Device for acquiring a position and orientation of an end effector of a robot

A position acquisition system comprising:

• a robot including an end effector, a first optical marker, a second optical marker, and a robot arm, the robot arm including a plurality of axes coupled to one another by a plurality of joints, the end effector being arranged on a first end of the robot arm, the first optical marker being arranged on a first axis of the plurality of axes, the second optical marker being arranged on a second axis of the plurality of axes, a first number of the plurality of joints being arranged between the end effector and the first axis, a second number of the plurality of joints being arranged between the end effector and the second axis, and the first number being lower than the second number;
• a device configured to acquire a position and an orientation of the end effector of the robot, the device including:
• an optical sensor configured to acquire image data of the first optical marker and/or of the second optical marker;
• a storage device storing a kinematic model of the robot arm;
• and
• an evaluation device configured to determine based on the image data whether the first optical marker and the second optical marker are visible to the optical sensor, and, if it is determined based on the image data that the first optical marker is visible to the optical sensor or that the first optical marker and the second optical marker are visible to the optical sensor, to determine a first position of the first optical marker based on the image data and to determine the position and the orientation of the end effector based on the first position, and, if it is determined based on the image data that the first optical marker is not visible to the optical sensor but the second optical marker is visible to the optical sensor, to determine a second position of the second optical marker based on the image data, to determine a relative position and a relative orientation of the end effector relative to the second position based on the kinematic model, and to determine the position and the orientation of the end effector based on the determined second position and the determined relative position and relative orientation of the end effector relative to the second position.

A method for acquiring a position and an orientation of an end effector of a robot, the robot having a robot arm including a plurality of axes coupled to one another by a plurality of joints, the end effector being arranged on a first end of the robot arm, a first optical marker being arranged on a first axis of the plurality of axes, a second optical marker being arranged on a second axis of the plurality of axes, a first number of plurality of joints being arranged between the end effector and the first axis, a second number of the plurality of joints being arranged between the end effector and the second axis, the first number being lower than the second number, the method comprising:

• acquiring image data of the first optical marker and/or of the second optical marker;
• providing a kinematic model of the robot arm;
• determining based on the image data whether the first optical marker and the second optical marker are detectable in the image data;
• and
• determining the position and the orientation of the end effector, wherein, if it is determined based on the image data that the first optical marker is detectable in the image data or that the first optical marker and the second optical marker are detectable in the image data, determining a first position of the first optical marker based on image data and determining the position and the orientation of the end effector based on the first position, and, if it is determined based on the image data that the first optical marker is not detectable in the image data but the second optical marker is detectable in the image data, determining a second position of the second optical marker based on the image data, determining a relative position and a relative orientation of the end effector relative to the second position based on the kinematic model, and determining the position and the orientation of the end effector based on the determined second position and the determined relative position and relative orientation of the end effector relative to the second position.