Abstract: According to the Lagrangian equation, this paper introduces the dynamical equation for the mechanisms with, an elastic bar. It 19 known that Hooke's law 59 tenable only for the static condition and the dynamical equation is a special case when both angular velocity and angular acceleration are always zero. Up-to-date, torque meters both in China and in other countries are based on Hooke's law, and they can not measure the dynamical rotary torque.
This paper based on the dynamical equation describes the way to measure the dynamical rotary torque. The trouble in practice is how to determine the equivalent moment of inertia J and the viscous damping k. We use the technique of parameter estimation to solve this problem. Two computing approaches are discussed. The kernel of the whole matter is the least square method. At last, the optimal estimation of the dynamical rotary torque is given by computation.