Extended Rule-Based Controls

Rule-Based Controls allow link status and settings to be based on a combination of conditions that might exist in the network over an extended period simulation. Rule-based controls will be either in the form of an action clause or a condition clause.

 

Figure: The Extended rule-based control editor

The following buttons are available at the top of the editor:

• Insert: Insert a new rule.
• Delete: Delete a rule.
• Load: Load rules from a text file (*).
• Save: Save rules into a text file (*).

(*) You can edit the rules within the ASCII file and import them back to MIKE+ by selecting Load from ASCII file. This is convenient in cases when you use Excel or other tools to create the list of rules for the model.

Format of rules

General format

Each rule is a series of statements of the form:

IF condition_1  
AND condition_2  
OR condition_3  
AND condition_4  
etc.

THEN action_1  
AND action_2  
etc.

ELSE action_3  
AND action_4  
etc.

PRIORITY value  

where:
- conditon_n is a Condition clause
- action_n is an Action clause
- priority is a priority value (e.g., a number from 1 to 5).

Remarks:

1. Keywords IF, AND, OR, THEN, ELSE, PRIORITY must always start at a new line.
2. Only the RULE, IF and THEN portions of a rule are required; the other portions are optional. The "RULE" portion is automatically created from the contents of Rule ID and Description fields. The portions "IF" (i.e. condition clause) and "THEN" (i.e. action clause) must be provided by the user.
3. When mixing AND and OR clauses, the OR operator has higher precedence than AND, i.e.,
   • IF A or B and C is equivalent to IF (A or B) and C
   • If the interpretation was meant to be IF A or (B and C) then this can be expressed using two rules as in
     IF A THEN ...
IF B and C THEN ...
4. The PRIORITY value is used to determine which rule applies when two or more rules require that conflicting actions be taken on a link. A rule without a priority value always has a lower priority than one with a value. For two rules with the same priority value, the rule that appears first is given the higher priority.
5. The decimal separator for numerical values must be a point.

Condition clause

A condition clause in a Rule-Based Control takes the form of:

object id attribute relation value

where:

• object is a category of network object
• id is the object's ID label
• attribute is an attribute or property of the object
• relation is a relational operator
• value is an attribute value

Some example conditional clauses are:

JUNCTION 23 PRESSURE > 20  
TANK T200FILLTIME BELOW 3.5  
LINK 44 STATUS IS OPEN  
SYSTEM DEMAND >= 1500  
SYSTEM CLOCKTIME = 7:30 AM

The Object keyword can be any of the following:

• NODE
• LINK
• SYSTEM
• JUNCTION
• PIPE
• RESERVOIR
• PUMP
• TANK
• VALVE.

When SYSTEM is used in a condition no ID is supplied.

The following attributes can be used with Node-type objects:

• DEMAND
• HEAD
• PRESSURE

The following attributes can be used with Tanks:

• LEVEL
• FILLTIME (hours needed to fill a tank)
• DRAINTIME (hours needed to empty a tank)

These attributes can be used with Link-Type objects:

• FLOW
• STATUS (OPEN, CLOSED, or ACTIVE)
• SETTING (Pump speed or Valve setting)
• LIKE (See Multiple Pumps, Valves with LIKE setting for more details)
• STARTTIME (hours from the last pump start)
• STOPTIME (hours from the last pump stop)

The SYSTEM object can use the following attributes:

• DEMAND (total system demand)
• TIME (hours from the start of the simulation)
• CLOCKTIME (24-hour clock time with AM or PM appended)

Relation operators consist of the following:

• = IS
• <> NOT
• < BELOW
• > ABOVE
• <=> =

Action clause

An action clause in a Rule-Based Control takes the form of:

object id STATUS/SETTING IS value

where

• object is LINK, PIPE, PUMP, or VALVE keyword
• id is the object's ID label
• value is a status condition (OPEN or CLOSED), pump speed setting, or valve setting

Some example action clauses are:

LINK 23 STATUS IS CLOSED  
PUMP P100 SETTING IS 1.5  
VALVE 123 SETTING IS 90

Multiple Pumps, Valves with LIKE setting

The LIKE setting allows to control multiple pumps or valves in efficient way. It is possible to set a pump speed to x % of another pump, for example. Such an option could also be used when the new value is the value of the object itself (e.g. to set a pump speed to increase by 20 %, or valve to open by 10 % and so on).

Setting Value = A (another link setting) B (multiplier) C (increment)

The default values for the B (multiplier) and C (increment) are B=1, C=0 and they do not need to be provided.

The setting value is calculated as:

Setting Value = Setting Value (link A) * B + C

Example 1

IF SYSTEM CLOCKTIME = 8 AM  
THEN PUMP 3 SETTING LIKE PUMP 4 1 0

The pump 3 setting will be set equal to the settings of the pump 4 (multiplier= 1 and increment = 0) at time 8 am.

Example 2

IF SYSTEM CLOCKTIME = 8 AM  
THEN PUMP 3 SETTING LIKE PUMP 4 1.10 0

The pump 3 setting will be higher by 10% than the settings of the pump 4 (multiplier = 1.10 and increment = 0) at time 8 am.

Example 3

IF SYSTEM TIME >= 12 AM  
THEN VALVE 10 SETTING LIKE VALVE 20 1.0 -10

The valve 10 setting (PRV setting, for example) will be lower by 10 (pressure units) than the settings of the valve 20 (multiplier = 1 and increment = -10) at any time (12 AM is the simulation start).

Example 4

IF SYSTEM TIME >= 12 AM  
THEN PUMP 3 STATUS LIKE PUMP 4

The pump 3 status (OPEN, CLOSED) will be set equal to the status of the pump 4 at any time (12 AM is the simulation start).

Example 5

IF PUMP 3 SETTING LIKE PUMP 4  
THEN …

If pump 3 setting is equal to the settings of the pump 4 (default multiplier = 1 and increment = 0) then …

Controls Examples

Control of a valve

This set of rules opens and closes a valve based on the water level in a storage tank.

 

 

Figure: Rules in EPANET .inp file

Control of a pump

This set of rules opens and closes a pump based on the water level in a storage tank.

 

 

Figure: Rules in EPANET .inp file