Specifications
9-68
9.5.2 Calibration of Robot Coordinates and Vision Coordinates
To visually correct the robot position using measured coordinates, it is
necessary to convert the vision coordinates to robot coordinates. To do this, it
is necessary to obtain the relationship between the vision and the robot
coordinates, in advance. The work for acquiring this relationship is called
camera calibration. It is possible to calculate coordinate conversion coefficients
(calibration data) by entering the vision coordinates (Vx, Vy) of 3 points (S1,
S2, and S3) determined in the camera field of view (vision coordinates) and the
robot coordinates (Rx, Ry and Rz) of the Vision Manager camera calibration
tool. Once obtained, coordinate conversion coefficients needs to be
transmitted to the Controller for registration. With the user program, convert
vision coordinates to robot coordinates by using the coordinate conversion
library (viTran6). The coordinate conversion library uses the coordinate
conversion coefficients registered to the Controller for converting coordinates.
- Calibration Data and Coordinate Conversion -
Camera calibration data registered to the Controller can be referred to
using the VISREFCAL command. (See Table 1) The coordinate
conversion library converts vision coordinates to robot coordinates by
using the calibration data referred to by VISREFCAL command. (See
equation 1)
Table 1 Relationship between VISREFCAL Command and
Vision Manager VISREFCAL (a,b)
b
01234567891011
a=0 to 31 NX OX AX RX NY OY AY RY NZ OZ AZ RZ
Equation 1 Conversion of coordinate conversion library (viTran6)
Vx1
Rx1
Vy1
1
V
x
Ry1
Vy
Ry
R
x
S3
S2
S1
Rx1, Ry1, Rz1: Robot coordinates o
f
Point S1
Vx1, Vy1: Vision coordinates of Point
S1
S1, S2, S3: Reference points
Robot
coordinates
Vision
coordinates
Rx1
Ry1
Rz1
Vx1
Vy1
=
RX NX OX AX RX VX
RY NY OY AY RY VY
RZ NZ OZ AZ RZ 0
1 0001 1
RX, RY, RZ : Robot coordinates
VX, VY : Vision coordinates
NX, NY, NZ : Table 1
OX, OY, OZ : Table 1
AX, AY, AZ : Table 1
RX, RY, RZ : Table 1
Conversion
coefficients
×