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Active seat isolation for hybrid electric vehicles

A feasibility study in the use of induced strain actuators for active seal isolation is described. The focus of the work is the isolation of lightweight automotive seats for hybrid-electric vehicles. The feasibility study is based on a numerical analysis of a three-degree-of-freedom vibration model of the seat. Mass and inertia properties are based on measurements from a powered seat that is found in current model year automobiles. Tradeoffs between vertical acceleration of the seat, actuator stroke requirements, and isolation frequency are determined through numerical analysis of the vibration model. Root mean square accelerations and actuator strokes are computed using power spectral densities that model broadband excitation and road excitation that is filtered by the vehicle suspension. Numerical results using the road excitation indicate that factors of two to three reduction in vertical acceleration are achieved when the active isolation frequency is reduced to approximately 1 Hz with damping factors on the order of 10 to 30 percent critical. More significant reductions are achieved in the case of broadband floor excitation. Root mean square actuator strokes for both case are int he range of 0.4 to 50 mm. Root mean square accelerations in the vertical direction are consistent with the levels found in standard comfort curves.