Basic Characteristics RAPID

Motion and I/O Principles Positioning during Program Execution
2 Positioning during Program Execution
2.1 General
During program execution, positioning instructions in the robot program control all
movements. The main task of the positioning instructions is to provide the following
information on how to perform movements:
- The destination point of the movement (defined as the position of the tool
centre point, the orientation of the tool, the configuration of the robot and the
position of the external axes).
- The interpolation method used to reach the destination point, e.g. joint
interpolation, linear interpolation or circle interpolation.
- The velocity of the robot and external axes.
- The zone data (defines how the robot and the external axes are to pass the
destination point).
- The coordinate systems (tool, user and object) used for the movement.
As an alternative to defining the velocity of the robot and the external axes, the time
for the movement can be programmed. This should, however, be avoided if the
weaving function is used. Instead the velocities of the orientation and external axes
should be used to limit the speed, when small or no TCP-movements are made.
In material handling and palletising applications with intensive and frequent
movements, the drive system supervision may trip out and stop the robot in order
to prevent overheating of drives or motors. If this occurs, the cycle time needs to
be slightly increased by reducing programmed speed or acceleration.
2.2 Interpolation of the position and orientation of the tool
2.2.1 Joint interpolation
When path accuracy is not too important, this type of motion is used to move the tool
quickly from one position to another. Joint interpolation also allows an axis to move from
any location to another within its working space, in a single movement.
All axes move from the start point to the destination point at constant axis velocity (see
Figure 13).
RAPID Reference Manual 6-13