Linear real-time estimation method of conductivity resistance-capacitance network parameter

Abstract

The invention relates to a linear real-time estimation method of a conductivity resistance-capacitance network parameter, belonging to the technical field of solution conductivity soft measurement. The method is characterized by comprising the following steps of: converting the measurement of solution conductivity into the parameter estimation of an equivalent resistance-capacitance network: on the basis of a mathematical model between a square wave excitation signal, a response direct-current voltage signal and two resistance and capacitance parameters of the equivalent resistance-capacitance network, carrying out multi-element polynomial fitting on the non-linear model off line; adopting an alternating-current square wave excitation resistance-capacitance network of various frequencies by taking the existence of various uncertainties into account during on-line measurement; meanwhile, establishing an over-determined equation set by utilizing the off line fitted multi-element polynomial model; and obtaining the real-time estimation of a resistance-capacitance parameter through a Gauss elimination finite step arithmetic operation and a radical operation of quartic equation solvingon the basis of linear least square principle. The method has the advantages of higher estimation speed and stronger anti-jamming capability and is suitable for the on-line real-time accurate measurement of the conductivity industry.

Description

technical field [0001] The invention belongs to the technical field of solution conductivity soft measurement, and relates to a method for decoupling and estimating parameters of a conductance cell equivalent resistance-capacitance network, in particular to the problem of nonlinear parameter estimation of a square-wave excitation resistance-capacitance network system through multivariate polynomial fitting Converts to a method for linear least squares parameter estimation. Background technique [0002] As a typical application of resistance measurement in the case of resistance-capacitance coupling, conductivity measurement has important research value. As an important electrochemical analysis parameter of electrolyte solution, conductivity has been widely used in production and scientific research departments such as environmental monitoring, chemical industry, medicine, biology, agriculture and manufacturing. When measuring the conductivity of the solution, due to the inf...

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Problems solved by technology

The document "ZHONG C Q, HAN H L, ZHANG L Y, et al. Summary of conductivity measurement [C]. IEEE Proceedings of the 6th World Congress on Intelligent Control and Automation, June, 2006, 6: 5106-5110" mentioned that currently commonly used The methods include phase-sensitive detection method, double-pulse method and dynamic pulse method, etc.: phase-sensitive detection method uses sinusoidal excitation to eliminate the polarization effect, and can effectively eliminate the influence of lead distributed capacitance, but ignores the existence of double-layer capacitance; The pulse method uses two pulse excitations with opposite polarities, and considers the influence of the electric double layer capacitance and the distributed capacitance of the leads. It has great advantages in principle, but the implementation requires extremely high time synchronization; the dynamic pulse method uses DC pulses As an excitation, the capacitive effect can be effectively eliminated, and at the same time, the influence of the polarization effect can be reduced by reducing the pulse amplitude, but it is difficult to completely eliminate; the above methods are all proposed based on the resistance-capacitance model of the electrical characteristics of the conductance cell, in principle and operation There are some deficiencies, but constitute the theoretical basis for conductivity measurement

Document "Cui Pengfei, Zhang Liyong, Zhong Chongquan, Li Dan. Numerical simulation of multi-frequency square wave excitation resistance-capacitance decoupling soft measurement. Journal of Instrumentation, 2010, 31(1): 154-160" in the resistance-capacitance model of conductivity cell On the basis of the AC square wave excitation resistance-capacitance network, a mathematical model between the excitation signal, the response signal and the two parameters of resistance and capacitance is established; considering the existence of various uncertainties in the measurement, the AC with multiple frequencies Excited by a square wave, the resistance-capacitance parameters are estimated by nonlinear least squares, which can simultaneously weaken the effects of polarization effects, capacitance effects, and various uncertainties in measurement; however, the optimization solution uses the steepest descent method, which requires Iterative calculation has the problem of uncertain number of iterations, which should be avoided as much as possible in real-time measurement

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