To analysis the influence factor for measurement of rotational inertia and eliminate the experiment error,this article studies the rotational of rigid body for trilinear pendulum with the theory of momentum.

By using digital millisecondmeter and phototube instead of manual operation,the improved trilinear pendulum experimental device improves measuring precision.

The differential equation of nonlinear vibration for trilinear pendulum was derived from the geometric constraint equation of a suspension point on the lower suspension disk.

For a trifilar pendulum, which is widely used to identify the inertial parameters of odd-shaped rigid bodies or structural assemblies, applicability of the governing equation and the conditions to avoid resonance are addressed.

The analysis of trifilar pendulums is simplified by a method which simultaneously determines all 10 inertia parameters of a complex rigid body,namely the mass,the coordinates of the center of gravity,the moments of inertia and the products of inertia,without any angular measurements.

A discussion of the torsion vibration of three-line pendulum using kinetic energy theorem;

The relation formula between vibrating period and angular amplitude ofthree-line pendulum is deduced according to the conservation law of mechanical energy.

A new kind of three-line pendulum system to measure moment of inertia was introduced.

According to the formation principle of the tritubercular cycloid in this paper, the rotor, whose bore curve is the inner envelope line of the cycloid, is made with the solid radius vector.