Buildings.Controls.OBC.CDL.Logical

Package with logical blocks

Information

Package with blocks for elementary mathematical functions for boolean variables.

Package Content

Name	Description
And	Logical 'and': y = u1 and u2
Change	Output y is true, if the input u has a rising or falling edge (y = change(u))
Edge	Output y is true, if the input u has a rising edge (y = edge(u))
FallingEdge	Output y is true, if the input u has a falling edge (y = edge(not u))
Latch	Maintains a true signal until change condition
MultiAnd	Logical MultiAnd, y = u[1] and u[2] and u[3] and ...
MultiOr	Logical MultiOr, y = u[1] or u[2] or u[3] or ...
Nand	Logical 'nand': y = not (u1 and u2)
Nor	Logical 'nor': y = not (u1 or u2)
Not	Logical not
Or	Logical 'or': y = u1 or u2
Pre	Breaks algebraic loops by an infinitesimal small time delay (y = pre(u): event iteration continues until u = pre(u))
Proof	Verify two boolean inputs
Switch	Switch between two boolean signals
Timer	Timer measuring the time from the time instant where the Boolean input became true
TimerAccumulating	Accumulating timer that can be reset
Toggle	Toggles output value whenever its input turns true
TrueDelay	Delay a rising edge of the input, but do not delay a falling edge.
TrueFalseHold	Block that holds an output signal for at least a specified duration
TrueHold	Block that holds a true signal for at least a requested duration
VariablePulse	Generate boolean pulse with the width specified by input
Xor	Logical 'xor': y = u1 xor u2
Sources	Package with blocks that generate source signals
Validation	Collection of models that validate the logical blocks of the CDL

Buildings.Controls.OBC.CDL.Logical.And

Logical 'and': y = u1 and u2

Information

Block that outputs true if all inputs are true. Otherwise the output is false.

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Change

Output y is true, if the input u has a rising or falling edge (y = change(u))

Information

Block that outputs true if the Boolean input has either a rising edge from false to true or a falling edge from true to false. Otherwise the output is false.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Edge

Output y is true, if the input u has a rising edge (y = edge(u))

Information

Block that outputs true if the Boolean input has a rising edge from false to true. Otherwise the output is false.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.FallingEdge

Output y is true, if the input u has a falling edge (y = edge(not u))

Information

Block that outputs true if the Boolean input has a falling edge from true to false. Otherwise the output is false.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Latch

Maintains a true signal until change condition

Information

Block that generates a true output when the latch input u rises from false to true, provided that the clear input clr is false or also became at the same time false. The output remains true until the clear input clr rises from false to true.

If the clear input clr is true, the output y switches to false (if it was true) and it remains false, regardless of the value of the latch input u.

At initial time, if clr = false, then the output will be y = u. Otherwise it will be y=false (because the clear input clr is true).

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.MultiAnd

Logical MultiAnd, y = u[1] and u[2] and u[3] and ...

Information

Block that outputs y = true if and only if all elements of the input vector u are true. If no connection to the input connector u is present, the output is y=false.

See Buildings.Controls.OBC.CDL.Logical.Validation.MultiAnd for an example.

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.MultiOr

Logical MultiOr, y = u[1] or u[2] or u[3] or ...

Information

Block that outputs y = true if any element in the input vector u is true. If no connection to the input connector u is present, the output is y=false.

See Buildings.Controls.OBC.CDL.Logical.Validation.MultiOr for an example.

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Nand

Logical 'nand': y = not (u1 and u2)

Information

Block that outputs true if at least one input is false. Otherwise the output is false.

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Nor

Logical 'nor': y = not (u1 or u2)

Information

Block that outputs true if none of the inputs is true. Otherwise the output is false.

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Not

Logical not

Information

Block that outputs true if the input is false, and false if the input is true.

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Or

Logical 'or': y = u1 or u2

Information

Block that outputs true if at least one input is true. Otherwise the output is false.

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Pre

Breaks algebraic loops by an infinitesimal small time delay (y = pre(u): event iteration continues until u = pre(u))

Information

This block delays the Boolean input by an infinitesimal small time delay and therefore breaks algebraic loops. In a network of logical blocks, in every closed connection loop, at least one logical block must have a delay, since algebraic systems of Boolean equations are not solvable.

This block returns the value of the input signal u from the last event iteration. The event iteration stops once both values are identical, i.e., if u = pre(u).

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Proof

Verify two boolean inputs

Information

Block that compares a boolean set point u_s with a measured signal u_m and produces two outputs that may be used to raise alarms about malfunctioning equipment.

The block sets the output yLocFal = true if the set point is u_s = true but the measured signal is locked at false, i.e., u_m = false. Similarly, the block sets the output yLocTru = true if the set point is u_s = false but the measured signal is locked at true, i.e., u_m = true. Hence, any output being true indicates an operational problem.

To use this block, proceed as follows: Set the parameter feedbackDelay ≥ 0 to specify how long the feedback of the controlled device is allowed to take to report its measured operational signal u_s after a set point change u_m. Set the parameter debounce ≥ 0 to specify how long the measured signal u_m need to remain constant for it to be considered stable. Connect the inputs for the set point u_s and the measured signal u_m to the output signals that need to be checked. If either output is true, raise an alarm, such as by connecting instances of Buildings.Controls.OBC.CDL.Utilities.Assert to the outputs of this block.

Any output being true indicates a problem.

The block has two timers that each start whenever the corresponding input changes. One timer, called feedbackDelay+debounce timer, starts whenever the set point u_s change, and it runs for a time equal to feedbackDelay+debounce. The other timer, called debounce timer, starts whenever the measured signal u_m changes, and it runs for a time equal to debounce. The block starts verifying the inputs whenever the feedbackDelay+debounce timer lapsed, or the debounce timer lapsed, (and hence the measurement is stable,) whichever is first.

Both outputs being true indicates that the measured signal u_m is not stable within feedbackDelay+debounce time. Exactly one output being true indicates that the measured signal u_m is stable, but u_s ≠ u_m. In this case, the block sets yLocFal = true if u_s = true (the measured signal is locked at false), or it sets yLocTru = true if u_s = false (the measured signal is locked at true).

Therefore, exactly one output being true can be interpreted as follows: Suppose true means on and false means off.
Then, yLocTru = true indicates that an equipment is locked in operation mode but is commanded off; and similarly, yLocFal = true indicates that it is locked in off mode when it is commanded on.

Detailed description

The block works as follows. Any change in set point u_s starts the feedbackDelay+debounce timer, and any change in measured signal u_m starts the debounce timer.

As soon as the feedbackDelay+debounce timer or the debounce timer lapsed, whichever happens first, the controller continuously performs these checks:

1. Check for stable measured signal.
   If u_m is stable, then
       goto step 2.
   Else:
       Set yLocFal = yLocTru = true.
       (Equipment is commanded on but we cannot conclude it is running;
       set both true to flag an unstable measurement signal.)
   
2. Check for commanded and measured input to be equal.
   If u_s ≠ u_m, then
       goto step 3.
   Else,
       set yLocFal = false and yLocTru = false.
       (Equipment is operating as commanded, verified using stable input.)
3. Inputs differ.
   If u_s = true , then
       set yLocFal = true and yLocTru = false.
       (The equipment is commanded on, but it is off.)
   Else,
       set yLocFal = false and yLocTru = true.
       (The equipment is commanded off, but it is on.)
   

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Switch

Switch between two boolean signals

Information

Block that outputs one of two boolean input signals based on a boolean input signal.

If the input signal u2 is true, the block outputs y = u1. Otherwise, it outputs y = u3.

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Timer

Timer measuring the time from the time instant where the Boolean input became true

Information

If the Boolean input u is true, the output y is the time that has elapsed since u became true. Otherwise, y is 0. If the output y becomes greater than the threshold time t, the output passed is true. Otherwise it is false.

In the limiting case where the timer value reaches the threshold t and the input u becomes false simultaneously, the output passed remains false.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.TimerAccumulating

Accumulating timer that can be reset

Information

Timer that accumulates time until it is reset by an input signal.

If the Boolean input u is true, the output y is the time that has elapsed while u has been true since the last time reset became true. If u is false, the output y holds its value. If the output y becomes greater than the threshold time t, the output passed is true. Otherwise it is false.

When reset becomes true, the timer is reset to 0.

In the limiting case where the timer value reaches the threshold t and the input u becomes false simultaneously, the output passed remains false.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Toggle

Toggles output value whenever its input turns true

Information

Block that generates a true output when toggle input u rises from false to true, provided that the clear input clr is false or also became at the same time false. The output remains true until

• the toggle input u rises from false to true again, or
• the clear input clr rises from false to true.

If the clear input clr is true, the output y switches to false (if it was true) and it remains false, regardless of the value of the toggle input u.

At initial time, if clr = false, then the output will be y = u. Otherwise it will be y=false (because the clear input clr is true).

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.TrueDelay

Delay a rising edge of the input, but do not delay a falling edge.

Information

Block that delays a signal when it becomes true.

A rising edge of the Boolean input u gives a delayed output. A falling edge of the input is immediately given to the output. If delayOnInit = true, then a true input signal at the start time is also delayed, otherwise the input signal is produced immediately at the output.

Simulation results of a typical example with a delay time of 0.1 second is shown below.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.TrueFalseHold

Block that holds an output signal for at least a specified duration

Information

Block that holds a true or false signal for at least a defined time period.

Whenever the input u switches, the output y switches and remains at that value for at least duration seconds, where duration is a parameter. After duration elapsed, the output will be y = u. If this change required changing the value of y, then y will remain at that value for at least duration. Otherwise, y will change immediately whenever u changes.

This block could for example be used to disable an economizer, and not re-enable it for 10 minutes, and vice versa.

The image below shows the implementation with a state graph in which each transition is only triggered when the input has the corresponding value, and the current state has been active for at least duration seconds.

Simulation results of a typical example with duration = 1000 seconds.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.TrueHold

Block that holds a true signal for at least a requested duration

Information

Block that holds a true input signal for at least a defined time period.

At initialization, the output y is equal to the input u. If the input u becomes true, or is true during intialization, a timer starts and the Boolean output y stays true for the time period provided by the parameter duration. When this time is elapsed, the input is checked again. If it is true, then the timer is restarted and the output remains true for another duration seconds. If the input u is false after holdTime seconds, then the ouput is switched to false, until the input becomes true again.

The figure below shows the state chart of the implementation. Note that the transition are done in zero time.

The figure below shows an example with a hold time of 3600 seconds and a pulse width period 9000 seconds that starts at t=200 seconds.

The figure below shows an example with a hold time of 60 seconds and a pulse width period 3600 seconds that starts at t=0 seconds.

The next two figures show the same experiment, except that the input u has been negated. The figure below has again a hold time of 3600 seconds and a pulse width period 9000 seconds that starts at t=200 seconds.

The figure below has again a hold time of 60 seconds and a pulse width period 3600 seconds that starts at t=0 seconds.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.VariablePulse

Generate boolean pulse with the width specified by input

Information

Block that outputs a boolean pulse.

The output of this block is a pulse with a constant period and a width as obtained from the input 0 ≤ u ≤ 1, which is the width relative to the period.

The block produces the following ouputs:

• If u = 0, the output y remains false.
• If 0 < u < 1, the output y will be a boolean pulse with the period specified by the parameter period and the width set to u*period.
• If u = 1, the output y remains true.

When the input u changes by more than deltaU and the output has been holding constant for more than minimum holding time minTruFalHol, the output will change to a new pulse with width equal to u*period.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Xor

Logical 'xor': y = u1 xor u2

Information

Block that outputs true if exactly one input is true. Otherwise the output is false.

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.VariablePulse.Cycle

Generate boolean pulse with the width specified by the input

Parameters

Connectors

Modelica definition