Design of an improved tracking differentiator

To improve the robustness of tracking differentiator,the nonlinear sliding mode tracking differentiator is analyzed in details in this paper.Then an improved second-order sliding mode tracking differentiator is presented using Lyapunov stability theory.Integrating the characteristics of linear and nonlinear tracking differentiators,the proposed tracking differentiator can track and differentiate any signal;meanwhile,its structure is simple and it is easy for application.Numerical simulations are carried out on this improved tracking differentiator and on a super-twisting tracking differentiator.Results show that the improved tracking differentiator can reduce the chartering of differential signal.