  In this paper, a continuous finite-time-convergent differentiator is
presented based on a strong Lyapunov function. The continuous differentiator
can reduce chattering phenomenon sufficiently than normal sliding mode
differentiator, and the outputs of signal tracking and derivative estimation
are all smooth. Frequency analysis is applied to compare the continuous
differentiator with sliding mode differentiator. The beauties of the continuous
finite-time-convergent differentiator include its simplicity, restraining
noises sufficiently, and avoiding the chattering phenomenon.
