  This paper presents a new improved nonlinear tracking differentiator (INTD)
with hyperbolic tangent function in the state space system. The stability and
convergence of the INTD are thoroughly investigated and proved. Through the
error analysis, the proposed INTD can extract differentiation of any piecewise
smooth nonlinear signal to reach a high accuracy. the INTD has the required
filtering features and can cope with th nonlinearities caused by the niose.
Through simulations, the INTD is implemented as signal derivative generator for
the closed loop feedback control system with a nolinear PID controller for the
nonlinear Mass Spring Damper system and showed that it could achieve the signal
tracking and differentiation faster with a minimum mean square error.
