Structural Modeling of a Flexible Reachtruck Mast as a Distributed Parameter System

The increasing need for storing goods efficiently in warehouses while maintaining the same floor area raises the challenge of designing vehicles with high lift capacity and with a high flexibility at the same time. Modern Reachtrucks with lift heights of up to fifteen meters belong to this category. This causes a vulnerability to structural bending of the material which can lower workspace safety and induce damage to the goods. To cope with this problem, mast damping systems are necessary. For a proper active mast damping by the forklift's actuators a precise knowledge of the system behavior in push direction, i.e. the system's eigenfrequency, is necessary. In the industry, a common procedure is therefore a time and resource intensive measurement of the system's eigenfrequencies for different lift heights. This study provides a precise mathematical formulation of the mast system as a flexible multibody system based on easy accessible parameters which models the eigenfrequencies sufficiently. The system's equations of motion are derived by formulating the total energy of the system and making use of the Lagrangian method. In the end, measurements with different masts of different heights and lift capabilities verify the presented method.