Vehicle/bridge vibration mitigation assembly

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings and more particularly to FIG.
1, a vibration mitigation assembly 10 constructed in accordance with the present invention is schematically shown mounted to a vehicle 12 that is traveling across a bridge 14.
As well known, the vehicle 12 has a chassis 15 and a plurality of axles 16 (only two of the axles 16 being shown in FIG.
1) for supporting elastic tires 17.
The elasticity of tires 17 is represented by the spring 17a.
A spring 19 is disposed between the chassis 15 and the axle 16.
The spring 19 can be any conventional spring, such as a leaf spring or a coil spring.
As described above, certain vehicles, in particular large trucks, exhibit modal frequencies between one and five Hertz.
Likewise, many of the bridges constructed along the U.
S.
interstate highway system with a span between 60 and 150 feet exhibit modal response frequencies between one and five Hertz.
Consequently, when such a vehicle travels over one of these bridges, the vehicle and the bridge often interact to cause a resonance condition, which in turn amplifies the vibration of the bridge to levels that far exceed the levels anticipated by standard bridge codes.
The vibration mitigation assembly 10 provides a low-cost means of fitting the suspension of a vehicle with technology that can automatically change the vehicle suspension vibration characteristics to avoid resonating with the bridge 14 while the vehicle 12 is passing over the bridge 14, and thereby mitigate vibration of the bridge 14.
The vibration mitigation assembly 10 described herein is commonly referred to as a semi-active device in that the power required to operate a semi-active vibration mitigation assembly is low relative to the amount of energy dissipated; whereas, the amount of power required to operate a fully active vibration mitigation assembly is approximately equal to or greater than the amount of energy to be dissipated.
The vibration mitigation assembly 10 can alternatively be outfitted with fully active devices to effectively alter the fundamental dynamics of the chassis 15 of the vehicle 12