VARIABLE_DELAY

Variable delay

Block Screenshot

Contents

• Variable delay +

  • Palette
  • Description
  • Dialog box
  • Default properties
  • Interfacing function
  • Computational function
  • Example

Palette

• Continuous time systems palette

Description

The Variable Transport Delay block can be used to simulate a variable time delay between an action and its effect. The block might be used, for example, to model a system with a pipe where the speed of a motor pumping fluid in the pipe is variable.

The block accepts two inputs and one output: the first input is the signal u(t) that passes through the block (data input); the second input is the variable time delay τ(t).

At the current time step t, the block outputs the delayed data input u(θ) where θ is the current simulation time t minus the time delay parameter τ.

The equation of the output signal is:

Dialog box

• Max delay It defines the largest value the time delay input can have. The value cannot be negative. Properties : Type ‘vec’ of size 1.
• initial input The output generated by the block until the simulation time first exceeds the time delay input. Properties : Type ‘vec’ of size 1.
• Buffer size The number of points the block can store. Properties : Type ‘vec’ of size 1.

Default properties

• always active: yes
• direct-feedthrough: no
• zero-crossing: no
• mode: no
• regular inputs: - port 1 : size [1,1] / type 1 - port 2 : size [1,1] / type 1
• regular outputs: - port 1 : size [1,1] / type 1
• number/sizes of activation inputs: 0
• number/sizes of activation outputs: 0
• continuous-time state: no
• discrete-time state: no
• object discrete-time state: no
• name of computational function: variable_delay

Example

In this example, the max time delay in the Block Parameters dialog box is set to 4. The input signal is a sine wave with amplitude 1 and frequency 0.2 Hz.

The constant block is set to 2 to introduce a delay of 2 second. The input and output waveforms of the VARIABLE_DELAY block are shown below:

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Interfacing function

• SCI/modules/scicos_blocks/macros/Linear/VARIABLE_DELAY.sci

Computational function

• SCI/modules/scicos_blocks/src/c/variable_delay.c (Type 4)