“…A robust controller with backstepping method was applied in Tomei (1999) and Yim, Yeon, Park, Lee, and Hur (2007). The trajectory tracking controllers designed by the methods in Jain and Khorrami (1998), Tomei (1999), Wang and Khorrami (2000) and Yim et al (2007) were complicated due to the 'explosion of terms' (mentioned in Section 1). As a numerical example, consider a single-link robot arm, whose rotary motion about one end is controlled by an elastically coupled actuator.…”