Research On Dynamic Charecteristics And Optimization Design Of Portal Crane Slewing Mechanism

With the growth of international trade and the rapid development of the logistics industry,portal crane,as an efficient lifting and transportation machinery,is widely used at the ports.Slewing mechanism is one of the most important parts of portal crane and greatly affects its dynamic performance.However,problems caused by vibration under poor working condition and complicated load challenge the safety and stability of portal crane.Therefore,research on vibration mechanism and dynamic characteristics of portal crane,as well as optimization design to promote its dynamic performance is meaningful.In this paper,dynamic characteristics and optimization design of the portal crane slewing mechanism is studied from the following aspects:(1)With Consideration of power transmission,gear meshing of slewing gear set and gears in the reducer,an analytical dynamic model of slewing mechanism includes driving motor,planetary gear reducer,slewing gear set and the slewing parts is established based on gear meshing theory and Lagrange method.This model reflects the inherent relationship between the dynamic performance and the structural parameters of the system.(2)The wind loads of the slewing mechanism during working process are analyzed.The average wind is calculated by the equivalent static method while the fluctuating wind is regarded as a Gauss averaged stochastic process and simulated via harmonic superposition method.Then the total slewing resistance moment including wind load,friction resistance moment and ramp resistance moment is obtained.(3)Relationship between the natural frequency of slewing mechanism and the rotational inertia is analyzed.Further more,factors that causes the changes of rotational inertia like work range and angle of boom are considered,then their effects on natural frequency are analyzed too.Besides,the trend of frequency when mesh stiffness vary is studied.The results shows that the rotational inertia of slewing parts and the mesh stiffness of slewing gear have significant effects on the first order natural frequency.(4)Vibration responses of slewing mechanism under wind loads and the varied torch during starting process are simulated.In order to promote the dynamic performance of portal crane,an optimization design aiming at the minimum dynamic response of vibration acceleration of the slewing mechanism with design variables of shaft size and teeth number is conducted.