A machine table has five kinds of straight motion errors, when it moves along a reference. Those are the errors of the vertical and horizontal positions, and the pitch, roll and yaw angle attitude errors. In this system, a steel block is floated and retained by some air pads. The block and the pads are mounted on a conventional mechanical sliding table. The straight motion errors of the block are detected by some optical and electronic devices. Then the block is controlled in its positions and angle attitudes by changing the supply pressure to each pad so that the block moves straightly. The working length of the system is 1 000 mm and the maximum working speed is 250 mm/min. The errors of the positions against reference are less than 0.1 μm and the changes of attitudes are less than 0.2 sec of arc.
