PRELIMINARY SIMULATION STUDY COMBINING OPERATIONAL MODAL ANALYSIS AND A TWO STEP PARAMETER IDENTIFICATION METHOD ON 6-SPS PARALLEL MANIPULATOR FOR MACHINING PURPOSES

摘要

Machining of large components, such as multi-megawatt wind turbine parts, is currently done using large expensive CNC machines. Using small parallel kinematic machines can provide an economical attractive alternative. Optimization of the conditions for a stable and accurate machining process is necessary. Knowledge of position dependent dynamic response is key when performing such optimization. This contribution is a part of current research striving towards efficient parameter identification for dynamic models of 6-SPS parallel kinematic manipulators for machining purposes. Stiffness and damping are updated for a small set of manipulator poses using Operational Modal Analysis and a two step parameter identification routine. The model obtained contains information of the dynamic response for all poses in the workspace. In this study a six degree of freedom 6-SPS model is derived and operational modal analysis experiments are simulated. The obtained modal parameters are used for parameter identification. It is concluded that the operational modal analysis performs well in estimating frequencies and mode shapes of the symmetric structure, but damping estimates are poor. Parameter identification routine performance is satisfactory, but the poor damping estimates from modal analysis causes incorrect and uncertain parameter identification.