Customizing Models

You can combine the blocks in the SimHydraulics libraries to create custom hydraulic models. In addition, Simscape (required by SimHydraulics) contains a foundation library that includes a set of basic building blocks for different physical domains; these blocks define the pressure/flow relationship for basic physical effects, such as fluid compressibility, fluid inertia, mechanical friction, energy transduction, and flow through fixed and variable orifices. You can combine these building blocks with SimHydraulics blocks to model a component that spans different physical domains. As with Simulink, you can then group this assembly of blocks into a subsystem and parameterize it to reuse and share the custom component.

Modeling a Custom Hydraulic Valve 3:41
Model a custom hydraulic servovalve with flapper and spool dynamics. Configure model to include or neglect hydraulic forces on the spool.

The Simscape language enables you to extend the libraries of physical components. It is based on the MATLAB programming language, well-known by engineers. Using this object-oriented modeling language, you can define custom components, complete with parameterization, physical connections, and equations represented as acausal implicit differential algebraic equations (DAEs). The Simulink block and dialog box for the component are automatically created from the Simscape file.

Simscape Language: Hydraulic Example 3:39
Model custom hydraulic components. A fixed hydraulic orifice is defined using implicit equations.

SimHydraulics models can include physical signals that have units associated with them. You specify the units and parameter values in block dialogs, and Simscape performs the necessary unit-conversion operations when solving a physical network. A Physical Signals block library in Simscape lets you perform math operations on physical signals and graphically input equations inside the physical network. Physical signal ports are used in Simscape block diagrams to better integrate physical signals into your physical system, which increases computational speed.

SimHydraulics Cylinder
Cross-section illustration of a hydraulic cylinder with snubber (bottom left). The colored blocks in the SimHydraulics model (top left) correspond to colored arrows in the cross-section illustration, which represent typical hydraulic flow paths. The graphs (right) track the velocity and position of the piston, and the pressure of the hydraulic fluid during the simulation.
Next: Defining Fluid Properties

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