Stability-Guaranteed Assist-as-Needed Controller for Powered Orthoses

Morbi, Aliasgar; Ahmadi, Mojtaba; Chan, Alvin C.; Langlois, Robert

doi:10.1109/tcst.2013.2259593

Cited by 21 publications

(11 citation statements)

References 34 publications

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“…Wang et al [32] applied admittance control to the active training stage of patient rehabilitation, and adjusted the admittance parameters to meet the different needs for strength and speed during training. Morbi et al [33] proposed that non-linear admittance control can promote a safer human-computer interaction in haptic devices. The above research results show that admittance control can effectively recognize the movement intention of exoskeleton wearers, and the control system using admittance control has a simple structure and is easy to implement.…”

Section: Introductionmentioning

confidence: 99%

An Adaptive Sliding Mode Variable Admittance Control Method for Lower Limb Rehabilitation Exoskeleton Robot

Zhu

Song

et al. 2020

Applied Sciences

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As passive rehabilitation training with fixed trajectory ignores the active participation of patients, in order to increase the active participation of patients and improve the effect of rehabilitation training, this paper proposes an innovative adaptive sliding mode variable admittance (ASMVA) controller for the Lower Limb Rehabilitation Exoskeleton Robot. The ASMVA controller consists of an outer loop with variable admittance controller and an inner loop with an adaptive sliding mode controller. It estimates the wearer's active muscle strength and movement intention by judging the deviation between the actual and standard interaction force of the wearer's leg and the exoskeleton, thereby adaptively changing admittance controller parameters to alter training intensity. Three healthy volunteers engaged in further experimental studies, including trajectory tracking experiments with no admittance, fixed admittance, and variable admittance adjustment. The experimental results show that the proposed ASMVA control scheme has high control accuracy. Besides, the ASMVA can not only increase training intensity according to the active muscle strength of the patient during positive movement intention (so as to increase active participation of the patient), but also increase the amount of trajectory adjustment during negative movement intention to ensure the safety of the patient.

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Section: Introductionmentioning

confidence: 99%

An Adaptive Sliding Mode Variable Admittance Control Method for Lower Limb Rehabilitation Exoskeleton Robot

Zhu

Song

et al. 2020

Applied Sciences

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“…In fact, the safety of human-robot interactions in haptics-enabled rehabilitation systems could be a major concern (Aguirre-Ollinger et al, 2012; Morbi et al, 2014; Vitiello et al, 2013; Zhang and Cheah, 2015). Most post-stroke rehabilitation robots are designed to generate powerful force fields in order to deliver sufficient energy for the required motor therapy while working in contact with post-stroke patients .…”

Section: Introductionmentioning

confidence: 99%

“…As a result, patient-robot interaction safety should be explicitly studied and guaranteed. This is an active line of research since conservative solutions can degrade the performance of robotics-assisted therapeutic systems (Morbi et al, 2014; Zhang and Cheah, 2015). In most HRR systems, predefined conservative force caps have been utilized as a safety mechanism (Culmer et al, 2010; Kim et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

A grasp-based passivity signature for haptics-enabled human-robot interaction: Application to design of a new safety mechanism for robotic rehabilitation

Atashzar

Shahbazi

Tavakoli

et al. 2017

The International Journal of Robotics Research

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In this paper, the biomechanical capability of the human upper limb in absorbing physical interaction energy during human-robot interaction is analyzed. The outcome is a graphical map that can quantitatively correlate the extent of the grasp pressure and the geometry of interaction to the extent of hand passivity. For this purpose, a user study has been conducted for 11 healthy human subjects to characterize the energy absorption capability in their arm and wrist. The above correlation is statistically validated. The identified user-specific grasp-based passivity signature map can be used as a graphical tool to assess the biomechanical capabilities of the upper limb in absorbing interaction energy. In this paper, the proposed grasp-based passivity signature map is utilized in the design of a new stabilizer for haptic systems, that takes into account the variation in energy absorption during haptic task execution. The goal is to optimize the haptic system fidelity while guaranteeing human-robot interaction stability despite the potential existence of delays and a non-passive environment. The controller is termed grasp-based passivity signature map stabilizer. If the user provides minimum to no energy absorption during the interaction, the controller makes the force reflection gate tight to guarantee stability. However, when the user demonstrates high capability in absorbing interaction energy, the controller allows the forces to be reflected. The grasp-based passivity signature map stabilizer is an alternative for both conventional stabilizers of haptic/telerobotic systems and fixed conservative force limits in rehabilitation systems where patient-robot interaction safety is a crucial requirement. This provides the practical motivation for this work. Experimental results are presented.

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“…The control torque of TUPLEE [6] behaves also as an amplifier of the knee torque, measured by means of electromyographical (EMG) electrodes placed at the thigh muscles, to assist the wearer during daily living activities. The amplification technique presents some limitations, since the estimated force depends mainly on some parameters such as muscular fatigue or electrode placements [7]. Admittance/impedance control has also been used for exoskeleton's control to increase the leg's natural frequency [8], [9] by modulating the damping parameter and inertia, respectively.…”

Section: Introductionmentioning

confidence: 99%

Toward Lower Limbs Functional Rehabilitation Through a Knee-Joint Exoskeleton

Rifaï

Mohammed

Djouani

2017

IEEE Trans. Contr. Syst. Technol.

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This paper presents a bounded control strategy of a knee-joint exoskeleton that ensures knee flexion/extension movements during the assistance and rehabilitation processes. The control strategy is easy to implement, since it does not require any prior knowledge of the human effort. The proposed control law is based on nested saturations with the main advantage of explicitly avoiding the actuator's saturation, guaranteeing and enhancing the wearer's security. Lyapunov-based analysis is stated to prove: 1) the asymptotic stability of the shank-foot-exoskeleton in the absence of a human active effort; 2) the trajectories ultimate boundedness in the presence of parameter uncertainties; and 3) the input-to-state stability with respect to a bounded human active torque. Preliminary realtime experiments show satisfactory results in terms of assistanceas-needed and passive/resistive rehabilitation performances following desired trajectories expressing knee flexion/extension movements.

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Stability-Guaranteed Assist-as-Needed Controller for Powered Orthoses

Cited by 21 publications

References 34 publications

An Adaptive Sliding Mode Variable Admittance Control Method for Lower Limb Rehabilitation Exoskeleton Robot

An Adaptive Sliding Mode Variable Admittance Control Method for Lower Limb Rehabilitation Exoskeleton Robot

A grasp-based passivity signature for haptics-enabled human-robot interaction: Application to design of a new safety mechanism for robotic rehabilitation

Toward Lower Limbs Functional Rehabilitation Through a Knee-Joint Exoskeleton

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