Using a flexible manipulator for grinding process in situ has become a cost effective engineering service in the recent years, especially for repair and refurbish of mechanical systems and components. In comparison with traditional rigid robot manipulators, the flexible manipulator has proved its superiorities in terms of accuracy and efficiency. However, because of compact and flexible structure, concerns arise regarding its dynamic behavior during machining process. This paper introduces a method using an ARX (autoregressive with exogenous excitation) model to experimentally analyze the vibration by using a flexible robot during grinding operation in different cases Single Input – Single Output (SISO), Multi Input – Multi Output (MIMO). Simultaneously, a dynamometer allows for triaxial input excitations measurement while 3 accelerometers mounted at the end effector represent the vibration outputs of the whole process. Thanks to the operational modal analysis, the dynamical properties of the robot can be identified directly in operation. The results show that the ARX model is efficient for analyzing the operational vibration in complex systems with multi degrees of freedom and multi directions. The determination of modal parameters and identified Frequency Response Functions (FRFs) enable to predict the dynamical behavior of the system and to simulate the vibration in real working conditions. Further study is promising on the inverse problem to estimate the excitation forces while these later are not available and not practically measured in industrial applications.

Keywords: Operational modal analysis, flexible manipulator, grinding process, ARX model.

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