ANALYSIS ON ANTI-OVERTURNING STABILITY OF A TRUCK CRANE BASED ON ZERO MOMENT POINT THEORY

Abstract

Truck crane stability has been a hot research issue. It is a conventional method used to calculate the moments equilibrium when analyzing stability. However, errors can occur because of the lack of dynamic simulation in conventional methods. Hence, to minimize errors, this study utilized the zero moment point (ZMP) theory to calculate the maximum lifting capacity of the truck crane considering the dynamic load, and proposed an anti-overturning detection method based on the theory. First, the model of the truck crane was established and the solution formula of ZMP was obtained. From the Lagrange equation, the dynamic model of payload oscillations was analyzed during crane operations. Second, the ZMP theory was used to analyze the stability of the truck crane and derive the maximum payload. Next, the experiment was conducted to measure the pressure of the four outriggers and their center of pressure (CoP) during hoisting, luffing, and slewing operations were calculated. Compared to stable movement, the CoP would vibrate irregularly, consequently reducing the lifting capacity of unstable motion. Finally, the anti-overturning detection method is proposed based on ZMP and CoP. Results demonstrate that the reduction of lifting capacity is caused by the dynamic load. The payload swing has a larger effect on the maximum lifting capacity than hoisting, luffing, and slewing motions. The maximum payload can decrease with the increase of the swing angle. The proposed method provides a correct judgment on the stability of the truck crane, which can accurately predict the overturning state of the crane and reduce the risk in the operation. Keywords: truck crane, overturning, zero moment point, center of pressure, stability