Three degrees of freedom (3DoFs) precision positioning wedge air bearing stage system (WABSS)

A three degrees of freedom (3DoFs) precision positioning Wedge Air Bearing Stage System (WABSS), comprising a movable central stage assembly (CSA) connected to a stationary base platform (BP) via three slide bar assemblies (SBAs) corresponding three carriage assemblies (CAs) and a vertical carriage column (CC), where the CSA can translate along three axes for precision positioning by controlled and coordinated motion of the three SBAs via parallel kinematic principles, when a linear air bearing based active prismatic joint (Ti, ∀i=1,2,3), and a flat pad air bearing based planar joint (Pi, ∀i=1,2,3) are provided in each kinematic sub-chain, (Mi, ∀i=1,2,3) such that linear actuation is provided through an ironless linear motor at each prismatic joint (Ti, ∀i=1,2,3) to make cogging free frictionless translations of slide bars along a Z-axis within corresponding CA;

• the linear actuation is controlled via position feedback obtained from an optical linear encoder with reading head and optical scale, such that the planar joints (Pi, ∀i=1,2,3) can maintain a stiffness in the presence of a magnetic preloading at each of the flat pad air bearing based planar joints;
• a pneumatic counterbalance attached to each prismatic joint (Ti, ∀i=1,2,3) can maintain quick settling as well as gravity compensation for achieving high precision and fault tolerant in sudden power off situation, in addition to provision for further enhancement of precision via three plane mirrors attached to the CSA with the help of mirror brackets and mounts, so that the Abbe error-free measurement, which is is followed along the three directions of translations, and a vertical topological design of the WABSS are responsible for independence of linear geometric error along the Z-axis from angular tolerances and a relatively small footprint of the system, to achieve smaller thermal and geometric errors.