Accuracy assessment of identification models and their influence on control systems
DOI:
https://doi.org/10.31548/energiya4(74).2024.039Abstract
The work investigates step-response system identification algorithms of the plant of the third and higher orders. A transfer function with a time delay that has multiple poles of the Nth order is considered as a general identification model. Also, certain cases of approximation are included: aperiodic first-order plus time delay (FOPTD) and Nth order transfer function without time delay. Provided an algorithm of finding optimal values of model parameters that minimize the integral criterion of identification error. They are presented the comparative results of the identification of the 7th order test model for two criteria: Integral Square Error (ISE) and Integral Absolute Error (IAE). Additionally, an area method of the identification algorithm was implemented and used. For comparison, the identification of the test model was made by using the process() function from the System Identification Toolbox / MATLAB library. As a result, 11 identification models were obtained. For each model, the coefficients of the PI controller were calculated with a predetermined optimality criterion. As a benchmark, the optimal values of the coefficients of the PI controller for the test model were found. When the obtained identification models were used for the design of the PI controller, similar values and a slight deterioration of the integral quality criterion were discovered. The best results have been received by using the developed method and ISE as a criterion for optimization. The best structure of the identification model is a transfer function with a time delay which has multiple poles of the Nth order. A good result was shown by the transfer function with multiple poles of the Nth order without time delay. The advantage of this model structure is a fast algorithm for searching needed parameters. Also, an effective result was obtained by the searchless method of areas. The advantage of the process function is the ability to work with different types of input and output signals. At the same time, it showed worse results when it was used in step-response system identification.
Key words: system identification, ISA, IAE, Area Method, FOPTD, PI controllerReferences
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