Mechanical Engineering Science

Robust Sliding Mode Control for a 2-DOF Lower Limb Exoskeleton Base on Linear Extended State Observer

CHENZhenlei, GUOQing, YANYao, JIANGDan


For the 2- Degree of Freedom (DOF) lower limb exoskeleton, to ensure the system robustness and dynamic performance, a linear-extended-state-observer-based (LESO) robust sliding mode control is proposed to not only reduce the influence of parametric uncertainties, unmodeled dynamics, and external disturbance but also estimate the unmeasurable real-time joint angular velocity directly. Then, via Lyapunov technology, the stability of the corresponding LESO and controller is proven. The appropriate and reasonable simulation was carried out to verify the effectiveness of the proposed LESO and exoskeleton controller.


lower limb exoskeleton; linear-extended-state-observer; robust sliding model control; uncertain nonlinearity

Full Text:



Li Z, Su C Y, Li G, et al. Fuzzy approximation-based adaptive backstepping control of an exoskeleton for human upper limbs[J]. IEEE Transactions on Fuzzy Systems, 2014, 23(3), 555-566.

Yang Y, Ma L, Huang D. Development and repetitive learning control of lower limb exoskeleton driven by electrohydraulic actuators[J]. IEEE transactions on industrial electronics, 2016, 64(5), 4169-4178.

He W, Li Z, Dong Y, et al. Design and adaptive control for an upper limb robotic exoskeleton in presence of input saturation[J]. IEEE transactions on neural networks and learning systems, 2018, 30(1), 97-108.

Han S, Wang H, Tian Y. A linear discrete-time extended state observer-based intelligent PD controller for a 12 DOFs lower limb exoskeleton LLE-RePA[J]. Mechanical Systems and Signal Processing, 2020, 138, 106547.

Meng W, Liu Q, Zhou Z, et al. Recent development of mechanisms and control strategies for robot-assisted lower limb rehabilitation[J]. Mechatronics, 2015, 31, 132-145.

Hussain S, Xie S Q, Jamwal P K. Robust nonlinear control of an intrinsically compliant robotic gait training orthosis[J]. IEEE Transactions on Systems, Man, and Cybernetics: Systems, 2012, 43(3), 655-665.

Saglia J A, Tsagarakis N G, Dai J S, et al. Control strategies for patient-assisted training using the ankle rehabilitation robot (ARBOT)[J]. IEEE/ASME Transactions on Mechatronics, 2012, 18(6), 1799-1808.

Hogan N. Impedance control: An approach to manipulation. 1984 American control conference. IEEE, 1984, 304-313.

Keemink A Q L, van der Kooij H, Stienen A H A. Admittance control for physical human–robot interaction. The International Journal of Robotics Research, 2018, 37(11), 1421-1444.

Li Z, Huang B, Ye Z, et al. Physical human–robot interaction of a robotic exoskeleton by admittance control[J]. IEEE Transactions on Industrial Electronics, 2018, 65(12), 9614-9624.

Yu X, He W, Li Y, et al. Bayesian Estimation of Human Impedance and Motion Intention for Human-Robot Collaboration. IEEE Transactions on Cybernetics, 2019.

Na J, Ren X, Zheng D. Adaptive control for nonlinear pure-feedback systems with high-order sliding mode observer[J]. IEEE transactions on neural networks and learning systems, 2013, 24(3), 370-382.

Guo B Z, Zhao Z. On the convergence of an extended state observer for nonlinear systems with uncertainty[J]. Systems & Control Letters, 2011, 60(6), 420-430.

Cui R, Chen L, Yang C, et al. Extended state observer-based integral sliding mode control for an underwater robot with unknown disturbances and uncertain nonlinearities[J]. IEEE Transactions on Industrial Electronics, 2017, 64(8), 6785-6795.

Guo Q, Zhang Y, Celler B G, et al. Backstepping control of electro-hydraulic system based on extended-state-observer with plant dynamics largely unknown[J]. IEEE Transactions on industrial Electronics, 2016, 63(11), 6909-6920.

Sun T, Cheng L, Wang W, et al. Semiglobal exponential control of Euler–Lagrange systems using a sliding-mode disturbance observer[J]. Automatica, 2020, 112, 108677.

Siciliano B, Sciavicco L, Villani L, et al. Robotics: modelling, planning and control. Springer Science & Business Media, 2010: 2.



  • There are currently no refbacks.

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.