A Singularity-Free Terminal Sliding Mode Control of an Uncertain Paediatric Exoskeleton System

Narayan, Jyotindra; Abbas, Mohamed; Patel, Bhavik; Dwivedy, Santosha K.

doi:10.1109/ic_aset53395.2022.9765884

Cited by 7 publications

(4 citation statements)

References 17 publications

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“…Furthermore, to address chattering phenomena, slow convergence, and sensor drift in existing SMCs, researchers have updated different attributes and tested preliminary designs of gait exoskeleton robots (for example, non-singular terminal SMC by Narayan et al [49], adaptive non-singular fast terminal SMC by Han et al [33], and super-twisting SMC by Hasan and Dhingra [58]). In other works on robust position control, Yang et al [29] proposed an SMC with a second command filter-aided backstepping to avoid the "explosion of terms" problem.…”

Section: Robust Controlmentioning

confidence: 99%

Hierarchical Classification of Subject-Cooperative Control Strategies for Lower Limb Exoskeletons in Gait Rehabilitation: A Systematic Review

et al. 2023

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Over the last decade, lower limb exoskeletons have seen significant development, with a particular focus on improving the interaction between the subject and the exoskeleton. This has been achieved by implementing advanced control strategies that enable the safe and efficient use of the exoskeleton. In this work, the control strategies for lower limb exoskeletons are divided into upper-level control (supervisory and high-level control) and lower-level control (the servo layer). Before discussing these control strategies, a brief introduction to lower limb exoskeletons and their control schemes is provided. The control hierarchy for lower limb exoskeletons is then systematically reviewed along with an overview of the techniques used. A Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement is used to highlight the systematic process of identifying relevant articles with inclusion and exclusion criteria. The details of supervisory control, high-level control, and servo control strategies are presented by citing relevant state-of-the-art studies, particularly from the past five years. The targeted lower limb joint, training mode, and development stage for different control strategies are highlighted in a tabulated form to articulate the overall hierarchy level. Finally, the potential opportunities and limitations of subject-cooperative control are discussed. Overall, this work aims to provide an in-depth understanding of the control strategies used in lower limb exoskeletons, focusing on subject cooperation. This knowledge can be used to improve the safety and efficacy of lower limb exoskeletons, ultimately benefiting individuals with mobility impairments.

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Section: Robust Controlmentioning

confidence: 99%

Hierarchical Classification of Subject-Cooperative Control Strategies for Lower Limb Exoskeletons in Gait Rehabilitation: A Systematic Review

et al. 2023

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“…The recently developed fast finite-time sliding mode control (FFTSMC) originated from the concept of terminal attractors [25][26][27][28][29][30][31], it holds the insensitivity to unknown disturbances, and more notably, it accelerates the movement of the state to the equilibrium point in a limited time [32][33][34][35][36]. This control form of sliding mode greatly expands the dynamic and steady-state response of the controlled plant, except for overestimating or underestimating the boundary due to strong uncertainty, which will still lead to chattering or steady-state error.…”

Section: Introductionmentioning

confidence: 99%

A State-Feedback Control Strategy Based on Grey Fast Finite-Time Sliding Mode Control for an H-Bridge Inverter with LC Filter Output

Chang,

Wu,

Chang

et al. 2024

Electronics

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An H-bridge inverter with LC (inductor-capacitor) filter output allows the conversion of DC (direct current) power to AC (alternating current) power that has been used in a variety of applications, such as uninterruptible power supplies, AC motor drives, and renewable energy source systems. The fast finite-time sliding mode control (FFTSMC) features acceleration of the system state towards the equilibrium position as well as conserving insensitivity against internal parameter fluctuations as well as external load disturbances falling within the predetermined bounds. However, the FFTSMC would potentially witness chattering or steady-state errors as indefinite margins come to be exaggerated or underestimated. The chattering in the sliding mode control practice is oscillatory defective behavior. It induces inefficient operation, higher switching power losses in the transistor circuits, as well as saturated actuators, thus impairing the inverter’s output energy efficiency and raising harmonic distortion. Therefore, this paper presents the H-bridge inverter with LC filter output, which is controlled by a grey prediction fast finite-time sliding mode trajectory tracking. A more highly accurate grey prediction model based on the centered approximation methodology is deployed to vanish the chattering as well as steady-state errors. Taking into account the union of grey prediction and FFTSMC, a feedback-controlled H-bridge inverter with LC filter output allows attaining a highly efficient as well as quality sine-wave output voltage. The presented state-feedback control strategy is robust, less complex, attains more rapid convergence, and is highly accurate. The design process, computer simulation, as well as experimental results of the proposed state-feedback control strategy established that the H-bridge inverter with LC filter output has the capability to exhibit fast dynamic response time as well as good steady-state tracking behavior of the output voltage under step-loading changes and nonlinear loading conditions.

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“…In particular, the sliding mode control can overcome the problems of external disturbances and uncertainties by constructing the reaching law and sliding mode surface in theory, so that the controlled system can achieve higher tracking accuracy. Non-singular terminal sliding mode control [9] and fast terminal sliding mode control [10] were applied to overcome parameter uncertainty and external disturbances to realize gait tracking control of lower limb exoskeleton rehabilitation robot, and theoretically analyzed the stability of controller design and tracking accuracy of trajectory. Sliding mode control technology can also be combined with the neural network, a recurrent neural network-based robust nonsingular sliding mode control is proposed for the non-holonomic spherical robot, it can enhance the robustness to control the system [11] .…”

Section: Introductionmentioning

confidence: 99%

Human gait tracking for rehabilitation exoskeleton: adaptive fractional order sliding mode control approach

Zhou¹,

Sun²,

Chen³

et al. 2023

Intell Robot

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To improve the rehabilitation training effect of hemiplegic patients, in this paper, a discrete adaptive fractional order fast terminal sliding mode control approach is proposed for the lower limb exoskeleton system to implement high-precision human gait tracking tasks. Firstly, a discrete dynamic model is established based on the Lagrange system discretization criterion for the lower limb exoskeleton robot. Then, in order to design a discrete adaptive fractional order fast terminal sliding mode controller, the Grünwald–Letnikov fractional order operator is introduced to combine with fast terminal attractor to construct a fractional order fast terminal sliding surface. An adaptive parameter adjustment strategy is proposed for the reaching law of sliding mode control, which drives the sliding mode to the stable region dynamically. Moreover, the stability of the control system is proved in the sense of Lyapunov, and the guidelines for selecting the control parameters are given. Finally, the simulations are tested on the MATLAB-Opensim co-simulation platform. Compared with the conventional discrete sliding mode control and discrete fast terminal sliding mode control, the results verify the superiority of the proposed method in improving lower limb rehabilitation training.

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A Singularity-Free Terminal Sliding Mode Control of an Uncertain Paediatric Exoskeleton System

Cited by 7 publications

References 17 publications

Hierarchical Classification of Subject-Cooperative Control Strategies for Lower Limb Exoskeletons in Gait Rehabilitation: A Systematic Review

Hierarchical Classification of Subject-Cooperative Control Strategies for Lower Limb Exoskeletons in Gait Rehabilitation: A Systematic Review

A State-Feedback Control Strategy Based on Grey Fast Finite-Time Sliding Mode Control for an H-Bridge Inverter with LC Filter Output

Human gait tracking for rehabilitation exoskeleton: adaptive fractional order sliding mode control approach

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