Here I 1 , I 2 , I 3 denote the object's principal moments of inertia, and we assume I 1 < I 2 < I 3 . The angular velocities around the object's three principal axes are ω ω 1 , ω ω 2 , ω ω 3 and their time derivatives are denoted by ω ω ˙ ˙ 1 , ω ω ˙ ˙ 2 , ω ω ˙ ˙ 3 .