R-3 Repository :: Browsing by Author "O'Malley, Marcia K"

Browsing by Author "O'Malley, Marcia K"

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Adaptive and Self-Adjusting Controllers for Safe and Meaningful Human-Robot Interaction during Rehabilitation
(2016-04-21) Losey, Dylan Patrick; O'Malley, Marcia K
This thesis discusses the use of adaptive control within human-robot interaction, and in particular rehabilitation robots, in order to change the perceived closed-loop system dynamics and compensate for unexpected and changing subject behaviors. I first motivate the use of controllers during robotic rehabilitation through a human-subjects study, in which I juxtapose interaction controllers and a novel motor learning protocol, and find that haptic guidance and error augmentation can improve the retention of trained behavior after feedback is removed. Next, I develop an adaptive controller for rigid upper-limb rehabilitation robots, which uses sensorless force estimation to minimize the amount of robotic assistance while also bounding the subject's trajectory errors. Finally, I discuss the use of time domain adaptive control in the context of physically compliant rehabilitation robots---in particular, series elastic actuators---where I discover that adaptive techniques enable passively rendering virtual environments not achievable using existing practices. Each of these adaptive controllers is developed using the theoretical framework of Lyapunov stability analysis, and is tested on single degree-of-freedom robotic hardware. I conclude that adaptive control provides an avenue for safe robotic interaction, both through stability analysis and physical compliance, and can adjust to subjects of various impairment levels to ensure that training is meaningful, in the sense that desired trajectories, interactions, and long-term effects are achieved.
Analytical investigation of vibration attenuation with a nonlinear tuned mass damper
(2015-04-24) Atzil, Aaron M; Dick, Andrew J; Ghorbel, Fathi H; O'Malley, Marcia K; Nagarajaiah, Satish
Vibration attenuation devices are used to reduce the vibrations of various mechanical systems and structures. In this work, an analytical method is proposed to provide the means to investigate the influence of system parameters on the dynamic response of a system. The method of multiple scales is used to calculate an approximate broadband solution for a two degree-of-freedom system consisting of a linear primary structure and a nonlinear tuned mass damper. The model is decoupled, approximate analytical solutions are calculated, and then they are combined to produce the desired frequency-response information. The approach is initially applied to a linear two degree-of-freedom system in order to verify its performance. The approach is then applied to the nonlinear system in order to study how varying the values of parameters associated with the nonlinear absorber affect its ability to attenuate the response of the primary structure. Finally, the analytical solution is compared to a numerical solution in order to determine how well it approximates the nonlinear system frequency-response.
Conveying Language through a Multi-sensory Haptic Device
(2019-04-18) Dunkelberger, Nathan; O'Malley, Marcia K
Communication is a valuable resource that is a part of everyone's life. However, there are many cases where the resource of communication is not available, either due to saturation or impairment of the typical auditory or visual communication channels. Haptics, or the sense of touch, provides an alternative to these traditional channels. Furthermore, multi-sensory haptics provides the potential of displaying large amounts of haptic information in a small form factor by providing different types of tactile information. In this thesis, a multi-sensory haptic device is presented which uses lateral skin stretch, radial squeeze, and vibration components. In a cue identification task, the multi-sensory device performed better than a single-sensory device, encouraging the use of multi-sensory devices for language transmission. The device was then used for language transmission and subjects learned to understand English through the presentation of phonemes as haptic cues through a 100 minute training protocol.
Design and Control of a Cable-Driven Actuation System for Soft Robotic Exoskeleton
(2016-04-26) McDonald, Craig Gaston; O'Malley, Marcia K
A robotic exoskeleton is a powered wearable device that is capable of actuating one or more of a person's joints to physically interact with the user in a significant and controlled manner. The work presented in this thesis is the result of a collaboration with NASA's Dexterous Robotics Laboratory (DRL) to design a soft, wearable exoskeleton for neuro-rehabilitation, an application that requires accurate sensing and control of the interaction forces and torques between the robot and the human to be successfully implemented. To achieve accurate interaction control, a well-established method of cascaded control with an inner velocity loop is applied to a series elastic actuator (SEA) on an experimental test bed. The test bed is made modular and reconfigurable to closely study the effect of the location of a custom-designed elastic force sensor placed within the conduit transmission. Proper implementation of the control scheme is verified through system identification techniques with comparison to model predictions. Having the force sensor as close to the user interaction point as possible predictably results in a more accurate rendering of a virtual impedance to the user, despite the no load motion torque controller showing issues of steady-state error when the sensor is in this location. When the force sensor is located close to the stationary DC motor, a choice that is attractive for designers of the human interface to a soft exoskeleton, the degradation in the device's ability to render virtual impedance can be characterized by a model of the nonlinear friction interaction between the cable and the conduit transmission.
Design of a Novel Compliant Sensor for Series Elastic Actuation and Control of a Flexible Cable Conduit Transmission
(2016-04-21) Blumenschein, Laura H; O'Malley, Marcia K
While robotic rehabilitation following neurological injury is gaining traction, traditional rigid systems are confined to use in a clinic and mechanical designs can limit their portability for use in an assistive mode. Soft robotic wearable exoskeletons offer potential solutions, yet the cable-based actuation systems commonly used introduce non-linear dynamics and friction, increasing control challenges. This thesis presents a novel compliant sensor design for use in flexible cable conduit transmissions that leverages the natural transmission compliance and utilizes series elastic actuation (SEA), a method of control previously shown effective for dynamic compensation. Dynamic simulations and static models are used to inform the analysis of physical experiments using the sensor in the transmission. The sensor is validated for use in force feedback for both force and impedance control scenarios. Experimental results provide insight to the design of soft exoskeleton devices regarding the effects of sensor location and the challenges of non-collocation of sensor and user interface.
Design, Characterization, and Modeling of the MAHI Open Exo
(2022-04-20) Berning, Jeff Thomas; O'Malley, Marcia K; Fregly, Benjamin J
Rehabilitation robots provide many theoretical benefits to augment the role of a physical therapist; however, to date, therapeutic outcomes following stroke and spinal cord injury have not been improved with the use of rehabilitation robots. Personalized neuromusculoskeletal models have been developed to model dynamic motion and control of the human body, and the state-of-the-art models are capable of including impairment in the model. Incorporating a dynamic model of a rehabilitation robot working in concert with the human limb would enhance the impact of such models in designing personalized treatments. To realize this, the dynamic model of the robot must be solvable in real-time. These combined models can then be used to create personalized, model-based control strategies with the goal of improving therapeutic outcomes through higher subject engagement following spinal cord injury or stroke. To address this need, this thesis describes the design of the MAHI Open Exoskeleton (MOE), a four degree of freedom, serial exoskeleton device for the upper-limb. A dynamic model of the MAHI Open Exo is presented, along with the characterization and friction modeling of the device. The dynamic model provides the basis for a future human-robot combined model, which will be used for personalized, model- based control strategies.
Design, Characterization, and Validation of the OpenWrist Exoskeleton
(2017-04-19) Pezent, Evan; O'Malley, Marcia K
Robotic devices have been clinically verified for use in long duration and high intensity rehabilitation needed for motor recovery after neurological injury. Targeted and coordinated hand and wrist therapy, often overlooked in rehabilitation robotics, is required to regain the ability to perform activities of daily living. To this end, a new coupled hand-wrist exoskeleton has been designed. This thesis details the design of the wrist module and several human-related considerations made to maximize its potential as a coordinated hand-wrist device. The serial wrist mechanism has been engineered to facilitate donning and doffing for impaired subjects and to insure compatibility with the hand module in virtual and assisted grasping tasks. Several other practical requirements have also been addressed, including device ergonomics, clinician-friendliness, and ambidextrous reconfigurability. The wrist module's capabilities as a rehabilitation training device are quantified experimentally in terms of functional workspace and dynamic properties. Finally, the device is validated as an rehabilitation assessment tool by considering its impact on commonly used assessment metrics. The presented wrist module's performance and operational considerations support its use in a wide range of future clinical investigations.
Effect of Interference on Multi-sensory Haptic Perception
(2020-04-22) Zook, Zane Anthony; O'Malley, Marcia K
All people experience the world around them by receiving information through their senses. While vision and hearing are generally sufficient, there are occasions when these senses become overwhelmed or are simply unavailable. One potential solution is haptics, the use of touch to convey information, which has recently become widespread in wearable devices. To improve the ability of these wearable devices to encode detailed information, new types of haptic sensations are being researched and developed. This pursuit of detailed encoding of information in wearable haptics has driven the development of multi-sensory haptic devices which stimulate multiple haptic channels simultaneously. Despite the diversity of development in multi-sensory haptic devices, little is known about how simultaneous haptic cues interact with one another. Understanding how combinations of simultaneous cues may interact and interfere with one another is crucial for the creation of better wearables for the future. Therefore, for this thesis, I focus on the study of interference between haptic cues to inform the future implementation of haptic technology into wearable devices.
Efficiency of One- and Two-Stage Compact Cycloidal Transmissions for Robotic Applications
(2018-03-30) Farrell, Logan C; O'Malley, Marcia K
Many robotic applications demand compact, high reduction drives for their actuators. To date, the most commonly used actuator for this application is a harmonic drive. However, cycloidal drives could be considered for these applications as they provide high reductions in a compact package, are highly customizable, and can be easily manufactured in comparison to harmonic drives. Single-stage cycloids have been well analyzed in the literature, but not well tested. In this work, a single-stage cycloid was built and run for 300+ hours and 129,000 output revolutions to determine in-use efficiency and lifetime. This testing demonstrated that the compact, pin-in-housing designs can achieve efficiencies near and above the efficiencies of a comparable harmonic drive with a peak efficiency of 81% as well as a 2x increase in specific torque. A substantial burn-in of approximately 8 hours was noted, and the efficiency did not degrade appreciably over the course of the testing. A new design for a two-stage cycloid has been recently proposed and the basic kinematic analysis conducted. A test article for this two-stage design was constructed and tested. This testing identified gaps in the literature regarding the losses associated with the lobe to pin interactions. This work developed the mathematics necessary to characterize these losses in theory and are then compared to the tested actuator. The actuator’s losses nearly match the predicted losses of the two-stage system. This work presents many additional design equations for a two-stage cycloid system, the primary result suggesting that a two-stage system must be built with rolling elements in the housing to achieve satisfactory (above 50%) efficiencies. This thesis demonstrates enables two key conclusions: first single-stage cycloids are a viable replacement for harmonic drives in high reduction applications where backlash is allowed, second, additional design equations are necessary for a two-stage cycloid design.
EMG Control of an Upper-Limb Rehabilitation Exoskeleton for SCI Affected Users
(2018-04-09) Dennis, Troy A; O'Malley, Marcia K
Robotic rehabilitation for individuals with spinal cord injury (SCI) has been shown to be most effective when the user is motivated and mentally engaged in the execution of therapeutic exercises. Consequently, designers of the human-robot interface are challenged with developing control schemes that can detect user intent and maximize their engagement. Electromyography (EMG) is a promising technique to address this challenge. In this thesis, an EMG control scheme for an upper-limb exoskeleton, the MAHI Exo-II, is designed and tested with a population of able-bodied users, as well as SCI affected subjects. The presented scheme utilizes pattern recognition techniques to monitor the user's muscle activation patterns and select their intended direction of motion in single or multiple degree-of-freedom (DoF) movements of the elbow and wrist joints. The results presented demonstrate that the control scheme was simple to use, highly adaptive across a range of subjects, and accurate in directional classification.
Enhancing Human-Machine Interaction with Wearable Haptic Devices
(2018-04-18) Bradley, Josh Mark; O'Malley, Marcia K
This thesis presents work done with wearable haptic devices for the purpose of enhancing human-machine interaction. Haptic devices capitalize on the unrealized potential of our body--and particularly our skin--to perceive stimuli by contact. To address the challenge of training motor skills, my first area of focus deals with the question of how best to provide guidance information for trajectory-following tasks. Results indicate that spatially-separated assistance rendered through a tactile device can be as effective for guidance as a the same information presented through a kinematic device. In addition to that, exploring the concept of communicating with a wearable haptic device, the remainder of this thesis focuses on a novel, multi-modal, wearable haptic device, MISSIVE, which is capable of rendering information-rich haptic cues. My experiments demonstrate that this approach can increase perceptual accuracy compared to a uni-modal vibrotactile system of comparable size and that users prefer the multi-modal device.
Estimation and Control of Series Elastic Actuators for Decentralized Systems
(2018-04-20) Holley, James; O'Malley, Marcia K
Robotic applications continue to move out of factories and laboratories into ev- eryday applications. This movement drives a different paradigm for robotics; towards softer, compliant actuators intended for interacting with unknown environments and humans. The series elastic actuator, a robotic actuator with intentionally designed compliance, is a leading candidate for use in robots making the transition to human environments. Compliance in actuation provides its own engineering challenges. Series elastic actuators provide an additional degree of freedom, resonances, and more complicated controllers to operate. A series elastic estimator is proposed that models additional degrees of freedom and provides disturbance rejection in order to provide more accu- rate signals to the control of the actuator, and to higher level systems that may be controlling several robotic actuators together. Furthermore, any system that may interact with humans necessarily requires a element of safety. Passive systems are systems that do not produce any energy of their own. Additionally, passive systems in parallel or in feedback yield a passive system. For this reason, providing a guarantee of passivity in a system is a safety measure for deeming a robotic system fit for human interaction. In this thesis, an extension of a novel series elastic torque controller, disturbance observer torque control, can beguaranteed passive with relatively little trade off. Finally, a nonlinear torque controller is proposed that allows torque control to converge at a rapid exponential rate. Such a controller is not only important for torque control of the actuator, but leverages a larger proof on dynamics of a robot comprised of series elastic actuators. It separates actuator dynamics from robot dynamics, allowing a high level controller to assume it is comprised of rigid actuators, opening the door for more control schemes to be developed for robots without having to consider the extra complexity introduced by compliant actuators.
Embargo
Evaluating Human Perception with Salient & Low-Cost Wearable Haptics
(2023-04-11) Zook, Zane A; O'Malley, Marcia K
Haptic or touch feedback has become a critical component of devices that enable the transfer of information to users. Example applications range from “feeling” objects in virtual reality to simulating physical interactions on smartphone and smartwatch surfaces. Haptic devices with sufficient capability to serve as research platforms are costly, difficult to reproduce, and require a high degree of prior knowledge and expertise to design and build. Experimental hardware platforms that leverage low-cost actuation would reduce the financial burden and required expertise to perform haptics research, increasing accessibility and encouraging collaboration among a broad range of developers. This thesis presents three low-cost haptic device platforms that are used to support rigorous haptics research. The Vibro-Tactile Sleeve, comprised of low-cost vibrotactile actuators modularly embedded in a modified athletic sleeve, was used to evaluate the effect of directing human subjects’ focus on their ability to accurately interpret vibrotactile sequences. Findings in these experiments suggest that multi-modal focus, spatial focus, and sense of agency all affect human vibrotactile sequence perception while temporal focus does not. Snaptics is presented as an open-source, low-cost, 3D-printed, and modular multi-sensory development platform for wearable haptic devices. Experiments conducted with Snaptics devices demonstrated similar multi-sensory cue saliency and user performance as those performed with research-grade haptic devices in comparable studies. Finally, this thesis presents a fluidic-actuated textile-based approach to rapidly fabricating low-cost wearable haptic devices. Devices built with this fabrication approach were capable of delivering salient and easily distinguishable haptic cues. A prototype device enabled the investigation of passive, active, and multi-scale haptic perception and demonstrated the potential for multi-scale haptics as a means to transmit salient and information-dense haptic cues. These three platforms demonstrate that well-designed, accessible and low-cost devices are capable of delivering high-quality and salient haptic cues, and can support rigorous experimental evaluation.
Functional Electrical Stimulation and Exoskeleton Hybrid Control: Using Model Predictive Control to Distribute Control Effort among Systems with Unequal Time Delays
(2022-12-15) Dunkelberger, Nathan; O'Malley, Marcia K
Many individuals who have suffered from a spinal cord injury require assistance to perform activities of daily living, and this population considers regaining upper limb function as a top priority to restore independence. Robotic exoskeletons and functional electrical stimulation are two technologies that can provide some amount of aid in these cases, but each technology alone has limitations that keeps it from providing meaningful assistance for daily activities. Combining these two technologies could counter these limitations by allowing functional electrical stimulation to provide large amounts of the general power requirements, while an exoskeleton can fine tune movements, allowing for meaningful assistance. However, this combination also raises a new challenge – effectively distributing control effort between the two sources with differing time delays while maintaining high accuracy in coordinated movements. This thesis presents a model predictive control-based hybrid controller which utilizes the cost function to achieve this goal. This hybrid controller is implemented and tested in both single and multi-joint movements in its ability perform trajectory tracking tasks. Findings from studies with healthy participants indicate that the hybrid controller is able to reduce exoskeleton control effort compared to an exoskeleton acting alone yet maintain high accuracy in controller implementations with one and two joints, and simulations in four joint movements show ideal controller behavior, outlining potential capabilities in highly complex movements.
Implementing Virtual Walls and High-Frequency Haptic Taps on a 3 Degree-of-Freedom Wrist Exoskeleton
(2023-04-21) Timpe, Nick Kendrick; O'Malley, Marcia K
Haptic interactions have traditionally been rendered using desktop devices that rely on stylus-based interactions with a virtual environment. Less explored is the potential to render salient kinesthetic and cutaneous haptic interactions via exoskeletonbased devices. To date, developers have used closed-loop control to create kinesthetic forbidden regions of the workshop that the user cannot enter, or simulating hard stops on the exoskeleton in software, usually based on joint range of motion limitations. Cutaneous cues such as vibration have typically be rendered in tandem to the kinesthetic feedback, requiring the incorporation of a second set of high bandwidth actuators to overlay vibraiton on the primary kinesthetic cues. This approach increases system cost an complexity. In this work, we present methods for realizing high-fidelity kinesthetic feedback in a wrist-based exoskeleton device, the MAHI OpenWrist. We also present a method for conveying high-frequency “taps” or vibrations through the exoskeleton, leveraging the gap between exoskeleton and actuator bandwidths to reduce wrist motion on cue application and provide high-frequency haptic cues without need for additional actuation. Our open-architecture virtual wall generation system was developed and implemented on the OpenWrist device. These virtual walls are defined with multiple wall parameters including location, surface friction coefficient, normal restoring force, and normal damping all configurable to generate unique haptic effects. The user experience with the rendered virtual walls is enhanced using the traditional God Object rendering technique. These haptic rendering methods extend the capabilities of the OpenWrist device, and can be extended to other exoskeleton type haptic feedback systems.
Embargo
Individualized Haptics: On relating Psychophysics, Contact Mechanics, and Physiology in Indenting and Skin Stretch Haptic Cues
(2022-04-22) Clark, Janelle; O'Malley, Marcia K
Wearable haptic devices are now an established research area, but we have reached a design bottleneck in saliency that persists across different modalities and mechanisms. In this work, we seek to understand the contributing factors by assessing haptic perception from an individual, rather than a group, perspective. In doing so we seek to understand the sources of unique haptic experiences between users, specifically for skin stretch and indentation. The problems that wearable haptic devices seek to address are important and timely. As the mechanical design and computational control of robots become more nuanced and dexterous and as we increasingly engage with the world through technology, haptic devices can provide a surrogate sense of touch for those controlling robots in dangerous or remote situations, as well in daily life as for an amputee to feel their environment through their prosthesis. Currently, the design and testing of haptic devices are done on large groups with set parameters and cue magnitudes, however, the sense of touch is more complex and noisy than other senses, likely due to widely varying body compositions of fat and muscle and material characteristics of the skin. In this work, we will collect information on multiple domains to look for correlations within a single set of subjects, specifically their allowable stimulus range, both perceptible and comfortable, in the normal and shear directions, psychophysical performance, contact mechanics between the skin and the haptic interface, and anthropomorphic features. We hypothesize that the allowable stimulus range varies from person to person, as well as their just-noticeable differences (JND), impacting the number of discrete stimuli they can differentiate, tested using classical psychophysical methods. We hypothesize conducting experiments in force and position control will show differences in performance and distribution across subjects. In addition, by collecting force-torque and displacement information, we use Hertzian contact models to gain insight on differences in material properties, stresses, strain, and losses between individuals. This new perspective on haptic testing opens new research questions on perception of skin stretch and indentation, considerations for device design, and a multi-faceted data set to support work in haptic simulations and contact mechanics.
Integration of Electromyography-Based Detection of User Intent for Control of an Assistive Glove
(2021-02-04) Britt, John Ellis; O'Malley, Marcia K
This thesis outlines the efforts undertaken to characterize and enhance the performance of the SeptaPose Assistive and Rehabilitative (SPAR) Glove. The SPAR Glove is a semi-rigid device intended to aid users with Spinal Cord Injury (SCI) to achieve common hand poses that are necessary to complete Activities of Daily Living (ADL). Previously, operation of the glove required an experimenter to command each motor individually to actuate the glove's degrees of freedom. In this work, the control capability of the glove is expanded to enable detection of user intent to command the glove to move to pre-defined poses associated with ADLs. User intent is detected using a commercially available electromyography (EMG) arm band, the MYO, placed on the user's forearm. A control scheme is demonstrated that uses existing pattern recognition tools to infer the desired pose from the EMG activity. The ability of the detection and classification methods to distinguish between ADL poses on both able-bodied subjects and subjects with Spinal Cord Injury is explored. The glove's performance was also characterized with a newly developed Instrumented Hand, a device that holds the potential to become a new standard method of evaluating semi-rigid exoskeleton devices for the hand.
Low-Cost Multi-Sensory Wrist Mounted Haptic Device
(2022-04-20) Fantini, Mike; O'Malley, Marcia K
Extended reality (XR) has been growing rapidly over the past several years, but there remains a noticeable gap in the immersiveness of the experience. This gap is due to the lack of effective haptic feedback that provides the user with a sense of touch. Haptic devices that convey such sensations have been a subject of research for several decades, but they are now entering the mainstream markets; expensive and complex systems will become affordable and accessible as the market solidifies and shifts towards the consumer. One example of a high-end wearable haptic display is Tasbi, or Tactile and Squeeze Bracelet Interface, which provides haptic feedback via a six linear resonant actuator (LRA) vibrotactile array and custom force feedback squeeze mechanism. This thesis presents a low-cost alternative to Tasbi, achieving the same haptic sensation with off-the-shelf hardware components and an Arduino-based control interface. TABIv3 utilizes eight eccentric rotating masses (ERMs) to produce vibration feedback with a servo position controlled squeeze mechanism. The vibrotactors and squeeze mechanism are controlled with simple pulse-width modulation through digital output pins on an Arduino Mega, though TABIv3 was designed to be controlled with a wide assortment of microcontrollers, not just Arduino. The vibrotactile characteristics of the ERMs showed strong vibration but lacked the fast time responses observed with Tasbi's LRAs. The position controlled servo squeeze mechanism provided effective and comfortable squeeze sensations that can be customized and scaled based on the user. Results validate that low-cost, off-the-shelf actuators, and open source microcontroller platforms can be used to achieve salient vibration and squeeze cues in a wearable device.
Myoelectric Sensing for Intent Detection and Assessment in Upper-Limb Robotic Rehabilitation
(2020-04-24) McDonald, Craig G.; O'Malley, Marcia K
This thesis explores how surface electromyography (EMG) -- the measurement of muscle force through voltage changes at the skin surface – can be of use to the field of upper-limb robotic rehabilitation. We focus on two main aspects: detecting human intention from measured muscle activity and assessing human motor coordination through synchronous muscle activations known as muscle synergies – each examples of the bidirectional communication found in tightly integrated human-robot interaction. EMG-based intent detection presents an opportunity to examine and promote human engagement at the neuromuscular level, enabling new protocols for intervention that could be combined with robotic rehabilitation, particularly for the most impaired of users. Meanwhile, the latest research in motor control proposes that natural, healthy human movement can be characterized by the presence of certain muscle synergies, and that the alteration of these synergies indicates a disruption, from neurological impairment or some other physical constraints, in natural movement. Wearable robotic devices are capable of altering muscle synergies, and though the mechanisms are not yet understood, a focus on altering muscle synergies is a promising new approach to neurorehabilitation. This thesis employs a robotic exoskeleton for the elbow and wrist joints designed for research in robotic rehabilitation of individuals with neurological impairments and now integrated with a myoelectric control interface. We first demonstrate the ability of a myoelectric interface to discern the user’s intended direction of motion in single-degree-of-freedom (DoF) and multi-DoF control modes with 10 able-bodied participants and 4 participants with incomplete cervical spinal cord injury (SCI). Predictive accuracy was high for able-bodied participants (averages over 99% for single-DoF and near 90% for multi-DoF), and performance in the SCI group was promising (averages ranging from 85% to 95% for single-DoF, and variable multi-DoF performance averaging around 60%), which is encouraging for the future use of myoelectric interfaces in robotic rehabilitation for SCI. Second, we explore the identification of synchronous muscle synergies in the muscles controlling the elbow and wrist, and the possible effects of robot-imposed task constraints on the neural constrains represented by synergy patterns. Our results indicate that constraining the unused degrees of freedom during a single-DoF movement inside the exoskeleton does not have a significant effect on the underlying muscle synergies in the task, and that methodological choices in muscle synergy analysis also do not have a large effect on the outcome. With all of these findings, we have achieved a deeper understanding of the value myoelectric sensing can bring to upper-limb robotic rehabilitation, and how much potential it has to advance the field toward greater accessibility to individuals of all levels of impairment.
Objective Assessment of Endovascular Navigation Proficiency using Offline and Online Velocity-domain Performance Measures
(2020-04-22) Murali, Barath; O'Malley, Marcia K
Minimally invasive endovascular surgery is increasingly becoming the technique of choice for a variety of procedures ranging from aneurysm repair to heart valve replacement. To guarantee the benefits of fewer complications and faster recovery times, among several others, it is necessary that surgeons acquire a strong proficiency in navigating flexible tools across sensitive anatomical structures. In addition to offline quantitative techniques for evaluating performance at the conclusion of a procedure, delivering performance measures online as feedback during training can ultimately provide the potential for improvements in surgical outcomes. This thesis evaluates a set of performance metrics calculated from direct tool tip motions provided by a commercial endovascular surgical simulator in their utility as online and offline measures. These metrics are compared to standard performance measures implemented on the simulator and to a gold-standard measure of movement smoothness used in prior motion studies. An online performance evaluation scenario demonstrates the general effectiveness of these metrics for further use as online performance measures for evaluation and feedback.

Browsing by Author "O'Malley, Marcia K"

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