BGMod Documentation / v3
BGMod handbook

Double-acting cylinder

Advanced component · equations, parameters and limits.

Hydraulics → Advanced · Translational mechanics → Advanced

Multiphysics component

One shared component, listed under both domains. A and B carry pressure [Pa] and flow [m³/s]; M carries force [N] and velocity [m/s]. Its internal transformers conserve power. Connect A/B to the hydraulic network and M to a mechanical junction or load.

CYLDouble-acting cylinderCylinderDA · Двухсторонний цилиндр

A cap end · B rod end · M mechanical output

Converts hydraulic power to translational mechanical power. Positive velocity and increasing position mean extension. Mass, damping and applied load belong to the separate MechanicalLoad block.

AA = πD²/4   ·   AB = π(D² − d²)/4
QA = AAv   ·   QB = −ABv
Fhyd = AApA − ABpB   ·   dx/dt = v
flocal,M = −v   ·   pAQA + pBQB − Fhydv = 0
ParameterMeaning / unitDefault
D / dPiston / rod diameter [m]0.05 / 0.025
L / x0Stroke / initial position [m]0.3 / 0.15
Limits
D > d > 0; 0 < x0 < L. Reaching x = 0 or L terminates simulation; velocity is not forcibly set to zero.
Outputs
Position, velocity, hydraulic force, A/B flows and mechanical output power F_hyd·v.
Scope
Two ideal internal TFs; x is a kinematic state, not energy storage. Add external C blocks for fixed chamber compliance. No leakage, seal friction, variable chamber compliance or contact continuation.

Classic bond graph

Classic bond graphA and B connect through transformers of coefficients A_A and minus A_B to one mechanical 1-junction, which connects M.ATF : A_A1MBTF : −A_BF_hyd, vQ_A = A_A v; Q_B = −A_B v
Implemented internal graph: two TFs + 1. Here the labels are the implementation’s area coefficients: Q_A = A_A v, Q_B = −A_B v and F_hyd = A_A p_A − A_B p_B. The negative rod-side coefficient accounts for opposite chamber motion with both hydraulic reference arrows pointing inward. TF conserves power and is internal, not a standalone library block. Position obeys dx/dt = v; chamber C elements and the mechanical load are external. Half-arrows set positive power references; dashed pink arrows carry signals only. Causal strokes are omitted because they depend on the connected model.

Related component: Mass and load