Space subsystems design: (navigation, control, structure and…)
Valiollah Shahbahrami; Milad َAzimi; َAlireza Alikhani
Volume 16, Issue 4 , December 2023, , Pages 1-13
Abstract
In this paper, a robust adaptive hybrid control approach based on a combination of super-twisting and non-singular terminal sliding mode control (STNSMC) approaches for vibration and attitude control of a flexible spacecraft with fully coupled dynamic is developed. The proposed adaptation law eliminates ...
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In this paper, a robust adaptive hybrid control approach based on a combination of super-twisting and non-singular terminal sliding mode control (STNSMC) approaches for vibration and attitude control of a flexible spacecraft with fully coupled dynamic is developed. The proposed adaptation law eliminates the need for bounds knowledge of external disturbances and uncertainties. Then an ST-based NSMC generates a continuous control signal to reject the Chattering phenomenon, the non-singular terminal switching control law with the ability to generate continuous control commands to eliminate the chattering phenomenon. Moreover, finite-time convergence is achieved, and the singularity problem has been avoided. The overall stability of the system has been demonstrated using the Lyapunov theory. One of the essential features of the proposed control algorithm is to prevent overestimation of control gains and faster convergence rates comparing to conventional ST and non-singular terminal SMC approaches. The simulations in the form of a comparative study for large-angle maneuver reveal the advantage of the proposed approach.
Space systems design (spacecraft, satellites, space stations and their equipment)
َAlireza Alikhani; Mohammad Reza Salimi
Volume 15, English Special Issue , May 2022, , Pages 55-64
Abstract
The cold gas thruster is one of the significant components of a satellite and its application possesses a marked impact on the entire system performance. The nonlinear function and order of magnitude, lead to increasing the importance of thruster function. Therefore, pre-mission performance assessment ...
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The cold gas thruster is one of the significant components of a satellite and its application possesses a marked impact on the entire system performance. The nonlinear function and order of magnitude, lead to increasing the importance of thruster function. Therefore, pre-mission performance assessment has a considerable effect on the risk reduction of space missions. In this article, an uncomplicated and efficient pendulum scheme for development and implementation of a Thruster Test Stand (TTS), to measure the thrust produced at the end of the nozzle is proposed. The TTS is capable of measuring thrust levels in the range of 0.1Newtons to 3N with operating frequencies up to 50 Hz which is used by various satellite ranges. The experimental results demonstrate that although the designed device is less sophisticated than other test devices, it is capable of measuring the produced thrust very precisely and with less than 15mN.
Seyed Moein Mahmoodzadeh Entezari; Alireza Alikhani; Meysam Mohammadi Amin
Volume 13, Issue 2 , June 2020, , Pages 51-61
Abstract
In this study, a method for designing a thermal optimum reentry path based on aerodynamic database management has been developed using the Kriging and Co-Kriging methods. For the design of the reentry path in the conceptual design phase, the more precise the dynamical model of the reentry vehicle, the ...
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In this study, a method for designing a thermal optimum reentry path based on aerodynamic database management has been developed using the Kriging and Co-Kriging methods. For the design of the reentry path in the conceptual design phase, the more precise the dynamical model of the reentry vehicle, the closer the path is to reality. One of the issues affecting the accuracy of the dynamic model of return vehicle is the aerodynamic coefficients in its flight envelope. For this purpose, in the present study using the new method, accurate aerodynamic data has been developed by combining the data from different solvers in the device flight envelope at the appropriate time. In the following, using the dynamic model and the developed reentry path design algorithm, the thermal optimal return path of the Orion device with constant coefficients and the exact aerodynamic database are compared, and the important parameters of reentry path, such as thermal flux and final velocity, are evaluated.
Ali Reza Alikhani; Seyed Aliakbar Kasaeian
Volume 8, Issue 4 , January 2016, , Pages 1-7
Abstract
Tracking guidance commands for a time-varying aerospace launch vehicle during the atmospheric flight is considered in this paper. Hence, the dynamic terminal sliding mode control law is constructed for this purpose and dynamic sliding mode control is utilized. The terminal sliding manifold causes the ...
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Tracking guidance commands for a time-varying aerospace launch vehicle during the atmospheric flight is considered in this paper. Hence, the dynamic terminal sliding mode control law is constructed for this purpose and dynamic sliding mode control is utilized. The terminal sliding manifold causes the dynamic sliding mode to converge asymptotically to zero in finite-time. The actuator and rate gyro dynamics are included in the model of launch vehicle. Dynamic sliding mode control accommodates unmatched disturbances, while the terminal sliding mode control is used to accelerate the system to reach the dynamic sliding manifold. Finally, the effectiveness of the proposed control is demonstrated in the presence of unmatched disturbances and is compared with the dynamic sliding mode.
Ali Reza Alikhani; Yosef Shamadi
Volume 8, Issue 3 , October 2015, , Pages 1-13
Abstract
Important issues in designing a controller for re-entry vehicles is environmental uncertainties such as rapid changes in atmospheric properties which is an explicit function of altitude and also uncertainties of itselfvehicle such as aerodynamic coefficient, moment of inertia and so on. This paper deals ...
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Important issues in designing a controller for re-entry vehicles is environmental uncertainties such as rapid changes in atmospheric properties which is an explicit function of altitude and also uncertainties of itselfvehicle such as aerodynamic coefficient, moment of inertia and so on. This paper deals with the design of a control in order to overcome the uncertainty thatuses bank angle as a trajectory control variable.Another issue raised in recent studies has been integration of adaptive controller with guidance systems of re-entry vehicles because in real re-entry vehicle the bank angle is not a predefined profile function of velocity or altitude buta guidance algorithm are usedto produce bank commands during the atmospheric flight. Hence, other objectives of the thesis is to study and implementing of a guidance algorithm and proving of desired performance of the designed controller in a perfect scenariofrom starting point of the re-entry path until the opening of parachutes. Performance of designed controller is studied through simulations ofsix degrees of freedom of re-entry vehicle.. The results showed good performance in the presence of parametric uncertainty andunknown initial condition.
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.