The stability of a linear time-invariant system is determined by the eigenvalues of its system matrix A. If all eigenvalues have negative real parts, the system is stable. If any eigenvalue has a positive real part, the system is unstable. Controllability of a linear time-invariant system can be assessed using the Kalman controllability criterion, which states that the system is controllable if the rank of the controllability matrix $[B \quad AB \quad ... \quad A^{n-1}B]$ is equal to the order of the system, $n$.