Estimation of interfacial forces in a multi-degree of freedom isolation system using a dynamic load sensing mount and quasi-linear models

Abstract

A new indirect measurement concept is developed to estimate interfacial dynamic forces by employing the hydraulic mount as a dynamic force sensor. The proposed method utilizes a combination of mathematical models and operating motion and/or pressure measurements. A laboratory experiment consisting of a powertrain, three powertrain mounts (including a dynamic load sensing hydraulic mount), a sub-frame, and four bushings is then constructed to verify the proof-of-concept. Quasi-linear fluid and mechanical system models of the experiment are proposed and evaluated in terms of transfer functions and forced sinusoidal responses. The lower chamber pressure in the hydraulic mount is estimated since it is not available from measurements. This leads to an improved estimation of the effective rubber and hydraulic path parameters with spectrally varying and amplitude-sensitive properties up to 50 Hz. Finally, the reverse path spectral method is employed to predict interfacial forces at both ends of the mount by using measured motions and upper chamber pressure signals. Overall, the proposed quasi-linear fluid system model yields better indirect estimates of forces from the measured responses when compared with direct force measurements, through a simpler mechanical system model provides some insights. This work also advances prior component and transfer path type studies by providing an improved multi-degree of freedom system perspective.