2. Force or torque equations

2.1 General equation

Force (or torque) equations express the equilibrium, in the broadest sense, of the moving parts of hydraulic components under the action of the forces or torques to which they are subjected.

It is convenient to separate these forces (or couples) into two groups:

• the group of those which are solely a function of the position x (or θ ) of the element under consideration, or a function of the successive derivatives of x (or θ ); they will be called F (x ) [or C (θ )] ;

• the group of those which are a function of other parameters, i.e. variables in the system under consideration, such as pressures, flow rates, rotational speeds, etc., or parameters outside the system,...