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Rate Limiter

Limit rate of change of signal

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  • Rate Limiter block

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=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)=Δt⋅R+y(i−1).

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

    y(i)=Δt⋅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=u(0)−y(−1)sample time

Limitations

Ports

Input

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The input signal to the rate limiter algorithm.

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

Output

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Output signal from the rate limiter algorithm.

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

Parameters

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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'

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'

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'

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'

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

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

See Also

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