The ProcessControlLoopType is the general description of a control loop consisting of the desired value (SetPoint) for a measured value (ProcessValue) which is obtained by acting on an actuator (ControlValue).
The ProcessControlLoopType is formally defined in the following table.
Table 133 – ProcessControlLoopType Definition
Attribute
Value
BrowseName
ProcessControlLoopType
IsAbstract
False
References
Node Class
BrowseName
DataType
TypeDefinition
Other
Subtype of the TMCDeviceType, i.e. inheriting the Instance Declarations of that Node.
0:HasComponent
Objects
ControlValue
ProcessControlItemType
M
0:HasComponent
Objects
ProcessValue
ProcessControlItemType
M
0:HasComponent
Objects
SetPoint
ProcessControlItemType
O
0:HasProperty
Variable
WatchdogEnabled
0:Boolean
0:PropertyType
M, RW
0:HasProperty
Variable
WatchdogTimeout
0:Duration
0:PropertyType
M, RW
0:HasComponent
Object
ExternalAlarms
0:FolderType
M
0:GeneratesEvent
ObjectType
ExternalAlarmType
Conformance Units
TMC Process Variables Ingestion and Control
BrowseName
Description
ControlValue
The ControlValue is the output of the control loop function. The control value directly drives the actuator.
ProcessValue
The value read by a sensor or other analog measurement of the physical quantity that is monitored.
SetPoint
The value we aim to obtain from the ProcessValue by means of driving the control value.
WatchdogEnable
When WatchdogEnable is True, if a ProcessControlLoop component’s RemoteControl is True and the time between two consecutive writes of the RemoteValue is longer than WatchdogTimeout, then the underlying system will generate an alarm, set RemoteControl to False and take control of the loop. When WatchdogEnable is False, no watchdog alarm is generated.
WatchdogTimeout
The longest time between two write actions before a watchdog alarm is generated by the underlying system. The value is expressed in milliseconds. If the written value is below (above) the minimum (maximum) value that can be managed by the underlying system, the underlying system will overwrite it with the minimum (maximum).
ExternalAlarms
The external alarms folder is used to organize external alarms.
The components of the ProcessControlLoopType have additional subcomponents which are defined in the following table.
The ExternalAlarms folder provides 10 spare external alarms that are mandatorily implemented by the underlying system. Additional ones can be added via the ExternalAlarmN optional placeholder.
