“…Industrial robots are naturally equipped with classical PID controllers, which theoretically assure semi-global asymptotic stability of the closed-loop system equilibrium for the regulation case (see, e.g., Arimoto & Miyazaki (1984), Arimoto et al, (1990), Kelly (1995b), Ortega et al, (1995), Alvarez-Ramirez et al, (2000), Kelly et al, (2005), Meza et al, (2007)). Uniform ultimate boundedness of the closed-loop solutions can be concluded when the desired position is a function of time (some stability analyzes for this case can be found in the works of Kawamura et al (1988), Wen & Murphy (1990), Qu & Dorsey (1991), Rocco (1996), Cervantes & Alvarez-Ramirez (2001), Choi & Chung (2004), and Camarillo et al, (2008)), but to the authors' knowledge, so far there is not a proof of global regulation for such controller.…”