THE DESIGN OF A CONTROL-SYSTEM FOR A SUPERIMPOSED FREQUENCY FATIGUE TEST MACHINE

The conjoint action of high- and low-frequency fatigue on a test speci men has been obtained using a servohydraulic test machine. A control s trategy was implemented such that only one servo-actuator was required to obtain both low- and high-frequency components. This paper describ es the test rig and the decoupled automatic controller developed for i t. Test results show that the decoupled strategy synthesis produces sa tisfactory separation of the low- and high-frequency modes of the clos ed-loop response.