“…The inchworm type given in Fig. 1(f) is usually employed for pipelines with very small diameters (Fukuda et al, 1989;Kondoh& Yokota, 1997;Anthierens et al, 2000;Shibata et al, 1998;Tsuruta et al, 2000;Jun et al, 1999;Landsberger & Martin, 1992;Menciassi et al, 2002;Mitsumoto et al, 2001;Takahashi et al, 1994;Bertetto & Ruggiu, 2001;Hayashi & Iwatsuki, 1998;Nishikawa et al, 1999;Anthierens et al, 1999). The screw type (or helical drive type) displays the motion of a screw when it advances in the pipelines as depicted in Fig.…”