Abstract：The traditional three-loop position control applied in the servo system with elasticity causes

residual vibration around the objected position and has long trailing time. To address this issue，a mathematical

model of the two-inertia system was established，and the causes of low-damping of the traditional position closedloop structure were analyzed in detail. It was proposed to modify the speed loop structure combined with

resonance-ratio control to guarantee the high-damping of the closed-loop system. The controller parameters were

designed by use of the equal real part design，zero-pole elimination and polynomial method to achieve the highdamping characteristics. Simulation results show that the proposed high-damping position control can well

suppress the fluctuation，achieve smooth position tracking，significantly reduce the trailing phenomenon compared with traditional P-PI method.

      Key words：two-inertia system；position control；resonance-ratio control；controller parameters design