Parker
Hannifin
Network Failsafe Assurances
Several measures help to ensure failsafe behavior in the event of any kind of
network problem. In an EPL cycle, the controller and drive exchange data,
and each tests for a loss of EPL cycles or unexpected network state.
A loss of EPL cycles could be caused by a disconnected cable or a problem
with the controller. The controller will respond to a disconnected EPL cable or
node error by disabling that axis, just as with a traditional drive. The Aries
EPL drive will detect any loss of EPL cycles within 20 milliseconds and treats
this as a fault. If the drive was enabled, it will disable itself and record the
fault.
An EPL drive axis is treated just the same as any other axis in the event that
the motion enable input on the ACR9030 or ACR9040 is lost. Although there
are no DACs or stepper outputs to clamp, the motion is killed and axes are
commanded to be disabled.
EPL Network Cycle Times
The EPL cycle time is automatically established with the ACR9030 or
ACR9040
PERIOD
command, and is exactly the same as their trajectory
period.
The ACR9030 and ACR9040 firmware uses the following formula with some
restrictions:
Minimum period in microseconds = 125 x (number of nodes)
The restrictions on allowable values for ACR9030 or ACR9040
PERIOD
when an EPL controller card is installed are as follows:
•
The minimum period is 500 microseconds. This accommodates the
minimum overhead involved with EPL cycle creation, reporting, and
error handling.
•
The period must be a multiple of 125 microseconds, allowing the Aries
EPL drive to synchronize its servo periods with trajectory data
received over the EPL network.
•
The period must be long enough to accommodate the added overhead
of adding nodes on the EPL network.
Support for CiA DSP-402
Drives controlled by the ACR9030 or ACR9040 must adhere to the CANopen
device profile for motion control, CiA DSP-402 V2.0, in order to ensure
interoperability with EPL motion products from other vendors. DSP-402
specifies object dictionary entries that correspond to drive setup as well as
periodic data transfer. In addition, DSP-402 specifies six different modes of
operation. All of these modes require some type of trajectory generator in the
drive whose function depends on the mode.
Interpolated Position Mode
The ACR9030 and ACR9040 generate trajectories for the drive, and only
expects the drive to close the position loop at each update. It does not want
the drive to generate its own trajectory.
Appendix H ETHERNET Powerlink 169
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Summary of Contents for ACR9000
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