Model-free based adaptive nonsingular fast terminal sliding mode control with time-delay estimation for a 12 DOF multi-functional lower limb exoskeleton

Han, Shuaishuai; Wang, Haoping; Tian, Yang

doi:10.1016/j.advengsoft.2018.01.004

Cited by 94 publications

(47 citation statements)

References 27 publications

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“…Compared with the widely used classical robot manipulators, the cable‐driven ones have much lower stiffness and smaller moving mass, which can effectively guarantee the safety for physical interactions with human. Due to above obvious advantages, cable‐driven manipulators have been widely used in medical care, flexible manufacturing, and academic studies …”

Section: Introductionmentioning

confidence: 99%

A new practical robust control of cable‐driven manipulators using time‐delay estimation

Wang

Yan

Zhu

et al. 2019

Intl J Robust & Nonlinear

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In this paper, a new practical robust control scheme is proposed and investigated for the cable-driven manipulators under lumped uncertainties. There are three parts in the proposed method, ie, a time-delay estimation (TDE) part, a modified super-twisting algorithm (STA) part, and a fractional-order nonsingular terminal sliding mode (FONTSM) error dynamics part. The TDE uses intentionally time-delayed system signals to estimate the lumped dynamics of the system and ensures an attractive model-free control structure. The STA is applied to guarantee high performance and chattering suppression simultaneously in the reaching phase. The FONTSM error dynamics is utilized to obtain fast convergence and strong robustness in the sliding mode phase. Thanks to the above three parts, the proposed control scheme is model free and can ensure high control performance under lumped uncertainties. The stability considering the FONTSM error dynamics and modified STA scheme is analyzed. Comparative simulation and experiments were conducted to demonstrate the effectiveness and superiorities of the newly proposed control scheme. Corresponding experimental results show that our newly proposed control scheme can provide more than 20% improvement of the steady control accuracy under three different reference trajectories. KEYWORDS cable-driven manipulators, fractional order, model free, nonsingular terminal sliding mode, super-twisting algorithm (STA), time-delay estimation (TDE) INTRODUCTIONRobot manipulators have been widely utilized in many practical fields benefitting from their excellent capability to execute automatic tasks. 1-4 Usually, the drive motors are directly installed in the joints to simplify the system structure and obtain good control accuracy, which in turn will bring in high stiffness and big moving inertia. This design performs well for the industrial applications, but it will not be safe for the physical interactions with human due to the high stiffness and large moving mass. Therefore, the cable-driven manipulators were proposed and utilized to efficiently settle the above issue. 5 Compared with the widely used classical robot manipulators, the cable-driven ones have much lower stiffness and smaller moving mass, which can effectively guarantee the safety for physical interactions with human. Due to above obvious advantages, cable-driven manipulators have been widely used in medical care, flexible manufacturing, and academic studies. [6][7][8][9][10][11][12] Int J Robust Nonlinear Control. 2019;29:3405-3425.wileyonlinelibrary.com/journal/rnc

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Section: Introductionmentioning

confidence: 99%

A new practical robust control of cable‐driven manipulators using time‐delay estimation

Wang

Yan

Zhu

et al. 2019

Intl J Robust & Nonlinear

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“…Han et al [13] developed a model-free based adaptive consists of intelligent Proportional-Integral (PI) controller, time-delay estimation, and adaptive sliding mode compensator for a 12 DoF LLE. Their control strategy in a simulated model was verified, and the stability was validated via Lyapunov theory.…”

Section: Introductionmentioning

confidence: 99%

Initialized Model Reference Adaptive Control for Lower Limb Exoskeleton

2019

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In this paper, a Proportional-Integral-Derivative (PID) controller tuning scheme by Initialized Model Reference Adaptive Control (IMRAC) for a Lower Limb Exoskeleton (LLE) is presented. Mathematical expression of the LLE structure is determined using Lagrangian and Kirchoff's equations. The transfer function of the structure based on the physical features of the links, and actuators is established under Range of Motion (RoM) condition. The PID controller of the LLE is tuned in a closed-loop control system using Ziegler-Nichols (Z-N) for initializing parameters of IMRAC. Adjustment mechanism is a gradient based method for real-time adaptation of tuned PID controller. A Lyapunov function has been applied to confirm the stability of IMRAC. The proposed IMRAC shows faster convergence in comparison with conventional non-initialized model reference adaptive control. It can be ascertained the proposed tuning scheme is applicable for real-time tuning of PID controller of LLE.

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“…The TDE-based controllers with compact structures are robust against external disturbances, modeling error, and parameters variation. TDE has been successfully applied in many robotic systems to realize mode-free control, such as autonomous underwater vehicle [41], robot manipulator [42], unmanned aerial vehicles [43], robotic exoskeleton [44], [45], multilateral teleoperation system [46], and series elastic actuators [47]. However, the TDE errors resulted from the measurement noise of discrete signals along sampling time would deteriorate the performance of time delay controllers during operation [44].…”

Section: Introductionmentioning

confidence: 99%

Integral Fuzzy Sliding Mode Impedance Control of an Upper Extremity Rehabilitation Robot Using Time Delay Estimation

Dawen

Chen

et al. 2019

IEEE Access

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Robot-assisted cooperative rehabilitation training has shown superiority in helping the individuals with motion impairment problems to regain their motor functions. This paper presents the development and evaluation of a new cooperative training control scheme for an end-effector-type rehabilitation robot to provide upper extremity rehabilitation training with desired compliance and intensity. Firstly, the overall mechanical structure and real-time control system of rehabilitation robot are introduced. Secondly, an integral fuzzy sliding mode impedance control strategy combined with time-delay estimation (IFSMIC-TDE) is proposed to induce the active participation of patients and suppress impedance error. The IFSMIC-TDE approach is free from nonlinear robot dynamics, and it is designed to be robust to the external uncertainties and inherent chattering characteristics. After that, the closed-loop system stability with IFSMIC-TDE is proved based on the Lyapunov stability theory. Finally, experimental investigations are conducted to illustrate the effectiveness of the proposed rehabilitation robot and control algorithm. The comparison results indicate that the proposed IFSMIC-TDE can achieve better control performance and less impedance error. Besides, the interaction compliance and training intensity can be qualitatively adjusted via appropriate impedance parameters. INDEX TERMS Upper extremity rehabilitation robot, cooperative training, sliding mode impedance control, fuzzy turner, time delay estimation.

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Model-free based adaptive nonsingular fast terminal sliding mode control with time-delay estimation for a 12 DOF multi-functional lower limb exoskeleton

Cited by 94 publications

References 27 publications

A new practical robust control of cable‐driven manipulators using time‐delay estimation

A new practical robust control of cable‐driven manipulators using time‐delay estimation

Initialized Model Reference Adaptive Control for Lower Limb Exoskeleton

Integral Fuzzy Sliding Mode Impedance Control of an Upper Extremity Rehabilitation Robot Using Time Delay Estimation

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