Mechanical end stop detection method

A method for detecting a mechanical end stop of a motion system comprising a base designed to receive a motion stage for an equipment, a machine frame resting on a floor and an active isolation system therebetween, wherein the active isolation system comprises a plurality of actuators arranged to impart a six degree-of-freedom (DOF) motion to the base, a plurality of inertial sensors arranged to provide a six DOF measurement of motion of the base, and dampers to support the base, the mechanical end stop being arranged to limit the motion of the base relative to the machine frame, the method comprising:

• (a) selecting a translational DOF among the six DOFs;
• (b) determining, using a process sensitivity matrix of a mechanical system comprising the base and the active isolation system, a force to be applied to the base by the actuators to cause an oscillatory motion of the base in the selected translational DOF, the oscillatory motion being of a predetermined amplitude;
• (c) applying the force to the base using the actuators to obtain the oscillatory motion of the base in the selected translational DOF;
• (d) detecting a mechanical contact between the base and the mechanical end stop using at least one of the inertial sensors.