The frequency range and isolation quality of linear isolation systems are usually affected and deteriorated due to the requirements to support a static load. This is usually the case in the aerospace applications where the airplane and the avionics are subjected to high G-loadings. Moreover, G-loading usually does not exist throughout the whole flight mission, meaning that, the avionics should be protected against vibrations in presence and absence of G-loading during a full flight mission. However, linear or simple softening or hardening isolation systems cannot fulfil the requirements to isolate the avionics from base vibrations in both presence and absence of G-loading, while opposing the G-loading if it exists, to reduce the total vibration travel. In this paper, a new passive isolation design is proposed that caters for the requirements mentioned where the vibration excitation is random and undeterministic. The new design integrates a linear isolation subsystem with a bilinear softening one to isolate the system in both absence and presence of the G-loading. The linear subsystem caters for the situation when there is no G-loading on the system while the bilinear softening subsystem together with the linear one, cater for vibration isolation of the payload when subjected to the G-loading. Design optimization problem of the isolation system is defined, and it is shown that the optimized new isolator has better performance than a linear or a simple hardening or softening isolator.
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