Ідентифікація параметрів математичних моделей та визначення діагностичних ознак

Abstract

In this article, the object of research is two main units of the AR20N aggregate – electrohydraulic amplifier (EHA) and power cylinder (PC). Detection of the occurrence and development of faults in them will be considered on the basis of the identification of parameters of the developed mathematical models. The main objectives of the research were to identify the parameters of mathematical models of EHA and PC using different steps of time quantization, determination of the optimal step of time quantization for numerical integration of differential equations; determination of diagnostic features that have the most probable influence on the operation of aggregate units at the occurrence of various faults. For achievement of the set objectives the following tasks were solved: mathematical models of EHA, PC, and simulation model of the aggregate research on the test bench were developed; identification of parameters of mathematical models of EHA and PC by the method of least squares (MLS) was carried out; the permissible step of time quantization was determined; upper and lower permissible limits of the identifiable parameters for a serviceable aggregate were determined; a methodology for determining the diagnostic features that are most probable to determine the emerging faults of the aggregate has been developed. Methods are used for this purpose: analytical, numerical, statistical, hydraulic systems theory, and system identification theory. The following results were obtained: differential equations describing the displacements of the distributive spool (DS) of the EHA and the output link (OL) of the PC; algorithms for identifying the parameters of mathematical models by MLS; the permissible step of time quantization was determined; and a technique for determining the diagnostic features using the Shewhart diagnostic chart for the parameters of mathematical models was developed. The scientific and practical novelty of the obtained results consists of the following: mathematical models of EHA and PC of the aggregate have been developed; simulation model of the aggregate on the test bench has been developed; simulation of various faults of the aggregate units has been carried out and identification of parameters of mathematical models of these units has been carried out; changes of estimations of parameters of mathematical models of EHA and PC depending on changes of each influencing factor have been obtained; upper and lower permissible limits of parameters and average values of these parameters have been determined; diagnostic features that are most probable to influence aggregate performance have been determined. It is shown that time quantization step D t = 0.01 (c) provides the determination of DS and OL displacements with errors of 1.914×10-6mm and 2.157×10-5 mm.