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In this paper, a nonlinear dynamic model for automotive cushion-human body combined structure is developed based on a nonlinear seat cushion model and a linear ISO human body model. Automotive seat cushions have shown to exhibit nonlinear characteristics. The nonlinear seat cushion model includes nonlinear stiffness and nonlinear damping terms. This model is verified by a series of tests conducted on sports car and luxury car seats. The transfer functions from the tests for human body sitting on an automotive seat changes with the vibration platform input magnitudes. This indicates that the combined structure possesses nonlinear characteristics. The nonlinear model is validated by the transfer functions from the test. The paper discusses the influence of the parameters of the nonlinear structure on the design of seat and assessment of human body comfort.

An automatic control approach based on the method of pole-placement is presented in this paper. This method is an alternative to the conventional frequency response approach and root locus design. Unit step response of the system is initially plotted and stability is tested. The unstable system is made stable to a specified settling times and overshoots by choosing system gains using Ackerman’s formula. The stability is finally ascertained with Bode diagrams. The approach is illustrated with two numerical mechanical systems.