The isolation performance of the GAS filter is evaluated by comparing the ground motion, z 0 , transmitted through the blades to the payload, which is moved by z . Such a transfer function is easily computed, as presented by [ Stochino2007 ], by writing down the Lagrangian of a simplified mechanical model, as shown in figure 5.4. The Lagrangian of the system is defined as the sum of the kinetic energies minus the potential energy: