Speed control of two-inertia system by PI/PID control

The purpose of this paper is to develop systematic analysis and design methods for a two-inertia system. A conventional proportional-integral speed control system with a torsional load is redesigned, and the damping characteristic of the system is derived and analyzed. It is shown that the dynamic characteristic of the system strongly depends on the inertia ratio of load to motor. Three kinds of typical pole assignments with identical radius/damping coefficient/real part are applied and compared, and the merits of each pole-assignment design are concluded. Furthermore, for small inertia ratio, we present how to improve the damping of the system by a derivative feedback of motor speed.