Controllability of tandem-connected systems

Necessary and sufficient conditions for the controllability of tandem-connected systems are given. Unlike previous methods, the subsystems need not be first transformed to the Jordan canonical form. Instead, a relatively simple transformation based on the input matrix B has to be applied before using the above conditions. Also, for the special case of subsystems with disjoint sets of eigenvalues, a necessary and sufficient condition is given in terms of the general state representation of the subsystems and is usually easier to apply than the one developed for the general case.