The ProcessControlItem ObjectType describes a generic control loop including the measured variable to be controlled (PV), the desired value for the variable (SP) and the signal to the actuator (CV) to bring the PV to match the SP.
The ProcessItemType is formally defined in the following table.
Table 131 – ProcessControlItemType Definition
|
Attribute |
Value |
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|
BrowseName |
ProcessControlItemType |
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|
IsAbstract |
False |
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|
References |
Node Class |
BrowseName |
DataType |
TypeDefinition |
Other |
|
Subtype of the ProcessItemType, i.e. inheriting the Instance Declarations of that Node. |
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|
0:HasProperty |
Variable |
OperatorControl |
0:Boolean |
0:PropertyType |
M, RO, HR |
|
0:HasProperty |
Variable |
RemoteControlEnable |
0:Boolean |
0:PropertyType |
M, RO, HR |
|
0:HasComponent |
Variable |
RemoteValue |
0:Double |
0:BaseDataVariableType |
M, RW, HR |
|
0:HasProperty |
Variable |
RemoteControl |
0:Boolean |
0:PropertyType |
M, RW, HR |
|
0:HasComponent |
Method |
SetRemoteControl |
See below. |
M |
|
The components of the ProcessControlItemType are further described below.
|
BrowseName |
Description |
|
RemoteValue |
The value set by the client to override the object value. |
|
RemoteControlEnable |
The RemoteControlEnable variable exposes when the underlying system is ready to activate the RemoteControl upon a request by a client. When RemoteControlEnable is False, the underlying system is not ready and will not activate a request to remotely control the ProcessControlItem. |
|
RemoteControl |
The RemoteControl variable lets the underlying system expose which system is currently in control of the ProcessControlItem. More specifically, if RemoteControl is True, the underlying system copies the RemoteValue to the ProcesControlItem Value to drive it, i.e. the ProcessControlItem is remotely controlled. If RemoteControl is False, the underlying system is not using RemoteValue to drive the ProcessControlItem, but another value that is exposed as the ProcessControlItem Value, i.e. the ProcessControlItem is locally controlled. A client requests (resp. releases) control of the ProcessControlItem by setting RemoteControl to True (resp. False) preferably by invoking the SetRemoteControl Method. If the client does not support methods, then the client sets RemoteControl to True. The underlying system will reset RemoteControl to False if remote control is not activated. |
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OperatorControl |
The OperatorControl variable qualifies the source of the ProcessControlItem Value when RemoteControl is False, otherwise OperatorControl is undefined. When OperatorControl is True, the underlying system exposes the information that the ProcessControlItem Value is modified by the operator with respect to the nominal value, e.g. NominalRate, a.k.a. design speed for a speed control loop. When OperatorControl is False, the underlying system exposes the information that the ProcessControlItem Value is not modified by the operator. |
The SetRemoteControl Method enables or disables the remote control mode.
The signature of this Method is specified below. Table 132 specifies the Arguments representation.
Signature
SetRemoteControl (
[in] 0:Boolean Enable,
[out]MethodExecutionFeedbackType ExecutionFeedback);
Table 132 – SetRemoteControl Method Arguments
|
Argument |
Description |
|
Enable |
The flag enables (True) or disables (False) the remote control mode. |
|
ExecutionFeedback |
The extended feedback returning a detailed message in case of execution failure. |
When the method SetRemoteControl completes successfully with input argument Enable equal to True, RemoteControl is set to True and the RemoteAnalogMeasurement persistently overrides the ProcessControlItem value.
When the method SetRemoteControl completes successfully with input argument Enable equal to False, RemoteControl is set to False and the ProcessControlItem value is generated by the underlying system.