Mehrdad Hoseiniasl; Javad Jafari Fesharaki
Abstract
Optimization the volume/weight of the gear train is more important for industries and researchers. In this paper using particle swarm optimization algorithm a general gear train is optimized. The main idea is to optimum the volume/weight of the gearbox in 3 directions. So, the optimization process based ...
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Optimization the volume/weight of the gear train is more important for industries and researchers. In this paper using particle swarm optimization algorithm a general gear train is optimized. The main idea is to optimum the volume/weight of the gearbox in 3 directions. So, the optimization process based on PSO algorithm occurs along height, length and width of the gearbox to achieve the smallest possible gearbox. The constraints divided into three types of constraints: geometrical, design and control constraints. The optimization process presented for two and three stage gear trains and by choosing different values for the gear ratio, input power and hardness of gears the practical graphs for value of the optimum weight/volume and all the necessary design parameters of gearbox such as number of stages, position and modulus of gears, face width of gears and diameter of shafts are presented. The results are validated by comparing to the results reported in the previous publication.
Mohammadreza Nozari; Sadegh Tabejamaat; Hasan Sadeghizade; Majid Aghayari
Abstract
The influence of fuel injector on the performance parameters of a can-type combustor were examined experimentally using LPG fuel and at atmospheric conditions. The first injector is a typical 45° conical injector with 6 holes on its curved surface, and the second injector is a swirl injector with ...
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The influence of fuel injector on the performance parameters of a can-type combustor were examined experimentally using LPG fuel and at atmospheric conditions. The first injector is a typical 45° conical injector with 6 holes on its curved surface, and the second injector is a swirl injector with 6 holes whose axes are not parallel with each other and are oriented at 19° in respect to the combustor’s axis. Three operating points were selected, and temperature distribution in the intermediate zone of the combustor and at the outlet section of the combustor was obtained using k-type thermocouples. Results reveal that the swirl injector provides better air-fuel mixing (due to the tangential motion forced on the fuel flow), more uniform temperature distribution in the combustor, lower liner temperature, higher combustion efficiency, and lower pattern factor. In addition, stability curve was also obtained for two configurations, and the results showed that the conical injector provides better stability for the combustor and is operable in a wider range of operating conditions. The results also show that the flame is generally shaped near the walls and the vicinity of the combustor’s liner and outlet walls are in contact with hot gases which reduces the combustor’s lifetime.
A. Abdoli; Seyed Hossein Taghavi
Abstract
It is always easier to measure the deviation of a product from its design commitments, in comparison to making it identical to plan obligations. In this paper, this simple fact is utilized to compensate the inherent error of fixture fabrication by a mathematical modeling of possible sources of ...
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It is always easier to measure the deviation of a product from its design commitments, in comparison to making it identical to plan obligations. In this paper, this simple fact is utilized to compensate the inherent error of fixture fabrication by a mathematical modeling of possible sources of error, in calibration of strapdown inertial navigation system (INS). Since an INS should be mounted on the fixture, all deviations are completely transferred to INS. Compensating the inherent errors of a fixture surely guarantees a more accurate calibration, but its effectiveness depends on specific factors. Proposed method can upgrade a fixture with any manufacturing quality to accuracy level of measurement tool. This technique is explained by two examples. Data of industrial-grade strapdown INS is used to proof of claims.
I. Khabbazi; Vahid Behnamgol
Abstract
This paper presents robust nonlinear control law for a quadrotor UAV using fast terminal sliding mode control. Fast terminal sliding mode idea is used for introducing a nonlinear sliding variable that guarantees the finite time convergence in sliding phase. Then in reaching phase for removing chattering ...
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This paper presents robust nonlinear control law for a quadrotor UAV using fast terminal sliding mode control. Fast terminal sliding mode idea is used for introducing a nonlinear sliding variable that guarantees the finite time convergence in sliding phase. Then in reaching phase for removing chattering and producing smooth control signal, continuous approximation idea is used. Simulation results show that the proposed algorithm is robust against parameter uncertainty and has better performance than conventional sliding mode for controlling a quadrotor UAV.
H. Chenarani; T. Binazadeh; M.H Shafiei
Abstract
This paper considers the problem of asymptotic stabilizing of velocity and body rates of a spacecraft in the presence of uncertainties and external disturbances. One of the important methods in controller design for nonlinear systems; is designing based on the passivity concept. This concept which provides ...
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This paper considers the problem of asymptotic stabilizing of velocity and body rates of a spacecraft in the presence of uncertainties and external disturbances. One of the important methods in controller design for nonlinear systems; is designing based on the passivity concept. This concept which provides a useful tool for analysis of nonlinear systems has been also used for asymptotic stabilizing of nonlinear dynamical systems especially mechanical systems. The passivity-based control law is a static output feedback and has valuable features. Because of existence of uncertainties and external disturbances in the state-space of equations of physical systems; first the robust version of passivity-based control method, which is recently developed in literature, is given and the control law for nonlinear uncertain systems with affine structure is presented. Then, this approach is used in controller design for a spacecraft. Since, this paper considers only the stabilization of velocity and body rates, therefore the reduced-order model is extracted from the state-space equation of a spacecraft with six degree of freedom and then the robust control law is designed. Computer simulations show the efficiency of the proposed controller in robust asymptotic stabilizing of the velocity and body rate vectors of the spacecraft in the presence of uncertainties and external disturbances.
Abstract
Optimization the volume/weight of the gear train is more important for industries and researchers. In this paper using particle swarm optimization algorithm a general gear train is optimized. The main idea is to optimum the volume/weight of the gearbox in 3 directions. So, the optimization process based ...
Read More
Optimization the volume/weight of the gear train is more important for industries and researchers. In this paper using particle swarm optimization algorithm a general gear train is optimized. The main idea is to optimum the volume/weight of the gearbox in 3 directions. So, the optimization process based on PSO algorithm occurs along height, length and width of the gearbox to achieve the smallest possible gearbox. The constraints divided into three types of constraints: geometrical, design and control constraints. The optimization process presented for two and three stage gear trains and by choosing different values for the gear ratio, input power and hardness of gears the practical graphs for value of the optimum weight/volume and all the necessary design parameters of gearbox such as number of stages, position and modulus of gears, face width of gears and diameter of shafts are presented. The results are validated by comparing to the results reported in the previous publication.
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
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
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.