The Rotational Position (or Position) component generates a forced angular position at the flange according to an input signal that specifies a reference angle.

The $\mathrm{Exact}$ boolean parameter determine how ${\mathrm{\phi }}_{\mathrm{ref}}$ is used:

When $\mathrm{Exact}$ is true, ${\mathrm{\phi }}_{\mathrm{ref}}$ is used as-is. The input signal must be twice-differentiable.

When $\mathrm{Exact}$ is false (the default), ${\mathrm{\phi }}_{\mathrm{ref}}$ is filtered and the second derivative of the filtered curve is used to compute the reference acceleration of the flange. This second derivative is not computed by numerical differentiation but rather by a second-order Bessel filter. The critical frequency of the filter (cut-off frequency) is defined by the parameter $f_{\mathrm{crit}}$. This frequency should be higher than the essential low frequencies in the signal.

$\{\begin{array}{cc}\left\{\begin{array}{c}\mathrm{\phi }\={\mathrm{\phi }}_{\mathrm{ref}}\\ w\=0\\ a\=0\end{array}\right\}& \mathrm{exact}\\ \left\{\begin{array}{c}a\=\left(\left({\mathrm{\phi }}_{\mathrm{ref}}-\mathrm{\phi }\right)w_{\mathrm{crit}}-a_{f}w\right)\frac{w_{\mathrm{crit}}}{b_f}\\ \stackrel{\.}{w}\=a\\ \stackrel{\.}{\mathrm{\phi }}\=w\end{array}\right\}& \mathrm{otherwise}\end{array}$

$w_{\mathrm{crit}}\=2\mathrm{\pi }{f}_{\mathrm{crit}}$

$\mathbf{if}\mathrm{Use\; Support\; Flange}\mathbf{then}{\mathrm{\tau }}_{\mathrm{support}}\=-\mathrm{\tau }$

$\mathrm{\phi }\={\mathrm{\phi }}_{\mathrm{flange}}-\{\begin{array}{cc}{\mathrm{\phi }}_{\mathrm{support}}& \mathrm{Use\; Support}\\ 0& \mathrm{otherwise}\end{array}$

The component described in this topic is from the Modelica Standard Library. To view the original documentation, which includes author and copyright information, click here.