We discuss two papers [Spong, M. W. (1989) Syst. Central. Lett., 13, 1
5-21; Chang, Y.-Z. and R. W. Daniel (1992) Automatica, 28, 969-974] on
the adaptive control of flexible joint robot manipulators. Our goal i
s to clarify the contributions of the two papers by correcting some te
chnical errors and to provide some additional insight into the applica
tion of singular perturbation methods for the control of flexible join
t robots.