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CMA USER MANUAL
E-VLMB-TT005-E April 2019 www.eaton.com
CMA User Manual
4.2 CANOpen networks
The following is not meant to be a comprehensive
description on how to work with CANOpen networks.
For further information on CANOpen, refer to the
CANOpen standards. The CANOpen version of the valve
utilizes an 11 bit identifier with configurable baud rates
of 125, 250, and 500 kb/sec. As with the J1939 version
of the valve, the valve system will be one node on the
CANOpen network. Individual nodes on the valve system
are communicated to through the VSM using service data
objects (SDO’s) and process data objects (PDO’s). State
messages from the valve can be received in CANopen
through a PDO. The valve also accepts commands through
a receive PDO. Monitoring of the valve’s object dictionary
parameters is done through one of ten transmit PDO’s that
are set aside in the valve. These PDO’s have event timers
which allow the user to determine the period at which the
valve will respond with the requested information. Reads
and writes to the valve occur with SDO’s. Events from the
valve are transmitted with emergency messages.
Network management for CANOpen systems is
significantly different compared to J1939 systems. There
are four defined states for all CANOpen slave devices.
These states are stopped, pre-operational, operational, and
initializing. Transition from initialization to pre operational
occurs automatically within the valve. During the transition
from initializing to pre-operational, the valve will issue a
boot up message to the master informing it that the valve
is ready for commands. The valve will not operate until it
has entered its operational state (only SDO messages are
allowed during the pre-operational state). This message has
to be issued from the network master. Further detail on
how to initiate this behavior can be found in the
CANOpen standards.
4.3 Anti-saturation setup (Flowshare)
The valve has three built in anti-saturation schemes;
Ratio, Uniform, and Cascade. These algorithms are
commonly referred to as the ‘Flowshare’ method (anti
saturation and flowshare will be used interchangeably
throughout this document). One of these schemes can
be selected to manage valve demands when they exceed
available flow. Flowshare can also be disabled, which
means the valve will do nothing to inhibit demands from
exceeding available flow.
All of the anti-saturation schemes allow you to give priority
to any service, meaning that particular section would not
be subject to flowshare. Also, for the cascade method,
you need to indicate to the valve which service has the
highest priority as it will reduce the lower priority service
flow demands first (further discussion is given below). A
value of 0 for the priority setting means that service is not
subject to flowshare. A priority of 1 is the highest priority
service and a value of 15 (or however many valves you have
on your system) is the lowest priority service. A table has
been enclosed below showing the object dictionary location
for each priority setting. Note that flowshare is applied to all
non-priority services that are in a flow control mode (Single
Spool or Twin Spool).
4.3.1 Ratio
The ratio method will reduce all non-priority flow demands
by the same relative amount (the same percentage). This
method permits the use of all flow services unless the
pump flow is fully consumed by priority services. As pump
flow decreases, all non-priority flow demands are reduced
by the same percentage and would all reach a demand
of zero at the same time. This method is similar to a post
compensated anti saturation mobile valve system.
4.3.2 Cascade
The cascade method will reduce all non-priority flow
demands according to the priority rating. As described
above, each non priority service is assigned a priority
rating. The rating specifies the order in which the flow
demands are reduced. This method allows higher priority
services to run with their demanded flow unchanged,
whilst lower priority flow demands are reduced. As pump
flow decreases, the higher priority flow demands remain
unchanged but the lower priority flow demands are reduced.
When the lowest priority flow demands hit zero, the next
lowest priority demands are reduced.
4.3.3 Uniform
The uniform method will reduce all non-priority flow
demands by the same actual amount. This method keeps
services with higher flow demands operating in preference
to services with low flow demands. As pump flow
decreases, all non-priority flow demands are reduced by the
same numerical value, so all demands are reduced, but the
lower flow demands reach zero before higher
flow demands.
Along with selecting the anti-saturation scheme, the valve
has two other built in parameters that allow the valve to
manipulate the available flow message that is received from
the application (reference Application Developers Guide for
message structure). This feature was added so the valve
implementer could have an easy method for correcting
inaccuracies in the available flow message and to allow
for some overhead so that the valve never saturates. The
available flow message is manipulated with an offset and a
gain so the available flow that is used in the anti-saturation
algorithm is as follows:
Available flow = available flow message * gain – offset