Browsing by Author "Dunkelberger, Nathan"

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    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.
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    Conveying language through haptics: a multi-sensory approach
    (ACM, 2018) Dunkelberger, Nathan; Sullivan, Jenny; Bradley, Joshua; Walling, Nickolas P.; Manickam, Indu; Dasarathy, Gautam; Israr, Ali; Lau, Frances W.Y.; Klumb, Keith; Knott, Brian; Abnousi, Freddy; Baraniuk, Richard; O'Malley, Marcia K.
    In our daily lives, we rely heavily on our visual and auditory channels to receive information from others. In the case of impairment, or when large amounts of information are already transmitted visually or aurally, alternative methods of communication are needed. A haptic language offers the potential to provide information to a user when visual and auditory channels are unavailable. Previously created haptic languages include deconstructing acoustic signals into features and displaying them through a haptic device, and haptic adaptations of Braille or Morse code; however, these approaches are unintuitive, slow at presenting language, or require a large surface area. We propose using a multi-sensory haptic device called MISSIVE, which can be worn on the upper arm and is capable of producing brief cues, sufficient in quantity to encode the full English phoneme set. We evaluated our approach by teaching subjects a subset of 23 phonemes, and demonstrated an 86% accuracy in a 50 word identification task after 100 minutes of training.
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    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.
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    Hybrid FES-exoskeleton control: Using MPC to distribute actuation for elbow and wrist movements
    (Frontiers Media S.A., 2023) Dunkelberger, Nathan; Berning, Jeffrey; Schearer, Eric M.; O'Malley, Marcia K.; Mechatronics and Haptics Interfaces Laboratory
    IntroductionIndividuals who have suffered a cervical spinal cord injury prioritize the recovery of upper limb function for completing activities of daily living. Hybrid FES-exoskeleton systems have the potential to assist this population by providing a portable, powered, and wearable device; however, realization of this combination of technologies has been challenging. In particular, it has been difficult to show generalizability across motions, and to define optimal distribution of actuation, given the complex nature of the combined dynamic system.MethodsIn this paper, we present a hybrid controller using a model predictive control (MPC) formulation that combines the actuation of both an exoskeleton and an FES system. The MPC cost function is designed to distribute actuation on a single degree of freedom to favor FES control effort, reducing exoskeleton power consumption, while ensuring smooth movements along different trajectories. Our controller was tested with nine able-bodied participants using FES surface stimulation paired with an upper limb powered exoskeleton. The hybrid controller was compared to an exoskeleton alone controller, and we measured trajectory error and torque while moving the participant through two elbow flexion/extension trajectories, and separately through two wrist flexion/extension trajectories.ResultsThe MPC-based hybrid controller showed a reduction in sum of squared torques by an average of 48.7 and 57.9% on the elbow flexion/extension and wrist flexion/extension joints respectively, with only small differences in tracking accuracy compared to the exoskeleton alone.DiscussionTo realize practical implementation of hybrid FES-exoskeleton systems, the control strategy requires translation to multi-DOF movements, achieving more consistent improvement across participants, and balancing control to more fully leverage the muscles' capabilities.