Flatness-Based Control of a Coriolis Mass Flowmeter
State of the art in Coriolis mass flow metering is the single straight tube oscillating in resonance and actuated by one electromagnetic actuator. The difference in time of two electro-magnetic sensors measuring the velocity of the vibrating tube at the up- and downstream side of the tube is directly proportional to mass flow. By using a lumped parameter model consisting of two coupled oscillating systems that represent the oscillation in the first and second eigenmode one can derive the characteristics of the device in terms of zero and sensitivity, two important parameters in today’s mass flowmeters. In [1, 2] these parameters are calculated from measurements obtained by additionally stimulating the device in the second eigenmode in a cyclic procedure. As only measurements in steady state can be used, the procedure is time consuming and up to now not generally applicable. However, these shortcomings can be overcome by using a new control strategy. In this strategy the oscillation of the first and second eigenmode is assigned in terms of amplitude, frequency and phase via a so called trajectory generator and is realized by a flatness-based control scheme derived from the lumped parameter model. In the paper we will present a method to identify the parameters zero and sensitivity without the need for a cyclic operation of the device.
Wei Gao, Yasuhiro Takaya, Yongsheng Gao and Michael Krystek
H. Röck et al., "Flatness-Based Control of a Coriolis Mass Flowmeter", Key Engineering Materials, Vols. 381-382, pp. 465-468, 2008