Contactless magnetic leadscrew: vibration control and resonance compensation

This paper addresses the vibration control of a high precision positioning system. The system considered is a contactless drive where magnetic coupling is employed between a nut and a leadscrew to achieve a resolution of about 10 nanometers over a range of 10 cm. Due to the use of aerostatic suspension between the spindle, the nut, and the leadscrew, a number of resonances exist in this system. A passband control scheme based on the Hilbert transform to generate the orthogonal components of the oscillating modes is developed. The components are extracted using a neural network to enhance the robustness of the controller. Performance of the controller is evaluated under self-resonance, forced oscillation and transient response. Self-resonance is shown to be completely eliminated while for forced oscillation, the disturbance is shown to be attenuated. Stabilization time of the transient response is also significantly reduced, thereby confirming the vibration suppression capabilities of the controller