On undershoot in SISO systems

We show that the step response of an asymptotically stable strictly proper nonminimum phase continuous time system with m₁ real open right half plane zeros, no conjugate complex zeros and poles, and with real open left half plane zeros and poles satisfying a given “bracketing” condition, exhibits undershoot exactly int m₁+½ times. Both qualitative and quantitative arguments are also introduced to highlight the main issues under discussion. Simple examples are given to illustrate and complement the main result of this paper