Integrated Modeling of Physical System Dynamics

Hydraulic Ram Figure 5.32 shows a sketch of a hydraulic actuator of the kind commonly used in heavy earth-moving machinery. The difference in fluid pressure acting on the two sides of the piston exerts a force on the rod. As pressure is defined as force per unit area, the power transduction phenomenon connecting the hydraulic and translational domains is that of a transformer. In general, the piston area in the two chambers need not be the same 1 , and the rate of increase of the volume of one chamber, Q c1 , need not equal the rate of decrease of the volume of the other chamber, Q c2 , so two transformers may be needed to describe the piston. They are connected to a one-junction on the translational side (representing the unique piston velocity) as shown in figure 5.33(a). cylinder rod fluid lines (a) F v Q piston o-ring seals supply line return line P P P Q c1 c2 1 2 1 P 2 (b) Figure 5.32: Sketch of a hydraulic actuator (a). A cross-sectional view is shown in (b). 1 For example, the sketch shows a rod protruding from each side of the piston, but single-rod cylinders are also common; with a single rod, the area on one side of the piston exceeds that on the other side by the area of the rod.