scholarly journals Sensitivity Analysis of Limit-Cycle Oscillating Hybrid Systems

2011 ◽  
Vol 33 (4) ◽  
pp. 1475-1504 ◽  
Author(s):  
Kamil A. Khan ◽  
Vibhu P. Saxena ◽  
Paul I. Barton
Keyword(s):  
Sensitivity Analysis ◽  
Hybrid Systems ◽  
Limit Cycle

Sensitivity analysis of limit cycle oscillations

2012 ◽  
Vol 231 (8) ◽  
pp. 3228-3245 ◽  
Author(s):  
Joshua A. Krakos ◽  
Qiqi Wang ◽  
Steven R. Hall ◽  
David L. Darmofal
Keyword(s):  
Sensitivity Analysis ◽  
Limit Cycle ◽  
Limit Cycle Oscillations

A self-consistent formulation for the sensitivity analysis of finite-amplitude vortex shedding in the cylinder wake

2016 ◽  
Vol 800 ◽  
pp. 327-357 ◽  
Author(s):  
P. Meliga ◽  
E. Boujo ◽  
F. Gallaire
Keyword(s):  
Sensitivity Analysis ◽  
Limit Cycle ◽  
Stokes Equations ◽  
Finite Amplitude ◽  
Cylinder Wake ◽  
Mean Flow ◽  
Cycle Frequency ◽  
Flow Perturbation ◽  
Self Consistent ◽  
The Mean

We use the adjoint method to compute sensitivity maps for the limit-cycle frequency and amplitude of the Bénard–von Kármán vortex street in the wake of a circular cylinder. The sensitivity analysis is performed in the frame of the semi-linear self-consistent model recently introduced by Mantič et al. (Phys. Rev. Lett., vol. 113, 2014, 084501), which allows us to describe accurately the effect of the control on the mean flow, but also on the finite-amplitude fluctuation that couples back nonlinearly onto the mean flow via the formation of Reynolds stress. The sensitivity is computed with respect to arbitrary steady and synchronous time-harmonic body forces. For a small amplitude of the control, the theoretical variations of the limit-cycle frequency predict well those of the controlled flow, as obtained from either self-consistent modelling or direct numerical simulation of the Navier–Stokes equations. This is not the case if the variations are computed in the simpler mean flow approach overlooking the coupling between the mean and fluctuating components of the flow perturbation induced by the control. The variations of the limit-cycle amplitude (that falls out the scope of the mean flow approach) are also correctly predicted, meaning that the approach can serve as a relevant and systematic guideline to control strongly unstable flows exhibiting non-small, finite amplitudes of oscillation. As an illustration, we apply the method to control by means of a small secondary control cylinder and discuss the obtained results in the light of the seminal experiments of Strykowski & Sreenivasan (J. Fluid Mech., vol. 218, 1990, pp. 71–107).

scholarly journals Optimality Condition-Based Sensitivity Analysis of Optimal Control for Hybrid Systems and Its Application

2012 ◽  
Vol 2012 ◽  
pp. 1-22
Author(s):  
Chunyue Song
Keyword(s):  
Optimal Control ◽  
Sensitivity Analysis ◽  
Hybrid Systems ◽  
Optimality Condition ◽  
Optimal Control Problems ◽  
Numerical Solutions ◽  
Equivalent Transformation ◽  
Control Problems ◽  
Continuous Control ◽  
Mode Transition

Gradient-based algorithms are efficient to compute numerical solutions of optimal control problems for hybrid systems (OCPHS), and the key point is how to get the sensitivity analysis of the optimal control problems. In this paper, optimality condition-based sensitivity analysis of optimal control for hybrid systems with mode invariants and control constraints is addressed under a priori fixed mode transition order. The decision variables are the mode transition instant sequence and admissible continuous control functions. After equivalent transformation of the original problem, the derivatives of the objective functional with respect to control variables are established based on optimal necessary conditions. By using the obtained derivatives, a control vector parametrization method is implemented to obtain the numerical solution to the OCPHS. Examples are given to illustrate the results.

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