Directional notch filters for motion control of flexible structures

A new method to design notch filters for MIMO motion control systems with flexible mechanical structures is proposed. The method involves so-called directional notch filters that work only in the direction of the targeted resonant mode. As a result, only one SISO notch filter is required per mode to suppress a resonance throughout the MIMO system. Compared to the conventional approach where a notch filter is placed and tuned in each of the separate control loops, the new approach reduces the order of the controller significantly and facilitates the design process. The directional notch filter is computed using either the input or output mode shapes of the system. A new numerical optimization method to obtain these mode shapes from frequency response data is described. Experiments on a flexible beam setup demonstrate the feasibility of the proposed method in practice.