Measurement fixture for use in determining position and orientation of object and method of determining position, orientation of object relative to reference

摘要

A measurement fixture 32, fig. 1, fig. 3(a), has a plurality of optically-detectable elements, preferably infrared LEDs, 42, 44. In use, the measurement fixture is attached in fixed spatial relationship to an object, such as a robot arm, and an optical measuring device detects the optically detectable elements to provide 6D relative tracking of the object relative to a reference. The measurement fixture 32 may comprise a substantially planar circular base 34 and a plurality of projections or posts 36 mounted to the base and extending substantially perpendicular to the plane of the base. Each post may have a substantially square cross-section and ends which are pyramidal in shape. Each post may further comprise a plurality of light-emitting diodes; the LEDs spaced apart on the sides and ends of each projection. The optically-detectable elements are distributed around the measurement fixture such that in use at least three reference points are within the field of view of the optical measuring device for all positions and orientations of the object. A method, also claimed, of determining the position and orientation of an object relative to a reference, comprises: mounting the object in a fixed spatial relationship with a measurement fixture having a plurality of optically detectable elements; detecting the positions of at least some of the elements; detecting the position and orientation of the reference; comparing the detected positions to determine the position and orientation of the measurement fixture relative to the reference.