In this paper, we study the exact controllability of a system of two wave equations coupled by velocities with boundary control acted on only one equation. In the first part of this paper, we consider the $ N $-d case. Then, using a multiplier technique, we prove that, by observing only one component of the associated homogeneous system, one can get back a full energy of both components in the case where the waves propagate with equal speeds (i.e. $ a = 1 $ in (1)) and where the coupling parameter $ b $ is small enough. This leads, by the Hilbert Uniqueness Method, to the exact controllability of our system in any dimension space. It seems that the conditions $ a = 1 $ and $ b $ small enough are technical for the multiplier method. The natural question is then : what happens if one of the two conditions is not satisfied? This consists the aim of the second part of this paper. Indeed, we consider the exact controllability of a system of two one-dimensional wave equations coupled by velocities with a boundary control acted on only one equation. Using a spectral approach, we establish different types of observability inequalities which depend on the algebraic nature of the coupling parameter $ b $ and on the arithmetic property of the wave propagation speeds $ a $.
Citation: |
[1] | F. Alabau, Observabilité frontière indirecte de systèmes faiblement couplés, C. R. Acad. Sci. Paris Sér. I Math., 333 (2001), 645-650. doi: 10.1016/S0764-4442(01)02076-6. |
[2] | F. Alabau-Bousouira, A two level energy method for indirect boundary obsevability and controllability of weakly coupled hyperbolic systems, SIAM J. Control. Optim, 42 (2003), 871-906. doi: 10.1137/S0363012902402608. |
[3] | F. Alabau-Boussouira and M. Léautaud, Indirect controllability of locally coupled wave-type systems and applications, J. Math. Pures Appl., 99 (2013), 544-576. doi: 10.1016/j.matpur.2012.09.012. |
[4] | F. Alabau-Boussouira, Z. Wang and L. Yu, A one-step optimal energy decay formula for indirectly nonlinearly damped hyperbolic systems coupled by velocities, ESAIM Control Optim. Calc. Var., 23 (2017), 721-749. doi: 10.1051/cocv/2016011. |
[5] | F. Ammar Khodja and A. Bader, Stabilizability of systems of one-dimensional wave equations by one internal or boundary control force, SIAM J. Control Optim., 39 (2001), 1833–1851 (electronic). doi: 10.1137/S0363012900366613. |
[6] | F. Ammar Khodja, A. Benabdallah and C. Dupaix, Null-controllability of some reaction-diffusion systems with one control force, J. Math. Anal. Appl., 320 (2006), 928-943. doi: 10.1016/j.jmaa.2005.07.060. |
[7] | Y. Bugeaud, Approximation by Algebraic Numbers, vol. 160 of Cambridge Tracts in Mathematics, Cambridge University Press, Cambridge, 2004, doi: 10.1017/CBO9780511542886. |
[8] | S. Gerbi, C. Kassem, A. Mortada and A. Wehbe, Exact controllability and stabilization of locally coupled wave equations: Theoretical Results, Z. Anal. Anwend., 40 (2021), 67–96, arXiv e-prints, arXiv: 2003.14001. doi: 10.4171/ZAA/1673. |
[9] | V. Komornik, Exact Controllability and Stabilization, RAM: Research in Applied Mathematics, Masson, Paris; John Wiley & Sons, Ltd., Chichester, 1994, The multiplier method. |
[10] | V. Komornik and P. Loreti, Ingham-type theorems for vector-valued functions and observability of coupled linear systems, SIAM J. Control Optim., 37 (1999), 461-485. doi: 10.1137/S0363012997317505. |
[11] | V. Komornik and P. Loreti, Fourier Series in Control Theory, Springer Monographs in Mathematics, Springer-Verlag, New York, 2005. |
[12] | J.-L. Lions, Contrôlabilité Exacte Perturbations et Stabilisation de Systèmes Distribués. Tome 1., Contrôlabilité Exacte, Recherches en Mathématiques Appliquées, Masson, Paris, Milan, Barcelone, 1988. |
[13] | P. Loreti and B. Rao, Compensation spectrale et taux de décroissance optimal de l'énergie de systèmes partiellement amortis, C. R. Math. Acad. Sci. Paris, 337 (2003), 531-536. doi: 10.1016/j.crma.2003.08.009. |
[14] | N. Najdi, Etude de la Stabilisation Exponentielle et Polynômiale de Certains Systèmes d'équations Couplées par des Contrôles Indirects Bornés ou non Bornés, PhD thesis, Université de Valenciennes et Université Libanaise, 2016. |
[15] | A. Pazy, Semigroups of Linear Operators and Applications to Partial Differential Equations, vol. 44 of Applied Mathematical Sciences, Springer-Verlag, New York, 1983 doi: 10.1007/978-1-4612-5561-1. |
[16] | B. Rao and Z. Liu, A spectral approach to the indirect boundary control of a system of weakly coupled wave equations, Discrete and Continuous Dynamical Systems, 23 (2009), 399-414. doi: 10.3934/dcds.2009.23.399. |
[17] | L. Toufayli, Stabilisation Polynomiale et Contrôlabilité Exacte Des Équations Des Ondes Par Des Contrôles Indirects et Dynamiques, PhD thesis, Université de Strasbourg, 2013. |
[18] | A. Wehbe and W. Youssef, Indirect locally internal observability and controllability of weakly coupled wave equations, Differential Equations and Applications-DEA, 3 (2011), 449-462. doi: 10.7153/dea-03-28. |
[19] | X. Zhang and E. Zuazua, Polynomial decay and control of a $1-d$ hyperbolic-parabolic coupled system, J. Differential Equations, 204 (2004), 380-438. doi: 10.1016/j.jde.2004.02.004. |