Application of blocked force methodology to an electrified beam axle from a medium-duty truck in vehicle and in a dynamometer test cell

The recent shift in propulsion choice away from internal combustion engines has increased the relevance of sound and vibration from electric motors and gearboxes. Electrified beam axles require different metrics from conventional beam axles for noise and vibration because they have multiple sources of vibration energy, including an electric motor and sometimes multiple reduction gearsets. They also require different metrics from electric drive units because they have stiff suspension connections and lack significant isolation. Blocked force is a good candidate because it can completely characterize the vibration energy transmitted into a receiver and is especially useful because it is theoretically independent of the vehicle-side structure. While the blocked force methodology is not new, its application to beam axles is relatively unexplored in the literature. This paper demonstrates a case study of blocked force measurement of an electrified beam axle from a battery electric medium-duty truck with a leaf spring suspension. The axle was tested both in vehicle and in a hemianechoic test cell. Measurement setup, including the selection of interface, instrumentation, and impact locations, is discussed. The resulting blocked forces at critical motor and gear orders are summarized, and comparisons are made between the results in vehicle and in dyno. Several key learnings, opportunities for measurement improvement, and ideas for future work are also addressed.