Output feedback adaptive control of multivariable nonlinear systems using Nussbaum gain method

1. INTRODUCTION Output feedback adaptive control of single input and single output (SISO) nonlinear systems with unknown constant parameters has been well developed via backstepping design[1]. In order to achieve asymptotic tracking of a known reference trajectory, a restrictive assumption is the sign of the high frequency gain to be known. Some results for relaxing this assumption have also been proposed [2]. It has been shown that if the sign of the high frequency gain is unknown, the …

Output feedback adaptive control of multivariable nonlinear systems using Nussbaum gain method

A new output feedback adaptive control scheme for multi-input and multi-output nonlinear systems with parametric uncertainty is presented based on the Nussbaum gain method and the backstepping approach. The high frequency gain matrix of the linear part of the system is not necessarily positive definite, but can be transformed into a lower or upper triangular matrix whose signs of diagonal elements are unknown. The new required condition for the high frequency gain matrix can be easily checked for certain plants so that the proposed method is widely applicable. The global stability of the closed loop systems is guaranteed through this control scheme, at the same time the tracking error converges to zero.