Models with Time Delays
Choose Approximate Versus Exact Time Delays
Simulink Control Design lets you choose whether to linearize models using exact
representation or Pade approximation of continuous time delays. How you treat time
delays during linearization depends on your nonlinear model.Simulink blocks that model time delays are:- Transport Delay block
- Variable Time Delay block
- Variable Transport Delay block
- Delay block
- Unit Delay block
By default, linearization uses Pade approximation for representing time delays in your
linear model.Use Pade approximation to represent time delays when:- Applying more advanced control design techniques to your linear plant, such as LQR
or H-infinity control design. - Minimizing the time to compute a linear model.
Specify to linearize with exact time delays for:- Minimizing errors that result from approximating time delays
- PID tuning or loop-shaping control design methods in Simulink Control Design
- Discrete-time models (to avoid introducing additional states to the model)
The software treats discrete-time delays as internal delays in the linearized model.
Such delays do not appear as additional states in the linearized model.Specify Exact Representation of Time Delays
Before linearizing your model:2 Linearization