A Flatness-Based Nonlinear Control Scheme for Wire Tension Control of Hoisting Systems

A double-rope winding hoisting system (DRWHS) is usually employed to transport weight or workers in mines usually from ultra-deep underground ( >1000m). An electro-hydraulic servo system (EHSS), which consists of two hydraulic cylinders, two movable headgear sheaves and lots of indispensable sensors, is employed to actively coordinate two wire tensions. The nonlinear dynamic model of the DRWHS is introduced and it is divided into two subsystems, i.e., the hoisting system and the EHSS with state space representations. However, as a complex machine-electricity-hydraulic system, the accurate dynamic model of the DRWHS is usually hard to obtain. Therefore, a flatness-based controller (FBC), which is insensitive to unmodeled characteristics of the dynamic model and measurement noises of sensors, is proposed to improve the tension coordination of two wire tensions of the DRWHS. The explicit FBC design schemes for the DRWHS and the control law are presented, and the stability of the proposed controller are proved by defining a Lyapunov function. The controller proposed is characterized by no derivatives of state variables and lower controller design complication so that measurement noises of sensors and unmodeled characteristics are not amplified. An experimental bench of the DRWHS is established to verify the performance of the proposed controller. Experimental results show that the proposed controller exhibits a better performance on the tension coordination control of two wire ropes compared with a backstepping controller (BC) and a conventional proportional-integral (PI) controller.