Interval type-2 fuzzy fractional harmonic-balance optimization of a quasi-zero-stiffness isolator for robust low-frequency vibration suppression
Abstract
Quasi-zero-stiffness (QZS) isolators possess a combination of high load capacity and low dynamic stiffness; however, their characteristics are sensitive to geometric nonlinearity, frequency-dependent dissipation, excitation amplitude and epistemic uncertainty. In this study, a new design scheme is proposed to produce the constant geometric restoring force of a three-spring QZS isolator subject to base excitation. Caputo fractional damping + exact first-harmonic stiffness (in terms of complete elliptic integrals) + multi-harmonic alternating frequency–time harmonic balance (to check the harmonic content and residual error). Interval type-2 fuzzy numbers account for uncertainty in the following quantities: geometric ratio, residual tangent stiffness, fractional damping intensity (or order), and base-motion amplitude. Differential evolution of upper-tail resonance risk and lower-tail isolation losses. A limiting-case validation against a literature benchmark verifies that the fractional-order models recover the classic viscously damped three-spring QZS equations for the case of approaching finite response amplitude and unity fractional order. For the 50 kg realization, the optimized design has a geometric ratio of 1.1824, residual stiffness of 0.02110, damping ratio of 0.02581 and fractional order of 0.9063. Its 95th-percentile peak transmissibility is 3.358 across 120 outer-footprint scenarios, which is 28.9% below the optimized viscous-limit QZS reference. Adverse-tail isolation onset is 23.3% earlier than deterministic fractional tuning completion, and adverse-tail mean attenuation improvements are as high as 1.08 dB. The five-harmonic verification ensures that the ratio of the third harmonic stays below 0.31% in all ranges mentioned in operating range.
Copyright (c) 2026 Suleiman Ibrahim Mohammad, Yogeesh Nijalingappa, Seif Al Bustanji, Poornachandran William, Asokan Vasudevan, Torki M. Al-Fawwaz

This work is licensed under a Creative Commons Attribution 4.0 International License.
References
[1]Ibrahim RA. Recent advances in nonlinear passive vibration isolators. Journal of Sound and Vibration. 2008; 314(3–5): 371–452. doi: 10.1016/j.jsv.2008.01.014
[2]Carrella A, Brennan MJ, Waters TP. Static analysis of a passive vibration isolator with quasi-zero-stiffness characteristic. Journal of Sound and Vibration. 2007; 301(3–5): 678–689. doi: 10.1016/j.jsv.2006.10.011
[3]Kovacic I, Brennan MJ, Waters TP. A study of a nonlinear vibration isolator with a quasi-zero stiffness characteristic. Journal of Sound and Vibration. 2008; 315(3): 700–711. doi: 10.1016/j.jsv.2007.12.019
[4]Carrella A, Brennan MJ, Kovacic I, et al. On the force transmissibility of a vibration isolator with quasi-zero-stiffness. Journal of Sound and Vibration. 2009; 322(4–5): 707–717. doi: 10.1016/j.jsv.2008.11.034
[5]Ding B, Li X, Chen SC, et al. Modular quasi-zero-stiffness isolator based on compliant constant-force mechanisms for low-frequency vibration isolation. Journal of Vibration and Control. 2024; 30(13–14): 3006–3020. doi: 10.1177/10775463231188160
[6]Sui G, Zhang X, Hou S, et al. Quasi-zero stiffness isolator suitable for low-frequency vibration. Machines. 2023; 11(5): 512. doi: 10.3390/machines11050512
[7]Xu D, Yu Q, Zhou J, et al. Theoretical and experimental analyses of a nonlinear magnetic vibration isolator with quasi-zero-stiffness characteristic. Journal of Sound and Vibration. 2013; 332(14): 3377–3389. doi: 10.1016/j.jsv.2013.01.034
[8]Zuo S, Wang D, Zhang Y, et al. Design and testing of a parabolic cam-roller quasi-zero-stiffness vibration isolator. International Journal of Mechanical Sciences. 2022; 220: 107146. doi: 10.1016/j.ijmecsci.2022.107146
[9]Liu J, Wang Y, Yang S, et al. Customized quasi-zero-stiffness metamaterials for ultra-low-frequency broadband vibration isolation. International Journal of Mechanical Sciences. 2024; 269: 108958. doi: 10.1016/j.ijmecsci.2024.108958
[10]Fu J, Huang Z, Li W, et al. A bidirectional-controllable magnetorheological elastomer-based quasi-zero-stiffness isolator. Smart Materials and Structures. 2024; 33(8): 085009. doi: 10.1088/1361-665X/ad53ad
[11]Chai Z, Zhang Z, Xu K, et al. An innovative nonlinear bionic X-shaped vibration isolator enhanced by quasi-zero stiffness characteristics: Theory and experimental investigation. Applied Mathematics and Mechanics (English Edition). 2025; 46(8): 1475–1492. doi: 10.1007/s10483-025-3277-8
[12]Lu JJ, Yan G, Qi WH, et al. Integrated vibration isolation and actuation via dual nonlinear stiffness regulation. International Journal of Mechanical Sciences. 2024; 263: 108760. doi: 10.1016/j.ijmecsci.2023.108760
[13]Yang JH, Yang XD. Theoretical and experimental study of a novel nonlinear quasi-zero-stiffness vibration isolator based on a symmetric link-rod-type structure. Engineering Structures. 2024; 301: 117284. doi: 10.1016/j.engstruct.2023.117284
[14]Ma Z, Zhou R, Yang Q. Recent advances in quasi-zero stiffness vibration isolation systems: An overview and future possibilities. Machines. 2022; 10(9): 813. doi: 10.3390/machines10090813
[15]Bagley RL, Torvik PJ. A theoretical basis for the application of fractional calculus to viscoelasticity. Journal of Rheology. 1983; 27(3): 201–210. doi: 10.1122/1.549724
[16]Rossikhin YA, Shitikova MV. Applications of fractional calculus to dynamic problems of linear and nonlinear hereditary mechanics of solids. Applied Mechanics Reviews. 1997; 50(1): 15–67. doi: 10.1115/1.3101682
[17]Caputo M. Linear models of dissipation whose Q is almost frequency independent–II. Geophysical Journal International. 1967; 13(5): 529–539. doi: 10.1111/j.1365-246X.1967.tb02303.x
[18]Podlubny I. Fractional Differential Equations. Academic Press; 1999.
[19]Sedlmayr M, Rysak A. Damping efficiency of the fractional Duffing system and an assessment of its solution accuracy. Journal of Sound and Vibration. 2024; 593: 118690. doi: 10.1016/j.jsv.2024.118690
[20]Xie J, Zhao F, He D, et al. Bifurcation and resonance of a fractional cubic nonlinear system. Chaos, Solitons & Fractals. 2022; 158: 112053. doi: 10.1016/j.chaos.2022.112053
[21]Cameron TM, Griffin JH. An alternating frequency/time domain method for calculating the steady-state response of nonlinear dynamic systems. Journal of Applied Mechanics. 1989; 56(1): 149–154. doi: 10.1115/1.3176036
[22]Detroux T, Renson L, Masset L, et al. The harmonic balance method for bifurcation analysis of large-scale nonlinear mechanical systems. Computer Methods in Applied Mechanics and Engineering. 2015; 296: 18–38. doi: 10.1016/j.cma.2015.07.017
[23]Nayfeh AH, Mook DT. Nonlinear Oscillations. John Wiley & Sons; 1979.
[24]Urabe M. Galerkin’s procedure for nonlinear periodic systems. Archive for Rational Mechanics and Analysis. 1965; 20: 120–152. doi: 10.1007/BF00284614
[25]Zadeh LA. Fuzzy sets. Information and Control. 1965; 8(3): 338–353. doi: 10.1016/S0019-9958(65)90241-X
[26]Mendel JM, John RIB. Type-2 fuzzy sets made simple. IEEE Transactions on Fuzzy Systems. 2002; 10(2): 117–127. doi: 10.1109/91.995115
[27]Karnik NN, Mendel JM. Centroid of a type-2 fuzzy set. Information Sciences. 2001; 132(1–4): 195–220. doi: 10.1016/S0020-0255(01)00069-X
[28]Mohammad AAS, Yogeesh N, Mohammad SIS, et al. An intuitionistic fuzzy graph model: Matrix representations and applications. Cybernetics and Information Technologies. 2025; 25(4): 3–19. doi: 10.2478/cait-2025-0030
[29]Liu Y, Yin H, Xia B, et al. Interval type-2 fuzzy set-theoretic control design for uncertain dynamical systems. International Journal of Fuzzy Systems. 2024; 26(3): 1069–1087. doi: 10.1007/s40815-023-01654-3
[30]Coupland S, John R. Geometric type-1 and type-2 fuzzy logic systems. IEEE Transactions on Fuzzy Systems. 2007; 15(1): 3–15. doi: 10.1109/TFUZZ.2006.889764
[31]Zhang C, Liu M, Mohammadzadeh A, et al. A fractional adaptive type-2 fuzzy structural control system: Theoretical/experimental study. Structures. 2024; 70: 107843. doi: 10.1016/j.istruc.2024.107843
[32]Chang YH, Chan WS. Adaptive dynamic surface control for uncertain nonlinear systems with interval type-2 fuzzy neural networks. IEEE Transactions on Cybernetics. 2014; 44(2): 293–304. doi: 10.1109/TCYB.2013.2253548
[33]Storn R, Price K. Differential evolution—A simple and efficient heuristic for global optimization over continuous spaces. Journal of Global Optimization. 1997; 11(4): 341–359. doi: 10.1023/A:1008202821328
[34]Das S, Suganthan PN. Differential evolution: A survey of the state-of-the-art. IEEE Transactions on Evolutionary Computation. 2011; 15(1): 4–31. doi: 10.1109/TEVC.2010.2059031
[35]McKay MD, Beckman RJ, Conover WJ. A comparison of three methods for selecting values of input variables in the analysis of output from a computer code. Technometrics. 1979; 21(2): 239–245. doi: 10.1080/00401706.1979.10489755
[36]Saltelli A, Annoni P, Azzini I, et al. Variance based sensitivity analysis of model output. Design and estimator for the total sensitivity index. Computer Physics Communications. 2010; 181(2): 259–270. doi: 10.1016/j.cpc.2009.09.018
[37]Spearman C. The proof and measurement of association between two things. The American Journal of Psychology. 1904; 15(1): 72–101. doi: 10.2307/1412159
[38]Chitaoui H, Megnounif A, Benadla Z. Optimal placement of vibration control systems in a smart civil engineering structure. Civil Engineering Journal. 2025; 11(8): 3495–3515. doi: 10.28991/CEJ-2025-011-08-022
[39]Chu TSC, Sorilla J, Chua AY. UAV-based structural health monitoring using a two-stage CNN model with Lighthouse localization in GNSS-denied environments. HighTech and Innovation Journal. 2025; 6(2): 398–410. doi: 10.28991/HIJ-2025-06-02-03
[40]Majima R, Yamasaki Y, Saito T. Shaking-table test on a multi-story continuous vibration-control system employing pulley amplification mechanism. Civil Engineering Journal. 2025; 11(1): 14–32. doi: 10.28991/CEJ-2025-011-01-02




