Adaptive command-filtered control for system with unknown control direction caused by input backlash

For nonlinear system subject to unknown control direction caused by input backlash, an adaptive commandfiltered control strategy is presented in this work. The proposed control method not only overcomes "computational complexity explosion"inherent in traditional backstepping method, but also guarantees rapid convergence of tracking error. Meanwhile, a salient characteristic of command -filtering error is that the finite convergence time is assigned in a prior, which is proved by Lyapunov stability method. Especially, unknown control gain caused by input backlash of controlled system is handled by Nussbaum -type function. Finally, simulation analysis and experimental case illustrate the feasibility and effectiveness of proposed control scheme.