Coriolis mass-flow meter with integrated multi-DOF active vibration isolation

Abstract

Vibration isolation of more than 40 dB is achieved for a Coriolis Mass-Flow Meter (CMFM) with integrated Active Vibration Isolation. A CMFM is an active device based on the Coriolis force principle for direct mass-flow measurements independent of fluid properties. The mass-flow measurement is derived from tube displacement measurements. Support excitations can introduce motions that cannot be distinguished from the Coriolis force induced motion, thus introducing a measurement error. Therefore, the measurement stage is passively suspended at 30 Hz in the 3 out-of-plane directions. Active vibration isolation is added to increase the attenuation. In this paper the system model and controller design are presented. Based on the model an on-scale proof of principle is built and the model and controller are validated in multi-DOF. Acceleration feedback and a novel adaptive feedforward control strategy are compared A filtered-reference least-mean-square (FxLMS) adaptive scheme is used to determine the optimal feedforward controller parameters to minimise a squared error signal; the motion of the measurement stage. Both strategies result in an attenuation of 10 – 20 dB at 175 Hz in addition to the 30 dB attenuation obtained by the 30 Hz passive vibration isolation stage. The performance of the feedback strategy is limited by robust stability and the the feedforward performance is limited by sensor noise.