Estimation-based adaptive backstepping designs for linear systems

The authors previously introduced a class of adaptive nonlinear controllers which abandon the certainty equivalence principle and employ the backstepping approach with tuning functions. In this paper the authors introduce estimation-based designs which use a linear backstepping controller combined with two types of identifiers-the passive identifier and the swapping identifier. The linear backstepping controller can guarantee stability and performance without adaptation. This is an advantage of the estimation-based designs in this paper over the traditional ones.