Two-delay digital robust control-avoiding the problem of unstable zeros

In the design of linear control systems, the existence of unstable zeros makes it difficult to construct many control systems. When the usual digital control scheme is used, unstable zeros appear in the discrete-time model even though the continuous-time plant is minimal-phase. To avoid this unstable zero problem, the authors propose two digital control schemes called two-delay controls, in which the control input is changed twice in one sampling interval, and apply them to the design of robust controllers