A novel approach to user controlled ambulation of lower extremity exoskeletons using admittance control paradigm

The robotic lower extremity exoskeletons address the ambulatory problems confronting individuals with paraplegia. Paraplegia due to spinal cord injury (SCI) can cause motor deficit to the lower extremities leading to inability to walk. Though wheelchairs provide mobility to the user, they do not provide support to all activities of everyday living to individuals with paraplegia. Current research is addressing the issue of ambulation through the use of wearable exoskeletons that are pre-programmed. There are currently four exoskeletons in the U.S. market: Ekso, Rewalk, REX and Indego. All of the currently available exoskeletons have 2 active Degrees of Freedom (DOF) except for REX which has 5 active DOF. All of them have pre-programmed gait giving the user the ability to initiate a gait but not the ability to control the stride amplitude (height), stride frequency or stride length, and hence restricting users’ ability to navigate across different surfaces and obstacles that are commonly encountered in the community. Most current exoskeletons do not have motors for abduction or adduction to provide users with the option for movement in coronal plane, hence restricting user’s ability to effectively use the exoskeletons. These limitations of currently available pre-programmed exoskeleton models are sought to be overcome by an intuitive, real time user-controlled control mechanism employing admittance control by using hand-trajectory as a surrogate for foot trajectory. Preliminary study included subjects controlling the trajectory of the foot in a virtual environment using their contralateral hand. The study proved that hands could produce trajectories similar to human foot trajectories when provided with haptic and visual feedback. A 10 DOF 1/2 scale biped robot was built to test the control paradigm. The robot has 5 DOF on each leg with 2 DOF at the hip to provide flexion/extension and abduction/adduction, 1 DOF at the knee to provide flexion and 2 DOF at the ankle to provide flexion/extension and inversion/eversion. The control mechanism translates the trajectory of each hand into the trajectory of the ipsilateral foot in real time, thus providing the user with the ability to control each leg in both sagittal and coronal planes using the admittance control paradigm. The efficiency of the control mechanism was evaluated in a study using healthy subjects controlling the robot on a treadmill. A trekking pole was attached to each foot of the biped. The subjects controlled the trajectory of the foot of the biped by applying small forces in the direction of the required movement to the trekking pole through a force sensor. The algorithm converted the forces to Cartesian position of the foot in real time using admittance control; the Cartesian position was converted to joint angles of the hip and knee using inverse kinematics. The kinematics, synchrony and smoothness of the trajectory produced by the biped robot was evaluated at different speeds, with and without obstacles, and compared with typical walking by human subjects on the treadmill. Further, the cognitive load required to control the biped on the treadmill was evaluated and the effect of speed and obstacles with cognitive load on the kinematics, synchrony and smoothness was analyzed

Bilateral Assessment of Functional Tasks for Robot-assisted Therapy Applications

This article presents a novel evaluation system along with methods to evaluate bilateral coordination of arm function on activities of daily living tasks before and after robot-assisted therapy. An affordable bilateral assessment system (BiAS) consisting of two mini-passive measuring units modeled as three degree of freedom robots is described. The process for evaluating functional tasks using the BiAS is presented and we demonstrate its ability to measure wrist kinematic trajectories. Three metrics, phase difference, movement overlap, and task completion time, are used to evaluate the BiAS system on a bilateral symmetric (bi-drink) and a bilateral asymmetric (bi-pour) functional task. Wrist position and velocity trajectories are evaluated using these metrics to provide insight into temporal and spatial bilateral deficits after stroke. The BiAS system quantified movements of the wrists during functional tasks and detected differences in impaired and unimpaired arm movements. Case studies showed that stroke patients compared to healthy subjects move slower and are less likely to use their arm simultaneously even when the functional task requires simultaneous movement. After robot-assisted therapy, interlimb coordination spatial deficits moved toward normal coordination on functional tasks

Swayed by sound: sonic guidance as a neurorehabilitation strategy in the cerebellar ataxias

Cerebellar disease leads to problems in controlling movement. The most common difficulties are dysmetria and instability when standing. Recent understanding of cerebellar function has expanded to include non -motor aspects such as emotional, cognitive and sensory processing. Deficits in the acquisition and processing of sensory information are one explanation for the movement problems observed in cerebellar ataxia. Sensory deficits result in an inability to make predictions about future events; a primary function of the cerebellum. A question therefore, is whether augmenting or replacing sensory information can improve motor performance in cerebellar disease. This question is tested in this thesis by augmenting sensory information through the provision of an auditory movement guide.A variable described in motor control theory (tau) was used to develop auditory guides that were continuous and dynamic. A reaching experiment using healthy individuals showed that the timing of peak velocity, audiomotor coordination accuracy, and velocity of approach, could be altered in line with the movement parameters embedded in the auditory guides. The thesis then investigated the use of these sonic guides in a clinical population with cerebellar disease. Performance on neurorehabilitation exercises for balance control was tested in twenty people with cerebellar atrophy, with and without auditory guides. Results suggested that continuous, predictive, dynamic auditory guidance is an effective way of improving iii movement smoothness in ataxia (as measured by jerk). In addition, generating and swaying with imaginary auditory guides was also found to increase movement smoothness in cerebellar disease.Following the tests of instantaneous effects, the thesis then investigated the longterm consequences on motor behaviour of following a two -month exercise with auditory guide programme. Seven people with cerebellar atrophy were assessed pre - and post -intervention using two measures, weight -shifting and walking. The results of the weight -shifting test indicated that the sonic -guide exercise programme does not initiate long -term changes in motor behaviour. Whilst there were minor, improvements in walking, because of the weight -shifting results, these could not be attributed to the sonic guides. This finding confirms the difficulties of motor rehabilitation in people with cerebellar disease.This thesis contributes original findings to the field of neurorehabilitation by first showing that on -going and predictive stimuli are an appropriate tool for improving motor behaviour. In addition, the thesis is the first of its kind to apply externally presented guides that convey continuous meaningful information within a clinical population. Finally, findings show that sensory augmentation using the auditory domain is an effective way of improving motor coordination in some forms of cerebellar disease

Computational neurorehabilitation: modeling plasticity and learning to predict recovery

Despite progress in using computational approaches to inform medicine and neuroscience in the last 30 years, there have been few attempts to model the mechanisms underlying sensorimotor rehabilitation. We argue that a fundamental understanding of neurologic recovery, and as a result accurate predictions at the individual level, will be facilitated by developing computational models of the salient neural processes, including plasticity and learning systems of the brain, and integrating them into a context specific to rehabilitation. Here, we therefore discuss Computational Neurorehabilitation, a newly emerging field aimed at modeling plasticity and motor learning to understand and improve movement recovery of individuals with neurologic impairment. We first explain how the emergence of robotics and wearable sensors for rehabilitation is providing data that make development and testing of such models increasingly feasible. We then review key aspects of plasticity and motor learning that such models will incorporate. We proceed by discussing how computational neurorehabilitation models relate to the current benchmark in rehabilitation modeling – regression-based, prognostic modeling. We then critically discuss the first computational neurorehabilitation models, which have primarily focused on modeling rehabilitation of the upper extremity after stroke, and show how even simple models have produced novel ideas for future investigation. Finally, we conclude with key directions for future research, anticipating that soon we will see the emergence of mechanistic models of motor recovery that are informed by clinical imaging results and driven by the actual movement content of rehabilitation therapy as well as wearable sensor-based records of daily activity

Time course of motor gains induced by Music-Supported Therapy after stroke : An exploratory case study

OBJECTIVE: Previous studies have shown that Music-Supported Therapy (MST) can improve the motor function and promote functional neuroplastic changes in motor areas; however, the time course of motor gains across MST sessions and treatment periods remain unknown. The aim of this study was to explore the progression of the rehabilitation of motor deficits in a chronic stroke patient for a period of 7 months. METHOD: A reversal design (ABAB) was implemented in a chronic stroke patient where no treatment was provided in the A periods and MST was applied in the B periods. Each period comprised of 4 weeks and an extensive evaluation of the motor function using clinical motor tests and 3D movement analysis was performed weekly. During the MST periods, a keyboard task was recorded daily. A follow-up evaluation was performed 3 months after the second MST treatment. RESULTS: Improvements were observed during the first sessions in the keyboard task but clinical gains were noticeable only at the end of the first treatment and during the second treatment period. These gains were maintained in the follow-up evaluation. CONCLUSIONS: This is the first study examining the pattern of motor recovery progression in MST, evidencing that gradual and continuous motor improvements are possible with the repeated application of MST training. Fast-acquisition in specific motor abilities was observed at the beginning of the MST training but generalization of these improvements to other motor tasks took place at the end or when another treatment period was provided.Peer reviewe

Effects of Cueing on Sit to Stand Transfers in Parkinson Disease

Problem Statement: Individuals with Parkinson Disease (PD) often experience difficulty transferring from sit to stand (STS). Current evidence suggests cues which promote an external attentional focus improve gait and transfers for individuals with PD. However, this research utilizes cues which are difficult to replicate in clinical or natural environments making the findings difficult to generalize or implement. Purpose: The primary purpose of this study is to determine the effect of 3 different explicit cues on STS for individuals with PD. Additionally we sought to determine if, in this population, a relationship exists between latency of movement initiation and postural sway in early standing, changes in joint angle between conditions and postural sway in early standing, and cue provided during the transfer and postural sway in early standing. Procedures/Methodology: Thirteen individuals in both the experimental and control groups participated in this cross-over design study. Both groups completed trials of self-initiated uncued STS transfers. Those in the experimental group also completed trials of STS transfers in 3 conditions: with an external attentional focus of reaching to targets, with an external attentional focus of concurrent modeling, and with an explicit cue for an internal attentional focus. Data was collected by trained testers and utilized valid and reliable body worn inertial measurement unit sensors. ANOVAs were used to compare performance between conditions and to the performance of the healthy control group. Bonferroni corrections were completed to reduce the likelihood of accepting a false positive. Results: Both cues that elicit an external attentional focus improved motor control during the sit to stand transfer. However, only modeling was able to improve both motor control and postural control. Cueing that promoted an internal attentional focus resulted in decreased motor control and postural control. Additionally, a moderate positive correlation was found between standing taller than typical and postural sway. Clinical Implications: Our results provide evidence for clinicians to better tailor treatment methodologies to the needs of individuals with PD. Optimal cueing can be utilized as compensations that reduce caregiver burden and increase independence of individuals with PD

The role of sound in robot-assisted hand function training post-stroke

In Folge eines Schlaganfalls leiden 90% aller Patienten an einer Handparese, die sich in 30-40% als chronisch manifestiert. Derzeit wächst seitens der Neurologie und Technologie das Forschungsinteresse an der Effektivität robotergestützter Therapieansätze, welche für schwer betroffene Patienten als besonders vielversprechend eingestuft werden. Die hierfür verwendeten Therapieroboter setzen sich aus einem mechanischen Teil und einer softwaregestützten virtuellen Umgebung zusammen, welche neben dem graphischen Interface, audio-visuelles Feedback sowie Musik beinhaltet. Bisher wurden Effekte der klanglichen Anteile dieses Szenarios noch nicht hinsichtlich möglicher Einflüsse auf Motivation, Bewegungsdurchführung, motorisches Lernen und den gesamten Rehabilitationsprozess untersucht. Die vorliegende Arbeit untersucht die Rolle von Sound in robotergestütztem Handfunktionstraining. Die Hauptziele im Rahmen dessen sind es, 1) Potentiale von Sound/ Musik für den Kontext robotergestützten Handfunktionstrainings zu explorieren, 2) spezifizierte klangliche Umgebungen zu entwickeln, 3) zu untersuchen, ob Schlaganfallpatienten von diesen spezifizierten Soundanwendungen profitieren, 4) ein besseres Verständnis über Wirkmechanismen von Sound und Musik mit Potential für robotergestützte Therapie darzulegen, und 5) Folgetechnologien über eine effektive Applikation von Sound/ Musik in robotergestützter Therapie zu informieren.90% of all stroke survivors suffer from a hand paresis which remains chronic in 30-40% of all cases. Currently, there is an increasing research interest in neurology and technology on the effectiveness of robot-assisted therapies. Robotic training is considered as especially promising for patients suffering from severe limitations. Commonly, rehabilitation robots consist of a mechanical part and a virtual training environment with a graphical user interface, audio-visual feedback, sound, and music. So far, the effects of sound and music that are embedded within these scenarios have never been evaluated in particular while taking into account that it might influence motivation, motor execution, motor learning and the whole recovery process. This thesis investigates the role of sound in robot-assisted hand function training post-stroke. The main goals of this work are 1) to explore potentials of sound/ music for robotic hand function training post-stroke, 2) to develop specified sound-/ music-applications for this context, 3) to examine whether stroke patients benefit from these specified sound/ music-application, 4) to gain a better understanding of sound-/ music-induced mechanisms with therapeutic potentials for robotic therapy, and 5) to inform further arising treatment approaches about effective applications of sound or music in robotic post-stroke motor training

Effects of patterned sensory enhancement on hemiparetic upper limb kinematics, The

2012 Spring.Includes bibliographical references.Loss of motor capabilities following a stroke can have a significant effect on a stroke survivor's quality of life, and the lack of conclusively effective therapeutic interventions often make it difficult to determine an effective treatment plan. Several empirical studies have found Neurologic Music Therapy (NMT) successful in producing more efficient muscular movements post-stroke (Malcolm, Massie, & Thaut, 2009; Thaut, Schleiffers, & Davis, 1991; Thaut, Kenyon, Hurt, McIntosh, & Hoemberg, 2002; Thaut et al., 2007; Yoo, 2009). The purpose of this pilot study was to assess the effect Patterned Sensory Enhancement (PSE), an NMT technique, had on movement in hemiparetic upper limbs of stroke survivors. Three subjects participated in two counterbalanced experimental trials in which a repetitive reaching movement was evaluated with (1) auditory rhythmic cueing and (2) with combined temporal, force and spatial auditory cueing (PSE). Target contact accuracy and mid-arc variability were statistically analyzed between the three trials (un-cued control, rhythm only, and PSE). Repeated measures ANOVA revealed a decrease in mid-arc variability in the PSE trial, but not at a statistically significant level. No further statistically significant results were discovered in this pilot study, however, more conclusive results may be observed in future studies adhering to the suggested revisions

Upper extremity rehabilitation using interactive virtual environments

Stroke affects more than 700,000 people annually in the U.S. It is the leading cause of major disability. Recovery of upper extremity function remains particularly resistant to intervention, with 80% to 95% of persons demonstrating residual upper extremity impairments lasting beyond six months after the stroke. The NJIT Robot Assistive Virtual Rehabilitation (NJIT-RAVR) system has been developed to study optimal strategies for rehabilitation of arm and hand function. Several commercial available devices, such as HapticMaster™, Cyberglove™, trakSTAR™ and Cybergrasp™, have been integrated and 11 simulations were developed to allow users to interact with virtual environments. Visual interfaces used in these simulations were programmed either in Virtools or in C++ using the Open GL library. Stereoscopic glasses were used to enhance depth perception and to present movement targets to the subjects in a 3-dimensional stereo working space. Adaptive online and offline algorithms were developed that provided appropriate task difficulty to optimize the outcomes. A pilot study was done on four stroke patients and two children with cerebral palsy to demonstrate the usability of this robot-assisted VR system. The RAVR system performed well without unexpected glitches during two weeks of training. No subjects experienced side effects such as dizziness, nausea or disorientation while interacting with the virtual environment. Each subject was able to finish the training, either with or without robotic adaptive assistance. To investigate optimal therapeutic approaches, forty stroke subjects were randomly assigned to two groups: Hand and Arm training Together (HAT) and Hand and Arm training Separately (HAS). Each group was trained in similar virtual reality training environments for three hours a day, four days a week for two weeks. In addition, twelve stroke subjects participated as a control group. They received conventional rehabilitation training of similar intensity and duration as the HAS and HAT groups. Clinical outcome measurements included the Jebsen Test of Hand Function, the Wolf Motor Function Test, and the ReachGrasp test. Secondary outcome measurements were calculated from kinematic and kinetic data collected during training in real time at 100 Hz. Both HAS and HAT groups showed significant improvement in clinical and kinematic outcome measurements. Clinical improvement compared favorably to the randomized clinical trials reported in the literature. However, there was no significant improvement difference between the two groups. Subjects from the control group improved in clinical measurements and in the ReachGrasp test. Compared to the control group, the ReachGrasp test showed a larger increase in movement speed during reaching and in the efficiency of lifting an object from the table in the combined HAS and HAT group. The NJIT-RAVR system was further modified to address the needs of children with hemiplegia due to Cerebral Palsy. Thirteen children with cerebral palsy participated in the total of nine sessions of one hour training that lasted for three weeks. Nine of the children were trained using the RAVR system alone, and another four had training with the combined Constraint-Induced Movement therapy and RAVR therapy. As a group, the children demonstrated improved performance across measurements of the Arm Range of Motion (AROM), motor function, kinematics and motor control. While subjects\u27 responses to the games varied, they performed each simulation while maintaining attention sufficient to improve in both robotic task performance and in measures of motor function

Effects of Movement Context on Reach-Grasp-Lift Motion and Grip Force after Stroke

Loss of upper extremity function after stroke is a significant problem resulting in enormous personal, societal, and economic costs. Neurophysiological discoveries over several decades have revealed great potential for use-dependent neural adaptation, and have revitalized the search for training strategies that optimize recovery. Although task-specific repetitive practice is recognized as a key stimulus to promote upper extremity function after stroke, choices of what to practice and how to practice remain challenging and poorly guided by evidence. This research was inspired by evidence in healthy individuals, that movement can be altered by characteristics of the task and the environment, together referred to as the movement context. The purpose of this research was to determine whether motor performance of the paretic upper extremity is affected by two specific movement context variations: 1) preferred speed versus fast, and 2) unilateral versus bilateral. Using electromagnetic motion tracking and pressure sensor quantification of grip force, we assessed upper extremity task performance in people with post-stroke hemiparesis. To evaluate effects of movement speed, we compared paretic-limb performance of a reach-grasp-lift task at a self-selected preferred speed to the same task performed as fast as possible. People with hemiparesis were able to move faster than their preferred speed, and when they did, movement quality was better. Reach paths were straighter, finger movements were more efficient, and the fingers opened wider. To evaluate effects of the bilateral movement context, we compared paretic-limb performance of a reach-grasp-lift-release task unilaterally versus bilaterally. We found no immediate improvement in the bilateral context. We further explored effects of the bilateral movement context by measuring maximal and submaximal grip force capacity using grip dynamometers. Unlike healthy controls and unlike the non-paretic side, the paretic side of people with hemiparesis produced more maximal force in the bilateral condition. In a submaximal task, however, the bilateral condition did not enhance the paretic side\u27s contribution. These results suggest that emphasizing speed during post-stroke rehabilitation may be worthwhile, that the bilateral movement context has little immediate impact on task performance, and that the paretic limb may benefit from the bilateral condition only at high force levels