of friction fields on object surfaces plays an important role in fluid mechanics. In this study, a hybrid method, which combines the cross-correlation algorithm and the optical flow algorithm, is developed to calculate the skin-friction field based on the oil distribution on the surface. The scientific basis of the method is presented. Based on this, a computational program is developed and applied to flow calculations over different object surfaces, including an aircraft wing at a high angle of attack, a wing with a low aspect ratio, a delta wing, and the axisymmetric boattail of a flying object. The computational results show that this method effectively determines the flow characteristics of the surface skin-friction field. Flow characteristics, including separation and reattachment locations, are analyzed. Additionally, the influence of computational parameters on the results is specifically presented. This method demonstrates high efficiency and can be applied to future research and aircraft designs.
STATIC BENDING RESPONSE OF VARIABLE THICKNESS FGM PLATES USING NEW SHEAR DEFORMATION PLATE THEORY
This study aims to investigate the static bending behavior of functionally graded material plates with variable thickness using a new shear deformation theory and the finite element method. Material and mechanical models are developed to establish the equations describing mechanical relationships. The calculation program is implemented in MATLAB, and its accuracy is verified by comparison with results from analytical methods presented in reputable scientific publications. The error between methods is no more than 1.5%. The program can calculate plate structures with variable thickness according to different rules such as linear and nonlinear. The effects of geometric and material parameters on the static bending of FGM plates with variable thickness are explored. Following this, the thickness change affects the bending of the plate. These results provide an essential foundation for addressing more complex problems in the future.
DEVELOPING A MODEL TO DETERMINE THERMAL BOUNDARY CONDITIONS ON PISTON-CYLINDER OF 4-STROKE DIRECT-INJECTION DIESEL ENGINES
Nowadays, thermal boundary conditions on piston-cylinder surfaces can be determined experimentally or based on the synthesis of experience from previous studies. However, the experimental method is too complicated, the remaining method has low reliability and does not ensure energy balance in the piston-cylinder group. Therefore, the author proposes a model combining thermal cycle calculation software, the thermal boundary condition calculation module "BCOPC" designed by the author and FEM simulation software to determine equivalent thermal boundary conditions on piston-cylinder surfaces. The model uses algorithms to model the relative motion between the details in the piston-cylinder group and establishes an uninterrupted heat transfer relationship between the working medium - piston - piston ring - cylinder - coolant. The model is applied to calculate the thermal boundary conditions on the piston-cylinder surfaces of Paxman185, D80, 4Ch9.5/11 engines. The energy balance results in the piston-cylinder group with the largest relative deviation of 3.9% when calculating for the Paxman185 engine. Thus, the model can be used to determine the thermal boundary conditions on the piston-cylinder surfaces of 4-stroke direct-injection diesel engines.
THE DYNAMICS OF A WHEEL LOADER IN MOTION CONSIDERING RANDOM ROAD SURFACE IRREGULARITIES
Wheel loaders are among the most widely used and popular construction machinery today. During operation, road surface irregularities significantly influence the vibrations of the wheel loader. This article investigates the dynamic model of a wheel loader in motion, considering the random roughness profile of the road surface. The inverse Fourier transform (IFT) method, based on the power spectral density (PSD) of the road surface, is employed to simulate road surface roughness. The developed dynamic model accounts for the elasticity and damping properties of the tires, the suspension system, and the hydraulic lift cylinder of the boom mechanism. Based on the dynamic model, the Lagrange equations of the second kind are applied to derive the system's differential equations of motion. The study results indicate that when the loader operates on a Class C road at a speed of 4.7 m/s, the base acceleration is less than 0.5 m/s², meeting the ISO 2631-1 standards for vibration exposure to operators. The findings of this research provide a basis for assessing the stability of wheel loaders and serve as a foundation for designing and improving suspension systems for these machines.
INVESTIGATION OF AERODYNAMIC CHARACTERISTICS OF BUSEMANN AIRFOIL INCORPORATING A FLAP AND SLAT IN LOW-SPEED FLOW
The Busemann biplane wing employs a unique design, with inter-wing spacing optimized to suppress shock wave formation and minimize drag and noise at supersonic speeds. However, the resulting thin profile leads to reduced lift, impacting takeoff and landing. The use of slats and flaps is a promising approach to enhance takeoff and landing performance. In this research, the low-speed aerodynamic characteristics of Busemann airfoil installed slat and flap are investigated. The slat and flap are configured with hinge points located at 0.3c from the leading and trailing edges. The slat and flap deflection angles are 15° and 30°, respectively. The experiments are performed at a freestream velocity of 15 m/s, corresponding to a Reynolds number of 2.1·105. Results showed that the model incorporating flaps led to increases in both total lift and drag. The maximum lift coefficient increased from 1.6 in the baseline configuration to over 2.15 with the deployed flaps, while the lift curve slope remained relatively unchanged. At positive angles of attack, the lower element's contribution to both total lift and drag diminished compared to the baseline model. The slats effectively increased the lift slope and maximum lift coefficient, fulfilling the lift coefficient requirements for takeoff and landing. Additionally, the slats mitigated flow separation on both the upper and lower element surfaces, resulting in a reduction in drag compared to the configuration with flaps only.
FLIGHT PATH PLANNING FOR FIXED-WING UNMANNED AERIAL VEHICLES, USING RANDOM TREE AND IMPROVED GENETIC ALGORITHM METHODS
This article presents the results of the research on flight path planning method for fixed-wing UAVs operating at sea in complex environments. A method of mapping the operational space of UAVs and the constraints on a feasible flight path are studied. On the basis of the constraints, the article presents a flight path planning method using intelligent random trees and improved genetic algorithm. In particular, the random tree method combined with nonlinear constraints is applied to initiate feasible flight paths, and improved genetic algorithm operators are applied to find the optimal flight path. The simulation results show the effectiveness and feasibility of the proposed method, which is the basis for application to planning systems, creating tasks for UAVs to operate in complex environments.
DETERMINING THERMODYNAMIC PARAMETERS OF METHANE FUEL DETONATION PRODUCTS IN DETONATION ENGINES
This article describes the development of a computational model for determining the thermodynamic state after the detonation wave of a methane fuel mixture in a detonation engine. The model is based on the Chapman-Jouguet hypothesis and its results are compared to experimental data for methane-oxygen fuel. The study explores how the characteristics of detonation in methane-air fuel mixtures change under different initial conditions, such as fuel-air ratios and pre-detonation pressures. It identifies the optimal conditions for the methane-air fuel mixture and confirms the energy efficiency and structural superiority of the detonation engine by examining the influence of initial fuel pressure.
MODELING AND ANALYZING THE DYNAMICS OF ARTICULATING BOOM LIFTS WHEN OPERATING IN COMBINATION TO LIFT THE LOAD
An articulating boom lift is used to perform work in high and difficult-to-reach locations. Dynamic stability is extremely important during the deployment and operation of an articulating boom lift. Therefore, this article builds a model and investigates the dynamics of an articulating boom lift when simultaneously performing operations during the lifting process to serve as a basis for determining the vehicle’s dynamic stability. The dynamic model considers the elasticity and damping of the hydraulic cylinders used for lifting the loads. The Lagrange equation of type II is used to build the system of differential equations describing the motion of the mechanical system. Based on this model, the article investigates the dynamic parameters when the forklift performs multiple operations for lifting objects. The results of the article are the basis for the control problem of the forklift, aiming to enhance its performance and reliability during operation.
TRAJECTORY PLANNING FOR SEARCH-AND-RESCUE UAVs USING A GREEDY ALGORITHM
This article presents a trajectory-planning program for research-and-rescue UAVs based on the use of a local optimization greedy algorithm. Trajectories are generated over a search domain characterized by a probabilistic score map. For multiple-UAV systems, the program can assign each device to a search mission based on the probabilistic property or the geometry of the search domain. Some parameters such as the maximum travelled distance and trajectory resolusion could be input into the program. In this study, the program was tested to run for a two-UAV system over a given probabilistic score map. The input trajectory paremerters were selected based on the properties of each UAV and the requirement of a search-and-rescue mission. The program may be seamlessly integrated with UAV flight control software, enabling a direct translation of the obtained trajectories into autonomous mission execution.
STUDY OF AERODYNAMIC NOISE OF PROPELLER CONSIDERING THE INFLUENCE OF BOUNDARY SURFACE USING CFD METHOD
This article focuses on the aerodynamic and acoustic characteristics of both an isolated propeller model and a propeller - boundary surface model. The study uses the Reynolds-averaged Navier-Stokes (RANS) method combined with Computational Fluid Dynamics techniques to analyze the flow field and wake flow behind the propeller and to determine its basic aerodynamic coefficients. The pressure on the surface of the propeller and boundary surface is used as input for the noise calculations. An acoustic analogy method, based on the Farassat 1A formulation derived from the Ffowcs Williams-Hawkings (FW-H) equation, is employed to calculate the propagation of noise from the surfaces of the propeller and boundary surface to designated positions (microphones). The research results lead to some significant conclusions drawn by the authors.
INVESTIGATING LARGE-SCALE STRUCTURES IN TURBULENT MIXING LAYERS USING TWO-POINT CORRELATION
The formation and development of large-scale structures are primary research subjects in the study of turbulent mixing layers. Visualizing these structures based on published experimental data enhances the understanding of complex flow behaviors, which is the main objective of this article. The authors employed a two-point statistical correlation method to evaluate the size of large vortex structures along the interaction region. Additionally, the article provides a guide for analyzing the turbulent energy spectrum at selected fixed points. The calculations were performed using MATLAB software. The results indicate that at the beginning of the mixing layer, the vortices are small and highly anisotropic, with large-scale structures stretching in irregular directions. Further downstream, the vortices increase in size in all directions, and the degree of anisotropy decreases. In the self-similar region, isotropic states are almost achieved. The energy spectrum analysis findings align with Kolmogorov's theory of energy cascade in turbulent flow. The two-point statistical correlation method proves to be highly effective for analyzing structures within turbulent flows.
A NOVEL PIPE-CLIMBING FLEXIBLE ROBOT FOR PIPE INSPECTIONS
For robots, crawling through curved or redirected pipe sections with different pipe diameters to inspect and survey pipes is quite a difficult task. To solve this problem, in this article we propose a new pipe inspection robot model that is a combination of rigid mechanical structures with a soft body to ensure the robot moves smoothly and is flexible. The mechanical design model of the robot includes the front radial actuator, the central axial actuator, and the rear radial actuator. In order to assist the robot in adhering tightly to the pipe wall and producing a fulcrum for stable movement, the front and rear actuators are made of a rigid mechanical framework that can expand radially. The central axial actuator is the soft body that can flow through curved pipes and expand rapidly in the axial direction when filled with air to aid in the robot’s forward motion. The robot’s flexibility in movement is made clear by kinematic models of mechanical structures and deformation simulations of soft bodies. Preliminary calculations and simulation results show that this new robot design has the potential to move flexibly and efficiently in pipes with variable diameters and diverse configurations.
DETERMINING IMPACT VELOCITY IN AN IMPACT TESTER USING A MATHEMATICAL MODEL
Testing on impact test hammer is one of the methods to evaluate the impact of impulses, accelerations, and stress waves on the details and parts of the test object in order to evaluate the operation or durability of the test object for research and testing. Those impacts depend on many factors such as the weight of the hammer, the weight of the test object, the hardness of the anvil, the angle of lifting the hammer, etc. The parameters of the hammer are only applicable to the default cases, other cases when necessary to determine velocity must be measured. The calculation method is suggested by this article to determine impact velocity so that it can be applied on all cases instead of having to measure many times. The calculation results are verified by experimentally measuring the hammer velocity on high-speed camera with an error not exceeding 3.42%.