Abstract: The position of a movable element such as the end of a robot arm (10) which has several degrees of freedom, being mounted on a base (11) and including a wrist mechanism, is determined by installing a multiplicity of base targets (32, 74) around the base of the robot, and a multiplicity of arm targets (42, 74) around the base (14) of the wrist mechanism (15), and an optical means (90) that moves with the movable element to determine the positions of at least some of the base targets and of at least some of the arm targets. The optical means may be a laser tracker or a camera system (90), and it may be mounted on the part (13) of the robot arm to which the base (14) of the wrist mechanism (15) is connected. This enables existing robots (10) to achieve absolute positional accuracy relative to a fixed external frame of reference.

Abstract: Positional measurements for a robot arm are made using a light ray projector (10) mounted on the robot arm and arranged to emit light rays (50) along a multiplicity of distinct paths that are fixed relative to the projector (10), and a removable support frame (20) carrying a multiplicity of image sensors (22) at fixed positions relative to the support frame (20), the support frame surrounding the base of the robot arm. A signal processor (25) connected to the light sensors (22) determines the positions at which light rays (50) are incident on the image sensors (22), and hence determines positional information of a system of axes associated with the projector (10) relative to the frame (20). This enables relative positional measurements to be made substantially in real time, and in an accurate and cost-effective manner.

Abstract: The position of a movable element such as the end of a robot arm (10) which has several degrees of freedom, being mounted on a base (11) and including a wrist mechanism, is determined by installing a multiplicity of base targets (32, 74) around the base of the robot, and a multiplicity of arm targets (42, 74) around the base (14) of the wrist mechanism (15), and an optical means (90) that moves with the movable element to determine the positions of at least some of the base targets and of at least some of the arm targets. The optical means may be a laser tracker or a camera system (90), and it may be mounted on the part (13) of the robot arm to which the base (14) of the wrist mechanism (15) is connected. This enables existing robots (10) to achieve absolute positional accuracy relative to a fixed external frame of reference.