Recent development of mechanisms and control strategies for robot-assisted lower limb rehabilitation

Robot-assisted rehabilitation and therapy has become more and more frequently used to help the elderly, disabled patients or movement disorders to perform exercise and training. The field of robot-assisted lower limb rehabilitation has rapidly evolved in the last decade. This article presents a review on the most recent progress (from year 2001 to 2014) of mechanisms, training modes and control strategies for lower limb rehabilitation robots. Special attention is paid to the adaptive robot control methods considering hybrid data fusion and patient evaluation in robot-assisted passive and active lower limb rehabilitation. The characteristics and clinical outcomes of different training modes and control algorithms in recent studies are analysed and summarized. Research gaps and future directions are also highlighted in this paper to improve the outcome of robot-assisted rehabilitation

Design and control of a robotic wrist orthosis for joint rehabilitation

Ageing society in many countries has led to an increasing number of stroke and cerebral palsy patients who require rehabilitation therapy. Affected wrist joints often show an increased spasticity and stiffness, caused by impairments of surrounding muscles and tendons. However, the medical devices for wrist joint assessment and rehabilitation are lacking. This paper proposes a robotic orthosis to assist the patient's wrist to perform rehabilitation exercise in a compliant way. A 1-DOF robotic device with parallel mechanism is designed for the wrist joint by utilising pneumatic artificial muscles (PAMs) that are compliant and lightweight. The mechanical design of the wrist orthosis and the corresponding development of pneumatic control system will be also presented. A model-based pressure close-loop control strategy is implemented for the PAMs in order to track the trajectory in high-performance. Experiments on the orthosis demonstrated that the robot could assist the hand to move along a torque-sensitive trajectory with relatively small errors and the differential forces were also kept stable

Musculoskeletal modelling of human ankle complex: Estimation of ankle joint moments

Background: A musculoskeletal model for the ankle complex is vital in order to enhance the understanding of neuro-mechanical control of ankle motions, diagnose ankle disorders and assess subsequent treatments. Motions at the human ankle and foot, however, are complex due to simultaneous movements at the two joints namely, the ankle joint and the subtalar joint. The musculoskeletal elements at the ankle complex, such as ligaments, muscles and tendons, have intricate arrangements and exhibit transient and nonlinear behaviour. Methods: This paper develops a musculoskeletal model of the ankle complex considering the biaxial ankle structure. The model provides estimates of overall mechanical characteristics (motion and moments) of ankle complex through consideration of forces applied along ligaments and muscle-tendon units. The dynamics of the ankle complex and its surrounding ligaments and muscle-tendon units is modelled and formulated into a state space model to facilitate simulations. A graphical user interface is also developed during this research in order to include the visual anatomical information by converting it to quantitative information on coordinates. Findings: Validation of the ankle model was carried out by comparing its outputs with those published in literature as well as with experimental data obtained from an existing parallel ankle rehabilitation robot. Interpretation: Qualitative agreement was observed between the model and measured data for both, the passive and active ankle motions during trials in terms of displacements and moments

Extension of ELM suppression window using n=4 RMPs in EAST

The q95 window for Type-I Edge Localized Modes (ELMs) suppression using n=4 even parity Resonant Magnetic Perturbations (RMPs) has been significantly expanded to a range from 3.9 to 4.8, which is demonstrated to be reliable and repeatable in EAST over the last two years. This window is significantly wider than the previous one, which is around q95=3.7pm0.1, and is achieved using n=4 odd parity RMPs. Here, n represents the toroidal mode number of the applied RMPs and q95 is the safety factor at the 95% normalized poloidal magnetic flux. During ELM suppression, there is only a slight drop in the stored energy (<=10%). The comparison of pedestal density profiles suggests that ELM suppression is achieved when the pedestal gradient is kept lower than a threshold. This wide q95 window for ELM suppression is consistent with the prediction made by MARS-F modeling prior to the experiment, in which it is located at one of the resonant q95 windows for plasma response. The Chirikov parameter taking into account plasma response near the pedestal top, which measures the plasma edge stochasticity, significantly increases when q95 exceeds 4, mainly due to denser neighboring rational surfaces. Modeling of plasma response by the MARS-F code shows a strong coupling between resonant and non-resonant components across the pedestal region, which is characteristic of the kink-peeling like response observed during RMP-ELM suppression in previous studies on EAST. These promising results show the reliability of ELM suppression using the n=4 RMPs and expand the physical understanding on ELM suppression mechanism.Comment: 25 pages, 11 figure

Adaptive Cooperative Control Strategy for a Wrist Exoskeleton using Model-based Joint Impedance Estimation

Wrist rehabilitation exoskeletons have gained much attention over the last decades, striving to restore motor functions for patients with neuromuscular disorders. Electromyography signal has been employed to estimate the motion intention to achieve interactive training schemes. However, it is a challenging task to estimate the joint impedance in real time, as it is a crucial parameter for control of exoskeletons. This article proposes an adaptive cooperative control strategy for a wrist exoskeleton based on a real-time joint impedance estimation approach. By explicitly interpreting the underlying transformation in the muscular and skeletal systems, the proposed approach estimates the motion intention and the joint impedance of a human subject simultaneously without additional calibration procedures and regulates the training trajectories and assistance accordingly. Results indicate the proposed method outperforms other training protocols, including the trajectory tracking control and the fixed cooperative control. The proposed control strategy provides an additional 66.25% motion deviation when estimated joint torque increases 12.36%, which enhances the training effectiveness and the interaction safety and promotes subjects' active engagement

Characteristics, Diagnosis and Prognosis of Acute-on-Chronic Liver Failure in Cirrhosis Associated to Hepatitis B

The study was supported by National Natural Science Foundation of China (NSFC), grant number: 30770962, 30971333, 81170421, 81470869 and Chinese High Technology “863” programme, grant number: 2006AA02A411 (Hai.Li); The CLIF Consortium Data Management Center is supported by an unrestricted grant from Grifols

A metallic phase in quantum Hall systems

The electronic eigenstates of a quantum Hall (QH) system are chiral states. Strong inter-Landau-band mixings among these states can occur when the bandwidth is comparable to the spacing of two adjacent Landau bands. We show that mixing of localized states with opposite chirality can delocalize electronic states. Based on numerical results, we propose the existence of a metallic phase between two adjacent QH phases and between a QH phase and the insulating phase. This result is consistent with non-scaling behaviors observed in recent experiments on quantum-Hall-liquid-to-insulator transition.Comment: 5 pages, 3 figures. Will be published in Phys. Rev. Let

Quantum Hall - insulator transitions in lattice models with strong disorder

We report results of numerical studies of the integer quantum Hall effect in a tight binding model on a two-dimensional square lattice with non-interacting electrons, in the presence of a random potential as well as a uniform magnetic field applied perpendicular to the lattice. We consider field magnitudes such that the area per flux quantum is commensurate with the lattice structure. Topological properties of the single electron wave functions are used to identify current carrying states that are responsible for the quantized Hall conductance. We study the interplay between the magnetic field and the disorder, and find a universal pattern with which the current carrying states are destroyed by increasing disorder strength, and the system driven into an insulating state. We also discuss how to interpolate results of lattice models to the continuum limit. The relationship to previous theoretical and experimental studies of quantum Hall-insulator transitions in strongly disordered systems at low magnetic fields is discussed.Comment: 20 pages, 6 figure

Measurement of the Inclusive Charm Cross Section at 4.03 GeV and 4.14 GeV

The cross section for charmed meson production at $\sqrt{s} = 4.03$ and 4.14 GeV has been measured with the Beijing Spectrometer. The measurement was made using 22.3 $pb^{-1}$ of $e^+e^-$ data collected at 4.03 GeV and 1.5 $pb^{-1}$ of $e^+e^-$ data collected at 4.14 GeV. Inclusive observed cross sections for the production of charged and neutral D mesons and momentum spectra are presented. Observed cross sections were radiatively corrected to obtain tree level cross sections. Measurements of the total hadronic cross section are obtained from the charmed meson cross section and an extrapolation of results from below the charm threshold.Comment: 11 pages, 13 figures. The top level tex file is paper.tex. It builds the paper from other tex files in this .tar and the .eps file

Measurement of the Total Cross Section for Hadronic Production by e+e- Annihilation at Energies between 2.6-5 Gev

Using the upgraded Beijing Spectrometer (BESII), we have measured the total cross section for $e^+e^-$ annihilation into hadronic final states at center-of-mass energies of 2.6, 3.2, 3.4, 3.55, 4.6 and 5.0 GeV. Values of $R$, $\sigma(e^+e^-\to {hadrons})/\sigma(e^+e^-\to\mu^+\mu^-)$, are determined.Comment: Submitted to Phys. Rev. Let