The Double Acting Cylinder component models a double-acting translational actuator. It transforms work between the hydraulic and translational domains.

A boolean parameter, Reversed, allows reversing the positive flow direction.

Variable port volumes calculated based on the piston relative position can be added to side A and side B.

Optional end cushions restrict the stroke length of the piston.

The following equations are used when $\mathrm{Reversed}\=\mathrm{false}$.

$A_a^f\=\{\begin{array}{cc}\frac{\mathrm{\pi }}{4}{\mathrm{D}}_{\mathrm{bore}}^2& \mathrm{Use\; diameters}\\ A_a& \mathrm{otherwise}\end{array}{A}_b^f\=\{\begin{array}{cc}\frac{\mathrm{\pi }}{4}\left({\mathrm{D}}_{\mathrm{bore}}^2-{\mathrm{D}}_{\mathrm{rod}}^2\right)& \mathrm{Use\; diameters}\\ A_b& \mathrm{otherwise}\end{array}$

$q_a^f\=\{\begin{array}{cc}{q}_a-q_{\mathrm{va}}& \mathrm{Use\; diameters}\\ q_a& \mathrm{otherwise}\end{array}{q}_b^f\=\{\begin{array}{cc}{q}_b-q_{\mathrm{vb}}& \mathrm{Use\; diameters}\\ q_b& \mathrm{otherwise}\end{array}$

$q_a^f\=A_a^f{v}_{\mathrm{rel}}{q}_b^b\=-A_b^b{v}_{\mathrm{rel}}$

$s_{\mathrm{rel}}\=s_b-s_a{v}_{\mathrm{rel}}\=\frac{\mathrm{d}{s}_{\mathrm{rel}}}{\mathrm{d}t}$

$f_a\=-f_b\=\{\begin{array}{cc}f\+f_{e_1}\+f_{e_2}& \mathrm{Use\; end\; cushions}\\ f& \mathrm{otherwise}\end{array}$

$f\=A_a^f{p}_a-A_b^f{p}_b-d{v}_{\mathrm{rel}}$

$f_{e_1}\=\{\begin{array}{cc}0& 0\le f_{c_1}\+f_{d_1}\\ f_{c_1}\+\max \left(f_{c_1}\,f_{d_1}\right)& \mathrm{otherwise}\end{array}{f}_{e_2}\=\{\begin{array}{cc}0& f_{c_2}\+f_{d_2}\le 0\\ f_{c_2}\+\min \left(f_{c_2}\,f_{d_2}\right)& \mathrm{otherwise}\end{array}$

$f_{c_1}\&equals;\{\begin{array}{cc}-k_c\left(s_{\mathrm{rel}}-L_{\max }\right)& L_{\max }<s_{\mathrm{rel}}\\ 0& \mathrm{otherwise}\end{array}{f}_{c_2}\&equals;\{\begin{array}{cc}-k_c\left(s_{\mathrm{rel}}-L_{\min }\right)& s_{\mathrm{rel}}<L_{\min }\\ 0& \mathrm{otherwise}\end{array}$

$f_{d_1}\&equals;\{\begin{array}{cc}-c_c{v}_{\mathrm{rel}}& L_{\max }<s_{\mathrm{rel}}\\ 0& \mathrm{otherwise}\end{array}{f}_{d_2}\&equals;\{\begin{array}{cc}-c_c{v}_{\mathrm{rel}}& s_{\mathrm{rel}}<L_{\min }\\ 0& \mathrm{otherwise}\end{array}$

If $\mathrm{Reversed}\&equals;\mathrm{true}$, the direction of the arrow on the component's icon changes to indicate that the direction of the positive flow is reversed.  This means, for example, if the cylinder is fixed and a positive flow is fed to side A then the direction of positive displacement for the piston is opposite that of the $\mathrm{Reversed}\&equals;\mathrm{false}$ case.

Volumes

Variable port volumes calculated based on the piston relative position, $s_{\mathrm{rel}}$, can be added to side A and side B using $\mathrm{Use}\mathrm{volumes}\=\mathrm{true}$. The equations for the variable port volumes are as follows. $V_a\=V_a^0\+A_a^f\min \left(\max \left(s_{\mathrm{rel}}\,0\right)\,L_h-L_p\right)$ $V_b\=V_b^0\+A_b^f\min \left(\max \left(L_h-L_p-s_{\mathrm{rel}}\,0\right)\,L_h-L_p\right)$ $q_{\mathrm{va}}\=E\frac{\mathrm{d}{p}_a}{\mathrm{d}t}{q}_{\mathrm{vb}}\=E\frac{\mathrm{d}{p}_b}{\mathrm{d}t}$ The equations for calculating $E$ are discussed in Constant Volume. If $\mathrm{Use\; volumes}\=\mathrm{true}$, the component icon changes to indicate that variable port volumes are being used. $\mathrm{Use\; volumes}\=\mathrm{false}$         $\mathrm{Use\; volumes}\=\mathrm{true}$