Transport Delay

Purpose

Delay continuous input signal by fixed or variable time

Library

Control / Delays

Description

The Transport Delay outputs a signal that a past value of the input signal:

\[y(t) = u(t-T_d)\]

For this purpose, the Transport Delay continuously records the input signals in an internal buffer. The output values are computed by looking up the samples nearest to \(t-T_d\) in the input buffer and performing a first order (linear) interpolation.

The input signal can be a scalar or vector. If the time delay is less than the previous simulation time step, the output signal is calculated by performing a linear interpolation from the preceding two samples. This is because the Transport Delay does not access the current input to calculate the outputs in order to avoid algebraic loops if the block is used in a feedback path.

If extrapolation is undesirable, you need to ensure that the maximum solver step size is less than or equal to the time delay.

Note

The Transport Delay should be used to delay non-smooth signals such as rectangular or triangular signals because the solver is not guaranteed to make a simulation step at the precise instants required to accurately reproduce the discontinuities in the delayed signal.

• To generate phase-shifted rectangular or triangular signals, use the Pulse Generator or the Triangular Wave Generator and set the parameter appropriately.

• To delay arbitrary signals that only change at discrete instants, use the Pulse Delay.

Example Model

• See the example model “Transport Delay”.

• Find it in PLECS under Help > PLECS Documentation > List of Example Models.

Parameters

Time delay source

Specifies whether the delay is determined by the Time delay parameter (internal) or by an external input signal (external).

Time delay

Time \(T_d\) by which the input signal is delayed, in seconds \((\mathrm{s})\).

Maximum time delay

Specifies the maximum possible delay for the external delay input signal, in seconds \((\mathrm{s})\).

Initial output

Output value after simulation start before the input values appear at the output.