New nonlinear tracking differential-estimators: Theory and practice

Differential estimation is required for many fields. This paper proposes novel nonlinear tracking differential-estimators to solve the problem of phase lag of traditional approach. In this study, the conventional structure of nonlinear tracking differentiator is expanded. First, the lowest-order design is proposed, which improves the rapidity by reducing one equation compared with the traditional method. Moreover, the idea of feedforward is introduced into constructing the equations set of the differential-estimator to improve the rapidity further. The numerical examples are given, and the practical application experiments are implemented in a servo system. According to the results, the proposals have smaller phase lag, and achieve better practical effect.