Patent ID: 8190288

Claim:
A method of controlling the movement of a load handling device using a flatness based control system, wherein the load handling device comprises a displacement unit displaceable by a displacement electrical drive, a vertical mast attached on the displacement unit and a lifting unit arranged on the vertical mast and vertically displaceable by a lifting electrical drive, wherein the method comprises the steps of: a) defining reference trajectories for the displacement unit and the lifting unit, wherein the reference trajectories are optimized with respect to maximum permissible mechanical and dynamic stress appearing on the vertical mast and on the electrical drives as well as with respect to a time-minimized operating displacement of the load handling device during operation between a start position and a target position, wherein the reference trajectories are adapted to system behavior of the load handling device in such a way that a permissible deformation of the vertical mast during operation of the load handling device between the starting and target positions is predefined at least by one mechanical threshold value, and a mast deflection is equal to zero when the load handling device is in the target position, b) calculating desired trajectories at least for desired positioning forces of the displacement and lifting units based on the reference trajectories, wherein the displacement and lifting units receive the desired positioning forces in time cycles; and c) controlling movement of the displacement and lifting units along the desired trajectories in such a way that the target position of the displacement and lifting units is reached largely free of vibration by an end of movement of the electrical drives.