If you have only Simscape, you can use a Translational Hydro-Mechanical Converter block. The conversion parameter between mechanical and hydraulic domains is the cross-sectional area of the cylinder.
If you have Simscape Fluids (formerly SimHydraulics), there's a whole specialized library of Hydraulic Cylinders, which may contain additional parameters such as hard stop dynamics.
Either way, the mechanical ports of both of these can transform force to pressure and velocity to fluid flow rate. It's all a matter of connecting them to force sources or to other Simscape blocks.
- Sebastian
