Positive observation of Takagi-Sugeno systems

This paper presents conditions for design of observers for nonlinear systems represented by a Takagi-Sugeno-type model, whose state variables take only nonnegative values at all times t for any nonnegative initial state (positive systems). The derived observers have a Takagi-Sugeno structure and ensure the nonnegativity of the observed states. The conditions are derived as Linear Programming and Linear Matrix Inequalities, and tested on a simulated practical problem.