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EFFECT OF THE CONTROL METHOD ON THE FATIGUE DAMAGE OF STRUCTURE IN A SERVO CONTROLLED LOG CRANE

The present paper shows the investigation of the fatigue life of a hydraulic servo controlled log crane boom structure. The coupled dynamics of the hydraulic driven log crane is simulated using ADAMS. After analyzing the dynamics of the system the results obtained are utilized in the ANSYS finite element program to determine the stress history of the boom. During the simulation the stress range occurrences are calculated using Rainflow-algorithm. The fatigue life at a certain location of structure is then calculated by means of the hot spot stress approach. In this approach the fatigue strength, in form of S-N curves, is based structural hot spot stresses.By employing the designing method mentioned above the effects of variations in the parameters of a P-, PD-and P+acceleration feedback joint controllers on the fatigue life of a crane boom structure are investigated. The goal of the study is to highlight the importance to compromise between the control properties and fatigue life in the design of a servo controlled working machine boom.