Nonlinear Tracking Differentiator Based on Feedforward and Arctangent Function

Nonlinear tracking differentiator (NTD) extracts the filtered continuous signals and differential signals from any noisy signals. Therefore, it is often used in several fields especially in high-precision motion control. In order to improve the tracking characteristics of NTD, this paper presents a design based on the arctangent function and feedforward. The arctangent function has the property of approximate saturation function and feedforward effectively solves the problem of phase lag that is common in differentiators. According to the simulation analysis of the proposal, it can be concluded that its tracking speed, differential characteristics and filtering ability are obviously improved.