Fault-tolerant control of dynamic systems with unknown control direction-input nonlinearities-actuator failures

This paper aims at investigating fault-tolerant tracking control designs for uncertain multivariable systems involving unknown floating dynamics, fading actuators, input nonlinearities with non-symmetric saturation and dead-zones, and unknown control direction. A robust adaptive control approach with simple structure is proposed to cope with these factors concurrently, where the lack of knowledge of control sign is handled by incorporating in the control law a Nussbaum-type function. Furthermore, of practical interest, the adaptive compensation of the effects of the nonlinear inputs requires neither the knowledge of their parameters nor the construction of their inverse.