Nur wie bekommt man nun die Beschriftung unter der Figur zentriert?
\documentclass[12pt]{article}
\usepackage{caption}
\usepackage{pst-all}
\begin{document}
\noindent\textbf{\Large{Aufgabe 1}}\\
\begin{center}
\begin{minipage}{\linewidth}
\psset{unit=.7cm}
\centering
\begin{tabular}{p{7.5cm}p{7.5cm}}
\begin{pspicture}(0,0)(9,2)
\psline[linewidth=1.5pt](0,1.5)(9,1.5)
\multiput(1,0)(2,0){4}{\psframe(0,0)(1,1)}
\end{pspicture}
\captionof*{figure}{Linear}
&
\begin{pspicture}(-5,0)(5,5)
\psframe[linewidth=1.5pt](0,0)(1,1)
\psarc[linewidth=1.5pt](0.5,0){3,35}{0}{180}
\psframe[fillstyle=solid,fillcolor=white,linewidth=1.5pt](0.2,3)(0.8,3.6)
\psframe[fillstyle=solid,fillcolor=white,linestyle=none](-3,0)(-2,1.4)
\psframe[fillstyle=solid,fillcolor=white,linestyle=none](3,0)(4,1.4)
\psline[linewidth=1.5pt](0.2,1)(0.4,3)
\psline[linewidth=1.5pt](0.8,1)(0.6,3)
\uput{4.8}[100](0,0){\rput{-80}{\psframe(0,0)(0.8,0.8)}}
\uput{4.6}[120](0,0){\rput{-60}{\psframe(0,0)(0.8,0.8)}}
\uput{4.4}[140](0,0){\rput{-40}{\psframe(0,0)(0.8,0.8)}}
\uput{4.2}[160](0,0){\rput{-20}{\psframe(0,0)(0.8,0.8)}}
\uput{4}[180](0,0){\psframe(0,0)(0.8,0.8)}
\uput{4.8}[80](1,0){\rput{80}{\psframe(0,0)(-0.8,0.8)}}
\uput{4.6}[60](1,0){\rput{60}{\psframe(0,0)(-0.8,0.8)}}
\uput{4.4}[40](1,0){\rput{40}{\psframe(0,0)(-0.8,0.8)}}
\uput{4.2}[20](1,0){\rput{20}{\psframe(0,0)(-0.8,0.8)}}
\uput{4}[0](1,0){\psframe(0,0)(-0.8,0.8)}
\end{pspicture}
\captionof*{figure}{Semicircular}
\tabularnewline
\tabularnewline
\tabularnewline
\begin{pspicture}(0,0)(7,4)
\multiput(2,0)(2,0){3}{\psframe(0,0)(1,1)}
\psline[linewidth=1.5pt](2,2.8)(7,2.8)
\psframe(0,1.5)(1,2.5)
\psarc[linewidth=1.5pt](2,2){0.8}{90}{270}
\psline[linewidth=1.5pt](2,1.2)(7,1.2)
\multiput(2,3)(2,0){3}{\psframe(0,0)(1,1)}
\end{pspicture}
\captionof*{figure}{U-Shaped}
&
\begin{pspicture}(0,0)(9,6)
\psline[linewidth=1.5pt](2,2)(2,5)
\psline[linewidth=1.5pt](2,2)(5,2)
\psline[linewidth=1.5pt](5,2)(5,5)
\psline[linewidth=1.5pt](5,5)(6.5,5)
\psline[linewidth=1.5pt](6.5,5)(6.5,0.5)
\psframe(0,1.5)(1,2.5)
\psframe(0,3)(1,4)
\psframe(0,4.5)(1,5.5)
\psframe(1.5,0)(2.5,1)
\psframe(3,0)(4,1)
\psframe(4.5,0)(5.5,1)
\psframe(3,3)(4,4)
\psframe(3,4.5)(4,5.5)
\psframe(7.5,0)(8.5,1)
\psframe(7.5,1.5)(8.5,2.5)
\psframe(7.5,3)(8.5,4)
\psframe(7.5,4.5)(8.5,5.5)
\end{pspicture}
\captionof*{figure}{Serpentine}
\end{tabular}
\end{minipage}
\end{center}
\end{document}