New tracking-differentiator design and analysis of its stability and convergence

A new simple linear tracking-differentiator (T-D) is presented. Stability and convergence of the T-D are thoroughly proved, which avoids inconvenience of stability proof for nonlinear T-D with switch function. Through error analysis, the presented T-D can extract differential of any piecewise smooth nonlinear signals to reach a high accuracy. Compared with the nonlinear T-D with switch function, shaking phenomenon is avoided at the switching point of the function. By further modifying the linear T-D, it can effectively restrain differential impulses produced by initial errors of signals or by signals suddenly changing. Finally, analysis of several simulation examples shows the effectiveness of the proposed theory.