For the conservatism problem of stability analysis of T-S fuzzy systems with the common Lyapunov approach, the
fuzzy Lyapunov approach and the piecewise fuzzy Lyapunov approach, this paper proposes a sufficient condition to check
the stability of open-loop discrete T-S fuzzy systems based on the definition of the efficient maximal overlapped-rules group
and the discrete piecewise fuzzy Lyapunov function. This condition only needs satisfying the condition of fuzzy Lyapunov
approach in each efficient maximal overlapped-rule group. Therefore, the proposed condition is less conservative and difficult
than former three approaches. A simulation example shows the effectiveness and advantage of the approach.