Control design for non-minimum phase-shift systems

The authors propose a procedure for the control design of any process with unstable zeros (open loop zeros configuration in the right half plane). The parameters of the control algorithm are quickly determined using a symmetry principle defined in the root locus. This root locus procedure aims to assign a second order dominant mode for the closed loop system transfer function. The proposed method can be applied to any digital process or to any continuous process which includes a delay time, provided that an equivalent linear analog transfer function is used. For that, the prewarped Tustin transformation or Pade approximation can be applied beforehand