Patent ID: 8422015

Claim:
A movable body apparatus including a movable body which substantially moves along a predetermined plane, the apparatus comprising: a reflection surface which is arranged at one of the movable body and an outside of the movable body, with a first direction within a plane parallel to the predetermined plane serving as a longitudinal direction, the reflection surface having a predetermined width in a second direction orthogonal to the first direction within the plane parallel to the predetermined plane; a measurement device which has a plurality of measurement points placed in a movement area of the movable body, and measures positional information of the reflection surface in a third direction orthogonal to the predetermined plane by irradiating measurement beams on the measurement points placed on the reflection surface within the predetermined width; and a controller which performs position control of the movable body, preferentially using a first measurement information including measurement information at a first measurement point out of n (wherein n is an integer of two or more) or more measurement points positioned within the predetermined width of the reflection surface, and which switches measurement information to preferentially use in position control of the movable body to a second measurement information including measurement information at a second measurement point different from the first measurement point when abnormality occurs in the first measurement information at the first measurement point due to abnormality of the reflection surface, wherein the controller determines whether the abnormality has occurred by comparing the first measurement information with a threshold.