Track maintenance machine and method for tamping sleepers of a track

A track maintenance machine comprising:

• a tamping unit for tamping sleepers of a track lying in a ballast bed,
• an assembly frame;
• tamping tools;
• a vertical adjustment drive;
• a tool carrier which is mounted for vertical adjustment on said assembly frame and on which said tamping tools are arranged so as to be squeezable towards one another, wherein the tool carrier is coupled to said vertical adjustment drive
• a control device, configured for actuating said vertical adjustment drive, wherein the control device comprises:
• a control circuit which is set up for controlling a lowering motion of the tool carrier, the control circuit including a controller, a setting device for the vertical adjustment drive and a measuring device for recording the lowering motion;
• wherein the control circuit is provided with a computing unit and wherein a pre-control comprising a filter is installed upstream of said controller by means of which a command variable (w) can be adjusted wherein a computer unit is iterative control algorithm is set up.