A PI controller configuration for robust control of a class of nonlinear systems (Q1850129)

The authors investigate the stabilization and signal tracking problems of a class of nonlinear systems having relative degree equal to one. The single-input nonlinear system has the form \(\dot y= f_1(y,z)+ g(y,z)u\), \(\dot z= f_2(y,z)\), where \(f_1(z,y)\in \mathbb{R}\), \(f_2(y,z)\in \mathbb{R}^{n-1}\), \(g(y,z)\in\mathbb{R}\) are smooth functions of their arguments, \(y\in\mathbb{R}\) is the measured output of the system and \(z\in\mathbb{R}^{n-1}\) is the internal state, \(u\) is the control input. For tracking with PI feedback and semiglobal asymptotic stability, a parametrization of the gain with constant integral term is obtained. The PI controller can be turned to produce nonlocal results.