A mini basket type mapping catheter consists of thin film flexible sensors and is applied in the medical field to measure the electrocardiography (ECG) signals in order to localize and quantize the physiological condition/status of heart. The flexible nature of the thin film changes the configuration with respect to the contact boundary conditions when it contacts a target surface. Therefore, to accurately localize the flexible sensor, the thin film flexible sensor’s configuration must be determined accurately in an on-line fashion. As a study of localizing the thin film flexible sensor, this study proposes an on-line thin film buckling configuration determination method using parametric optimization and interpolation technique. With the specific modulus of elasticity and dimensions of the thin film flexible sensor of the mapping catheter prototype, the buckling configuration with two point boundary condition under axial load can be calculated in desktop environment. The proposed calculation method is validated by mapping catheter sensor prototype test. The calculation/test results showed that the maximum overall length L,x\documentclass[12pt]{minimal}
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				\begin{document}$$_{a}$$\end{document}a, andy\documentclass[12pt]{minimal}
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				\begin{document}$$_{a}$$\end{document}avalue error between the calculation and experiment are approximately 0.16 mm, − 0.12 mm. − 0.10 mm in 50 ms calculation time. The calculation result of the proposed method is also compared with that of the numerical simulation by FEM, which has approximately 0.44 mmy\documentclass[12pt]{minimal}
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				\begin{document}$$_{a}$$\end{document}avalue error compared with that of the experiment.