Påverkan av mastsvaj på fordonsdynamik : en modelleringsmetod

The purpose of the thesis was to model the effect of mast sway on the velocity of a forklift. This was done in collaboration with Toyota Material Handling. In this thesis, the forklift was modeled as a multibody system (MBS) consisting of two parts, the chassi and the mast. The bodies were considered rigid and connected by a rotational joint, and the chassis was connected to the ground by a prismatic joint. A rotational spring and damper were also placed between the two bodies to model mast sway. The simulations were performed in a Python script where the external force acting on the forklift was the torque generated by the engine. By conducting accelerating and braking experiments in a lab environment, the spring and damper coefficients were determined by matching the frequency and energy decay of the experimental sway in the simulation to the experimental values. This was done for multiple heights, with and without load. Lastly, the model was validated by using PI-control to follow the same reference as the experiments and reviewing whether or not the oscillating behavior from the experiments could be seen in the simulation. The results showed promising agreement with the experimental data, although there are some improvements that could increase its accuracy such as implementing an accurate velocity controller. The model manages to capture most of the behavior seen in the experiments.