The Development of a Kinesthetic Feedback System for Lower-Limb Prosthetic Use

  • Author / Creator
    Keri, McNiel-Inyani
  • Limb amputation affects many individuals worldwide, with the majority of amputations occurring in the lower extremity. In addition to losing structure and motor function with amputation, the body loses important sensory organs and information required to optimize performance (e.g., ambulation). Specifically, the loss of proprioception (spatial awareness of limbs) and kinesthesia (sense of limb movement) has profound implications for individuals using lower-limb prostheses. This lack of sensory feedback may result in decreased balance, which may lead to falling, and a decreased quality of life. The kinesthetic illusion (KI), a phenomenon whereby mechanical vibration administered to the musculotendinous region of a limb may illicit a perception of limb movement, offers a method in which intuitive movement information might be relayed to prosthesis users. The body of work focusing on kinesthetic feedback attempts a somatotopic approach to restore kinesthetic sensations in individuals with transhumeral amputations that have undergone targeted reinnervation (TR); a surgical technique where the sensory and motor nerves formerly innervating amputated limbs are reinnervated to new muscle and skin sites. To date, no work has been published on restoring movement sensations for individuals with lower-limb amputations. The objectives of this thesis were to (1) perform an exploratory study to determine whether it is possible to provide kinesthetic feedback to lower-limb prosthesis users who have not undergone TR, using the KI; and (2) developing a low-cost wireless inertial measurement unit-based system (WIbS) which can track the movement of a single-axis prosthetic knee, to bridge the movement of a prosthesis to actuators responsible for administering the KI. Accomplishing the two objectives will then allow demonstration of the ability to close the sensory feedback loop for a participant with lower-limb amputation as a proof of concept. To accomplish the objectives, the following methods were implemented. The explorative study was achieved by using a vibration motor to identify sites on the residual limb which elicit strong and consistent movement percepts. Motion capture (mocap) and a 5-point Likert scale was used for quantifying both kinematics and the strengths of the experienced movement percepts respectively. To satisfy the second objective, a movement sensor comprised of a microcontroller, Bluetooth radio, inertial measurement unit, and battery with corresponding circuitry was developed. Computing the joint angle of a prosthetic knee was achieved using two movement sensors. This joint angle computation was validated through comparison with a commercial inertial measurement (cIMU) system and mocap using the root-mean-square error (RMSE) with two motion profiles (Gaussian and sinusoidal) and three velocities (60, 120, 180 degrees/second) chosen based on the properties of gait. Moreover, a benchtop system, comprised of two WIbS and a threshold-based controller, was used in a case study to test the developed system’s ability to elicit movement percepts. Through the exploratory study, 4 out of 9 participants spontaneously reported movement percepts about their phantom knee or ankle. Out of the 4, half the participants experienced movement percepts in the direction characteristic of the KI. The other half experienced a sensation like the patellar reflex (i.e., a singular outward jerk of the knee). The remaining participants experienced a variety of sensations related to stimulation of cutaneous receptors. Results for the developed movement sensor showed that, the sensor can track a gaussian motion profile with a RMSE less than 1 degree when compared to both the cIMU and mocap system at all tested velocities. For cyclic motion, the RMSE is within 2 (cIMU) and 8 degrees (mocap) at velocities up to 120 degrees/second, with greater error at faster velocities. These results suggest that, the developed sensor may be able to provide reliable movement detection during typical walking speeds for prosthesis users. Lastly, a participant with an above-knee lower-limb amputation that can experience the KI, as determined through the exploratory study, participated in a proof of concept demonstration. The benchtop system was successful in eliciting movement percepts on the participant by reliably detecting the movement of the single-axis robotic system and activating the vibration motor appropriately with no false triggers. Altogether, this work takes the first steps toward clinical translation of the KI for users of a lower-limb prosthesis. This approach has the potential to restore lost sensation and improve the quality of life for many prosthesis users.

  • Subjects / Keywords
  • Graduation date
    Spring 2019
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
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