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Thorsten Schröder, Kourosh Kolahi, Helmut Röck
A Novel Control Algorithm for Coriolis Mass Flowmeters
Coriolis mass flowmeters (CMF) are characterized by a high measurement accuracy and a low cross sensitivity towards fluid properties. However field applications show that particularly CMF using a single straight pipe sometimes suffer from an offset shift and sensitivity variations particularly under difficult process conditions. A model-based approach presented in this paper will allow to determine these characteristics of the meter during normal operation. The approach is based on a compensation of the Coriolis forces as well as the internal couplings of the CMF. To realize the compensation method, a novel control algorithm consisting of two cascaded controllers is presented. The outer control loop is based on a phasor method and an optimal state feedback regulator (LQ regulator) for the output signals of the CMF. The inner loop controls the phase shift between the input and output signal of the first mode of the measurement pipe by adjusting the actuation frequency. Therefore operation of the CMF in its first mode eigenfrequency is guaranteed.
tm – Technisches Messen, Oldenbourg Wissenschaftsverlag
Print ISSN: 0171-8096
Volume: 71, 04/2004
Pages: 259 - 268