  This paper develops a novel force observer for bilateral teleoperation
systems. Type-2 fuzzy logic is used to describe the overall dynamic system, and
Moving Horizon Estimation (MHE) is employed to assess clean states as well as
the values of dynamic uncertainties, and simultaneously filter out the
measurement noises, which guarantee the high degree of accuracy for the
observed forces. Compared with the existing methods, the proposed force
observer can run without knowing exact mathematical dynamic functions and is
robust to different kinds of noises. A force-reflection four-channel
teleoperation control laws is also proposed that involving the observed
environmental and human force to provide the highly accurate force tracking
between the master and the slave in the presence of time delays. Finally,
experiments based on two haptic devices demonstrate the superiority of the
proposed method through the comparisons with multiple state-to-the-art force
observers.
