  This paper develops a new exponential forgetting algorithm that can prevent
so-called the estimator windup problem, while retaining fast convergence speed.
To investigate the properties of the proposed forgetting algorithm, boundedness
of the covariance matrix is first analysed and compared with various
exponential and directional forgetting algorithms. Then, stability of the
estimation error with and without the persistent excitation condition is
theoretically analysed in comparison with the existing benchmark algorithms.
Numerical simulations on wing rock motion validate the analysis results.
