Two-dimensional X pendulum vibration isolation table

We have extended to two dimensions a previously developed vibration isolati on table using crossed wire suspensions (X mechanisms). A load table is sus pended using a combination of normal and upside-down X mechanisms so that i t moves freely with a very long period in both horizontal directions but is moderately stiff in all other degrees of freedom. Periods of 5 s are easil y achievable. The transfer function of the prototype reported here contains a number of elastic mode resonance peaks, but it is shown by analysis how to reduce or eliminate nearly all of these. (C) 1999 American Institute of Physics. [S0034-6748(99)02304-7].