Raviraj Nataraj

Raviraj Nataraj
Stevens Institute of Technology · Department of Chemistry, Chemical Biology & Biomedical Engineering

PhD

About

106
Publications
10,920
Reads
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745
Citations
Introduction
Our current research interests are focused on better integration of users with movement disability and assistive devices, such as prostheses and powered exoskeletons. We are developing visual-driven methods to provide users with greater agency and combined function with their devices. Our platforms for development include virtual reality, musculoskeletal modeling, and real-time feedback control systems.
Additional affiliations
September 2016 - present
Stevens Institute of Technology
Position
  • Professor (Assistant)
Description
  • Principal Investigator for Movement Control Rehabilitation (MOCORE) Laboratory
January 2015 - August 2016
Cleveland State University
Position
  • Research Associate
December 2013 - present
Case Western Reserve University School of Medicine
Position
  • PostDoc Position
Education
January 2005 - December 2010
Case Western Reserve University
Field of study
  • Ph.D. Biomedical Engineering
January 2003 - December 2004
Case Western Reserve University
Field of study
  • M.S. Biomedical Engineering
September 2001 - December 2002
Stanford University
Field of study
  • M.S. Mechanical Engineering

Publications

Publications (106)
Article
Full-text available
This paper reviews the field of feedback control for neuroprosthesis systems that restore advanced standing function to individuals with spinal cord injury. Investigations into closed-loop control of standing by functional neuromuscular stimulation (FNS) have spanned three decades. The ultimate goal for FNS standing control systems is to facilitate...
Article
Full-text available
The linear quadratic regulator (LQR) is a classical optimal control approach that can regulate gait dynamics about target kinematic trajectories. Exoskeletons to restore gait function have conventionally utilized time-varying proportional-derivative (PD) control of leg joints. But these PD parameters are not uniquely optimized for whole body (full-...
Article
Full-text available
To effortlessly complete an intentional movement, the brain needs feedback from the body regarding the movement’s progress. This largely nonconscious kinesthetic sense helps the brain to learn relationships between motor commands and outcomes to correct movement errors. Prosthetic systems for restoring function have predominantly focused on control...
Article
Full-text available
This study investigated how modified control of a virtual hand executing reach-to-grasp affects functional performance and agency (perception of control). The objective of this work was to demonstrate positive relationships between reaching performance and grasping agency and motivate greater consideration of agency in movement rehabilitation. We h...
Article
Full-text available
This study investigated the effects of visual feedback (VF) complexity on movement performance to potentially optimize the design of VF-based rehabilitation. We evaluated the effects of VF complexity on performance of the two-legged squat during training with concurrent (real-time) VF and short-term retention with no VF. Four VF cases were employed...
Article
Full-text available
Introduction: Physical therapy is crucial to rehabilitating hand function needed for activities of daily living after neurological traumas such as traumatic brain injury (TBI). Virtual reality (VR) can motivate participation in motor rehabilitation therapies. This study examines how multimodal feedback in VR to train grasp-and-place function will i...
Article
Background: The bidirectional communication between the hand and brain is profoundly reliant on tactile perception. Transcutaneous electrical nerve stimulation (TENS) can evoke tactile sensation, but its role in fingertip force control is not well understood. Purpose: We examined the tactile sensation evoked by TENS, especially the effects of concu...
Article
Full-text available
This study examined the effects of different modes of augmented visual feedback of joint kinematics on the emerging joint moment patterns during the two-legged squat maneuver. Training with augmented visual feedback supports improved kinematic performance of maneuvers related to sports or daily activities. Despite being representative of intrinsic...
Article
Full-text available
This paper aims to present previous works in augmented sensory guidance for motor learning and psychophysiological factors and contextualize how these approaches may facilitate greater optimization of motor rehabilitation after neurotraumas with virtual reality. Through library resources at Stevens Institute of Technology, we searched for related w...
Article
Powered orthoses that employ virtual muscle models for specifying motor commands may better produce natural, human-like joint torque and motion outputs. Here, we design and implement a muscle controller based on the standard 3-element Hill model that outputs a joint torque signal prescribed to the electric motors of a powered orthosis. Real-time si...
Article
Full-text available
Previous studies have demonstrated how augmented feedback can accelerate motor learning. Still, how specific feedback features of complexity and intermittency can influence learning a challenging, force-driven motor task remains largely unknown. This study is an initial investigation of how variations in the complexity and intermittency of augmente...
Data
An unpiloted Parker Hannifin Indego exoskeleton (hereafter, Indego) was controlled to perform basic isokinetic and isometric knee exercises on a Biodex-2 using a virtual muscle model of the Vasti (extension) and Hamstrings + Gastroc (flexion). The isometric testing conditions are as follows: 15, 30, 45, 60, 75 degrees of knee flexion. Each posi...
Conference Paper
Full-text available
Support vector machines (SVM) were used to classify visual attention (based on eye-tracking measures) from EEG inputs during variations in augmented sensory feedback (ASF). During a virtual reality (VR) task using myoelectric control, ASF was provided under either unimodal (visual only) or multimodal (visual + haptic) conditions. It was hypothesize...
Conference Paper
Each year in the United States, over 2,000,000 individuals suffer from neuromuscular disorders that severely impair movement abilities. Physical therapy is the predominant option for rehabilitating motor function for these patients; however, traditional therapies often focus on physical training without greater cognitive engagement or leveraging of...
Article
Full-text available
Purpose Efforts to optimize human-computer interactions are becoming increasingly prevalent, especially with virtual reality (VR) rehabilitation paradigms that utilize engaging interfaces. We hypothesized that motor and perceptional behaviors within a virtual environment are modulated uniquely through different modes of control of a hand avatar dep...
Article
Full-text available
Production of functional forces by human motor systems require coordination across multiple muscles. Grip and pinch are two prototypes for grasping force production. Each grasp plays a role in a range of hand functions and can provide an excellent paradigm for studying fine motor control. Despite previous investigations that have characterized musc...
Conference Paper
Full-text available
Neurotrauma such as spinal cord injury (SCI) traumatic brain injury (TBI) and stroke can have significant impact on people’s activities of daily livings (ADLs), especially reaching and grasping [1, 2]. Physical therapy (PT) has been the primary method to help individuals suffered from these neurotrauma to regain or retrain hand functions such as gr...
Conference Paper
Full-text available
Neuromuscular trauma including traumatic brain injury (TBI) and spinal cord injury (SCI) can significantly impair individuals’ activities of daily living, especially hand movement [1]. As a traditional method, physical therapy (PT) often helped people to regain hand functions such as grasping. However, commitment to PT can be challenging, which inv...
Conference Paper
Full-text available
After neurotraumas (e.g., spinal cord injury, stroke), persons undergo physical therapy to reformulate neuromotor connections and restore physical functions, such as grasp. Traditional rehabilitation relies on repetitive physical practice of skills of daily living, while advanced protocols may also utilize computerized interfaces to elicit greater...
Conference Paper
Full-text available
Neuromuscular pathologies including traumatic brain injury (TBI) and stroke can be detrimental to people's activities of daily living (ADL), especially hand movement [1, 2]. Physical therapy (PT) has been the primary way to help individuals with compromising hand functions after neurotrauma to regain functional capabilities such as grasping [3]. Ho...
Conference Paper
Full-text available
Cognitive-based motor rehabilitation with computerized interfaces Raviraj Nataraj1*, Sean Sanford1, Mingxiao Liu1, Noam Y. Harel2,3, Soha Saleh4 1Stevens Institute of Technology, USA; 2Icahn School of Medicine at Mount Sinai, USA; 3James J. Peters Bronx VA Medical Center, USA; 4Kessler Foundation, USA Presenter* Contact Details: rnataraj@stevens.ed...
Conference Paper
Full-text available
Neuromotor rehabilitation technologies with computerized interfaces, as with virtual reality, are increasingly prevalent. Persons with neurological disruptions, such as stroke or spinal cord injury, can train with such interfaces to repeatedly practice functional movements and reformulate neuromotor connections. It is crucial for computerized inter...
Article
Full-text available
Electromyography (EMG) signals can be classified by machine learning (ML) algorithms to command prosthetic devices that functionally assist persons after neuromuscular traumas, including amputation and spinal cord injury. This pilot study evaluated several ML algorithms in mapping isometric EMG signals from the upper body (dominant-side arm, chest,...
Conference Paper
Full-text available
Neurotrauma such as traumatic brain injury (TBI) and spinal cord injury (SCI) can be detrimental to individuals' activities of daily living, especially hand movement [1]. As a conventional method, physical therapy (PT) helped people to regain hand functions such as grasping. However, commitment to PT can be challenging, which involves repetitive an...
Article
Full-text available
Sensory feedback from wearables can be effective to learn better movement through enhanced information and engagement. Facilitating greater user cognition during movement practice is critical to accelerate gains in motor function during rehabilitation following brain or spinal cord trauma. This preliminary study presents an approach using an instru...
Article
Full-text available
Context: Continuous visual feedback (VF) can improve abilities to achieve desired movements and maximize rehabilitation outcomes by displaying actual versus target body positions in real time. Bandwidth VF reduces the reliance on feedback by displaying movement cues only when performance errors exceed specified thresholds. As such, bandwidth VF ma...
Article
Full-text available
This study investigated how modifications in the display of a computer trace under user control of grasp forces can co-modulate agency (perception of control) and performance of grasp on rigid and compliant surfaces. We observed positive correlation (p < 0.01) between implicit agency, measured from time-interval estimation for intentional binding,...
Conference Paper
Full-text available
Improving grasp performance for activities of daily living is an essential rehabilitation objective following neuromuscular traumas such as spinal cord injury, traumatic brain injury, stroke, and amputation [1]. Traditional upper-extremity rehabilitation methods help people to relearn motor skills with intensive or repetitive physical training [2]....
Conference Paper
Full-text available
Improving hand grasp function is an essential rehabilitation objective following a neurotrauma such as traumatic brain injury, spinal cord injury, or stroke. Traditional rehabilitation protocols involve intensive or repetitive physical training to reformulate neuro-motor connections. Advanced technologies including rehabilitative device (prosthetic...
Conference Paper
Full-text available
Improving grasp performance for activities of daily living is a key rehabilitation objective following neuromuscular traumas such as stroke, traumatic brain injury or spinal cord injury. Typical rehabilitation protocols involve intensive or repetitive physical training to reformulate motor connections. Few approaches consider cognitive factors to b...
Conference Paper
Improving grasp performance for activities of daily living is an essential objective following neuromuscular trauma such as spinal cord injury, traumatic brain injury, stroke or amputations. Traditional rehabilitation methods involve intensive or repetitive physical training to relearn motor skills. Few of them consider or leverage cognitive factor...
Conference Paper
Post-stroke rehabilitation, occupational and physical therapy, and training for use of assistive prosthetics leverages our current understanding of bilateral motor control to better train individuals. In this study, we examine upper limb lateralization and model transference using a bimanual joystick cursor task with orthogonal controls. Two groups...
Conference Paper
This paper outlines the construction, current state, and future goals of HERCULES, a three degree-of-freedom (DoF) pneumatically actuated exoskeleton for stroke rehabilitation. The exoskeleton arm is capable of joint-angle control at the elbow in flexion and extension, at the shoulder in flexion and extension, and at the shoulder in abduction and a...
Article
Full-text available
This study investigated the generalized effects of positive feedback (PF) versus negative feedback (NF) during training on performance and sense of agency for a reach-to-touch task with a virtual hand. Virtual reality (VR) is increasingly employed for rehabilitation after neuromuscular traumas such as stroke and spinal cord injury. However, VR meth...
Data
PLOS ONE publication entitled "Disproportionate positive feedback facilitates sense of agency and performance for a reaching movement task with a virtual hand"
Chapter
Full-text available
Motor prostheses act to restore function to persons with movement disability through device actions triggered by command or intent of the user. There are various modes by which device actions may power or inform the person’s movement. For any device mode, actions are based on what the person is intending to do. Regardless of the device, user, or me...
Conference Paper
Full-text available
Improving grasp performance for activities of daily living (ADLs) is a key rehabilitation objective following stroke or spinal cord injury. We hypothesize that provision of sensory feedback that promotes grasp performance and sense of agency (SoA) may accelerate neuromotor rehabilitation. Agency is the perception of control of neuromuscular action,...
Conference Paper
Full-text available
Improving grasp performance for activities of daily living (ADLs) is a key rehabilitation objective following stroke or spinal cord injury. We hypothesize that provision of sensory feedback that promotes grasp performance and sense of agency (SoA) may accelerate neuromotor rehabilitation. Agency is the perception of control of neuromuscular action,...
Thesis
Neural disorders or traumas can significantly impact an individual's quality of life, due to impaired motor function. Electromyography (EMG) signals arising from muscle activation have become popular for providing inputs to advanced prosthetics that help these patients. Machine learning (ML) methods such as artificial neural networks (ANN) and adap...
Conference Paper
Full-text available
Sense of agency (SoA) is the neural perception of true authorship of a neuromuscular action and related consequences. Functional movements such as reaching and grasping are vital in performing activities of daily living (ADL) and engaging to the environment. Previous studies have shown that neuromuscular disorders can affect not only the functional...
Article
This work describes a methodological framework that can be used to explicitly and implicitly characterize the sense of agency developed over the neural-machine interface (NMI) control of sensate virtual or robotic prosthetic hands. The formation of agency is fundamental in distinguishing the actions that we perform with our limbs as being our own....
Conference Paper
Full-text available
Introduction: The Multidimensional Health Locus of Control (MHLOC) questionnaire [1] was developed to assess the attitudes and perceptions a person may have towards health performance. Decades of related research support the notion that external stimuli, can aid progress in rehabilitation [2]. This strongly indicates that rehabilitation paradigms m...
Conference Paper
Full-text available
Clinical rehabilitation of hand grasp compromised by neuromuscular pathology is critical to improve performance of activities of daily living. Functional hand prostheses used following amputation or spinal cord injury can restore basic grasp but leave the user feeling disconnected from the device as a true extension of self. We hypothesize that gre...
Conference Paper
Full-text available
Improving hand grasp function impaired by neuromuscular pathology is a critical clinical objective to rehabilitate performance in activities of daily living. Standard rehabilitation protocols following neuromuscular pathology, such as stroke, rely on the repetitive practice of grasp to better re-formulate neuromotor connections. Virtual reality (VR...
Conference Paper
Full-text available
Improving hand grasp function impaired by neuromuscular pathology is a critical objective in rehabilitating performance of activities of daily living. Standard rehabilitation protocols rely on the repetitive practice of grasp to better learn operation of an assistive device or re-formulate neuromotor connections. Virtual reality (VR) environments t...
Article
Full-text available
In this simulation study, we present and examine methods to develop a feedback controller for a neuroprosthesis that restores forward and side leaning function during standing following complete thoracic-level spinal cord injury. Achieving leaning postures away from erect stance with functional neuromuscular stimulation (FNS) would allow users to e...
Article
Full-text available
This study investigates the mechanics of the thumb and index finger in relation to compliant endpoint forces during precision pinch. The objective was to gain insight into how individuals modulate motor output at the digit endpoints and joints according to compliance-related sensory feedback across the digits. Thirteen able-bodied subjects performe...
Article
Full-text available
Background: Functional neuromuscular stimulation (FNS) can restore standing capabilities following spinal cord injury. Feedback control of these systems can optimize performance by reducing the required upper extremity support. However, tuning these control systems can be intensive and clinically inconvenient. Objective: This case study investigate...
Article
Full-text available
Functional neuromuscular stimulation (FNS) can restore standing capabilities following spinal cord injury. Feedback control of these systems can optimize performance by reducing the required upper extremity support. However, tuning these control systems can be intensive and clinically inconvenient. This case study investigated a clinical method to...
Conference Paper
Full-text available
This study examined the potential of estimating total-body center of mass (CoM) kinematics for feedback control of a proposed networked neuroprosthesis for standing. The system includes implantable modules with tri-axial accelerometers distributed across the body. Utilizing a 3-D musculoskeletal model, we simulated accelerometer signals from each m...
Article
Full-text available
We used a three-dimensional biomechanical model of human standing to test the feasibility of feed-forward control systems that vary stimulation to paralyzed muscles based on the user's posture and desire to effect a postural change. The con-trollers examined were (1) constant baseline stimulation, which represented muscle activation required to mai...
Conference Paper
Full-text available
Purpose: This study assessed the joint mechanics of the thumb and index finger in relation to low-force endpoint compliance during precision pinch. Low forces were examined to permit greater possible combinations of joint output such that selective motor patterns could be identified according to the compliant force sensed at the digit endpoints. Me...
Article
Full-text available
Purpose: This study investigated novel kinematic performance parameters to understand regulation by visual feedback (VF) of the reaching hand on the grasp and transport components during the reach-to-pinch maneuver. Conventional metrics often signify discrete movement features to postulate sensory-based control effects (e.g., time for maximum velo...