Adaptive self-organizing map using optimal control

Alkawaz, Ali Najem and Kanesan, Jeevan and Badruddin, Irfan Anjum and Kamangar, Sarfaraz and Hussien, Mohamed and Baig, Maughal Ahmed Ali and Ahammad, N. Ameer (2023) Adaptive self-organizing map using optimal control. Mathematics, 11 (9). ISSN 2227-7390, DOI

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The self-organizing map (SOM), which is a type of artificial neural network (ANN), was formulated as an optimal control problem. Its objective function is to minimize the mean quantization error, and the state equation is the weight updating equation of SOM. Based on the objective function and the state equations, the Hamiltonian equation based on Pontryagin's minimum principle (PMP) was formed. This study presents two models of SOM formulated as an optimal control problem. In the first model, called SOMOC1, the design is based on the state equation representing the weight updating equation of the best matching units of the SOM nodes in each iteration, whereas in the second model, called SOMOC2, it considers the weight updating equation of all the nodes in the SOM as the state updating equation. The learning rate is treated as the control variable. Based on the solution of the switching function, a bang-bang control was applied with a high and low learning rate. The proposed SOMOC2 model performs better than the SOMOC1 model and conventional SOM as it considers all the nodes in the Hamiltonian equation, and the switching function obtained from it is influenced by all the states, which provides one costate variable for each. The costate determines the marginal cost of violating the constraint by the state equations, and the switching function is influenced by this, hence producing a greater improvement in terms of the mean quantization error at the final iteration. It was found that the solution leads to an infinite order singular arc. The possible solutions for the suitable learning rates during the singular arc period are discussed in this study.

Item Type: Article
Funders: Ministry of Higher Education, Malaysia (FRGS/1/2020/ICT02/UM/02/2), Deanship of Scientific Research, King Khalid University (RGP.1/74/43)
Uncontrolled Keywords: Self-organizing map; Artificial neural network; Optimal control problem; Pontryagin's minimum principle
Subjects: T Technology > TJ Mechanical engineering and machinery
T Technology > TK Electrical engineering. Electronics Nuclear engineering
Divisions: Faculty of Engineering > Department of Electrical Engineering
Depositing User: Ms Zaharah Ramly
Date Deposited: 23 Jun 2023 02:25
Last Modified: 23 Jun 2023 02:25

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