
Geometries with orientation support
Chapter 4
Rockwell Automation Publication MOTION-UM002F-EN-P - February 2018
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The reference frame is a Cartesian frame which is the base frame for the robot and
all the target points are specified with respect to this base frame. The robot
transformations are set up from base frame to end of arm frame to transform any
Cartesian target positions in to joint space and vice versa. In order for the
transformations to work correctly, it is required to establish the origins for all the
axes in the joint space with respect to the robot base Cartesian frame.
Establish the Base frame
The reference XYZ frame (Base frame) for the Delta geometry is located near the
center of the base plate, between Joint 1 and Joint 2, placed 180 apart. Top link
of one of the arm is aligned along the positive X axis and the other to negative X
axis. Based on the right hand rule, Z axis positive is the axis pointing up (out of the
paper in the top view), as shown in the illustration.
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+J1 rotation is measured clockwise around the -Y axis at the Base frame (+Y
axis is pointing inside).
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Direction of Joint Axis (J1 and J2) in positive direction causes movement of
the top link (associated with J1 or J2 axis) in the downward direction. The
two joints are configured as linear axes.
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Directions of Rz orientations at the Base frame as shown in the illustration.
Establish the End of Arm frame
End of Arm (EOA) in XYZ reference frame is set at the end of the End Plate. This
frame is rotated by Rx =180 with reference to the Base frame. As a result, the X
axis is in the same direction as the Base frame X axis but the Z axis direction is
pointing down, towards the direction of Tool approach vector.
Establish the reference frame
for a Delta J1J2J6 robot