Momentum-Based Balance Control of a Lower-Limb Exoskeleton During Stance.

In this work, we present the implementation of a momentum-based balance controller in a lower-limb exoskeleton that can successfully reject perturbations and self-balance without any external aid. This controller is able to withstand pushes in the order of 30 N in forward and sideways directions with little sway. Additionally, with this controller, the system can perform balanced weight-shifting motions without the need for an explicit joint reference trajectory.

Assisting walking balance using a bio-inspired exoskeleton controller.

Background: Balance control is important for mobility, yet exoskeleton research has mainly focused on improving metabolic energy efficiency. Here we present a biomimetic exoskeleton controller that supports walking balance and reduces muscle activity.

Methods: Humans restore balance after a perturbation by adjusting activity of the muscles actuating the ankle in proportion to deviations from steady-state center of mass kinematics.

Identification of Hip and Knee Joint Impedance During the Swing Phase of Walking.

Knowledge on joint impedance during walking in various conditions is relevant for clinical decision-making and the development of robotic gait trainers, leg prostheses, leg orthotics and wearable exoskeletons. Whereas ankle impedance during walking has been experimentally assessed, knee and hip joint impedance during walking have not been identified yet. Here we developed and evaluated a lower limb perturbator to identify hip, knee and ankle joint impedance during treadmill walking.

Cooperative ankle-exoskeleton control can reduce effort to recover balance after unexpected disturbances during walking.

Background: In the last two decades, lower-limb exoskeletons have been developed to assist human standing and locomotion. One of the ongoing challenges is the cooperation between the exoskeleton balance support and the wearer control. Here we present a cooperative ankle-exoskeleton control strategy to assist in balance recovery after unexpected disturbances during walking, which is inspired on human balance responses.

Whole Body Center of Mass Feedback in a Reflex-Based Neuromuscular Model Predicts Ankle Strategy During Perturbed Walking.

Active prosthetic and orthotic devices have the potential to increase quality of life for individuals with impaired mobility. However, more research into human-like control methods is needed to create seamless interaction between device and user. In forward simulations the reflex-based neuromuscular model (RNM) by Song and Geyer shows promising similarities with real human gait in unperturbed conditions.

Can Momentum-Based Control Predict Human Balance Recovery Strategies?

Human-like balance controllers are desired for wearable exoskeletons in order to enhance human-robot interaction. Momentum-based controllers (MBC) have been successfully applied in bipeds, however, it is unknown to what degree they are able to mimic human balance responses. In this paper, we investigated the ability of an MBC to generate human-like balance recovery strategies during stance, and compared the results to those obtained with a linear full-state feedback (FSF) law.

Differential Inverse Kinematics of a Redundant 4R Exoskeleton Shoulder Joint.

Most active upper-extremity rehabilitation exoskeleton designs incorporate a three sequential rotational shoulder joint with orthogonal axes. This kind of joint has poor conditioning close to singular configurations when all joint axes become coplanar, which reduces its effective range of motion. We investigate an alternative approach of using a redundant non-orthogonal 4R shoulder joint.

Comparison between sEMG and force as control interfaces to support planar arm movements in adults with Duchenne: a feasibility study.

Background: Adults with Duchenne muscular dystrophy (DMD) can benefit from devices that actively support their arm function. A critical component of such devices is the control interface as it is responsible for the human-machine interaction. Our previous work indicated that surface electromyography (sEMG) and force-based control with active gravity and joint-stiffness compensation were feasible solutions for the support of elbow movements (one degree of freedom).

Implementation of EMG- and Force-Based Control Interfaces in Active Elbow Supports for Men With Duchenne Muscular Dystrophy: A Feasibility Study.

While there is an extensive number of studies on the development and evaluation of electromyography (EMG)- and force-based control interfaces for assistive devices, no studies have focused on testing these control strategies for the specific case of adults with Duchenne muscular dystrophy (DMD). This paper presents a feasibility study on the use of EMG and force as control interfaces for the operation of active arm supports for men with DMD. We have built an experimental active elbow support, with a threefold objective: 1) to investigate whether adult men with DMD could use EMG- and force-based control interfaces; 2) to evaluate their performance during a discrete position-tracking task; and 3) to examine users' acceptance of the control methods.

Evaluation of EMG, force and joystick as control interfaces for active arm supports.

Background: The performance capabilities and limitations of control interfaces for the operation of active movement-assistive devices remain unclear. Selecting an optimal interface for an application requires a thorough understanding of the performance of multiple control interfaces.

Methods: In this study the performance of EMG-, force- and joystick-based control interfaces were assessed in healthy volunteers with a screen-based one-dimensional position-tracking task.