The present invention provides a method and apparatus for accurately
positioning a robotic pool-playing device. The system comprises a
computer controlled robotic positioning device, such as a gantry robot,
that can position a cue over the pool table and place a shot. A global
camera is mounted on the ceiling looking down at the table, and the
acquired images are transmitted to the computer for analysis to determine
the identity and locations of the balls within the table coordinate
reference frame. The computer also automatically determines which ball to
strike. An aspect of the invention is the use of a local camera, mounted
on or near the robotic end-effector in a fixed relationship with the cue,
to improve the positioning error of the robotic device prior to placing a
shot. By comparing the ball locations perceived from the vantage of the
local camera with the known ball locations determined from the global
camera image, the invention can calculate the acquired robotic
positioning error, which can then be corrected for prior to placing the
shot.