In this paper, we consider the design of tracking controllers for flexible joint robots with unknown and possibly variable elasticity, achieving pre-set performance attributes on the link position error. The developed full state feedback controller, is realized without incorporating knowledge relative to the actual system nonlinearities. Furthermore, no approximators are employed to acquire such information. Comparative simulation results on a 2-d.o.f. flexible joint manipulator, illustrate the efficiency of the approach. (C) 2013 Elsevier Ltd. All rights reserved.