Dear Community
I am a graduate student working on a Hybrid III lower torso inertial surrogate for drop testing. My lab has proposed using a universal joint mechanism as a surrogate for the lower torso itself. My understanding is that a mechanism cannot have a fixed inertia tensor — unlike a rigid body segment.
Its mass distribution changes with configuration, so Ixx, Iyy, and Izz are not fixed quantities.
Even if the joint is locked rigidly for each test, the inertial properties in the lab frame will only match the target values at one specific reference angle, and will need to be re-tuned at every other angle — making angle-variable testing impractical
I would greatly value a brief opinion on whether this reasoning is correct, and whether such an approach has any precedent in the literature.
Thank you very much