What are the limitations of AKD EtherNet/IP?

Important Limitations Of The AKD Ethernet/IP Drive

Update rate and determinism:
The AKD's Ethernet port that EtherNet/IP uses as the communications interface can only
process messages from the PLC at a maximum rate ( minimum RPI ):
1. 20mS without Workbench
2. 40ms with Workbench.
This is generally not a problem unless the application is at a high cycle rate motion.. If
the application cycle time is faster than 20msec then this architecture is not the correct
selection. Also, EtherNet/IP is a non-deterministic fieldbus so if you want or need
determinism you will need to consider our KAS/PCMM/PDMM platform with Ethercat
slaves. The PCMM/PDMM can serve as the motion controller and interface to the AB
PLC via EtherNet/IP if the PLC is a must. Keep in mind some functions take longer to
execute than others ( i.e. the enable may take upwards of 300-350msec to complete ).

Motion Control:
 Ethernet IP Standard: Declared as a Generic Ethernet Module with the EIP assemblies for
controllers that support cyclic communications. The AKD EIP drive also supports acyclic
(explicit) messaging.

 Motion supported OVER Ethernet IP
1. Torque Move
2. Jogging
3. Homing
4. Point to Point Relative or Absolute Moves
5. Starting predefined Motion Tasks.

 Motion NOT Supported OVER Ethernet IP
1. Camming
2. Electronic Gearing
3. Move on top of a move
4. Blended moves
5. Changing a move on the fly
6. Registration Moves
7. S-Curve acceleration
8. Synchronized ( i.e. interpolated ) moves between axes

The AKD is declared as a Generic Ethernet Module. This means the AKD doesn't use or need CIP
Motion/CIP Sync. This can result in a cost savings. Example: 1769-L30ERM has 4 axis of motion
and the 1769-L30ER has only EIP communications. Both PLCs will work with the AKD EIP drive
but the motion ready processor costs more.
Implications:

Indexing:
The AKD Ethernet IP drive works as follows: You load a block with typical motion task
parameters ( indexing ) and trigger the enable ( typically using the Add On Instructions for AB
PLC users). This means that you can start two axes at the same time but you cannot guarantee
synchronism over Ethernet IP ( remember motion tasking is point to point motion ).

Electronic Gearing:
In that case you will need to either use Electronic Gearing between a master and slave drives
with traditional hardwiring of the EEO output to the Encoder input of the slave drives and
communicate Ethernet IP to each drive for diagnostics, etc. or use the KAS/PDMM/PCMM
platform where synchronism is required between axes or where events must be on a clock and
deterministic.

S-curve acceleration and Blended Moves:
Although these cannot be accomplished OVER Ethernet/IP it is possible to accommodate them
using the Motion Task table.
 The AKD_Move AOI is not designed for blended moves ( start one move and blend into
another ).
 If blended moves are absolutely required for the application, the block method will be
required. The block method is where the user creates a chain of predefined motion
tasks using Workbench and sets one or more motion tasks to blend into the other.
.
 Using pre-defined motion tasks also allows the use of S-Curve acceleration using the
Motion Profile Table since this is achieved in the drive and not over Ethernet IP.

 The Ethernet IP landing page has a link where additional AOIs (AKD_Start_MotionTask
& AKD_Set_Motion_Task Block ) can be downloaded and added to your project for
using the block method. In that zip file there are 2 AOIs: One is for setting the motion
task parameters ( if the predefined moves need to be created from the PLC or HMI ( i.e.
recipes ) and the other is for pointing to the motion task number ( the first move to
start the chain of blended moves ) and executing it.
 For non-AB controllers that support Ethernet IP cyclic messaging, the programmer will
have to set the correct byte in the command assembly for setting the block number and
use the control word to start the block.AOIs can be downloaded and added to your
project for using the block method. In that zip file there are 2 AOIs: One is for setting
the motion task parameters ( if the predefined moves need to be created from the PLC
or HMI ( i.e. recipes ) and the other is for pointing to the motion task number ( the first
move to start the chain of blended moves ) and executing it.

Drive setup, tuning, and parameter downloads:
Most familiar with AB drives are used to performing the drive setup and tuning using the PLC
and PLC programming software.
They are also accustomed to having the ability to have the PLC download all parameters/setup
to a drive in the case a drive is replaced due to failure or other reason.

Functions NOT supported OVER Ethernet IP:
 Tuning and drive commissioning
 Downloading all parameters or parameter file to a drive ( i.e. a spare/replacement
drive )

Implications:
 Tuning and drive commissioning must be performed using Workbench
 Downloading parameter to a drive ( i.e. a spare/replacement drive ) must be performed
by Workbench.

There is no practical way to do this with the AKD over EtherNet/IP. The user will have to
commission the AKD drive, archive the parameter file, and in the case of drive replacement
download the parameters ALL using Workbench.

Maximum Axis Count:
The limitation is primarily the bandwidth of your network. Use a managed switch to limit
crashes and IP address conflicts. If the axis count is high, you may want to consider the
KAS/PCMM/PDMM platform as a different architecture where the KAS/PCMM/PDMM can
handle the motion control (EtherCAT based ) and the PLC handles the system/machine
supervision, HMI, recipe data, other non-motion devices and operations, etc. assuming the PLC
is required in the application as a supervisor.