A continuous-time, linear, time-invariant control system with a fixed time delay in the feedback loop is considered. We investigate the problem of feedback stabilization. Some easy-to-check criteria to the two-dimensional systems are presented.
Bo Hu. "Stabilization of two-dimensional linear systems by time-delay feedback controls." Differential Integral Equations 9 (2) 409 - 420, 1996. https://doi.org/10.57262/die/1367603356