Robust Adaptive Fractional‐Order Terminal Sliding Mode Control for Lower‐Limb Exoskeleton

Ahmed, Saim; Wang, Haoping; Tian, Yu‐Ping

doi:10.1002/asjc.1964

Cited by 59 publications

(92 citation statements)

References 34 publications

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“…Fractional calculus (FC), as a branch of mathematical analysis, investigates the extension of derivatives and integrals to non‐integer orders [1]. Nowadays, new aspects of FC are growing rapidly and its applications are found in different areas like electro‐hydrolic servo systems [2], UAV [3], robust adaptive control [4], and power systems [5]. Additionally, the utility of FC in the problem of optimal control has attracted the attention of many researchers.…”

Section: Introductionmentioning

confidence: 99%

On the fractional optimal control problems with a general derivative operator

Jajarmi

Băleanu

2019

Asian Journal of Control

135

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This paper deals with a general form of fractional optimal control problems involving the fractional derivative with singular or non‐singular kernel. The necessary conditions for the optimality of these problems are derived and a new numerical method is designed to solve these equations effectively. Simulation results indicate that the proposed method works well and provides satisfactory results with regard to accuracy and computational effort. Comparative results also verify that a particular case with Mittag‐Leffler kernel improves the performance of the controlled system in terms of the transient response compared to the other fractional‐ and integer‐order derivatives.

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Section: Introductionmentioning

confidence: 99%

On the fractional optimal control problems with a general derivative operator

Jajarmi

Băleanu

2019

Asian Journal of Control

135

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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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“…Consider x as a virtual control input. Thus, using (13), (16), and (17), the ideal controller x* is of the form…”

Section: Proposed Drug Dosage Regimensmentioning

confidence: 99%

“…Obtaining a suitable nominal model is not straightforward [15]. Thus, model-free and robust/adaptive controllers are preferred [16][17][18][19]. During the last two decades, various neuro-fuzzy control approaches have been applied to robust control of many uncertain non-linear systems [20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Adaptive back‐stepping cancer control using Legendre polynomials

Khorashadizadeh

Kalat

2020

IET Systems Biology

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Here, a model-free controller for cancer treatment is presented. The treatment objective is to find a proper drug dosage that can reduce the population of tumour cells. Recently, some solutions have been proposed according to the control theory. In these approaches, based on the mathematical description of the number of effector cells, tumour cells, and concentration of the interleukin-2 (IL-2), a non-linear controller is designed. Here, based on the back-stepping design procedure and function approximation property of Legendre polynomials, a novel controller for MIMO cancer immunotherapy is presented. In fact, Legendre polynomials play the role of uncertainty estimation and compensation. In comparison with other uncertainty estimators such as neural networks, Legendre polynomials have simpler structure. Thus, the contribution of this study is simplifying the design procedure and reducing the controller computational load in comparison with Neuro-Fuzzy controllers. The resulting closed-loop system is capable of overcoming various uncertainties. Simulation results verify the efficiency of the proposed method in the fast reduction of tumour cells. Moreover, a comparison between the performance of Legendre polynomials and a radial basis functions neural network (RBFN) is presented.

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Robust Adaptive Fractional‐Order Terminal Sliding Mode Control for Lower‐Limb Exoskeleton

Cited by 59 publications

References 34 publications

On the fractional optimal control problems with a general derivative operator

On the fractional optimal control problems with a general derivative operator

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

Adaptive back‐stepping cancer control using Legendre polynomials

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