“…In the last years, the controller design for the flexible link or flexible joint manipulator has been extensively studied. Many advanced technologies have been applied in the flexible link, such as sliding mode control (Xu et al, 2000; Mujumdar et al, 2015), boundary control (Jiang et al, 2018; Mamani et al, 2012), neural network (NN) control (Gao et al, 2019; Hu et al, 2020a, 2020b; Xu, 2018), fuzzy control (Jnifene and Andrews, 2005; Lin and Lewis, 2003; Tinkir et al, 2010), robust control (Lee and Lee, 2002; Shafei et al, 2020), and singular perturbation (SP) approach (El-Badawy et al, 2010; Siciliano and Book, 1988). In Choi and Cheon (2004), a sliding mode controller was already reported.…”