Lf. Ho, CONTROLLABILITY AND STABILIZABILITY OF COUPLED STRINGS WITH CONTROL APPLIED AT THE COUPLED POINTS, SIAM journal on control and optimization, 31(6), 1993, pp. 1416-1437
Controllability and stabilizability of a system of coupled strings wit
h control applied at the coupled points is studied. By investigating t
he properties of certain exponential series, it is shown that the syst
em is approximate controllable if and only if related systems of uncou
pled strings do not share a common eigenvalue. A sufficient condition
for exact controllability is also obtained in terms of the Riesz basis
properties of those exponential series.