S.-K. Ro, G. Khim, J.-K. Park
Korea Institute of Machinery and Materials, Korea
pp. 69 - 72
Keywords: air bearings, active compensation of motion errors, magnetic preloads
In this paper, we introduce rotary and linear motion units with active magnetic preloads and show experimental results for active compensation of motion errors by feedforward method. To compensate motion errors, linear stage and rotary units supported air bearings preloaded by magnetic actuators were developed. Each magnetic actuator has permanent magnet for nominal preload and coil to change the preload force. The characteristic of the actuation was measured as linear in the small range of motion, and the compensation inputs were able to be calculated. The 5-DOF motion errors were measured with combination of a multi-beam laser interferometer and gap sensors with straight edge target. The measured motion errors could modeled as functions of position, and the compensation inputs could be calculated from error functions and motion gains. The motion errors were reduced as level of measurement repeatability with feedforward compensation using magnetic preload control, under 0.1 um in 200 mm of movement range in straightness errors for example.