Basic Characteristics RAPID

Positioning during Program Execution Motion and I/O Principles
Start point
Figure 13 Joint interpolation is often the fastest way to move between two points as the robot
axes follow the closest path between the start point and the destination point (from the
perspective of the axis angles).
The velocity of the tool centre point is expressed in mm/s (in the object coordinate
system). As interpolation takes place axis-by-axis, the velocity will not be exactly the
programmed value.
During interpolation, the velocity of the limiting axis, i.e. the axis that travels fastest
relative to its maximum velocity in order to carry out the movement, is determined.
Then, the velocities of the remaining axes are calculated so that all axes reach the
destination point at the same time.
All axes are coordinated in order to obtain a path that is independent of the velocity.
Acceleration is automatically optimised to the max performance of the robot.
2.2.2 Linear interpolation
During linear interpolation, the TCP travels along a straight line between the start and
destination points (see Figure 14).
e
Joint interpolated
path
Figure 14 Linear interpolation without reorientation of the tool.
Destination point
Start point Destination point
To obtain a linear path in the object coordinate system, the robot axes must follow a
non-linear path in the axis space. The more non-linear the configuration of the robot is,
the more accelerations and decelerations are required to make the tool move in a
straight line and to obtain the desired tool orientation. If the configuration is extremely
non-linear (e.g. in the proximity of wrist and arm singularities), one or more of the axes
will require more torque than the motors can give. In this case, the velocity of all axes
will automatically be reduced.
The orientation of the tool remains constant during the entire movement unless a
reorientation has been programmed. If the tool is reoriented, it is rotated at constant
velocity.
6-14 RAPID Reference Manual