Saturation

Limit input signal to the upper and lower saturation values

• 

Libraries:
Simulink / Commonly Used Blocks
Simulink / Discontinuities
HDL Coder / Discontinuities

Description

The Saturation block produces an output signal that is the value of the input signal bounded to the upper and lower saturation values. The upper and lower limits are specified by the parameters Upper limit and Lower limit.

Input	Output
Lower limit ≤ Input value ≤ Upper limit	Input value
Input value < Lower limit	Lower limit
Input value > Upper limit	Upper limit

Examples

Using the Quantizer and Saturation blocks in sldemo_boiler

This example shows how the Quantizer and Saturation blocks are used in the model ex_sldemo_boiler. The ADC subsystem digitizes the input analog voltage by:

• Multiplying the analog voltage by 256/5 with the Gain block

• Rounding the value to integer floor with the Quantizer block

• Limiting the output to a maximum of 255 (the largest unsigned 8-bit integer value) with the Saturation block

Extended Examples

Inverted Pendulum with Animation

Use Simulink® to model and animate an inverted pendulum system. An inverted pendulum has its center of mass above its pivot point. To stably maintain this position, the system implements control logic to move the pivot point below the center-of mass as the pendulum starts to fall. The inverted pendulum is a classic dynamics problem used to test control strategies.

• Open Model

Ports

Input

Port_1 — Input signal

scalar | vector

The input signal to the saturation algorithm.

Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | fixed point

Output

Port_1 — Output signal

scalar | vector

Output signal that is the value of the input signal, upper saturation limit, or lower saturation limit.

Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | fixed point

Parameters

Main

Upper limit — Upper saturation boundary for the input signal

0.5 (default) | scalar | vector

Specify the upper bound on the input signal. If the input signal is greater than this boundary, then the output signal is set to this saturation value. The Upper limit parameter is converted to the output data type using round-to-nearest and saturation. Upper limit must be greater than the Output minimum parameter and less than the Output maximum parameter.

Programmatic Use

Block Parameter: UpperLimit

Type: character vector

Value: real scalar or vector

Default: '0.5'

Lower limit — Lower saturation boundary for the input signal

-0.5 (default) | scalar | vector

Specify the lower bound on the input signal. If the input signal is less than this boundary, then the output signal is set to this saturation value. The Lower limit parameter is converted to the output data type using round-to-nearest and saturation. Lower limit must be greater than the Output minimum parameter and less than the Output maximum parameter.

Programmatic Use

Block Parameter: LowerLimit

Type: character vector

Value: real scalar or vector

Default: '-0.5'

Treat as gain when linearizing — Specify the gain value

on (default) | off

Select this parameter to cause the commands to treat the gain as 1. The linearization commands in Simulink^® software treat this block as a gain in state space. Clear this parameter to have the commands treat the gain as 0.

Programmatic Use

Block Parameter: LinearizeAsGain

Type: character vector

Values: 'off' | 'on'

Default: 'on'

Enable zero-crossing detection — Enable zero-crossing detection

on (default) | off

Select to enable zero-crossing detection. For more information, see Zero-Crossing Detection.

Programmatic Use

Block Parameter: ZeroCross

Type: character vector | string

Values: 'off' | 'on'

Default: 'on'

Sample time (-1 for inherited) — Interval between samples

-1 (default) | scalar | vector

Specify the time interval between samples. To inherit the sample time, set this parameter to -1. For more information, see Specify Sample Time.

Dependencies

This parameter is visible only if you set it to a value other than -1. To learn more, see Blocks for Which Sample Time Is Not Recommended.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

Parameter:	SampleTime
Values:	"-1" (default) | scalar or vector in quotes

Signal Attributes

The Data Type Assistant helps you set data attributes. To use the Data Type Assistant, click . For more information, see Specify Data Types Using Data Type Assistant.

Output minimum — Minimum output value for range checking

[] (default) | scalar

Lower value of the output range that the software checks.

The software uses the minimum to perform:

• Parameter range checking (see Specify Minimum and Maximum Values for Block Parameters) for some blocks.

• Simulation range checking (see Specify Signal Ranges and Enable Simulation Range Checking).

• Automatic scaling of fixed-point data types.

• Optimization of the code that you generate from the model. This optimization can remove algorithmic code and affect the results of some simulation modes such as SIL or external mode. For more information, see Optimize using the specified minimum and maximum values (Embedded Coder).

Tips

Output minimum does not saturate or clip the actual output signal. Use the Saturation block instead.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

Parameter:	OutMin
Values:	'[]' (default) | scalar in quotes

Output maximum — Maximum output value for range checking

[] (default) | scalar

Upper value of the output range that the software checks.

The software uses the maximum value to perform:

• Parameter range checking (see Specify Minimum and Maximum Values for Block Parameters) for some blocks.

• Simulation range checking (see Specify Signal Ranges and Enable Simulation Range Checking).

• Automatic scaling of fixed-point data types.

• Optimization of the code that you generate from the model. This optimization can remove algorithmic code and affect the results of some simulation modes such as SIL or external mode. For more information, see Optimize using the specified minimum and maximum values (Embedded Coder).

Tips

Output maximum does not saturate or clip the actual output signal. Use the Saturation block instead.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

Parameter:	OutMax
Values:	'[]' (default) | scalar in quotes

Output data type — Specify the output data type

Inherit: Same as input (default) | Inherit: Inherit via back propagation | double | single | int8 | int32 | uint32 | int64 | uint64 | fixdt(1,16,2^0,0) | <data type expression> | ...

Choose the data type for the output. The type can be inherited, specified directly, or expressed as a data type object such as a Simulink.NumericType object. For more information, see Control Data Types of Signals.

Programmatic Use

Block Parameter: OutDataTypeStr

Type: character vector

Values: 'Inherit: Same as input' | 'Inherit: Inherit via back propagation' | 'double' | 'single' | 'int8' | 'uint8' | int16 | 'uint16' | 'int32' | 'uint32' | 'int64' | 'uint64' | fixdt(1,16,0) | fixdt(1,16,2^0,0) | fixdt(1,16,2^0,0) | '<data type expression>'

Default: 'Inherit: Same as input'

Lock output data type setting against changes by the fixed-point tools — Option to prevent fixed-point tools from overriding Output data type

off (default) | on

Select this parameter to prevent the fixed-point tools from overriding the Output data type you specify on the block. For more information, see Use Lock Output Data Type Setting (Fixed-Point Designer).

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

Parameter:	LockScale
Values:	'off' (default) | 'on'

Integer rounding mode — Specify the rounding mode for fixed-point operations

Floor (default) | Ceiling | Convergent | Nearest | Round | Simplest | Zero

Choose one of these rounding modes.

Ceiling

Rounds both positive and negative numbers toward positive infinity. Equivalent to the MATLAB^® ceil function.

Convergent

Rounds number to the nearest representable value. If a tie occurs, rounds to the nearest even integer. Equivalent to the Fixed-Point Designer™ convergent function.

Floor

Rounds both positive and negative numbers toward negative infinity. Equivalent to the MATLAB floor function.

Nearest

Rounds number to the nearest representable value. If a tie occurs, rounds toward positive infinity. Equivalent to the Fixed-Point Designer nearest function.

Round

Rounds number to the nearest representable value. If a tie occurs, rounds positive numbers toward positive infinity and rounds negative numbers toward negative infinity. Equivalent to the Fixed-Point Designer round function.

Simplest

Automatically chooses between round toward floor and round toward zero to generate rounding code that is as efficient as possible.

Zero

Rounds number toward zero. Equivalent to the MATLAB fix function.

Programmatic Use

Block Parameter: RndMeth

Type: character vector

Values: 'Ceiling' | 'Convergent' | 'Floor' | 'Nearest' | 'Round' | 'Simplest' | 'Zero'

Default: 'Floor'

See Also

For more information, see Rounding Modes (Fixed-Point Designer).

Block Characteristics

Data Types	double | fixed point | integer | single
Direct Feedthrough	yes
Multidimensional Signals	no
Variable-Size Signals	no
Zero-Crossing Detection	yes

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

HDL Code Generation

Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.

HDL Coder™ provides additional configuration options that affect HDL implementation and synthesized logic.

HDL Architecture

This block has one default HDL architecture.

HDL Block Properties

ConstrainedOutputPipeline	Number of registers to place at the outputs by moving existing delays within your design. Distributed pipelining does not redistribute these registers. The default is 0. For more details, see ConstrainedOutputPipeline (HDL Coder).
InputPipeline	Number of input pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is 0. For more details, see InputPipeline (HDL Coder).
OutputPipeline	Number of output pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is 0. For more details, see OutputPipeline (HDL Coder).

PLC Code Generation
Generate Structured Text code using Simulink® PLC Coder™.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Version History

Introduced before R2006a