Modified time delay control for nonlinear systems

This paper proposes a modified scheme of time delay control for nonlinear systems. Time delay control is useful because its structure is simple and it does not need to know full knowledge of uncertainties. But it still requires knowing the range of uncertainties. The modified scheme is to adjust a controller parameter, and does not have to know the range of uncertainties. Therefore it can be applied to less known nonlinear systems. The adjustment of controller parameter is performed by estimating the convergency ratio of output derivative whose order is the same as the relative degree of a system. The scheme may be sensitive to noise because it uses the output derivative. This problem is solved by replacing the output derivative by the corresponding input which converges to the derivative as time goes on. Simulation results show that the proposed scheme is effective and it can be applied to systems subject to noise.<>