Spin-Off Maneuvers of Flexible Satellite Using PD Based Constant-Amplitude Inputs

2013 ◽  
Vol 465-466 ◽  
pp. 337-344
Author(s):  
Parman Setyamartana ◽  
Radzuan B. Razali ◽  
Azman Zainuddin
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Steady State ◽  
Input Shaping ◽  
Structural Flexibility ◽  
Main Body ◽  
Solar Panels ◽  
The Finite Element Method ◽  
Constant Amplitude ◽  
The Earth

Spin-off maneuver of a flexible satellite using constant-amplitude thrusters is studied in this paper. The satellite consists of a rigid main body and two symmetrical solar panels. The panels are having structural flexibility and their motions are discretized following the finite element method. Under constant-amplitude thrusts, steady-state attitude angle oscillations may occur in large amplitude after the maneuvers. Since in operation the satellite should point to certain area on the earth precisely, these oscillations of course are not acceptable. To reduce the oscillations, proportional derivative (PD) based constant-amplitude input shaping logic is proposed to determine time locations of thruster switching. Then, under such inputs, spin-downs of the satellite are simulated numerically. Results of simulations indicate that the precise orientation of the satellite can be achieved.

scholarly journals Finite Element Analysis of Thermoelastic Contact Stability

1994 ◽  
Vol 61 (4) ◽  
pp. 919-922 ◽  
Author(s):  
Taein Yeo ◽  
J. R. Barber
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Steady State ◽  
Eigenvalue Problem ◽  
Linear Perturbation ◽  
Dimensional System ◽  
The Finite Element Method ◽  
One Dimensional ◽  
Thermoelastic Contact ◽  
Element Method

When heat is conducted across an interface between two dissimilar materials, theimoelastic distortion affects the contact pressure distribution. The existence of a pressure-sensitive thermal contact resistance at the interface can cause such systems to be unstable in the steady-state. Stability analysis for thermoelastic contact has been conducted by linear perturbation methods for one-dimensional and simple two-dimensional geometries, but analytical solutions become very complicated for finite geometries. A method is therefore proposed in which the finite element method is used to reduce the stability problem to an eigenvalue problem. The linearity of the underlying perturbation problem enables us to conclude that solutions can be obtained in separated-variable form with exponential variation in time. This factor can therefore be removed from the governing equations and the finite element method is used to obtain a time-independent set of homogeneous equations in which the exponential growth rate appears as a linear parameter. We therefore obtain a linear eigenvalue problem and stability of the system requires that all the resulting eigenvalues should have negative real part. The method is discussed in application to the simple one-dimensional system of two contacting rods. The results show good agreement with previous analytical investigations and give additional information about the migration of eigenvalues in the complex plane as the steady-state heat flux is varied.

A Computational Method for Modeling Interface Corner Crack under Steady-State Delamination

2012 ◽  
Vol 486 ◽  
pp. 457-463
Author(s):  
Badrinath Veluri ◽  
Henrik Myhre Jensen
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Steady State ◽  
Crack Front ◽  
Strain Energy Release ◽  
Computational Method ◽  
The Finite Element Method ◽  
Corner Crack ◽  
Corner Cracks ◽  
Element Method

Corner cracks under steady-state delamination were investigated. The fracture mechanics parameters that include the strain energy release rate and the three-dimensional mode-mixity along the interface crack front are estimated. A numerical approach was then applied for coupling the far field solutions based on the Finite Element Method to the near field (crack tip) solutions based on the J-integral methodology. A quantitative approach was formulated based on the finite element method with iterative adjustment of the crack front nodal coordinates to estimate the critical delamination stresses as a function of the fracture criterion and corner angles.

scholarly journals Investigations on the Performance of Grounding Device with Spike Rods (GDSR) with the Effects of Soil Resistivity and Configurations

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3538 ◽  
Author(s):  
Abdul Wali Abdul Ali ◽  
Nurul Nadia Ahmad ◽  
Normiza Mohamad Nor ◽  
Nur Farahi Idris ◽  
Farhan Hanaffi
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Steady State ◽  
Electric Field ◽  
Optimum Design ◽  
Test Data ◽  
The Finite Element Method ◽  
Soil Resistivity ◽  
Low Resistivity ◽  
High Magnitude

In a recently published work, the characteristics of a new grounding device with spike rods (GDSR) with various arrangements of ground electrodes under high magnitude impulse currents (up to 16 kA), was investigated. In an earlier study, the ground electrodes were installed in low resistivity test media, with resistance at steady state (Rdc) values ranging from 11 Ω to 75 Ω. In practice, various soil resistivity, ranging from a few Ohm-metres to several kiloOhm-metres, have been reported in the standards. It is, therefore, necessary to investigate the characteristics of GDSR with different arrangements of ground electrodes in various soil resistivities under high impulse currents. In this present paper, six configurations of ground electrodes are used, installed at three different sites and subjected to high impulse conditions. Impulse test data of all the grounding systems are analyzed. The Finite Element Method (FEM) is used to compute the electric field values of the ground electrodes achieved. It is found that the highest electric field occurs in the presence of electrodes with the highest Rdc, soil resistivity and current magnitudes. This new data would be useful in bolstering the performance of GDSR in various types of soil resistivities, electrode arrangements and current magnitudes, which may allow for optimum design of grounding systems.

Steady-state multiphysics analysis of stator bar using finite element method

2020 ◽  
pp. 1-14
Author(s):  
José William Ribeiro Borges ◽  
Wellington da Silva Fonseca ◽  
Fernando de Souza Brasil ◽  
Ramon C.F. Araújo
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Steady State ◽  
Thermal Effects ◽  
Experimental Measurements ◽  
The Finite Element Method ◽  
Insulation System ◽  
State Behavior ◽  
Steady State Behavior ◽  
Element Method

The electrical insulation is one of the main sources of failures in hydro-generators, therefore it is important to research the insulation system of stator bars. In this paper, it is developed a steady-state multiphysics analysis of a stator bar using the Finite Element Method to assess its steady-state behavior in the electrical, magnetic and thermal domains. Different aspects are analyzed in simulations, such as capacitance, mechanical stress and thermal effects. Numerical results are compared with experimental measurements for validation.

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