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
And3	Logical 'and3': y = u1 and u2 and u3
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 an on signal until conditions changes
LogicalSwitch	Logical Switch
MultiAnd	Logical MultiAnd, y = u[1] and u[2] and u[3] and ...
Nand	Logical 'nand': y = not (u1 and u2)
Nor	Logical 'nor': y = not (u1 or u2)
Not	Logical not
OnOffController	On-off controller
Or	Logical 'or': y = u1 or u2
Or3	Logical 'or': y = u1 or u2 or u3
Pre	Breaks algebraic loops by an infinitesimal small time delay (y = pre(u): event iteration continues until u = pre(u))
Switch	Switch between two Real signals
Timer	Timer measuring the time from the time instant where the Boolean input became true
Toggle	Toggles output value whenever its input turns on
TriggeredTrapezoid	Triggered trapezoid generator
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
TrueHoldWithReset	Block that holds a true signal for at least a requested duration
Xor	Logical 'xor': y = u1 xor u2
ZeroCrossing	Trigger zero crossing of input u
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.And3

Logical 'and3': y = u1 and u2 and u3

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 an on signal until conditions changes

Information

The block maintains a true output signal until the input u0 switches to false. When the latch input u switches to true, the output y becomes true and remains true, even if u turns false, until the clear input u0 becomes true. When the clear input u0 becomes true, then the output y becomes false.

The table below shows the different scenarios.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.LogicalSwitch

Logical Switch

Information

Block that is a logical switch.

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.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. The dimension of the input vector u is automatically enlarged when a new connection is made.

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.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.OnOffController

On-off controller

Information

Block that represents and on/off controller.

The block outputs true when the input signal u falls below the reference signal minus half of the bandwidth. It sets the output signal to false when the input signal u exceeds the reference signal plus half of the bandwidth. The parameter pre_y_start is used to initialize the previous value of the output pre(y).

Parameters

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.Or3

Logical 'or': y = u1 or u2 or u3

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.Switch

Switch between two Real signals

Information

Block that represents a logical switch.

If the input u2 is true, the block outputs the input u1. Otherwise it outputs the input 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

Block that represents a timer.

When the Boolean input u becomes true, the timer is started and the output y is the time from the time instant where u became true. The timer is stopped and the output is reset to zero, once the input becomes false.

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.Toggle

Toggles output value whenever its input turns on

Information

The block toggles output value whenever input turns ON. For instance, when the toggle input u turns ON, the output y turns ON and remains ON when the input u turns OFF again. When the input u turns back ON, the output turns OFF. When the clr input turns ON, the output turns OFF.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Logical.TriggeredTrapezoid

Triggered trapezoid generator

Information

Block that represents a triggered trapezoid.

The block has a Boolean input and a Real output signal and requires the parameters amplitude, rising, falling and offset. The output signal y represents a trapezoidal signal dependent on the input signal u.

The behaviour is as follows: Assume the initial input to be false. In this case, the output will be offset. After a rising edge (i.e., the input changes from false to true), the output is rising during rising to the sum of offset and amplitude. In contrast, after a falling edge (i.e., the input changes from true to false), the output is falling during falling to a value of offset.

Note, the case of edges before expiration of rising or falling is handled properly.

Parameters

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.

Simulation results of a typical example with a delay time of 0.1 s is shown in the next figure.

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.TrueHoldWithReset

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.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.ZeroCrossing

Trigger zero crossing of input u

Information

Block that detects zero crossings.

The output y is true at the time instant when the input u becomes zero, provided the input enable is true. At all other time instants, the output y is false. If the input u is zero at a time instant when the enable input changes its value, then the output y is false.

Note, that in the plot window of a Modelica simulator, the output of this block is usually identically to false, because the output may only be true at an event instant, but not during continuous integration. In order to check that this component is actually working as expected, one should connect its output to, e.g., component Buildings.Controls.OBC.CDL.Discrete.TriggeredSampler.

Connectors

Modelica definition