Sains Malaysiana 55(3)(2026): 517-529

http://doi.org/10.17576/jsm-2026-5503-13
 

Bifurcation Analysis and Chaos Control in a Discrete Fractional- Order Model of Immune Response to Abnormal Cells

(Analisis Bifurkasi dan Kawalan Kekacauan dalam Model Tertib Pecahan Diskret bagi Tindak Balas Imun terhadap Sel Abnormal)

 

ALEH A. AL-SHAMMARI, A.S. RAMBELY* & N.S. KAMARUDIN

 Mathematics Program, Faculty of Science & Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

 

Received: 25 February 2025/Accepted: 19 February 2026

 

Abstract

This study investigates the complex dynamics and control of a discrete-time fractional-order model describing the immune response to abnormal cells. We establish the local asymptotic stability of the equilibrium points and derive the specific parametric conditions governing the emergence of Neimark-Sacker and flip bifurcations. Numerical simulations not only confirm these bifurcations but also show the subsequent onset of chaos. To mitigate this, we successfully implement and demonstrate the efficacy of three control strategies state feedback, pole placement, and hybrid control in stabilizing the chaotic regimes and suppressing undesirable bifurcations. The numerical results provide strong validation of the theoretical analysis, underscoring the value of these control techniques for managing pathological dynamics in immune system models.

Keywords: Discrete immune system model with fractional-order; flip bifurcation; Hopf bifurcation; N-S bifurcation

 

Abstrak

Penyelidikan ini mengkaji dinamik kompleks dan kawalan model tertib pecahan masa diskret yang menggambarkan tindak balas imun terhadap sel yang tidak normal. Kami mewujudkan kestabilan asimptotik tempatan bagi titik keseimbangan dan memperoleh keadaan parametrik khusus yang mengawal kemunculan bifurkasi Neimark-Sacker dan flip. Simulasi berangka bukan sahaja mengesahkan bifurkasi ini tetapi juga mendedahkan permulaan huru-hara berikutnya. Untuk mengurangkan ini, kami berjaya melaksana dan menunjukkan keberkesanan tiga strategi kawalan maklum balas keadaan, penempatan kutub dan kawalan hibrid dalam menstabilkan rejim huru-hara dan menyekat bifurkasi yang tidak diingini. Keputusan berangka memberikan pengesahan yang kukuh terhadap analisis teori, menggariskan nilai teknik kawalan ini untuk mengurus dinamik patologi dalam model sistem imun.

Kata kunci: Bifurkasi flip; bifurkasi Hopf; bifurkasi N-S; model sistem imun diskret dengan tertib pecahan

 

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*Corresponding author; email: asr@ukm.edu.my

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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