User Manual

b. The rc_visard is not mounted on the robot but is fixed to a table or other place in the robot’s vicinity and
remains at a static position w.r.t. the robot.
While the general Calibration routine (Section 6.7.3) is very similar in both use cases, the calibration process’s
output, i.e., the resulting calibration transform, will be semantically different, and the fixture of the calibration
grid will also differ.
Calibration with a robot-mounted sensor When calibrating a robot-mounted rc_visard with the robot, the cal-
ibration grid has to be secured in a static position w.r.t. the robot, e.g., on a table or some other fixed-base
coordinate system as sketched in Fig. 6.7.1.
Warning: It is extremely important that the calibration grid does not move during step 2 of the Cal-
ibration routine (Section 6.7.3). Securely fixing its position to prevent unintended movements such as
those caused by vibrations, moving cables, or the like is therefore strongly recommended.
The result of the calibration (step 3 of the Calibration routine, Section 6.7.3) is a pose T
robot
camera
describing
the (previoulsy unknown) relative positional and rotational transformation between the rc_visard’s camera
frame and the user-selected robot frame such that
p
robot
= R

T
robot
camera

· p
camera
+ t

T
robot
camera

,
(6.7.1)
where p
robot
= (𝑥, 𝑦, 𝑧)
𝑇
is a 3D-point with its coordinates expressed in the robot frame, p
camera
is the same
point represented in the camera coordinate frame, and R(T) as well as t(T) are the corresponding 3 × 3
rotation matrix and 3 × 1 translation vector to a pose T, respectively.
robot
ext
camera
T
robot
ext
T
camera
robot
Calibration grid
Fig. 6.7.1: Important frames and transformations for calibrating a robot-mounted rc_visard: The sensor is mounted
with a fixed relative position to a user-defined robot frame (e.g., flange or TCP). It is important that the pose T
ext
robot
of this robot frame w.r.t. a user-defined external reference frame ext is observable during the calibration routine.
The result of the calibration process is the desired calibration transformation T
robot
camera
, i.e., the pose of the camera
frame within the user-defined robot frame.
Calibration with a statically-mounted sensor In use cases where the rc_visard is positioned statically w.r.t. the
robot, the calibration grid needs to be mounted to the robot as shown for example in Fig. 6.7.2 and Fig.
6.7.3.
Note: The hand-eye calibration component is completely agnostic about the exact mounting and posi-
tioning of the calibration grid w.r.t. the user-defined robot frame. That is, the relative positioning of the
calibration grid to that frame neither needs to be known, nor it is relevant for the calibration routine, as
shown in Fig. 6.7.3.
6.7. Hand-eye calibration 55