Space subsystems design: (navigation, control, structure and…)
Milad َAzimi
Articles in Press, Accepted Manuscript, Available Online from 07 April 2022
Abstract
This paper deals with semi-analytical modeling and stability analysis of a coupled slosh-tank dynamics as a multibody system using the Homotopy Perturbation Method (HPM). The sloshing motion of the liquid inside the tank is considered as the equivalent pendulum model. The nonlinear equations of the motion ...
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This paper deals with semi-analytical modeling and stability analysis of a coupled slosh-tank dynamics as a multibody system using the Homotopy Perturbation Method (HPM). The sloshing motion of the liquid inside the tank is considered as the equivalent pendulum model. The nonlinear equations of the motion under lateral and longitudinal excitations (compressive oscillations) are derived using the Lagrangian approach. In this model, the effects of essential parameters such as viscous damping, amplitude, and frequency of the excitation are studied for two typical points inside and outside the stability regions. It has been shown that viscous damping, compared to other principle parameters, brings the points located in the unstable region closer to the stable region. The simulations in terms of stability diagrams, phase portraits, and time histories of sloshing amplitude are achieved using HPM and compared to the numerical Runge-Kutta method to follow the stability phenomena and highlight the analytical approach's validity.
Space subsystems design: (navigation, control, structure and…)
Abbas Dideban; Alireza Ahangarani Farahani
Volume 16, English Special Issue , November 2023, , Pages 25-38
Abstract
This paper presents a new control methodology based on Continuous Time Delay Petri Nets (CTDPN) tool for the attitude control of satellite simulator. The graphical and mathematical features of this tool help the expert designer to design an appropriate controller using graphical model easily, and then ...
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This paper presents a new control methodology based on Continuous Time Delay Petri Nets (CTDPN) tool for the attitude control of satellite simulator. The graphical and mathematical features of this tool help the expert designer to design an appropriate controller using graphical model easily, and then apply the necessary changes to the mathematical model. In this approach, the controller gains are derived from the states and some other variables. Thus, the system states and variables must be available. The new gain tuning algorithm consists of three stages. First, A simulation environment is made for mathematical modeling based on the CTDPN tool and controller design. Secondly, using optimal methods, the controller gains are calculated at any given time and the data are collected. Finally, using the database, a relationship between the set of variables and the gains are derived. Experimental results indicate the promising performance of the controller in comparison to the conventional controller applied to the satellite simulator platform. The results indicate that the designed controller is robust against variation of parameters, as the controller gains are tuned based on the system state and variables.
Space subsystems design: (navigation, control, structure and…)
Milad َAzimi; Samad Moradi
Volume 14, Issue 3 , September 2021, , Pages 51-63
Abstract
The free and forced vibration analysis of a rotating large flexible structure with a single crack is investigated using the Homotopy Perturbation Method (HPM). The crack is modeled with a torsional spring element on a structure that follows the Euler-Bernoulli theory. The nonlinear equations of motion ...
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The free and forced vibration analysis of a rotating large flexible structure with a single crack is investigated using the Homotopy Perturbation Method (HPM). The crack is modeled with a torsional spring element on a structure that follows the Euler-Bernoulli theory. The nonlinear equations of motion of the co-rotational system considering centrifugal forces are derived using the calculus of variation and the Assumed Mode Method (AMM). Applying the Galerkin method, the spatial domain is extracted and the time domain is transformed into a second-order nonlinear differential equation. The results of time response, phase plane, and bifurcation diagrams for different functional parameters variations such as base angular velocity, crack position and stiffness have been analyzed. Moreover, it is shown that as the base angular velocity increases, a tensile force appears along the cracked structure axis, stiff it, and shifts the backbone to the right, this can highly affect the nonlinear features of the system.
Valiollah Ghaffari; Paknoosh Karimaghaee
Volume 11, Issue 1 , June 2018, , Pages 31-40
Abstract
Usually vehicles are equipped with guidance algorithm based on line of sight (LOS) angle. In this way, some measurements like target acceleration, LOS rate, and closing velocity are provided for the guidance algorithm. The noise effect on the guidance loop would be neglected when the variance of the ...
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Usually vehicles are equipped with guidance algorithm based on line of sight (LOS) angle. In this way, some measurements like target acceleration, LOS rate, and closing velocity are provided for the guidance algorithm. The noise effect on the guidance loop would be neglected when the variance of the measurement noise is small. However, the stability property and/or performance of the guidance loop may be effected when the measurement noise is considerable. In this paper, a suitable guidance law is proposed in the presence of measurement noise. Then, a numerical example is provided. The effectiveness of the proposed method in the simulation results is shown in comparison with the previous results.
