Tahere Binazadeh; Mohammad Hossein Shafiei; Elham Bazregarzadeh
Volume 8, Issue 1 , April 2015, Pages 1-7
Abstract
This paper presents a novel approach in design of missile guidance law against highly maneuvering targets. This approach is based on the principles of partial stability and finite-time stability (finite-time partial stability). Also, it is shown that the designed guidance law is in conformity with a ...
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This paper presents a novel approach in design of missile guidance law against highly maneuvering targets. This approach is based on the principles of partial stability and finite-time stability (finite-time partial stability). Also, it is shown that the designed guidance law is in conformity with a real guidance scenario that leads to collision. In the design procedure the acceleration vector of the target is assumed as an external bounded disturbance and only this bound is required in the design of the guidance law. Therefore, the maneuver of the target is not restricted to any known and predetermined structure and measurement or estimation of the target acceleration vector during the maneuver is not necessary. The performance of the proposed guidance law is shown through analysis and computer simulations.
Milad Behzadi; Mohammad Farshchi
Volume 8, Issue 1 , April 2015, Pages 9-18
Abstract
Dynamics of laminar premixed conical flame in acoustic-velocity field was studied via numerical simulation. Methane/air combustion was modeled using a single-step, irreversible reaction and diffusion phenomena with a simple but efficient method. First, the steady flame was obtained and its corresponding ...
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Dynamics of laminar premixed conical flame in acoustic-velocity field was studied via numerical simulation. Methane/air combustion was modeled using a single-step, irreversible reaction and diffusion phenomena with a simple but efficient method. First, the steady flame was obtained and its corresponding parameters were verified. Then this steady state solution was excited by modulation of the inlet velocity. After the initial transients, heat release rate of the flame kept fluctuating with the forced frequency. The response function for various modulation intensities and frequencies agrees satisfactorily with experiments. Also, like the experimental observations the flame wrinkles and the convex sections which convert to sharp edges travel from the base to the tip of the cone at the speed of the flow.
Hamed R. Najafi; Esmaiel Moeini; Seyed Mohammad Hossein Karimian; Hamed Alisadeghi
Volume 8, Issue 1 , April 2015, Pages 19-25
Abstract
The intention of this paper is to discuss the results obtained from tests conducted at Amirkabir University of Technology Thermal Control Lab on multilayer insulation (MLI) blankets designed and fabricated in university, describing the thermal performance of test specimens at different environmental ...
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The intention of this paper is to discuss the results obtained from tests conducted at Amirkabir University of Technology Thermal Control Lab on multilayer insulation (MLI) blankets designed and fabricated in university, describing the thermal performance of test specimens at different environmental temperatures. We have evaluated the MLI performance by experimentally measuring our MLI’s emissivity factor. For this purpose we have defined our experiments based on the effective emissivity model. Fabricated MLI blankets are tested in a vacuum chamber at an approximate pressure of 10-6mbar and temperatures of approximately 30°C and -70°C, while subjected to heat with the power input in the range of 1.0 to 2.5 Watts. Results show that the measured effective emissivity is within the range of other reported experimental data.
Mohammad Reza Mortazavi; Ali Reza Alikhani
Volume 8, Issue 1 , April 2015, Pages 27-41
Abstract
This paper presents a suitable technique for nonlinear control of a flexible spacecraft in proximity operations. To do proximity operations well, the pursuer spacecraft must place itself in a pre specified location relative to target and align its docking port to target’s docking port while keeping ...
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This paper presents a suitable technique for nonlinear control of a flexible spacecraft in proximity operations. To do proximity operations well, the pursuer spacecraft must place itself in a pre specified location relative to target and align its docking port to target’s docking port while keeping their attitude compatible. This procedure usually needs large, fast and accurate manoeuvres which can cause flexible structure vibrations. In addition, external disturbances, actuator saturation and model uncertainties increase difficulties of achieving such a goal. Consequently it is necessary to utilize an effective and nonlinear controller design approach to overcome these challenges. To perform considered scenario successfully, in this paper we use a method in nonlinear optimal control called State Dependent Riccati Equation (SDRE). Simple formulation and tuning as well as good performance and satisfactory robustness are some advantages of this approach in unified control of the spacecraft position, attitude and flexible motion during a proximity operation. 6DoF simulations show good performance of controller in presence of structure flexibility, parametric uncertainties, input uncertainty and saturation and external disturbance.
Emad Azadi; Seyed Ahmad Fazelzadeh; Mohammad Azadi
Volume 8, Issue 1 , April 2015, Pages 43-51
Abstract
In this paper, vibration suppression and maneuver control of a smart flexible satellite moving in acircular orbit are studied. The satellite is considered as a rigid hub and two flexible appendages withpiezoelectric layersattached on them as actuators. The satellite is moving in a circular orbit and ...
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In this paper, vibration suppression and maneuver control of a smart flexible satellite moving in acircular orbit are studied. The satellite is considered as a rigid hub and two flexible appendages withpiezoelectric layersattached on them as actuators. The satellite is moving in a circular orbit and has pitch angle rotation maneuver. The heat radiation effects on the appendages are considered. When the satellite is rotating around the Earth, the appendages experience periodic heating and cooling in the sunlight and shadow region of the Earth with the variation of the thermal environment.These nonlinear transient heat equations depends on the satellite maneuver angle and the panels vibrations, too. The thermally induced vibrations of the appendages and the heat transfer equation are coupled and should be solved simultaneously.Aninverse dynamic controller is proposed to control the satellite maneuver and appendage vibrations. Finally, the whole system is simulated and the effects of the heat radiation and piezoelectric actuators on the response of the system are studied. Also, the effectiveness and the capability of the controller are analyzed.
Mehran Nosrat Elahi; Ali Reza Basohbat Novinzadeh; Mostafa Zakeri
Volume 8, Issue 1 , April 2015, Pages 53-60
Abstract
The design method presented in this paper is for utilizing, fast and easy system designing of orbital transfer block for transferring satellite from park orbit to destination orbit. The main purpose of this paper is system designing liquid propellant orbital transfer block with a new approach for ideal ...
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The design method presented in this paper is for utilizing, fast and easy system designing of orbital transfer block for transferring satellite from park orbit to destination orbit. The main purpose of this paper is system designing liquid propellant orbital transfer block with a new approach for ideal orbital transfer and presenting a simple interfered systematic method for designing aerospace products. Designing orbital transfer block consists of designing all subsystems and integrating all parts of design. Designing all subsystems can be achieved with a meaningful connection between all system and subsystem constraints. In addition to systematic design approach to each of the design sub algorithms, creating subsystem optimization environment according to physical performance of subsystem and also general integration of orbital transfer block system design in an optimized environment have been carried out. Final result of orbital transfer block design for a specific mission is through mass-dimension convergence of equations in integrated design. Design integration according to design matrix and optimizations and convergences of the design is discussed in the paper. According to presented method, which is scientific, functional and extensible to final design of the product, parametric process of results is briefly validated. So in this paper new method is provided for integrating the design in an optimized and collaborative convergence environment maintaining all systemic constraints and limitations to specify specifications of orbital transfer block systems and subsystems.
Reza Mohsenipour; Mehrzad Nasirian; Abdol Reza Kashaninia; Mohsen Fathi
Volume 8, Issue 1 , April 2015, Pages 61-71
Abstract
Increasing in dimensions of the satellites and using light movingstructures, causes flexibility and uncertainty in their models. Therefor to control the attitude of the satellites, should use those methods which resist against the plant’s model uncertainty and could reject the disturbance and the ...
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Increasing in dimensions of the satellites and using light movingstructures, causes flexibility and uncertainty in their models. Therefor to control the attitude of the satellites, should use those methods which resist against the plant’s model uncertainty and could reject the disturbance and the measurementnoise. One of these methods is the robust control. But due to the location of the poles in the dynamic equations of the satellite, the design of robust controllers faces some problems. In this paper, using aninternal feedback, the dynamic equations are changed so that the poles are located in a more proper place. And then,considering flexibility affects as uncertainty and also, uncertainty in inertia matrix of the satellite, a H∞ controller, and finally to improve the performance, a µ-controller will be designed for the new equations. But these two controllers will be analyzed and compared for the primary equations and not for the new equations.For comparison, a classical controller is also designed forthe primary system.
Ali Reza Aghalari; Ahmad Kalhor; Farhad Shamim
Volume 8, Issue 1 , April 2015, Pages 73-77
Abstract
In this paper, a designing procedure of a Variable Speed Control Moment Gyro (VSCMG) for performing an agile maneuver in an attitude control simulator is described, then a prototype is fabricated and finally the test results are presented. The design of actuator mechanism is based on simulator limitations ...
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In this paper, a designing procedure of a Variable Speed Control Moment Gyro (VSCMG) for performing an agile maneuver in an attitude control simulator is described, then a prototype is fabricated and finally the test results are presented. The design of actuator mechanism is based on simulator limitations (power consumption, dimensions and weight, simplicity) and direction of produced torque.Two DC electrical motors are used for controlling the angular velocity of flywheel and the gimbal slew rate. The motors controller and driver units are designed and implemented, so that the maximum accuracy, minimum errors and best response time could be accessible. Structural Design is based on strength, stiffness, volume and weightalso Necessary analysis are performed using ANSYS. Finally the functional tests of actuator such as measuring the produced torque (using simulator and load transducer), accuracy of gimbal position and gimbal slew rate, accuracy of flywheel rotational speed and power consumption are performed and then the results are presented.