A Hexapod Motion Bases typically consists of a base frame that is actuated in 6 degrees of freedom by means of electric or hydraulic pistons. These hexapods are used commonly in the dynamic tests of structures, such as car or helicopter chassis. The chassis is mounted on top of the base frame and the hexapod is used to subject the structure to various base excitations. The dynamic response of the structure is measured and used to validate structural models. Moreover, the hexapods can be used in motion simulators, used to provide realistic training conditions for car drivers, pilots and captains.
In particular for base excitation tests, one need to be able to prescribe base motions accurately in a specified frequency range. In many situations, the internal dynamics of the hexapod motion base limits the bandwidth in which these base excitations can be predicted accurately. To be able to push the boundaries of the performance of hexapod motion bases, it becomes important to model the flexible behavior of the base frame throughout the large range of motion of the machine.
To this end, a flexible multibody dynamics model is proposed. From a CAD model of the base frame, a linear FEM model is created. This model is reduced and integrated in a multibody dynamics model of the entire machine. Simulations should be performed in which the influence of the base frame’s flexibility on dynamic behavior of the machine is studied.
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