J Intell Robot Syst (2015) 80:3–14 DOI 10.1007/s10846-014-0141-7 Nonlinear Robust Control of Tendon–Driven Robot Manipulators Beytullah Okur · Orhan Aksoy · Erkan Zergeroglu · Enver Tatlicioglu Received: 22 November 2013 / Accepted: 25 September 2014 / Published online: 11 October 2014 © Springer Science+Business Media Dordrecht 2014 Abstract This work addresses the position tracking control problem for tendon–driven robotic mecha- nisms in the presence of parametric uncertainty and additive external disturbances. Specifically, a full state feedback nonlinear robust controller is proposed to tackle the link position tracking problem for tendon– driven robot manipulators with uncertain dynamical system parameters. A robust backstepping approach has been utilized to achieve uniformly ultimately bounded tracking performance despite the lack of exact knowledge of the dynamical parameters and presence of additive but bounded disturbance terms. Stability of the overall system is proven via Lya- punov based arguments. Simulation studies performed This research is supported by Grants of the Scientific and Technological Research Council of Turkey, TUBITAK Project No: 112E561 B. Okur · O. Aksoy · E. Zergeroglu () Department of Computer Engineering, Gebze Institute of Technology, Gebze, Kocaeli 41400, Turkey e-mail: ezerger@bilmuh.gyte.edu.tr E. Tatlicioglu Department of Electrical & Electronics Engineering, Izmir Institute of Technology, Izmir 35430, Turkey O. Aksoy DSYSTM Havelsan A.S., Istanbul 34890, Turkey B. Okur Department of Mechatronics Engineering, Yildiz Technical University, Istanbul 34349, Turkey on a two link planar robot manipulator driven by a six tendon mechanism are presented to illustrate the effectiveness and viability of the proposed approach. Keywords Nonlinear systems · Robot manipulators · Tendon driven system systems · Robust control 1 Introduction The idea of separating the actuators from the links of the robot and remote actuating each joint has always attracted the robot designers as this will reduce the bulk and extra inertia from the mechanical system. Among other remote power transmitting methods, tendon–driven transmission systems present a less noisy, clean (as they do not require lubrication), and shock absorbent characteristics. Therefore tendon– driven mechanisms have been used in the design of both small [1–3] and large robot manipulators [4–6]. However the use of tendon–driven actuation has been more popular in dexterous hands [2, 3, 7] as the resultant task–space motion in robotic hand designs does not need to be accurate and relatively simple controllers can handle desired objectives. For robot manipulators where the main aim is to track a task–space trajectory as closely as possible, the use of tendon–driven mechanisms are limited. We believe that the main reason for this is the additional com- plexity of the overall system dynamics. For better control performance, it is necessary to consider the