In order to accommodate actuator failures which are uncertain in time pattern and value we propose two adaptive backstepping control schemes for parametric strict feedback systems Firstly a basic design scheme on the basis of existing approaches is considered It is analyzed that when actuator failures occur transient performance of the adaptive system cannot be adjusted through changing controller design parameters Then we propose a new controller design scheme based on a prescribed performance bound (PPB) which characterizes the convergence rate and maximum overshoot of the tracking error It is shown that the tracking error satisfies the prescribed performance bound all the time Simulation studies also verify the established theoretical results that the PPB based scheme can improve transient performance compared with the basic scheme while both ensure stability and asymptotic tracking with zero steady state error in the presence of uncertain actuator failures (C) 2010 Elsevier Ltd All rights reserved