การหาพารามิเตอร์ไม่เชิงเส้นของระบบระดับความเสรีขั้นเดียวที่มีตัวหน่วงแบบของเหลวหนืด

Abstract

This research presents the method for finding nonlinear parameters of quadratic springs by presenting calculations of mathematical models. It is found that the calculation results are very accurate, with the calculation error percentage of 10^-17 % which comes as a result of fast convolution by using the direct and inverse Fourier transforms. In the experiment with the actual system, the nonlinear parameters of cedar wood, the wood that is used in making electric guitars, were determined by measuring the signal three times with each impulse being loaded with different amplitudes. Then, the obtained signal is calculated for the nonlinear parameters of the spring. The nonlinearity is very low at  = 5.4275x´10^-9 N/m² which is consistent with the theory because the force of the spring will change according to the direction of movement, but   is multiplied by the term y²(t), so the force does not change in the direction of the motion of the mass.