Testing and Modeling of Shock Mitigating Seats for High Speed Craft
Liam, Christopher Charles
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This study conducted a series of tests on a shock mitigating seat designed for high speed craft using various input excitations to better understand the relationship between various seat and operational conditions, and the response of the seat. A seat model of the test seat is used for a parametric study of various spring, damping and operational configurations. A seat shake rig is implemented to simulate motions of multiple high-speed craft as well as various defined inputs. At each test input the occupant weight and suspension preload is varied and the response is analyzed to find changes in acceleration, which is representative of the changes in force and displacement. By representing the seat as a based-excitation two-degree-of-freedom system, we develop the equations of motion and model them in Simulink to analyze the effects of various spring rates and damping coefficients. Based on the results it is found that an increase in occupant mass results in a decrease in observed acceleration. Increasing suspension preload is found to be detrimental to the mitigating abilities of the seat, changing the dynamics to those similar of a rigid-mounted seat. An analysis of the defined inputs resulted in confirming various seat characteristics. The analysis of the Simulink model revealed that increasing the spring rate results in an increase in acceleration. An increase in damping coefficient resulted in an increase in acceleration and ride harshness.
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