Learn more about Simulink Control Design

Creating or Opening a Simulink Model

To begin linearization using functions, you must first create or open a Simulink model of your system. The model can have any number of inputs and outputs (including none) and any number of states. The model can include user-defined blocks or S-functions. Your model can involve a plant only, a plant with a feedback loop and controller, or any number of subsystems.

To continue with the water-tank example, type

watertank

at the MATLAB prompt. This opens a Simulink model containing the water-tank system as shown in this figure.

Simulink Model of the Water-Tank System

The watertank model consists of

• The water-tank system itself

• A PID Controller to control the height of water in the tank by varying the voltage applied to the pump

• A reference signal that sets the desired water level

• A Scope block that displays the height of water as a function of time

Double-click a block to view its contents. The Water-Tank System block is shown in this figure.

Water-Tank System Block

The input to the Water-Tank System block, which is also the output of the PID Controller block, is the voltage, V. The output is the height of water, H. The system contains just one state (within the integrator), H. Values of the parameters are given as a=2 cm^2.5/s, A=20 cm², b=5 cm³/(s·V).

Example: Water-Tank System

Computing Operating Points from Specifications

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