An application of gain-scheduled control using state-space interpolation to hydroactive gas bearings

Sinusoidal disturbances are common, especially in rotordynamics where mass imbalance causes undesirable vibrations. When the frequency of the disturbance is constant and known, it can be rejected using robust control techniques by including notches in the weights. For a known time-varying frequency, it is possible to design a gain-scheduled controller using multiple controllers optimised for a single frequency. Gain-scheduling strategies using the Youla parametrisation can guarantee stability at the cost of increased controller order and performance loss in the interpolation region. This paper contributes with a gain-scheduling strategy using state-space interpolation, which avoids both the performance loss and the increase of controller order associated to the Youla parametrisation. The proposed state-space interpolation for gain-scheduling is applied for mass imbalance rejection for a controllable gas bearing scheduled in two parameters. Comparisons against the Youla-based scheduling demonstrate the superiority of the state-space interpolation.