A tangible structure includes a set of removable and parallel rods, each rod including a head; a set of drive devices, each drive device including a motor element generating a rotational motion to a transverse shaft to transmit a translational motion to a rod, the drive device being piloted in order to transmit a motion to the rod at a given speed and in a given direction; a holding system for the drive devices making the drive devices integral with each other, and a calculator determining a set of pilot set points, each pilot set point being transmitted to a drive device on the basis of a first digital set point.