A methodology for calculating limit deceleration of flexible hoisting system: A case study of mine hoist

Abstract

Mine hoist is a typical flexible lifting system. Due to the cable flexibility, the system is prone to severe shocks and even slippage during emergency braking. To establish a safe emergency braking operation for mine hoist, retarded velocity should be less than the limit deceleration value. The simplified mathematical model shows that the system dynamic response along the longitudinal axis of the wire rope (longitudinal dynamics) is a typical second-order underdamped one. Due to the inherent characteristics of the flexible lifting system, the longitudinal dynamic response under slippage condition exhibits the following characteristics: the response curve deviates from the input signal, that is, the retarded velocities of cable and pulley at their contact points are no longer equal. Based on this finding, deceleration deviation coefficient is defined to normalize the longitudinal response curves, which can help us to determine the extent to which the output signal deviates from the input one; and the sudden increase in the deceleration deviation coefficient is considered as an indicator of rope slippage during emergency braking. The proposed scheme is verified and evaluated by means of simulation model. Subsequent results indicate that the limit deceleration valves obtained by the proposed approach have the same trend and magnitude as those obtained by conventional one, which illustrates that the proposed methodology is feasible. The advantage of the proposed approach is that the solution for each set of operating parameter is unique and certain. As for the conventional approach, the solution is not unique because of the introduction of safety factor, which will cause some trouble to the user. In subsequent work, a test bench will be set up to verify and optimize the proposed scheme.