The above figure shows a measurement of a task with a periodic time of
t#1ms. In this case, the task uses more than the specified interval time. The
100% mark again corresponds to the net time intended for the task within one
millisecond. Here the task requires more time, so the measured percentage
value at the "rLoad" output displays more than 100%. The "rFreeTime" output
displays 0 (µs).
4.5.7
Task configuration
It is possible, but not necessary, to control the processing of the project (con‐
trol of the program) via tasks; if there is no task configuration available, the
project has to contain the "PLC_PRG" function block. In this case, a default
task with a periodic time of 10 ms and a watchdog is automatically created.
As soon as the user has defined a task, this default task is deactivated.
4.5.8
Task cycle times and timing
PLC cycle time
The PLC cycle time T
PLC
of MLD defines the periodic time for cyclic tasks.
The T
PLC
consists of one or several PLC time slices.
PLC time slice
The integrated PLC (IndraMotion MLD) works cyclically in time slices, regard‐
less of the task type used. Since the integrated PLC is calculated by the drive
processor, it must share the resources with the rest of the system (position
controller, velocity controller, current controller, different background tasks
[such as command task], etc.). Depending on the system load, a certain cal‐
culating time is available to the MLD for each PLC time slice. All PLC IEC
tasks run in the context of PLC time slices.
Minimum PLC cycle time
The minimum PLC cycle time (T
PLC,min
) is one PLC time slice; it also defines
the reaction time of the event tasks. The minimum PLC cycle time (T
PLC,min
)
does not depend on the control unit and is 1 ms.
The maximum configurable cycle time is 2000 s (or 33 minutes)!
See also Functional Description of firmware "Performance data"
Event task reaction times
Event tasks are also started within the PLC time slices, i.e., their reaction
time also depends on the PLC cycle time.
Timing
The attainable program cycle time or timing depends on the integration of the
PLC in the task system of the drive.
The performance of devices with MPB-18 and MPC-18 firmware can be
modified by the setting in P-0-0556:
●
P-0-0556, bit 2="0" ⇒ Basic performance
●
P-0-0556, bit 2="1" ⇒ Advanced performance
If the "MLD-M system mode" has been configured in the MPC
firmware (P-0-1800.0.1), the "Advanced" performance level is un‐
available.
Performance [µs]
Current
controller
clock
(T
A_current
)
Velocity controller
clock
(T
A_velocity
)
Position controller
clock
(T
A_position
)
PLC cycle time
(IndraMotion MLD)
[T
MLD
]
Master
communication
cycle time
(T
MastCom
)
Basic
125
250
500
1000
500
Advanced
62.5
125
250
1000
250
Tab. 4-6:
Performance settings (performance level)
The figures below illustrate the functional principle (interruptions by velocity
controller, current controller, etc., are not shown):
DOK-INDRV*-MLD3-**VRS*-AP02-EN-P
Bosch Rexroth AG
69/267
Rexroth IndraDrive Rexroth IndraMotion MLD (2G) as of MPx-18
Basic functions of Rexroth IndraMotion MLD
LSA Control S.L. www.lsa-control.com [email protected] (+34) 960 62 43 01