A Method to Improve the Accuracy of Bridge Cranes Overload Protection Using the Signal Graph

Often during the bridge cranes operation, there occur the crane major components’ breakdowns, due to overload. Therefore, to prevent these breakdowns, overhead cranes are equipped with safety devices to protect the mechanism from the overload. The system of bridge cranes protection against overload should expediently provide the crane securing against peak overloads as well as systematic overloads, another necessary requirement being to ensure such protection high accuracy, assessed using the accuracy coefficient. To determine the overhead crane overload protection accuracy coefficient, the “crane–limiter–load” system movement is presented in the form of a signal graph. Transfer functions’ dependencies are found by determining the dynamic loads applied to on the hoisting ropes. A method has been developed to improve the accuracy of bridge cranes protection from systematic and peak overloads by the means of a quasi-zero stiffness load limiter designed. It is proposed to use in this load limiter design a roller transmission mechanism that allows to achieve the load limiter’s quasi-zero stiffness.