油圧管路の動特性を利用した遠隔瞬時流量計測手法

第3報パラメータ変化による推定誤差の検討

抄録

We have proposed a remote instantaneous flowrate measurement method, a quasi-remote instantaneous flowrate measurement method and an instantaneous flowrate measurement method by using pressure measurements at two separated points along the pipeline for estimating unsteady flowrate through an arbitrary cross section of the pipeline in hydraulic control systems. In these approaches, unsteady flowrate can be accurately estimated by using the distributed parameter models of the hydraulic pipeline with considering unsteady velocity distribution over the cross section of the pipeline. Under unsteady laminar oil flow conditions, the excellent agreement of estimated and measured flowrate waveforms by a cylindrical choke type instantaneous flowmeter is obtained.
Because these approaches make use of the distributed parameter models for estimating unsteady flowrate, the spatial resolution along the axial direction of the pipeline has an outstanding ability. The accuracy and dynamic response of the estimated unsteady flowrate depend on the values of the parameters used such as the length of the pipeline, kinematic viscosity of the oil, sonic velocity inside the oil-filled pipeline, radius of the pipeline; therefore, it is possible that such variations would cause the estimation errors of unsteady flowrate measurement due to parameter changes accompanied by varying an operating conditions.
The paper describes the estimation errors of unsteady flowrate measurement due to parameter changes in quasi-remote instantaneous flowrate measurement method and instantaneous flowrate measurement method using pressure measurements at two separated points along the pipeline. By introducing error performance index, the influence of parameter changes on the accuracy and dynamic response of the estimated unsteady flowrate are evaluated. Of the four parameters, the variations of the length of the pipeline and sonic velocity produce large errors in the estimated unsteady flowrate during transient periods. The kinematic viscosity is relatively insensitive in the estimated unsteady flowrate.