Browsing by Author "Pezent, Evan"

Now showing 1 - 5 of 5
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    Assessing Wrist Movement With Robotic Devices
    (IEEE, 2018) Rose, Chad G.; Pezent, Evan; Kann, Claudia K.; Deshpande, Ashish D.; O'Malley, Marcia K.
    Robotic devices have been proposed to meet the rising need for high intensity, long duration, and goal-oriented therapy required to regain motor function after neurological injury. Complementing this application, exoskeletons can augment traditional clinical assessments through precise, repeatable measurements of joint angles and movement quality. These measures assume that exoskeletons are making accurate joint measurements with a negligible effect on movement. For the coupled and coordinated joints of the wrist and hand, the validity of these two assumptions cannot be established by characterizing the device in isolation. To examine these assumptions, we conducted three user-in-the-loop experiments with able-bodied participants. First, we compared robotic measurements to an accepted modality to determine the validity of joint- and trajectory-level measurements. Then, we compared those movements to movements without the device to investigate the effects of device dynamic properties on wrist movement characteristics. Last, we investigated the effect of the device on coordination with a redundant, coordinated pointing task with the wrist and hand. For all experiments, smoothness characteristics were preserved in the robotic kinematic measurement and only marginally impacted by robot dynamics, validating the exoskeletons for use as assessment devices. Stemming from these results, we propose design guidelines for exoskeletal assessment devices.
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    Design and characterization of the OpenWrist: A robotic wrist exoskeleton for coordinated hand-wrist rehabilitation
    (IEEE, 2017) Pezent, Evan; Rose, Chad G.; Deshpande, Ashish D.; 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 paper 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 device are quantified experimentally in terms of functional workspace and dynamic properties. Specifically, the device possesses favorable performance in terms of range of motion, torque output, friction, and closed-loop position bandwidth when compared with existing devices. The presented wrist module's performance and operational considerations support its use in a wide range of future clinical investigations.
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    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.
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    Referred Haptic Feedback for Virtual Hand Interactions Through a Bracelet Interface
    (2021-03-11) Pezent, Evan; O'Malley, Marcia K
    A revolution in mobile interfaces is unfolding, as researchers and large corporations race toward all-day wearable technology for virtual and augmented reality. In a future where interacting with digital entities and objects is a facet of everyday life, an important aspect emerges: our ability to touch and feel objects that do not physically exist. Tactile feedback for virtual interaction is currently limited to either simple handheld controllers or obtrusive wearable devices for the hand, both unsuited to all-day use. This thesis presents an alternate approach: referred haptic feedback through bracelet interfaces. The design of a compact yet robust multimodal haptic bracelet is presented, along with novel control solutions for wrist squeeze force and high density vibrotactile arrays. The haptic rendering capabilities of the device are experimentally characterized and evaluated through psychophysical studies. Leveraging the multisensory combination of wrist squeeze and vibration with visual illusions, we explore the potential of providing substitutive feedback for interaction forces that would otherwise occur at the hands and fingertips. Findings from two human subject studies suggest that referred haptic feedback to the wrist provides more than just a metaphor for interaction forces, and instead invokes genuine perceptions of object stiffness.
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    The effect of robot dynamics on smoothness during wrist pointing
    (IEEE, 2017) Erwin, Andrew; Pezent, Evan; Bradley, Joshua; O’Malley, Marcia K.
    The improvement of movement smoothness over the course of therapy is one of the positive outcomes observed during robotic rehabilitation. Although movements are generally robust to disturbances, certain perturbations might disrupt an individual's ability to produce these smooth movements. In this paper, we explore how a rehabilitation robot's inherent dynamics impact movement smoothness during pointing tasks. Able-bodied participants made wrist pointing movements under four different operating conditions. Despite the relative transparency of the device, inherent dynamic characteristics negatively impacted movement smoothness. Active compensation for Coulomb friction effects failed to mitigate the degradation in smoothness. Assessment of movements that involved coupled motions of the robot's joints reduced the bias seen in single degree of freedom movements. When using robotic devices for assessment of movement quality, the impact of the inherent dynamics must be considered.