Aerospace Science and Technology
Mohammad Hassan Pachenari
Abstract
Flexible ropes have wide-ranging applications in aerospace engineering, yet accurately measuring their motion state without disrupting dynamic characteristics remains a challenge. This study introduces a visual measurement method aimed at precisely assessing flexible rope motion to support the development ...
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Flexible ropes have wide-ranging applications in aerospace engineering, yet accurately measuring their motion state without disrupting dynamic characteristics remains a challenge. This study introduces a visual measurement method aimed at precisely assessing flexible rope motion to support the development and validation of an accurate cable dynamics model. Addressing non-uniform movement speeds attributed to the rope's large length-diameter ratio, a novel tether edge segmentation operator is proposed to delineate motion blur regions into exposure beginning and ending time tethers. This operator enhances accuracy over existing centerline extraction methods, particularly in asymmetric motion blur regions. The proposed approach not only resolves accuracy issues during high-speed motion but also leverages the camera's inherent image acquisition frame rate, reducing system complexity and cost. Validation of the material point tracking algorithm through mathematical and physical simulations underscores its effectiveness in monitoring any point on the tether. Furthermore, verifying the tether dynamics model through the absolute nodal coordinate method highlights the novelty and significance of this research in advancing aerospace engineering applications.
Aerospace Science and Technology
Hamid reza Ali mohamadi; Hassan Naseh; Fathollah Ommi
Abstract
The present paper strives for optimization of the Liquid-Propellant Engine (LPE)’s feed system. To this end, the new hybrid meta-model methodology by utilizing the Design of Experiment (DOE) method and the Response Surface Method (RSM) were developed and implemented as two effective means of designing, ...
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The present paper strives for optimization of the Liquid-Propellant Engine (LPE)’s feed system. To this end, the new hybrid meta-model methodology by utilizing the Design of Experiment (DOE) method and the Response Surface Method (RSM) were developed and implemented as two effective means of designing, analyzing and optimizing. The input design variables, constraints, objective function, and their surfaces were identified. Then, the design and development strategy was clarified by utilizing the combination of RSM, DOE and regression analysis. Hence, 64 different experiments were carried out on the RD-253 propulsion system. The response surface curves were drawn and the related objective function equation was obtained. The Analysis of Variance (ANOVA) results indicate that, the developed hybrid model is capable to predict the responses adequately within the limits of input parameters. In addition, the precision of the model was assessed by comparing with the existing samples and the output was interpreted and analyzed that shown highly accuracy. Therefore, desirability function analysis has been applied to LPE’s feed system for achieving to maximize the power and minimize the weight, simultaneously. Finally, confirmatory tests have been conducted with the optimum parametric conditions to validate the optimization techniques. In conclusion, the methodology capability is to optimize the LPE system, an 11% increase in the power to feed system weight ratio and a 2% increase the thrust to engine weight ratio. These values are considerably large for LPE design.
Aerospace Science and Technology
Mohammad Reza Hashemi; Seyyed Majid Malek Jafarian; Mojtaba Dehghan Manshadi
Abstract
In this research, the effects of canard flow on a diamond wing equipped with LEX, same as new-generation fighters, have been investigated, using a closed-circuit wind tunnel. All tests were performed at a speed of 12.5 meters per second, which is equivalent to Reynolds number 214000 based on model length. ...
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In this research, the effects of canard flow on a diamond wing equipped with LEX, same as new-generation fighters, have been investigated, using a closed-circuit wind tunnel. All tests were performed at a speed of 12.5 meters per second, which is equivalent to Reynolds number 214000 based on model length. The pressure measurement is conducted by the five-hole probe, which is normalized by the dynamic pressure of the free stream velocity in four cross-sections over the wing. The results showed that at a low angle of attack, a strong vortex is produced at the leading-edge of the wing, called the leading-edge vortex. As the leading-edge vortex moves downstream, the diameter of its core and distance from the wing surface increases. At higher angles of attack, LEX, canard and body vortices are also present, which combine with the leading-edge vortex and cover a large cross-flow area over the wing. At these angles of attack, the movement of the vortical flow downstream leads to an increase in the pressure coefficient of the vortex core, which indicates the beginning of instability and vortex breakdown. The results showed that the pressure increase in the vortex core was not sudden and this results in that the breakdown phenomenon in the diamond wing equipped with LEX and canard occurs slowly.
Aerospace Science and Technology
Ali Alizadeh; Mohsen Heydari Beni; Jafar Eskandari Jam
Abstract
In this research, aluminum/alumina/graphite hybrid composite was prepared by horizontal centrifugal casting method, and the microstructure and distribution of alumina and graphite particles in the radial direction of the cross-sectional area of the samples were investigated. The distribution of graphite ...
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In this research, aluminum/alumina/graphite hybrid composite was prepared by horizontal centrifugal casting method, and the microstructure and distribution of alumina and graphite particles in the radial direction of the cross-sectional area of the samples were investigated. The distribution of graphite and alumina particles has led to the creation of a gradual structure (FGM) along the cross section. As a result of the centrifugal force, the graphite particles separated in the inner part of the sample and the alumina particles gradually increased from the inner region to the outer region. The samples were obtained with 3, 5 and 7% by volume of graphite particles added to the melt and with the rotation speed of the mold RPM1000, RPM1500 and RPM2000, and the formation of the inner zone rich in graphite was investigated. In all samples, 3% by volume of alumina particles were used and the effect of the presence of alumina particles on the distribution of graphite particles was studied. Optical microscope (OM) was used to investigate the microstructure and distribution of graphite and alumina particles. By increasing the amount of graphite from 3 to 7 percent by volume, the collision and interaction between graphite particles increases and leads to an increase in the thickness of the inner layer rich in graphite, and increasing the speed of rotation of the mold first causes an increase in the thickness of the inner layer and then leads to It was reduced. The presence of alumina particles prevented the complete separation of graphite particles
Aerospace Science and Technology
Heshmatollah MohammadKhanlo; Ali Nouri; Seyed Mohammad Kamali
Abstract
Exposure to vibrations of certain frequencies can pose a risk to the pilot's body. During flight, the maneuvers performed by the pilot expose them to sudden and unfavorable accelerations, which can cause physical, physiological, and psychological problems. Research suggests that the use of seat suspension ...
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Exposure to vibrations of certain frequencies can pose a risk to the pilot's body. During flight, the maneuvers performed by the pilot expose them to sudden and unfavorable accelerations, which can cause physical, physiological, and psychological problems. Research suggests that the use of seat suspension systems is effective in reducing high-frequency vibrations. However, for small movements, which occur at low frequencies between 2 to 15 Hz, the cushion of the pilot's seat plays a more significant role. In this research, we investigate the effect of the cushion on reducing vibrations on the pilot's body. Firstly, we compare and validate the results of the biodynamic equations of motion of a 4-degree-of-freedom model of the helicopter pilot's body with the experimental results. Next, we compare the biodynamic response of the motion in the finite element model (numerical solution) with the experimental results. Finally, we obtain and evaluate the biodynamic responses of the pilot's body movement by considering the cushion with different mechanical characteristics and in two stiffness and parallel (Kelvin-Voight model) and series (Maxwell model) damper modes. The Kelvin-Voight model was found to be more accurate than the COMSOL model.
Aerospace Science and Technology
Reza mahmoodpoor; amir kiyoumarsioskouei; amin taraghi; leila donyaparast
Abstract
The focus on different energy harvesting methods has led to various studies on the mechanism of flow-induced vibration phenomena, including vortex-induced vibration, galloping, and wake-galloping. In this study, an experimental investigation on flow around a cylinder with an elastic cantilever beam has ...
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The focus on different energy harvesting methods has led to various studies on the mechanism of flow-induced vibration phenomena, including vortex-induced vibration, galloping, and wake-galloping. In this study, an experimental investigation on flow around a cylinder with an elastic cantilever beam has been conducted to develop new energy harvesting devices based on its dynamic behavior. Therefore, the basic principles for the design of a high resolution open-circuit subsonic wind tunnel were systematically studied and a specific small scale wind tunnel was constructed based on the requirements. The test chamber cross section for the designed wind tunnel is square with a side length of 50 centimeters which can be used for investigation of different micro wind turbines performance up to velocity of 8 m/s with resolution of less than 0.1 m/s. The vibration of two prototype micro-turbines in the presence of obstacles and without obstacles has been studied in different Reynolds numbers. The results show that a circular cylinder oscillates with larger amplitude in the VIV range in comparison to the square cylinder, however, when galloping starts by increasing Reynolds number, the oscillation amplitude of the square cylinder severely increases. The experimental findings show that the presence of an obstacle in upstream of the flow considerably increases the amplitude of oscillation, however, does not have a meaningful effect on the vibration frequency. Also, results indicate that the vibration amplitude of the bluff body in the wake-galloping phenomenon for the square obstacle is greater in comparison to the circular obstacle.
Aerospace Science and Technology
Majid Bakhtiari; Amirhossein Panahyazdan; Siavash Sabzy
Abstract
The Earth Orientation parameters (EOPs), such as polar motion, universal time, and length of day, play a prominent role in procedures such as monitoring the Earth's rotation, weather modeling, and disaster prevention. This paper estimates the EOPs series based on a combined series approach proposed ...
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The Earth Orientation parameters (EOPs), such as polar motion, universal time, and length of day, play a prominent role in procedures such as monitoring the Earth's rotation, weather modeling, and disaster prevention. This paper estimates the EOPs series based on a combined series approach proposed by the International Earth Rotation and Reference System Observatory between 1962 and 2023, incorporating data from diverse space geodetic techniques, including DORIS, laser ranging (LLR and SLR), GNSS, and VLBI to create EOPs series. This paper proposes a hybrid deep-learning prediction model, combining a Convolutional Neural Network (CNN) and Gated Recurrent Unit (GRU) with an attention mechanism. The CNN effectively extracts and enhances features, while the GRU facilitates medium- to long-term predictions based on historical time series data. The attention mechanism prioritizes relevant data aspects, enhancing the Model's ability to discern intricate patterns, particularly for Length of Day (LOD) variations, where some covariants affect its pattern and should be considered. One of the most practical applications of these parameters is mapping the points in the terrestrial and celestial reference systems to each other. These predicted EOPs are used to create a high-accuracy coordinate transformation matrix from ECEF to ECI for applications such as high-precision navigation.
Aerospace Science and Technology
Gholamhosein Pouryoussefi; sara javanmard; MohamadAli Heidari
Abstract
In this study, the performance of a cold atmospheric pressure plasma jet using neutral helium gas was experimentally investigated. Cold atmospheric pressure helium plasma jets have gained popularity in various processing applications due to their stability and enhanced reaction chemistry. The researchers ...
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In this study, the performance of a cold atmospheric pressure plasma jet using neutral helium gas was experimentally investigated. Cold atmospheric pressure helium plasma jets have gained popularity in various processing applications due to their stability and enhanced reaction chemistry. The researchers examined the effect of applied voltage, flow rate, and electrode configurations on the length of the helium plume and analyzed the physical parameters of the plasma plume, including discharge voltage and average gas and discharge gap temperatures. The study revealed the presence of three operational modes: plasma bullets, a chaotic mode, and a continuous mode. Initially, the plasma jet operated in a deterministic chaotic mode after breakdown. Transitioning to the turbulent mode, increasing the gas flow rate resulted in a decrease in the plasma jet length. The flow rate required for laminar-to-turbulent transition increased with the applied voltage. By increasing the electrode separation and flow rate, the continuous mode was observed, where excited species remained within the inter-electrode space throughout the voltage cycle. Additionally, it was observed that the temperature of the discharge gap was close to room temperature. These findings provide valuable insights into plasma jet formation mechanisms and highlight the potential of tailoring plasma jet modes for specific processing applications.
Aerospace Science and Technology
Sahel Alasvand; Mostafa Kazemi; Mahmood Mani
Abstract
The noise of wind turbines is mainly of aerodynamic origin and is caused by the impact of the flow on the turbine blade. Therefore, improving the behaviour of the flow around the turbine and reducing aeronoise can result in reducing its annoying noise. In the first step of this research, a suitable serration ...
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The noise of wind turbines is mainly of aerodynamic origin and is caused by the impact of the flow on the turbine blade. Therefore, improving the behaviour of the flow around the turbine and reducing aeronoise can result in reducing its annoying noise. In the first step of this research, a suitable serration is selected according to the physics of the flow, and then it is installed on the leading edge of the blade in such a way that it does not cause the power loss of the turbine. All the studies have been done experimentally in the wind tunnel and with the help of power, pressure and air velocity measurements in the wake and in the different free stream velocities. The results showed that the pressure fluctuations in the model equipped with a serrated blade have decreased by 4-9% on average in different areas compared to the simple Savonius. On the other hand, the results of the frequency analysis of the anemometer sensors also showed that in the dominant frequencies, the serration caused the range of phenomena to decrease. These results were obtained in such a way that the power measurement showed that the maximum power value of the turbine equipped with serrated blade experienced an increase of nearly 19%. On the other hand, the velocity profile in the wake also shows a greater deficit in the flow around the modified Savonius, which confirms the decrease in the output momentum from the turbine and consequently the increase in power.
Aerospace Science and Technology
Mohammadreza Varshavi; Sahar Noori
Abstract
Air-breathing hypersonic flight is presumed by many of the savants in the field of aeronautical engineering as the last boundary of aerial vehicle design to be pushed back. An auspicious design configuration for the prospective hypersonic transport vehicles of the future is a “Waverider,” ...
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Air-breathing hypersonic flight is presumed by many of the savants in the field of aeronautical engineering as the last boundary of aerial vehicle design to be pushed back. An auspicious design configuration for the prospective hypersonic transport vehicles of the future is a “Waverider,” using the Scramjet engine cycle as its propulsive system. Two-dimensional CFD Analysis and case-to-case study of three pre-defined waverider configurations with 2-ramp, 3-ramp, and 4-ramp inlet geometries are carried out in the hypersonic flight regime of Mach numbers 5, 6, and 7. This is done in an attempt to study the single-oriented and also correlative-oriented impacts of increasing/decreasing the number of inlet ramps and increasing/decreasing the flight Mach number upon the behavior of final aerodynamic coefficients and ratios. The paramount outcome of the present work is the generation of some tables which can be utilized as primary guidelines for aeronautical design engineers who are designing waverider configurations on a preliminary basis.
Aerospace Science and Technology
Seyyed Reza Ghaffari-Razin; Reza Davari-Majd; Behzad Voosoghi; Navid Hooshangi
Abstract
Computerized Ionospheric Tomography (CIT) is a method to reconstruct ionospheric electron density image by computing Total Electron Content (TEC) values from the recorded GPS signals. Due to the poor spatial distribution of GPS stations, limitations of signal viewing angle and discontinuity of observations ...
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Computerized Ionospheric Tomography (CIT) is a method to reconstruct ionospheric electron density image by computing Total Electron Content (TEC) values from the recorded GPS signals. Due to the poor spatial distribution of GPS stations, limitations of signal viewing angle and discontinuity of observations in time and space domain, CIT are an inverse ill-posed problem. In order to solve these problems, two new methods are developed and compared with the initial method of Residual Minimization Training Neural Network (RMTNN). Modified RMTNN (MRMTNN) and Ionospheric Tomography based on the Neural Network (ITNN) is considered as new methods of CIT. In all two methods, Empirical Orthogonal Functions (EOFs) are used to improve accuracy of vertical domain. Also, Back Propagation (BP) and Particle Swarm Optimization (PSO) algorithms are used to train the neural networks. To apply the methods for constructing a 3D-image of the electron density, 23 GPS measurements of the International GNSS Service (IGS) with different geomagnetic indexes are used. For validate and better assess reliability of the proposed methods, 4 ionosondee stations have been used. Also the results of proposed methods have been compared to that of the NeQuick empirical ionosphere model. Based on the analysis and comparisons, the RMSE of the ITNN model at high geomagnetic activity in DOUR, JULI, PRUH and WARS ionsonde stations are 1.22, 1.46, 1.18 and 1.19 (1011 ele./m3), respectively. The results show that RMSE of the ITNN model is less than other models in both high and low geomagnetic activities and in ionosonde stations.
Aerospace Science and Technology
Benyamin Ebrahimi; Jafar Roshanian; Ali Asghar Bataleblu
Abstract
Significant attention has been given to the field of multi-agent systems in recent years due to its potential to solve complex problems that cannot be addressed by a single agent. One such problem is the cooperative search and coverage application, which requires multiple agents to efficiently search ...
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Significant attention has been given to the field of multi-agent systems in recent years due to its potential to solve complex problems that cannot be addressed by a single agent. One such problem is the cooperative search and coverage application, which requires multiple agents to efficiently search and cover a given area. However, the effectiveness of such systems is dependent on various factors, including mission definition parameters and the approach used to achieve mission performance optimality. In this paper, an optimal strategy for segregating multi-agent missions for search and coverage applications is proposed. The proposed strategy involves dividing a single mission into several simultaneous missions based on the optimal division of the environment that ensures system performance optimality while achieving a common goal. The mission area is divided into sub-areas, and each sub-area is assigned to specific agents to improve overall system performance. The effectiveness of the proposed strategy is demonstrated through simulations and relevant comparisons.
Aerospace Science and Technology
Mohammad Hossein Moghimi EsfandAbadi; Adnan Mohammadi; Mohammad Hassan Djavareshkian
Abstract
This research delves into the intricate realm of supersonic inlet design for ramjet engines, honing in on the critical aerodynamic considerations and optimization of performance factors. At Mach 2.5, the study meticulously scrutinizes pivotal design parameters, including the placement and number of inclined ...
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This research delves into the intricate realm of supersonic inlet design for ramjet engines, honing in on the critical aerodynamic considerations and optimization of performance factors. At Mach 2.5, the study meticulously scrutinizes pivotal design parameters, including the placement and number of inclined shocks, cowl-lip positioning, throat area, spike location, and diffuser length. Computational fluid dynamics simulations are harnessed to unravel the intricate flow dynamics and assess the proposed inlet geometry's performance.The findings reveal a nuanced relationship between back pressure and shock wave positioning, where increasing back pressure initiates a shift in the shock wave, impacting the flow state. The paper delineates this transition, emphasizing the pivotal back pressure range of 300,000 to 350,000 pascals, where optimal shock wave alignment corresponds with design parameters, achieving a supercritical state.However, elevating back pressure beyond this range triggers a sub-critical state and mass flow overflow as the shock exits the throat.the study explores various performance metrics, encompassing drag coefficient, distortion coefficient, mass flow ratio and total pressure recovery under varying back pressure conditions. The outcomes underscore the merits of higher back pressures, which mitigate drag coefficient and distortion while amplifying TPR.In the sub-critical state, MFR diminishes due to shock wave displacement beyond the intake opening.This research illuminates the intricate dance of aerodynamics within ramjet engine inlets and underscores the paramount significance of optimizing inlet geometry to unlock heightened performance. It effectively encapsulates the essence of the full article, enticing readers to embark on a deeper exploration of this crucial area of aerospace engineering.
Aerospace Science and Technology
Sevda Rezazadeh Movahhed; Mohammad Ali Hamed
Abstract
The fixed-wing unmanned aerial vehicles (UAVs) have gained significant attention across diverse civilian and military applications in recent years, where precision control, advanced manoeuvrability, and elevated stealth capabilities are paramount. In order to design a robust control system to enable ...
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The fixed-wing unmanned aerial vehicles (UAVs) have gained significant attention across diverse civilian and military applications in recent years, where precision control, advanced manoeuvrability, and elevated stealth capabilities are paramount. In order to design a robust control system to enable different tracking and path-following purposes, it is desired to establish a precise aerodynamic model. The research introduces a straightforward approach for accurately computing aerodynamic coefficients, essential for deriving aerodynamic forces and moments, particularly focusing on the rudderless flying-wing UAV models. Utilizing Digital DATCOM software, the study outlines a procedure for calculating the requisite aerodynamic coefficients of fixed-wing aircrafts. The data input card is prepared based on the design and physical attributes of the rudderless flying-wing Freya UAV model and its associated airfoil structure. Through the utilization of the input card in DATCOM software, computations are performed to determine static longitudinal/lateral stability, dynamic stability, and control coefficients, along with their derivatives. Additionally, a 3D model is constructed. The ensuing output file is then imported into the MATLAB environment for comprehensive analysis and integration into dynamic modelling for the design of control systems. The open-loop and closed-loop system performance analysis based on the obtained aerodynamic coefficients, shows acceptable values in terms of control surfaces and flight dynamics variables in the category of small-sized rudderless flying-wing UAVs which proves the reliability of the obtained results.
Aerospace Science and Technology
Amirali Nikkhah; Moein Ebrahimi; Morteza Tayfi; Navid Mohammadi
Abstract
The paper compares the performance of two altitude controllers, model predictive controller (MPC) and linear quadratic requlator (LQR), for aircraft in cruise flight and height change conditions. The design of the controllers is based on the linearized state space matrix of the aircraft’s longitudinal ...
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The paper compares the performance of two altitude controllers, model predictive controller (MPC) and linear quadratic requlator (LQR), for aircraft in cruise flight and height change conditions. The design of the controllers is based on the linearized state space matrix of the aircraft’s longitudinal motion around the trim conditions. The controllers’ ability to track the desired altitude while satisfying input and state constraints is evaluated, and it is found that both controllers are effective in maintaining the desired height. However, the MPC controller performs less overshoot, settling time and transient error than the LQR controller and achieves a more efficient control input by predicting the future behavior of the system. The proposed altitude controllers provide a promising solution for maintaining the desired aircraft altitude in cruise flight conditions, and the comparative analysis of the two control methods can assist in selecting the appropriate control strategy for a given aircraft system based on the desired performance requirements.
Aerospace Science and Technology
Seyed mohammad navid Ghoreishi; Bahar Salimi
Abstract
In this study, a comprehensive investigation of the fracture parameters in a grooved rotating disc containing a three-dimensional semi-elliptical crack under different working conditions has been investigated. In this regard, three models of radial, circumferential and inclined crack with an angle of ...
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In this study, a comprehensive investigation of the fracture parameters in a grooved rotating disc containing a three-dimensional semi-elliptical crack under different working conditions has been investigated. In this regard, three models of radial, circumferential and inclined crack with an angle of 45 degree have been considered in the rotating disk, and the fracture parameters under mixed mode loading (I, II, III) have been extracted. The effects of various parameters such as rotational speed, crack location, aspect ratio, material and presence of grooves on SIFs and crack opening displacement have been studied simultaneously. The finite element results indicated that in the crack with a low aspect ratio (0.4 and 0.6) where the shape of the crack is more like a semi-elliptical, the maximum value of the mode I SIF occurs at the central point of the crack front, while the crack with a high aspect ratio (0.8 and 1) where the shape of the crack is more like a semi-circular, the maximum value of the mode I SIF occurs at the free surface of the crack. The mode II SIF for the rotating disk containing an inclined crack before the central point of the crack front, has the highest value for steel, titanium and aluminium rotating disk, respectively. Also, the numerical results indicated that the highest value of the SIF is related to the grooved rotating disk containing a circumferential crack, and the lowest value of the SIF is for the grooved rotating disk containing a radial crack
Aerospace Science and Technology
Ali Mirzaee kahagh; Alireza Sekhavat Benis
Abstract
The current research was conducted with the aim of identifying the role of unmanned aerial vehicles in future smart cities. The current research was conducted in terms of mixed statistical methods (qualitative-quantitative). The participants of the qualitative part, which was implemented based on the ...
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The current research was conducted with the aim of identifying the role of unmanned aerial vehicles in future smart cities. The current research was conducted in terms of mixed statistical methods (qualitative-quantitative). The participants of the qualitative part, which was implemented based on the method of thematic analysis, were 14 knowledgeable experts, including specialized and experienced managers in the fields of urban security, transportation, road, and urban development, aviation organization and aviation industry, and The Information and Communication Technology Organization of Greater Tehran cities until reaching theoretical saturation and in the quantitative part, all the expert experts of the relevant devices were 134 people, and using Cochran's formula and targeted sampling method, the number of 99 people was were selected as sample members. The reliability coefficient of the qualitative part was recorded by the method of two coders with the final result (83%) and the reliability of the quantitative part was recorded with Cronbach's alpha coefficient with the final result (0.91). MAXQDA software was used for qualitative data analysis and SPSS software was used for quantitative data analysis. The findings showed that in the process of explaining the role of unmanned aerial vehicles in future smart cities; There are 5 comprehensive themes, 16 organizing themes, and 58 basic themes. The results showed that unmanned aerial vehicles can play a significant role in creating future smart cities through 1- intelligent air transportation, 2- agile monitoring and inspection, 3- smart agriculture, 4- smart urban and citizen services, and 5- smart law enforcement.
Aerospace Science and Technology
Fahimeh Barzamini; Jafar Roshanian; Mahdi Jafari-Nadoushan
Abstract
This paper aimed to utilize a Deep Neural Network (DNN) to achieve optimal path planning for a spacecraft during a landing mission on an asteroid. A minimum energy-consumption mission is evaluated in which a DNN is utilized to predict the optimal path in case of any failures or unforeseen alterations. ...
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This paper aimed to utilize a Deep Neural Network (DNN) to achieve optimal path planning for a spacecraft during a landing mission on an asteroid. A minimum energy-consumption mission is evaluated in which a DNN is utilized to predict the optimal path in case of any failures or unforeseen alterations. The paper uses a DNN and employs a polyhedral model, which is renowned as the most precise method for modelling the irregular shapes of asteroids. The DNN, is utilized for path planning and incorporates data calculated by the network into a spacecraft dynamics equations where an intelligent supporter model has been developed to handle the high computation load of the gravitational field of polyhedral models. Moreover, this study indicates that the prediction errors of final locations are less than 1 kilometer, as the training errors of networks are deemed entirely satisfactory. Eventually, the feasibility of the proposed approach is demonstrated through corresponding simulations
Aerospace Science and Technology
S.H. Jalali Naini; Rahim Asadi; amir hossein Mirzaei
Abstract
A complete miss distance analysis of true proportional navigation is carried out due to initial heading error, step target maneuver, and seeker noise sources assuming a first-order control system using forward and adjoint methods. For this purpose, linearized equations are utilized for deterministic ...
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A complete miss distance analysis of true proportional navigation is carried out due to initial heading error, step target maneuver, and seeker noise sources assuming a first-order control system using forward and adjoint methods. For this purpose, linearized equations are utilized for deterministic and stochastic analyses. Worst case analysis shows that the maximum value of the final time-miss distance plots reduces by increasing the value of the effective navigation ratio due to initial heading error and step target acceleration. The number of peaks of these curves obeys the relation of the effective navigation ratio minus 1 (or 2) due to heading error (or step target maneuver). Moreover, the normalized miss coefficients due to seeker noise sources and miss due to random target maneuver are computed and approximate formulas are presented using the curve fitting method. This leads to an approximate formula for miss distance budget. Therefore, optimum values of the effective navigation ratio and control system time constant are obtained. Finally, the preferred values of these parameters are calculated for increased RMS miss of 5%, 10%, and 20% compared to its minimum value for two scenarios.
Aerospace Science and Technology
Mahsa Azadmanesh; Jafar Roshanian; Mostafa Hassanalian
Abstract
This paper employs the fast terminal sliding mode control with the sign and the saturation function to track the landing trajectory of a probe on an asteroid and to further improve the dynamic tracking performance. Then the controller is enhanced by adding the fuzzy control to both fast terminals. To ...
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This paper employs the fast terminal sliding mode control with the sign and the saturation function to track the landing trajectory of a probe on an asteroid and to further improve the dynamic tracking performance. Then the controller is enhanced by adding the fuzzy control to both fast terminals. To make fair judgments on the performance of the suggested method, the proportional derivative sliding mode control with both the sign function and the saturation function is simulated as well. The two-point barycentric gravitational model is used to describe the weak gravity around the asteroid. The proposed fuzzy fast terminal method raises the convergence speed, improves the desired trajectory tracking accuracy and ensures that the system modes are placed on the sliding surface in a short, limited time. The absolute errors for the proportional derivative sliding mode controller, fast terminal sliding mode controller and improved fast terminal sliding mode controller are about 244, 139 and 113. The trajectories along all three coordinate axes in the proportional derivative sliding mode controller, fast terminal sliding mode controller and improved fast terminal sliding mode controller were tracked in 8 seconds, 5 seconds and 4 seconds. The results show how the fuzzy-fast terminal sliding mode control with the saturation function is the better choice of controller and how the fuzzy system is able to adapt to the momentary fluctuations and cover them successfully.
Aerospace Science and Technology
Alireza Ekrami Kivaj; Alireza Novinzadeh; farshad pazooki; Ali Mahmoodi
Abstract
This study aims to investigate the spacecraft returning from the atmosphere. Due to high speed, prolonged flight duration, and numerical sensitivity, returning from the atmosphere is regarded as one of the more challenging tasks in route design. Our suborbital system is subjected to a substantial thermal ...
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This study aims to investigate the spacecraft returning from the atmosphere. Due to high speed, prolonged flight duration, and numerical sensitivity, returning from the atmosphere is regarded as one of the more challenging tasks in route design. Our suborbital system is subjected to a substantial thermal load as a result of its return at high speed and the presence of uncertainty. In addition, the current study aims to lessen the thermal load in the system to meet the needs of the initial and final conditions through multi-subject optimization, comparison of the two fields of aerodynamics and flight dynamics, assistance from optimal control theory, and consideration of uncertainties The heat load in the sub-orbital system could be reduced by around 9.6% using these algorithms and optimum control theory. Artificial bee colonies, genetic algorithms, and the combined genetic algorithms and particle swarm algorithms were utilized as exploratory optimization techniques. The objective of the flight mechanics system is also to create the best trajectory while taking into account uncertainty and minimizing thermal load. The conduction law based on heat reduction is described in the search for the ideal trajectory. We reduced the heat rate during the first part of the spacecraft's return journey from the atmosphere by concentrating on the angle of attack. By more accurately specifying the angle of attack and the angle of the bank in the second stage of the split guidance legislation, the ultimate return requirements could be achieved significantly .
Aerospace Science and Technology
Sayed Hossein Moravej Barzani; Mahdi Mortazavi; Hossein Shahverdi
Abstract
In this paper, the effects caused by the combination of folding angles simultaneously with changing the stiffness ratio of different parts of a folding wing are investigated. The geometrically exact fully intrinsic equations are employed to simulated the wing nonlinear dynamic behavior. The important ...
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In this paper, the effects caused by the combination of folding angles simultaneously with changing the stiffness ratio of different parts of a folding wing are investigated. The geometrically exact fully intrinsic equations are employed to simulated the wing nonlinear dynamic behavior. The important advantages of these geometrically exact equations can be seen as complete modeling without simplifying assumptions in large deformations, low-order nonlinearities, and thus less complexity. In this research, folding angles have been used in the geometrically exact fully intrinsic beam equations and the combination of different folding angles is studied. The applied aerodynamic loads in an incompressible flow regime are determined employing Peter’s unsteady aerodynamic model. In order to check the stability of the system, first the resulting non-linear partial differential equations are discretized, and then linearized about the nonlinear steady-state condition. By obtaining the eigenvalues of the linearized system, the stability of the wing is evaluated. Furthermore, investigation of the effects of the stiffness on the flutter speed and frequency of the folding wing for various folding angles, is another achievement of this study. It is observed that the combination of folding angles can significantly delay the flutter speed and improve the performance of the bird.
Aerospace Science and Technology
Mohammad Yavari; Nemat Allah Ghahremani; Reza Zardashti; Jalal Karimi
Abstract
In this paper a new mid-course guidance algorithm for intercepting high altitude target is proposed. A part of target flight path is outside the atmosphere. The maximum acceleration command is designed as a variable constraint that varies with altitude. This physical limitation is happened for the aerodynamically ...
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In this paper a new mid-course guidance algorithm for intercepting high altitude target is proposed. A part of target flight path is outside the atmosphere. The maximum acceleration command is designed as a variable constraint that varies with altitude. This physical limitation is happened for the aerodynamically control interceptors at high altitudes because of decreasing air density. Based on generalized incremental predictive control approach, a new formulation for parallel navigation guidance law is proposed. Using the nonlinear kinematic equations of target-interceptor, the commands of the new guidance method are computed by optimization of a cost function involved the velocity perpendicular to the line of sight errors and guidance commands. An important feature of the proposed method is the minimization of the line- of - sight angular rate in a finite period of time. The various simulation results of the proposed guidance law shows the higher effectiveness of the designed guidance law in comparison with proportional navigation and sliding mode guidance.
Aerospace Science and Technology
Reza Jamilnia
Abstract
In this paper, in order to simultaneously optimize the staging and trajectory of launch vehicles, changes are made in the structure of the trajectory optimization problem. In this approach, the flight times of all stages are considered freely and as optimization variables. During the solution and in ...
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In this paper, in order to simultaneously optimize the staging and trajectory of launch vehicles, changes are made in the structure of the trajectory optimization problem. In this approach, the flight times of all stages are considered freely and as optimization variables. During the solution and in each iteration, by using the values of the flight times in that iteration and the fuel consumption rate of each stage, the masses of the fuel and structure of the stages and the initial and instantaneous masses of the vehicle are calculated. By minimizing the initial mass as the objective function of the integrated optimization problem, the optimal flight trajectory is obtained in the form of the optimal state and control values, and the optimal budget of the fuel and structure masses between different stages is calculated. In this paper, to implement the dynamic equations, the direct collocation method is used, and to approximate the variables, the B-spline curves are used. By using the B-spline curves, despite the discreteness of the relevant parameters as optimization variables, a continuous concept for the optimal solution can be created. The presented approach in this paper for integrated optimization of staging and trajectory and the use of B-spline curves in the approximation of the multiphase problem with free final times can lead to reduce the initial weight of the Europa 2 launch vehicle by 30% to perform a specific mission.
Aerospace Science and Technology
Morteza Sharafi; Mahdi Jafari; mojtaba alavipour
Abstract
In this paper, optimal guidance law design considering fixed final state and time for the final phase a spacecraft or launch vehicle is investigated and studied. This guidance law, not only satisfied a specific optimality criterion, but it also has the least sensitivity to the initial state’s deviations; ...
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In this paper, optimal guidance law design considering fixed final state and time for the final phase a spacecraft or launch vehicle is investigated and studied. This guidance law, not only satisfied a specific optimality criterion, but it also has the least sensitivity to the initial state’s deviations; which is due to the inclusion of the nonlinear terms in the mathematical modeling using the high order expansions method. The main goal of this research, is to investigate the development and to augment the capability of the high order expansions method for guidance law design. Different implementations of this approach including the differential algebra high order, the generating function based high order and vectorized high order expansions methods have been investigated. After reviewing the implementation concepts of the high order expansions method, the effectiveness of this method has been studied. Then a 3-dimensional injection of a satellite problem has been chosen as the case study and after extracting the mathematical model and nominal optimal solution, the sensitivity variables have been extracted up to the 3rd order. Afterwards, to investigate the performance of the designed guidance law, the Monte Carlo simulations have been performed and it has been shown that the designed guidance law on the basis of the Taylor series and high order expansions method has a good accuracy and is a valuable alterative to the nominal trajectory tracking guidance approach.
