Motion and vibration are major components of these tests, but simulators have difficulty reproducing some relatively highfrequency (above 400-Hz) movements. The Model 353.1 multiaxis simulation table (MAST) from MTS Eden Prairie, Minn. (, uses six servohydraulic actuators to deliver motion with degrees of freedom at up to 500 Hz. The table small footprint, with its six rigid, body-mounted actuators arranged in a hexapod or Stewart platform and connected to the table by swivels. The swivels prevent backlash and simplify maintenance. The actuators use hydrostatic bearings to reduce friction. They also work without seals, further reducing friction, and are engineered to be stiff. Stiffness improves controllability and lets the table deliver stable, coherent responses. A digital servocontroller using feedback from displacement and acceleration sensors controls table position. The entire unit is packaged as a single unit mounted on a monolithic base.