Furthermore, if for example there is any motion of actuators 74 and/or 75 that result in rotation ??, although the relative distance between pucks Y1 70 a, and Y2 71 a, along the Y rail will change, the position of one Y puck will be controlled and the other will be free to move and assume an explicit position depending on the position of X1, X2 and Y and other geometrical parameters as shown in t