Integrated Observer-based Fixed-time Control with Backstepping Method for Exoskeleton Robot
To achieve the fast convergence and tracking precision of a robotic upper-limb exoskeleton, this paper proposes an observer-based integrated fixed-time control scheme with a backstepping method. Firstly, a typical 5 DoF (degrees of freedom) dynamics is constructed by Lagrange equations and processed for control purposes. Secondly, second-order sliding mode controllers (SOSMC) are developed and novel sliding mode surfaces are introduced to ensure the fixed-time convergence of the human-robot system. Both the reaching time and settling time are proved to be bounded with certain values independent of initial system conditions. For the purpose of rejecting the matched and unmatched disturbances, nonlinear fixed-time observers are employed to estimate the exact value of disturbances and compensate the controllers online. Ultimately, the synthesis of controllers and disturbance observers is adopted to achieve the excellent tracking performance and simulations are given to verify the effectiveness of the proposed control strategy.
KeywordsUpper-limb exoskeleton sliding mode control (SMC) fixed-time control disturbance observe backstepping
Unable to display preview. Download preview PDF.
This work was supported by National Natural Science Foundation of China (Nos. 61703134, 61703135, 61773151, 61503118 and 61871173), Natural Science Foundation of Hebei Province (Nos. F2015202150, F2016202327 and F2018202279), Natural Science Foundation of Tianjin (No. 17JCQNJC04400), the Foundation of Hebei Educational Committee (Nos. QN2015068 and ZD2016071), the Colleges and Universities in Hebei Province Science and Technology Research Youth Fund (No. ZC2016020) and the Graduate Innovation Funding Project of Hebei Province (No. CXZZBS2017038).
- B. Brahmi, M. Saad, C. Ochoa-Luna, M. H. Rahman, A. Brahmi. Adaptive tracking control of an exoskeleton robot with uncertain dynamics based on estimated time-delay control. IEEE-ASME Transactions on Mechatronics, vol. 23, no. 2, pp. 575–585, 2018. DOI: https://doi.org/10.1109/TMECH.2018.2808235.CrossRefGoogle Scholar
- Z. J. Li, C. Y. Su, L. Y. Wang, Z. T. Chen, T. Y. Chai. Nonlinear disturbance observer-based control design for a robotic exoskeleton incorporating fuzzy approximation. IEEE Transactions on Industrial Electronics, vol. 62, no. 9, pp. 5763–5775, 2015. DOI: https://doi.org/10.1109/TIE.2015.2447498.CrossRefGoogle Scholar
- H. D. Lee, B. K. Lee, W. S. Kim, J. S. Han, K. S. Shin, C. S. Han. Human-robot cooperation control based on a dynamic model of an upper limb exoskeleton for human power amplification. Mechatronics, vol. 24, no. 2, pp. 168–176, 2014. DOI: https://doi.org/10.1016/j.mechatronics.2014.01.007.CrossRefGoogle Scholar
- J. Niu, Q. Q. Yang, X. Y. Wang, R. Song. Sliding mode tracking control of a wire-driven upper-limb rehabilitation robot with nonlinear disturbance observer. Frontiers in Neurology, vol. 8, Article number 646, 2017. DOI: https://doi.org/10.3389/fneur.2017.00646.
- N. Sun, T. Yang, H. Chen, Y. C. Fang, Y. Z. Qian. Adaptive anti-swing and positioning control for 4-DOF rotary cranes subject to uncertain/unknown parameters with hardware experiments. IEEE Transactions on Systems, Man, and Cybernetics: Systems, vol. 49, no. 7, pp. 1309–1321, 2019. DOI: https://doi.org/10.1109/TSMC.2017.2765183.CrossRefGoogle Scholar
- J. X. Liu, Y. B. Gao, X. J. Su, M. Wack, L. G. Wu. Disturbance-observer-based control for air management of PEM fuel cell systems via sliding mode technique. IEEE Transactions on Control Systems Technology, vol. 27, no. 3, pp. 1129–1138, 2019. DOI: https://doi.org/10.1109/TCST.2018.2802467.CrossRefGoogle Scholar
- Y. F. Yin, J. X. Liu, J. A. Sánchez, L. G. Wu, S. Vazquez, J. I. Leon, L. G. Franquelo. Observer-based adaptive sliding mode control of NPC converters: An RBF neural network approach. IEEE Transactions on Power Electronics, vol. 34, no. 4, pp. 3831–3841, 2019. DOI: https://doi.org/10.1109/TPEL.2018.2853093.CrossRefGoogle Scholar
- T. Madani, B. Daachi, K. Djouani. Non-singular terminal sliding mode controller: Application to an actuated exoskeleton. Mechatronics, vol. 33, pp. 136–145, 2016. DOI: https://doi.org/10.1016/j.mechatronics.2015.10.012.CrossRefGoogle Scholar
- B. L. Tian, L. H. Liu, H. C. Lu, Z. Y. Zuo, Q. Zong, Y. P. Zhang. Multivariable finite time attitude control for quadrotor UAV: Theory and experimentation. IEEE Transactions on Industrial Electronics, vol. 65, no. 3, pp. 2567–2577, 2018. DOI: https://doi.org/10.1109/TIE.2017.2739700.CrossRefGoogle Scholar
- J. K. Ni, L. Liu, C. X. Liu, X. Y. Hu, S. L. Li. Fast fixed-time nonsingular terminal sliding mode control and its application to chaos suppression in power system. IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 64, no. 2, pp. 151–155, 2017. DOI: https://doi.org/10.1109/TCSII.2016.2551539.CrossRefGoogle Scholar
- J. P. Li, Y. N. Yang, C. C. Hua, X. P. Guan. Fixed-time backstepping control design for high-order strict-feedback non-linear systems via terminal sliding mode. IET Control Theory & Applications, vol. 11, no. 8, pp. 1184–1193, 2017. DOI: https://doi.org/10.1049/iet-cta.2016.1143.MathSciNetCrossRefGoogle Scholar
- Y. Huang, Y. M. Jia. Adaptive fixed-time relative position tracking and attitude synchronization control for non-co-operative target spacecraft fly-around mission. Journal of the Franklin Institute, vol. 354, no. 18, pp. 8461–8489, 2017. DOI: https://doi.org/10.1016/j.jfranklin.2017.10.006.MathSciNetCrossRefGoogle Scholar
- G. W. Zhang, P. Yang, J. Wang, J. J. Sun, Y. Zhang, L. L. Chen. Fixed-time control for upper-limb exoskeleton with bounded disturbances. In Proceedings of the 24th International Conference on Automation and Computing, IEEE, Newcastle upon Tyne, UK, 2018. DOI: https://doi.org/10.23919/IConAC.2018.8748956.Google Scholar
- M. Basin, C. B. Panathula, Y. Shtessel. Multivariable continuous fixed-time second-order sliding mode control: Design and convergence time estimation. IET Control Theory & Applications, vol. 11, no. 8, pp. 1104–1111, 2017. DOI: https://doi.org/10.1049/iet-cta.2016.0572.MathSciNetCrossRefGoogle Scholar
- Q. Dong, Q. Zong, B. L. Tian, F. Wang. Integrated Finite-Time Disturbance Observer and Controller Design for Reusable Launch Vehicle in Reentry Phase. Journal of Aerospace Engineering, vol. 30, no. 1, Article number 04016076, 2017. DOI: https://doi.org/10.1061/(ASCE)AS.1943-5525.0000670.