In order to solve the problem of too large rotating machinery vibration around the critical speed

a rotor system test bench was established. Without changing the original supports of the rotors system

one magneto-rheological damper was installed onto each shaft. Different working conditions were set to study the influences of the magneto-rheological dampers on rotor system's vibration. The results showed that the magneto-rheological damper could reduce the vibration of the rotor system near the critical speed

and the decreasing amplitude was 90%. According to the test results

a servo control strategy based on vibration amplitude feedback of rotor was proposed to control the rotor vibration amplitude

which could follow the vibration amplitude

change the current of magneto-rheological damper according to the vibration amplitude to control the rotor system's vibration on line. The results show that the servo control method can adjust the current varying with rotor system's vibration in real time

and make the amplitude stay stable around the target value

so as to achieve the auto control of rotor system vibration.