Identification of forklift mast system modal parameters

In order to provide reliable data for the dynamic design or modification of a forklift, and to diagnose the forklift's faults, the modal parameters of its mast system, which is the main component of it to bear moment, have to be obtained precisely. It is proposed that according the modal theory, instead of the finite element method (FEM), an approach based on experiments was applied to identify the modal parameters of the mast system. An experiment of single-point excitation by a hammer and multi-point collection by an accelerometer was performed on the mast system under its three kinds of typical working states - the lift height situations. With the ensemble average curve, which reflects the amplitude frequency characteristic of the frequency-response function practically tested on each point the free-frequency, damping ratio and the mode shapes of the mast system were identified under each working state. According to these modal parameters, the weak points of the mast system, as well as some other problems like the roller fixing or crushing were analyzed specifically and an improvement was put forward. A conclusion was drawn that some reasonable reinforce positions could greatly improve dynamic characteristic of the system and this approach was proved to be precise and reliable.