Rate Limiter

Limit rate of change of signal

• 

Libraries:
Simulink / Discontinuities

Description

The Rate Limiter block limits the first derivative of the signal passing through it. The output changes no faster than the specified limit. The derivative is calculated using this equation:

$$rate=\frac{u(i)-y(i-1)}{t(i)-t(i-1)}$$

where u(i) and t(i) are the current block input and time, and y(i-1) and t(i-1)) are the output and time at the previous step. The output is determined by comparing rate to the Rising slew rate and Falling slew rate parameters:

• If rate is greater than the Rising slew rate parameter (R), the output is calculated as

  $$y(i)=\Delta t\cdot R+y(i-1).$$

• If rate is less than the Falling slew rate parameter (F), the output is calculated as

  $$y(i)=\Delta t\cdot F+y(i-1).$$

• If rate is between the bounds of R and F, the change in output is equal to the change in input:

  $$y(i)=u(i)$$

When the block is running in continuous mode (for example, Sample time mode is inherited and Sample time of the driving block is zero), the Initial condition is ignored. The block output at t = 0 is equal to the initial input:

$$y(0)=u(0)$$

When the block is running in discrete mode (for example, Sample time mode is inherited and Sample time of the driving block is nonzero), the Initial condition is preserved:

$$y(-1)=Ic$$

where Ic is the initial condition. The block output at t = 0 is calculated as if rate is outside the bounds of R and F. For t = 0, rate is calculated as follows:

$$rate=\frac{u(0)-y(-1)}{sampletime}$$

Limitations

• You cannot use a Rate Limiter block inside a Triggered Subsystem. Use the Rate Limiter Dynamic block instead.

Ports

Input

Port_1 — Input signal

scalar | vector

The input signal to the rate limiter algorithm.

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

Output

Port_1 — Output signal

scalar | vector

Output signal from the rate limiter algorithm.

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

Parameters

Rising slew rate — Limit of derivative for increasing input

1 (default) | real number

Specify the limit of the rising rate of the input signal. This parameter is tunable for fixed-point inputs.

Programmatic Use

Block Parameter: RisingSlewLimit

Type: character vector

Values: real number

Default: '1'

Falling slew rate — Limit of derivative for decreasing input

-1 (default) | real number

Specify the lower limit on the falling rate of the input signal. This parameter is tunable for fixed-point inputs.

Programmatic Use

Block Parameter: FallingSlewLimit

Type: character vector

Values: real number

Default: '-1'

Sample time mode — Sample time mode

inherited (default) | continuous

Specify the sample time mode, continuous or inherited from the driving block.

Programmatic Use

Block Parameter: SampleTimeMode

Type: character vector

Values: 'inherited' | 'continuous'

Default: 'inherited'

Initial condition — Initial output

0 (default) | scalar | vector

Set the initial output of the simulation. Simulink^® does not allow you to set the initial condition of this block to inf or NaN.

Programmatic Use

Block Parameter: InitialCondition

Type: character vector

Values: scalar

Default: '0'

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'

Block Characteristics

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

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

Cannot be used inside a triggered subsystem hierarchy.

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