Farhad Fani saberi; Ali Kasiri
Abstract
This paper studies an output feedback second-order sliding mode control problem of spacecraft attitude control in the presence of the inertia tensor uncertainty and external disturbance. Mathematical modeling is presented based on spacecraft nonlinear equations of motion and quaternion parameters. Firstly, ...
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This paper studies an output feedback second-order sliding mode control problem of spacecraft attitude control in the presence of the inertia tensor uncertainty and external disturbance. Mathematical modeling is presented based on spacecraft nonlinear equations of motion and quaternion parameters. Firstly, a new sliding surface based on only attitude error is selected, then the standard second-order sliding mode control approach is followed. Finally, controller stability and tracking problem are guaranteed by choosing suitable auxiliary control input. The stability is proven by using concepts of a strong Lyapunov function and Lyapunov stability theory. Numerical simulations of attitude control of spacecraft equipped with 6 PWPF thrusters are given to demonstrate the performance of the proposed controller.
Amirreza Kosari; Javad Bahremandjouy
Abstract
In this paper, a Force Control Solution on Space Docking is proposed providing low impact and safe connection between space modules in different missions. In this solution, the force control concept has been employed along with traditional position control in space docking process because the interaction ...
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In this paper, a Force Control Solution on Space Docking is proposed providing low impact and safe connection between space modules in different missions. In this solution, the force control concept has been employed along with traditional position control in space docking process because the interaction forces between those parties involved (the chaser spacecraft and the target) in this phase are quite significant. Among the available methods in the force control field, Position Based Impedance Control strategy has been used as this strategy controls neither position nor force but the dynamic relationship between relative positions and interaction forces which is used widely in robotic science; however, other methods exhibit instability problems at the connection stage due to change between the position controller and the force controller. As we know, there are different kinds of space vehicles with particular connection scenarios and various connection latches; in order that, each vehicle demands specific interaction force in the connection phase; therefore, Position Based Impedance Control combined with Hill's Equations, which is used for space docking in circular orbit as relative position, is presented to be applied to different docking strategies and mechanisms. For the position controller that lies into Position Based Impedance Control structure, a nonlinear-PID Controller has been utilized possessing an anti-windup property and good capability to track the reference signal. The results show that we can ensure low impact connection by modifying target impedance coefficients in addition to precise position control.
Mohammad Reza Hashemi; Farhad Salek; Alireza Naghavi Moghaddam
Abstract
Nowadays, Light aircrafts play key role in the aviation industry. Therefore, it is important to select the right equipment in airplane propulsion system. In this paper, at first, airplane propulsion system blades are designed in SOLIDWORKS software, then they are analyzed in ANSYS software using fluid-structure ...
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Nowadays, Light aircrafts play key role in the aviation industry. Therefore, it is important to select the right equipment in airplane propulsion system. In this paper, at first, airplane propulsion system blades are designed in SOLIDWORKS software, then they are analyzed in ANSYS software using fluid-structure interaction analysis (FSI) method. The blades pressure contours under various conditions obtained in ANSYS fluent software. After that, the output data of analysis in fluent software is transferred to ANSYS static structural to perform tension and deflection analysis of blades. The results demonstrate the sections which are near the blade tip are imposed by higher pressure than other sections. For determination of blade material, three materials such as stainless steel, copper and aluminum have been chosen as blade material. At next, deflection and stress applied to each blade with different material are compared with each other. The stress and deflection values were calculated based on van Mises criteria and maximum deflection. By comparing the values of stress and deflection of each blade made by mentioned materials, the blade made by stainless steel which has the lowest deflection was selected as the best material.
Alireza Moghaddasi; Mohammad Hassan Djavareshkian
Abstract
In this paper a comparison of Weighted Essentially Non-Oscillatory (WENO) scheme is presented and different kinds are compared. High resolution schemes are one of the best ways decreasing the cost of processes and also increasing the resolution as is clear. Different WENO’s influence on the weights ...
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In this paper a comparison of Weighted Essentially Non-Oscillatory (WENO) scheme is presented and different kinds are compared. High resolution schemes are one of the best ways decreasing the cost of processes and also increasing the resolution as is clear. Different WENO’s influence on the weights that applies on the neighborhood of the cells that is supposing to be calculated. Mentioned schemes, were tested on wave equation at first and in continued with the first and second dimension test cases. 3rd ,5th, 7th and 9th order of JS-WENO, MWENO, ZWENO and MZWENO are compared in Goethe tests. This scheme was applied in finite volume characteristic wise algorithm in order to reach much more accuracy. Buckley-Leverette, Sod shock tube, Shu-Osher, Lax test, Riley-Taylor instability and double Mach reflection test cases was compared. As the result, MZWENO in equal order with the other ones would report more accurate reply. But as a new research here we showed that e.g. although MZWENO 5th order could promote the accuracy of the scheme up to about two times higher, but the cost of computing will increase more than the JS 7th order one. So, it is concluded that employing 7th order of JSWENO leads to higher accuracy with less computational costs.
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 ...
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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.
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.
