Perfect tracking control of discrete-time quadratic TS fuzzy systems via feedback linearisation
Published in International Journal of Systems Science, 2019
Xiaojun Ban, Liwei Ren, Zhibin Yan, Hao Ying
From Equation (13), we have
The right side of the equation can be expressed in a matrix form , where and with
Let , where is defined in Equations (14)–(16), with . Hence,
Because of Equations (3) and (4) ( and ), it is obvious that at least one of is not zero, and the same for . It should be clear that , which consists of , are nonzero column vectors. Matrix is composed by with the rest of its elements being 0. Hence all column vectors of are linearly independent. Therefore, is a nonzero column vector. Note that is a symmetrical matrix. Thus, is in quadratic form. According to Sylvester’s criterion, , (or ) if and only if is positive definite (or negative definite).