Question:
What has to be observed for the real and the Cartesian axes when using the software limits?
How do the axes behave when stopping after actuation of the monitoring functions?
Answer:
The response of the monitoring functions for the software limits is different for real and Cartesian axes:
Real axes (A1, A2, A3,...):
The software limits of the real axes should be set in accordance with the mechanically permissible traversing range of the corresponding real axis.
The monitoring of the software limits only refers to the movements of the corresponding real axis.
Since dependencies on other real axes are not considered, the path accuracy will no be longer observed during the stop ramp.
Cartesian axes (X, Y, Z,...):
The software limits of the Cartesian axes should be set in accordance with the permissible motion range of the robot mechanics (kinematics).
If the monitoring function of one of the Cartesian axes is actuated, all axes connected to the kinematics are decelerated to standstill in a coordinated fashion that is accurate to the path.
Tip:
--> If possible, select the software limits such that the monitoring functions of the Cartesian axes will primarily be actuated.
Fundamentals:
Robots usually consist of several driven axes coupled to each other via mechanics (kinematics):
Real axes (A1, A2, A3,...): The controllers drive the input side of the kinematics via the connected motors.
Cartesian axes (X, Y, Z,...): The output side of the kinematics is represented by the Cartesian axes (X, Y, Z,...). The Tool Center Point (TCP) is at the end.
"Transformation" is used to convert the positions and movements between the real and the Cartesian axes.
The software limits are used to monitor the permissible traversing and motion range for robot applications. The corresponding parameters are set via the motion parameter subcodes 50 to 53 of the corresponding axis. The SW limits are only active if the axis is referenced and monitoring is activated via subindex 50.
The behaviour of the SW limits can be selected under subindex 53.
By default, positioning FB movements as a result of which the software limits would be exceeded will not even be started.
Differening from the default setting, you can also select that the monitoring function shall only be triggered when a software limit is actually exceeded. In practical operation, this setting can, however, only be used for jogging or movements requested via MC_MoveVelocity.
