Browsing by Author "Pehlivan, Ali Utku"

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    Current trends in robot-assisted upper-limb stroke rehabilitation: promoting patient engagement in therapy
    (Springer, 2014) Blank, Amy A.; French, James A.; Pehlivan, Ali Utku; O'Malley, Marcia K.
    Stroke is one of the leading causes of long-term disability today; therefore, many research efforts are focused on designing maximally effective and efficient treatment methods. In particular, robotic stroke rehabilitation has received significant attention for upper-limb therapy due to its ability to provide high-intensity repetitive movement therapy with less effort than would be required for traditional methods. Recent research has focused on increasing patient engagement in therapy, which has been shown to be important for inducing neural plasticity to facilitate recovery. Robotic therapy devices enable unique methods for promoting patient engagement by providing assistance only as needed and by detecting patient movement intent to drive to the device. Use of these methods has demonstrated improvements in functional outcomes, but careful comparisons between methods remain to be done. Future work should include controlled clinical trials and comparisons of effectiveness of different methods for patients with different abilities and needs in order to inform future development of patient-specific therapeutic protocols.
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    Design and Control of an Exoskeletal Rehabilitation Device for Stroke and Spinal Cord Injury Patients
    (2012) Pehlivan, Ali Utku; O'Malley, Marcia K.
    Robotic rehabilitation has gained significant traction in recent years, due to the clinical demonstration of its efficacy in restoring function for upper extremity movements and locomotor skills, demonstrated primarily in stroke populations. In this thesis, I present the design of MAHI Exo-II, a robotic exoskeleton for rehabilitation of the upper extremity after stroke, spinal cord injury, or other brain injuries. The five degree-of-freedom robot enables elbow flexion-extension, forearm pronation-supination, wrist flexion-extension, and radial-ulnar deviation. In the first part of this thesis, hardware design of the system is presented. The device offers several significant design improvements compared to its predecessor, MAHI Exo I. Specifically, issues with backlash and singularities in the wrist mechanism have been resolved, torque output has been increased in the forearm and elbow joints, a passive degree of freedom has been added to allow shoulder abduction thereby improving alignment especially for users who are wheelchairbound, and the hardware now enables simplified and fast swapping of treatment side. These modifications are discussed in the thesis, and results for the range of motion and maximum torque output capabilities of the new design and its predecessor are presented. In the second part of this thesis. I present the modification and implementation of a previously reported linear position and force control to MAHI Exo-II. The modified controller includes three different modes which are designed for use with patients with different levels of severity of injury. These modes either completely assist or resist the patient during the movement. Next, I present the implementation of a previously proposed nonlinear control algorithm in simulation for the forearm and wrist module of MAHI Exo-II. The proposed nonlinear controller aims to provoke a compliant characteristic to the device and assist the patient only as much as needed. Finally, the result of clinical testing of the feasibility of the mechanical design and the efficacy of the control modes with a 28-year-old female SCI patient are presented.
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    Design of a parallel-group balanced controlled trial to test the effects of assist-as-needed robotic therapy
    (IEEE, 2015) Sergi, Fabrizio; Pehlivan, Ali Utku; Fitle, Kyle; Nedley, Kathryn; Yozbatiran, Nuray; Francisco, Gerard E.; O’Malley, Marcia K.; Mechatronics and Haptic Interfaces Laboratory
    In this methods paper, we report on the design of a clinical study testing the efficacy of a newly developed control scheme for robot-aided rehabilitation. To measure the value added by a new control scheme, we pursued a parallel-group controlled clinical study design. This approach enables comparing the effects of the novel scheme, based on the Assist-As-Needed (AAN) paradigm, with those of a less sophisticated, fixed gain, Subject-Triggered (ST) controller. We describe the steps followed in the design of this clinical study, including details on the implementation of the two control modes, and a power analysis to determine the required number of subjects to test a clinically significant difference hypothesis. Finally, we present a method for sequential group assignment with co-variates minimization, capable of guaranteeing a desired level of balance of prognostic factors in the two study groups, a crucial requisite for small-scale clinical studies in rehabilitation. To the best of our knowledge, the study presented is the first one testing, in a controlled fashion, the differential effects of a specific control mode in upper extremity rehabilitation after incomplete spinal cord injury.
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    Effects of Assist-As-Needed Upper Extremity Robotic Therapy after Incomplete Spinal Cord Injury: A Parallel-Group Controlled Trial
    (Frontiers Media S.A., 2017) Frullo, John Michael; Elinger, Jared; Pehlivan, Ali Utku; Fitle, Kyle; Nedley, Kathryn; Francisco, Gerard E.; Sergi, Fabrizio; O’Malley, Marcia K.
    Background: Robotic rehabilitation of the upper limb following neurological injury has been supported through several large clinical studies for individuals with chronic stroke. The application of robotic rehabilitation to the treatment of other neurological injuries is less developed, despite indications that strategies successful for restoration of motor capability following stroke may benefit individuals with incomplete spinal cord injury (SCI) as well. Although recent studies suggest that robot-aided rehabilitation might be beneficial after incomplete SCI, it is still unclear what type of robot-aided intervention contributes to motor recovery. Methods: We developed a novel assist-as-needed (AAN) robotic controller to adjust challenge and robotic assistance continuously during rehabilitation therapy delivered via an upper extremity exoskeleton, the MAHI Exo-II, to train independent elbow and wrist joint movements. We further enrolled seventeen patients with incomplete spinal cord injury (AIS C and D levels) in a parallel-group balanced controlled trial to test the efficacy of the AAN controller, compared to a subject-triggered (ST) controller that does not adjust assistance or challenge levels continuously during therapy. The conducted study is a stage two, development-of-concept pilot study. Results: We validated the AAN controller in its capability of modulating assistance and challenge during therapy via analysis of longitudinal robotic metrics. For the selected primary outcome measure, the pre–post difference in ARAT score, no statistically significant change was measured in either group of subjects. Ancillary analysis of secondary outcome measures obtained via robotic testing indicates gradual improvement in movement quality during the therapy program in both groups, with the AAN controller affording greater increases in movement quality over the ST controller. Conclusion: The present study demonstrates feasibility of subject-adaptive robotic therapy after incomplete spinal cord injury, but does not demonstrate gains in arm function occurring as a result of the robot-assisted rehabilitation program, nor differential gains obtained as a result of the developed AAN controller. Further research is warranted to better quantify the recovery potential provided by AAN control strategies for robotic rehabilitation of the upper limb following incomplete SCI.
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    Maintaining subject engagement during robotic rehabilitation with a minimal assist-as-needed (mAAN) controller
    (IEEE, 2017) Pehlivan, Ali Utku; Losey, Dylan P.; Rose, Chad G.; O’Malley, Marcia K.
    One challenge of robotic rehabilitation interventions is devising ways to encourage and maintain high levels of subject involvement over long duration therapy sessions. Assist-as-needed controllers have been proposed which modulate robot intervention in movements based on measurements of subject involvement. This paper presents a minimal assist-as-needed controller, which modulates allowable error bounds and robot intervention based on sensorless force measurement accomplished through a nonlinear disturbance observer. While similar algorithms have been validated using healthy subjects, this paper presents a validation of the proposed mAAN control algorithm's ability to encourage user involvement with an impaired individual. User involvement is inferred from muscle activation, measured via surface electromyography (EMG). Experimental validation shows increased EMG muscle activation when using the proposed mAAN algorithm compared to non-adaptive algorithms.
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    Robot-Assisted Training of Arm and Hand Movement Shows Functional Improvements for Incomplete Cervical Spinal Cord Injury
    (Wolters Kluwer, 2017) Francisco, Gerard E.; Yozbatiran, Nuray; Berliner, Jeffrey; O'Malley, Marcia K.; Pehlivan, Ali Utku; Kadivar, Zahra; Fitle, Kyle; Boake, Corwin
    Objective The aim of the study was to demonstrate the feasibility, tolerability, and effectiveness of robotic-assisted arm training in incomplete chronic tetraplegia. Design Pretest/posttest/follow-up was conducted. Ten individuals with chronic cervical spinal cord injury were enrolled. Participants performed single degree-of-freedom exercise of upper limbs at an intensity of 3-hr per session for 3 times a week for 4 wks with MAHI Exo-II. Arm and hand function tests (Jebsen-Taylor Hand Function Test, Action Research Arm Test), strength of upper limb (upper limb motor score, grip, and pinch strength), and independence in daily living activities (Spinal Cord Independence Measure II) were performed at baseline, end of training, and 6 mos later. Results After 12 sessions of training, improvements in arm and hand functions were observed. Jebsen-Taylor Hand Function Test (0.14[0.04]–0.21[0.07] items/sec, P = 0.04), Action Research Arm Test (30.7[3.8]–34.3[4], P = 0.02), American Spinal Injury Association upper limb motor score (31.5[2.3]–34[2.3], P = 0.04) grip (9.7[3.8]–12[4.3] lb, P = 0.02), and pinch strength (4.5[1.1]–5.7[1.2] lb, P = 0.01) resulted in significant increases. Some gains were maintained at 6 mos. No change in Spinal Cord Independence Measure II scores and no adverse events were observed. Conclusions Results from this pilot study suggest that repetitive training of arm movements with MAHI Exo-II exoskeleton is safe and has potential to be an adjunct treatment modality in rehabilitation of persons with spinal cord injury with mild to moderate impaired arm functions.
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    Subject Adaptive Control Paradigms for Robotic Rehabilitation
    (2016-04-26) Pehlivan, Ali Utku; O'Malley, Marcia K
    As the majority of the activities of daily living involve distal upper extremity movement, eff ective rehabilitation of the upper limbs, especially the distal joints, is crucial. Due to their inherent capabilities to deliver intensive and repetitive therapy, robotic devices are increasingly being used for the rehabilitation of neurologically impaired individuals. However, not every robotic device or therapy protocol has been shown to promote plasticity-mediated recovery. It is necessary that the robotic therapy must be capable of engaging the participant. Furthermore, the mechanical design of the robotic device must exhibit specifi c properties, such as low apparent inertia and friction, isotropic dynamic characteristics, and minimal backlash, to support sophisticated interaction modes. In this thesis a subject adaptive controller, capable of adaptively estimating position-dependent subject input and providing only the required amount of assistance is presented. This controller aims to maximize the participants' engagement in their therapy. Features of the controller were validated via simulations and experiments, and clinical validation was conducted with an elbow-forearm-wrist exoskeleton, the MAHI Exo-II. Results highlighted limitations in both the hardware's workspace and in the controller's performance. To address this limitations a novel wrist-forearm exoskeleton, the RiceWrsit-S, is proposed and an improved minimally assistive (mAAN) controller is presented. The controller is capable of estimating subject input as a function of time, hence it can estimate subject input regardless of position dependency, as opposed to the subject adaptive controller proposed in the rst part of the thesis. Novel features of the controller algorithm for maintaining subject engagement via performance based challenge modulation while still satisfying ultimately bounded error performance are presented. The mAAN controller and consistency of the accompanying algorithms are demonstrated experimentally with healthy subjects and with one subject with incomplete spinal cord injury in the RiceWrist-S. The proposed controllers and the novel exoskeletal device provide a means for a more eff ective robot-aided rehabilitation of neurologically impaired individuals.