Technology instructions
10.3 Motion control
S7-1200 Programmable controller
764 System Manual, V4.2, 09/2016, A5E02486680-AK
Monitoring the MC_Velocity
The tasks of the motion control instruction "MC_MoveVelocity" implement a move at the
specified velocity:
● The tasks of motion control instruction "MC_MoveVelocity" do not have a defined end.
The task objective is fulfilled when the parameterized velocity is reached for the first time
and the axis travels at constant velocity. When the parameterized velocity is reached, this
is indicated by the value TRUE in output parameter "InVelocity".
● The task is complete when the parameterized velocity has been reached and input
parameter "Execute" has been set to the value FALSE. However, the axis motion is not
yet complete upon completion of the task. For example, the axis motion can be stopped
with motion control task "MC_Halt".
● The output parameters "Busy", "CommandAborted", and "Error" signal that the task is still
being processed, has been aborted or an error is pending.
– During execution of the motion control task, output parameter "Busy" indicates the
value TRUE. If the task has been completed, aborted, or stopped by an error, the
output parameter "Busy" changes its value to FALSE. This change occurs regardless
of the signal at input parameter "Execute".
– The output parameters "InVelocity", "CommandAborted", and "Error" indicate the
value TRUE for at least one cycle, when their conditions are met. These status
messages are latched while input parameter "Execute" is set to TRUE.
The behavior of the status bits is presented below for various example situations:
● The first example shows the behavior when the axis reaches the parameterized velocity.
If the motion control task has been executed by the time the parameterized velocity is
reached, this is indicated by the value TRUE in output parameter "InVelocity". The signal
status of the input parameter "Execute" influences the display duration in the output
parameter "InVelocity".
● The second example shows the behavior if the task is aborted before achieving the
parameterized velocity. If the motion control task is aborted before the parameterized
velocity is reached, this is indicated by the value TRUE in output parameter
"CommandAborted". The signal status of input parameter "Execute" influences the
display duration in output parameter "CommandAborted".
● The third example shows the behavior of the axis if an error occurs before achieving the
parameterized velocity. If an error occurs during execution of the motion control task
before the parameterized velocity has been reached, this is indicated by the value TRUE
in the output parameter "Error". The signal status of the input parameter "Execute"
influences the display duration in the output parameter "Error".
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