An improved non-singular fast terminal sliding mode control scheme for 5-DOF tower cranes with the unknown payload masses, frictions and wind disturbances

Abstract

The accurate positioning and swing suppression of tower cranes remain open problems, especially when considering unknown payload masses, frictions and wind disturbances, making the controller design more challenging. Therefore, considering the factors, without linearization to 5-DOF tower crane dynamics, an improved non-singular fast terminal sliding mode control (INFTSMC) scheme is proposed, which can drive the trolley, jib and cable to the desired positions accurately within finite time while suppressing payload swings effectively under the unknown payload masses, frictions and wind disturbances. Specifically, an improved sliding mode surface is designed to suppress payload swings; a chattering problem is attenuated by constructing an enhanced convergence law; a payload mass estimation strategy is designed to eliminate the vertical positioning error; adaptive schemes are proposed to counteract the effects of unknown frictions and wind disturbances. The stability of the closed-loop system is proven rigorously by using the Lyapunov principle and LaSalle’s invariance theorem. Comparative simulations are implemented to validate the superior control performances and robustness of the proposed method.