Propagation Delay

Model loop delay, latency, pulse delay

Since R2022b

Libraries:
Simulink / Discrete

Description

The Propagation Delay block delays the current value for a signal into the future by an amount specified by a delay signal. The Propagation Delay block is well suited for implementing time delay in a discrete system.

On each simulation step k, the block samples the signal input U_k and the delay input D_k. The block output value becomes the signal value after the delay time D_k has elapsed from the current simulation time T_k.

y(t) = U_k when t = T_k + D_k

At the start of the simulation, the block output value is the Initial output block parameter value Y₀. The first sample of the delay signal D₀ determines when the block output changes from the Initial output value to the delayed input signal values.

y(t) = Y₀ when t < T₀ + D₀

When the simulation reaches the time T₀ + D₀, the block output is determined by the signal and delay samples.

y(t) = U_k when T_k + D_k ≤ t ≤ T_k+1 + D_k+1,

where:

U_k is the sample of the input signal taken at t = T_k.
D_k is the sample of the delay signal taken at t = T_k.
T_k+1 is the simulation time at which the next signal and delay samples were taken.
D_k+1 is the delay sample taken at time T_k+1.

Examples

Model Constant Propagation Delay

Implement constant propagation delay for variable-step and fixed-step simulations using the Propagation Delay block.

Open Live Script

Model Variable Propagation Delay

Model variable propagation delay for a step delay signal.

Open Live Script

Ports

Input

expand all

u — Signal to delay
scalar

The Propagation Delay block supports real, scalar input signals with continuous or discrete sample time. The input signal data type can be any built-in type besides int64 and uint64.

dt — Delay signal
scalar

The delay signal specifies the amount of delay to apply at each time step in the simulation. You can use the Propagation Delay block to implement a constant or variable delay.

The delay signal values must satisfy these constraints:

The delay signal must contain scalar, real, finite, positive values larger than 128*eps, which is the smallest time resolution the software supports.
The output times for delayed input signal samples must increase monotonically.
For example, suppose the delay signal value is 0.6 at simulation time 0 and the next simulation step occurs at time 0.5. The delay signal at time 0.5 must be greater than 0.1 so that the delayed output time for the input signal sample U_0.5 is greater than the output time for input signal sample U₀ (0.6).
When you select Run at fixed time intervals, the delay signal values must be greater than the value you specify for the Sample time parameter.

Data Types: double

Output

expand all

y — Delayed signal
scalar

The output signal has the same data type as the input signal. By default, the output signal has fixed-in-minor-step sample time. When you select Run at fixed time intervals, the output signal has the discrete sample time you specify for the Sample time parameter.

Parameters

expand all

Initial output — Initial value for output signal
`0` (default) | scalar

Specify the initial output signal value Y₀. The first sample of the delay signal D₀ determines when the block output changes from the Initial output value to the delayed input signal values.

y(t) = Y₀ when t < T₀ + D₀

Programmatic Use

Block Parameter: InitialOutput

Type: string | character vector

Values: numeric scalar

Default: 0

Run at fixed time intervals — Option to execute block at fixed rate
`off` (default) | `on`

This parameter specifies how the block executes and the sample time for the output signal.

off — Block executes each time the delay for an input sample elapses. Output signal has fixed-in-minor sample time.
on — Block executes at a fixed rate that you specify using the Sample time parameter. Output signal has the sample time you specify using the Sample time parameter.

When you select Run at fixed time intervals:

The delay signal values must be greater than the value you specify for the Sample time parameter.
Delay signal values that are not integer multiples of the specified sample time are rounded down to the nearest integer multiple of the sample time. For example, if the sample time is 0.1 and the delay signal value is 0.68, the software rounds the delay to 0.6.

Programmatic Use

Block Parameter: RunAtFixedTimeIntervals

Type: string | character vector

Values: 'on' | 'off'

Default: 'off'

Sample time — Output sample time
`0.1` (default) | scalar

Specify the sample time for the block output signal. The delay signal values must be greater than the specified sample time.

When the delay signal value is not an integer multiple of the specified sample time, the software rounds the delay value down to the closest value that is an integer multiple of the sample time. For example, if the sample time is 0.1 and the delay value is 0.68, the software rounds the delay to 0.6.

Dependencies

To enable this parameter, select Run at fixed time intervals.

Programmatic Use

Block Parameter: SampleTime

Type: string | character vector

Values: numeric scalar

Default: 0.1

Block Characteristics

Data Types	`Boolean` \| `double` \| `integer` \| `single`
Direct Feedthrough	`no`
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™.

To generate code from a model that uses the Propagation Delay block, you must configure the Propagation Delay block to produce an output with discrete sample time. Select Run at fixed sample intervals and specify a discrete rate for the Sample time parameter.

The Propagation Delay block dynamically allocates memory to store input signal and delay signal samples. The target for code generation must support dynamic memory allocation.

Version History

Introduced in R2022b

Propagation Delay

Description