Computer Controlled Precise Positioning for Electromagnetic Linear Motor with Correction of Periodic Error

The authors have developed a positioning system of high accuracy using a dual-axis Sawyer linear motor. The fundamental characteristics of the motor are described. Absolute positioning errors on the positioning plane were mechanically improved to within a maximum of 12 μ m. A Fizeau-type laser interferometer with a resolution of 0.2 μ m was used for displacement measurements. The positioning accuracy was improved to within 1 μ m by using a microstep operation and correction of periodic positioning errors by a computer controlled open-loop operation.