The Experts below are selected from a list of 2331 Experts worldwide ranked by ideXlab platform

Alena M Grabowski - One of the best experts on this subject based on the ideXlab platform.

  • Use of a powered ankle-Foot Prosthesis reduces the metabolic cost of uphill walking and improves leg work symmetry in people with transtibial amputations.
    Journal of the Royal Society Interface, 2018
    Co-Authors: Jana R. Montgomery, Alena M Grabowski
    Abstract:

    People with transtibial amputations (TTAs) who use a powered ankle-Foot Prosthesis have equivalent metabolic costs and step-to-step transition work for level-ground walking over a range of speeds compared to non-amputees. The effects of using a powered compared to passive-elastic Prosthesis for sloped walking are unknown. We sought to understand how the use of passive-elastic compared to powered ankle-Foot prostheses affect metabolic cost and step-to-step transition work during sloped walking. Ten people (six M, four F) with TTAs walked 1.25 m s-1 at 0°, ±3°, ±6° and ±9° using their own passive-elastic Prosthesis and the BiOM powered ankle-Foot Prosthesis, while we measured metabolic rates, kinematics and kinetics. We calculated net metabolic power, individual leg step-to-step transition work and individual leg net work symmetry. The net metabolic power was 5% lower during walking on +3° and +6° uphill slopes when subjects used the BiOM compared to their passive-elastic Prosthesis (p 0.05), but did improve individual leg net work symmetry on +6° and +9° uphill slopes (p < 0.01). People with TTAs who use a powered ankle-Foot Prosthesis have the potential to reduce metabolic costs and increase symmetry during walking on uphill slopes.

  • Individual Leg and Joint Work during Sloped Walking for People with a Transtibial Amputation Using Passive and Powered Prostheses
    Frontiers in Robotics and AI, 2017
    Co-Authors: Jana R. Jeffers, Alena M Grabowski
    Abstract:

    People with a transtibial amputation using passive-elastic prostheses exhibit reduced prosthetic ankle power and push-off work compared to non-amputees and compensate by increasing their affected leg (AL) hip joint work and unaffected leg (UL) ankle, knee, and hip joint and leg work during level-ground walking. Use of a powered ankle-Foot Prosthesis normalizes step-to-step transition work during level-ground walking over a range of speeds for people with a transtibial amputation, but the effects on joint work during level-ground, uphill and downhill walking have not been assessed. We investigated how use of passive-elastic and powered ankle-Foot prostheses affect leg joint biomechanics during level-ground and sloped walking. 10 people with a unilateral transtibial amputation walked at 1.25 m/s on a dual-belt force-measuring treadmill at 0°, ±3°, ±6°, and ±9° using their own passive-elastic and a powered Prosthesis (BiOM T2, BionX Medical Technologies, Inc. Bedford, MA, USA) while we measured kinematic and kinetic data. We calculated AL and UL prosthetic, ankle, knee, hip, and individual leg positive, negative, and net work. Use of a powered compared to passive-elastic ankle-Foot Prosthesis resulted in greater AL prosthetic and individual leg net work on uphill and downhill slopes. Over a stride, AL prosthetic positive work was 23-30% greater (p

  • Does Use of a Powered Ankle-Foot Prosthesis Restore Whole-body Angular Momentum During Walking at Different Speeds?
    Clinical Orthopaedics and Related Research®, 2014
    Co-Authors: Susan D’andrea, Natalie Wilhelm, Anne K. Silverman, Alena M Grabowski
    Abstract:

    Background Whole-body angular momentum (H) influences fall risk, is tightly regulated during walking, and is primarily controlled by muscle force generation. People with transtibial amputations using passive-elastic prostheses typically have greater H compared with nonamputees. Questions/purposes (1) Do people with unilateral transtibial amputations using passive-elastic prostheses have greater sagittal and frontal plane H ranges of motion during walking compared with nonamputees and compared with using powered prostheses? (2) Does use of powered ankle-Foot prostheses result in equivalent H ranges in all planes of motion compared with nonamputees during walking as a result of normative prosthetic ankle power generation? Methods Eight patients with a unilateral transtibial amputation and eight nonamputees walked 0.75, 1.00, 1.25, 1.50, and 1.75 m/s while we measured kinematics and ground reaction forces. We calculated H for participants using their passive-elastic Prosthesis and a powered ankle-Foot Prosthesis and for nonamputees at each speed. Results Patients using passive-elastic prostheses had 32% to 59% greater sagittal H ranges during the affected leg stance phase compared with nonamputees at 1.00 to 1.75 m/s (p 

  • Effects of a powered ankle-Foot Prosthesis on kinetic loading of the unaffected leg during level-ground walking
    Journal of NeuroEngineering and Rehabilitation, 2013
    Co-Authors: Alena M Grabowski, Susan D’andrea
    Abstract:

    Background People with a lower-extremity amputation that use conventional passive-elastic ankle-Foot prostheses encounter a series of stress-related challenges during walking such as greater forces on their unaffected leg, and may thus be predisposed to secondary musculoskeletal injuries such as chronic joint disorders. Specifically, people with a unilateral transtibial amputation have an increased susceptibility to knee osteoarthritis, especially in their unaffected leg. Previous studies have hypothesized that the development of this disorder is linked to the abnormally high peak knee external adduction moments encountered during walking. An ankle-Foot Prosthesis that supplies biomimetic power could potentially mitigate the forces and knee adduction moments applied to the unaffected leg of a person with a transtibial amputation, which could, in turn, reduce the risk of knee osteoarthritis. We hypothesized that compared to using a passive-elastic Prosthesis, people with a transtibial amputation using a powered ankle-Foot Prosthesis would have lower peak resultant ground reaction forces, peak external knee adduction moments, and corresponding loading rates applied to their unaffected leg during walking over a wide range of speeds. Methods We analyzed ground reaction forces and knee joint kinetics of the unaffected leg of seven participants with a unilateral transtibial amputation and seven age-, height- and weight-matched non-amputees during level-ground walking at 0.75, 1.00, 1.25, 1.50, and 1.75 m/s. Subjects with an amputation walked while using their own passive-elastic Prosthesis and a powered ankle-Foot Prosthesis capable of providing net positive mechanical work and powered ankle plantar flexion during late stance. Results Use of the powered Prosthesis significantly decreased unaffected leg peak resultant forces by 2-11% at 0.75-1.50 m/s, and first peak knee external adduction moments by 21 and 12% at 1.50 and 1.75 m/s, respectively. Loading rates were not significantly different between prosthetic feet. Conclusions Use of a biomimetic powered ankle-Foot Prosthesis decreased peak resultant force at slow and moderate speeds and knee external adduction moment at moderate and fast speeds on the unaffected leg of people with a transtibial amputation during level-ground walking. Thus, use of an ankle-Foot Prosthesis that provides net positive mechanical work could reduce the risk of comorbidities such as knee osteoarthritis.

  • effects of a powered ankle Foot Prosthesis on kinetic loading of the unaffected leg during level ground walking
    Journal of Neuroengineering and Rehabilitation, 2013
    Co-Authors: Alena M Grabowski, Susan E Dandrea
    Abstract:

    People with a lower-extremity amputation that use conventional passive-elastic ankle-Foot prostheses encounter a series of stress-related challenges during walking such as greater forces on their unaffected leg, and may thus be predisposed to secondary musculoskeletal injuries such as chronic joint disorders. Specifically, people with a unilateral transtibial amputation have an increased susceptibility to knee osteoarthritis, especially in their unaffected leg. Previous studies have hypothesized that the development of this disorder is linked to the abnormally high peak knee external adduction moments encountered during walking. An ankle-Foot Prosthesis that supplies biomimetic power could potentially mitigate the forces and knee adduction moments applied to the unaffected leg of a person with a transtibial amputation, which could, in turn, reduce the risk of knee osteoarthritis. We hypothesized that compared to using a passive-elastic Prosthesis, people with a transtibial amputation using a powered ankle-Foot Prosthesis would have lower peak resultant ground reaction forces, peak external knee adduction moments, and corresponding loading rates applied to their unaffected leg during walking over a wide range of speeds. We analyzed ground reaction forces and knee joint kinetics of the unaffected leg of seven participants with a unilateral transtibial amputation and seven age-, height- and weight-matched non-amputees during level-ground walking at 0.75, 1.00, 1.25, 1.50, and 1.75 m/s. Subjects with an amputation walked while using their own passive-elastic Prosthesis and a powered ankle-Foot Prosthesis capable of providing net positive mechanical work and powered ankle plantar flexion during late stance. Use of the powered Prosthesis significantly decreased unaffected leg peak resultant forces by 2-11% at 0.75-1.50 m/s, and first peak knee external adduction moments by 21 and 12% at 1.50 and 1.75 m/s, respectively. Loading rates were not significantly different between prosthetic feet. Use of a biomimetic powered ankle-Foot Prosthesis decreased peak resultant force at slow and moderate speeds and knee external adduction moment at moderate and fast speeds on the unaffected leg of people with a transtibial amputation during level-ground walking. Thus, use of an ankle-Foot Prosthesis that provides net positive mechanical work could reduce the risk of comorbidities such as knee osteoarthritis.

Steven H. Collins - One of the best experts on this subject based on the ideXlab platform.

  • teleoperation of an ankle Foot Prosthesis with a wrist exoskeleton
    IEEE Transactions on Biomedical Engineering, 2020
    Co-Authors: Cara G Welker, Vincent L. Chiu, Alexandra S. Voloshina, Steven H. Collins, Allison M Okamura
    Abstract:

    Objective: We aimed to develop a system for people with amputation that non-invasively restores missing control and sensory information for an ankle-Foot Prosthesis. Methods: In our approach, a wrist exoskeleton allows people with amputation to control and receive feedback from their prosthetic ankle via teleoperation. We implemented two control schemes: position control with haptic feedback of ankle torque at the wrist; and torque control that allows the user to modify a baseline torque profile by moving their wrist against a virtual spring. We measured tracking error and frequency response for the ankle-Foot Prosthesis and the wrist exoskeleton. To demonstrate feasibility and evaluate system performance, we conducted an experiment in which one participant with a transtibial amputation tracked desired wrist trajectories during walking, while we measured wrist and ankle response. Results: Benchtop testing demonstrated that for relevant walking frequencies, system error was below human perceptual error. During the walking experiment, the participant was able to voluntarily follow different wrist trajectories with an average RMS error of 1.55° after training. The ankle was also able to track desired trajectories below human perceptual error for both position control (RMSE = 0.8°) and torque control (RMSE = 8.4%). Conclusion: We present a system that allows a user with amputation to control an ankle-Foot Prosthesis and receive feedback about its state using a wrist exoskeleton, with accuracy comparable to biological neuromotor control. Significance: This bilateral teleoperation system enables novel Prosthesis control and feedback strategies that could improve Prosthesis control and aid motor learning.

  • Shortcomings of human-in-the-loop optimization for an ankle-Foot Prosthesis: a case series
    2020
    Co-Authors: Cara G Welker, Vincent L. Chiu, Alexandra S. Voloshina, Steven H. Collins
    Abstract:

    Human-in-the-loop optimization allows for individualized device control based on measured human performance. This technique has been used to produce large reductions in energy expenditure during walking with exoskeletons but has not yet been applied to prosthetic devices. In this series of case studies, we applied human-in-the-loop optimization to the control of an active ankle-Foot Prosthesis used by participants with unilateral transtibial amputation. We optimized the parameters of five control architectures that captured aspects of successful exoskeletons and commercial prostheses, but none resulted in significantly lower metabolic rate than generic control. In one control architecture, we increased the exposure time per condition by a factor of five, but the optimized controller still resulted in higher metabolic rate. Finally, we optimized for self-reported comfort instead of metabolic rate, but the resulting controller was not preferred. There are several reasons why human-in-the-loop optimization may have failed for people with amputation. Control architecture is an unlikely cause given the variety of controllers tested. The lack of effect likely relates to adaptation protocol or differences in the learning mechanisms or objectives of people with amputation. Future work should investigate these causes to determine whether human-in-the-loop optimization for prostheses could be successful.

  • teleoperation of an ankle Foot Prosthesis with a wrist exoskeleton
    bioRxiv, 2020
    Co-Authors: Cara G Welker, Vincent L. Chiu, Alexandra S. Voloshina, Steven H. Collins, Allison M Okamura
    Abstract:

    ObjectiveWe aimed to develop a system for people with amputation that non-invasively restores missing control and sensory information for an ankle-Foot Prosthesis. Methods: In our approach, a wrist exoskeleton allows people with amputation to control and receive feedback from their prosthetic ankle via teleoperation. We implemented a position control scheme and torque control scheme, both of which provide haptic feedback at the wrist. We also investigated two low-level position controllers, and measured tracking error and frequency response for each system component. To demonstrate feasibility and evaluate system performance, we conducted an experiment in which one participant with a transtibial amputation tracked desired wrist trajectories during walking, while we measured wrist and ankle response. Results: Benchtop testing demonstrated that for relevant walking frequencies, system error was below human perception error. During the walking experiment, the participant was able to voluntarily follow different wrist trajectories with an average RMS error of 1.55{degrees} after training. A position control scheme using feedforward control with iterative learning and haptic feedback at the wrist resulted in the most accurate ankle tracking (RMS error = 0.8{degrees}). The torque control scheme achieved an ankle torque RMS error of 8.3 N m. Conclusion: We present a system that allows a user with amputation to control an ankle-Foot Prosthesis and receive feedback about its state using a wrist exoskeleton with accuracy comparable to biological neuromotor control. Significance: This bilateral teleoperation system enables novel Prosthesis control and feedback strategies that could result in improved Prosthesis control and aid motor learning.

  • An Ankle-Foot Prosthesis Emulator Capable of Modulating Center of Pressure
    IEEE transactions on bio-medical engineering, 2019
    Co-Authors: Vincent L. Chiu, Alexandra S. Voloshina, Steven H. Collins
    Abstract:

    Objective: Several powered ankle-Foot prostheses have demonstrated moderate reductions in energy expenditure by restoring pushoff work in late stance or by assisting with balance. However, it is possible that center of pressure trajectory modulation could provide even further improvements in user performance. Here, we describe the design of a Prosthesis emulator with two torque-controlled foreFoot digits and a torque-controlled heel digit. Independent actuation of these three digits can modulate the origin and magnitude of the total ground reaction force vector. Methods: The emulator was designed to be compact and lightweight while exceeding the range of motion and torque requirements of the biological ankle during walking. We ran a series of tests to determine torque-measurement accuracy, closed-loop torque control bandwidth, torque-tracking error, and center of pressure control accuracy. Results: Each of the three digits demonstrated less than 2 Nm of RMS torque measurement error, a 90% rise time of 19 ms, and a bandwidth of 33 Hz. The untethered end-effector has a mass of 1.2 kg. During walking trials, the emulator demonstrated less than 2 Nm of RMS torque-tracking error and was able to maintain full digit ground contact for 56% of stance. In fixed, standing, and walking conditions, the emulator was able to control center of pressure along a prescribed pattern with RMS errors of about 10% the length of the pattern. Conclusion: The proposed emulator system meets all design criteria and can effectively modulate center of pressure and ground reaction force magnitude. Significance: This emulator system will enable rapid development of controllers designed to enhance user balance and reduce user energy expenditure. Experiments conducted using this emulator could identify beneficial control behaviors that can be implemented on autonomous devices, thus improving mobility and quality of life of individuals with amputation.

  • an ankle Foot Prosthesis emulator with control of plantarflexion and inversion eversion torque
    IEEE Transactions on Robotics, 2018
    Co-Authors: Myunghee Kim, Tianjian Chen, Tianyao Chen, Steven H. Collins
    Abstract:

    Ankle inversion–eversion compliance is an important feature of conventional prosthetic feet, and control of inversion, or roll, in active prostheses could improve balance for people with amputation. We designed a tethered ankle–Foot Prosthesis with two independently actuated toes that are coordinated to provide plantar-flexion and inversion–eversion torques. A Bowden cable tether provides series elasticity. The Prosthesis is simple and lightweight, with a mass of 0.72 kg. Strain gauges on the toes measure torque with less than 1% root mean squared (RMS) error. Benchtop tests demonstrated a step response rise time of less than 33 ms, peak torques of 250 N $\cdot$ m in plantarflexion and $\pm$ 30 N $\cdot$ m in inversion–eversion, and peak power above 3 kW. The phase-limited closed-loop torque bandwidth is 20 Hz with a chirp from 10 to 90 N $\cdot$ m in plantarflexion, and 24 Hz with a chirp from $-$ 20 to 20 N $\cdot$ m in inversion. The system has low sensitivity to toe position disturbances at frequencies of up to 18 Hz. Walking trials with an amputee subject demonstrated RMS torque tracking errors of less than 5.1 N $\cdot$ m in plantarflexion and less than 1.5 N $\cdot$ m in inversion–eversion. These properties make the platform suitable for testing inversion-related Prosthesis features and controllers in experiments with humans.

Hugh M Herr - One of the best experts on this subject based on the ideXlab platform.

  • An Ankle-Foot Prosthesis for Rock Climbing Augmentation
    IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society, 2021
    Co-Authors: Emily Rogers, Matthew Eli Carney, Seong Ho Yeon, Tyler R. Clites, Dana Solav, Hugh M Herr
    Abstract:

    This research presents the design and preliminary evaluation of an electromyographically (EMG) controlled 2-degree-of-freedom (DOF) ankle-Foot Prosthesis designed to enhance rock climbing ability in persons with transtibial amputation. The Prosthesis comprises motorized ankle and subtalar joints, and is capable of emulating some key biomechanical behaviors exhibited by the ankle-Foot complex during rock climbing maneuvers. The free space motion of the device is volitionally controlled via input from EMG surface electrodes embedded in a custom silicone liner worn on the residual limb. The device range of motion is 0.29 radians of each dorsiflexion and plantar flexion, and 0.39 radians each of inversion and eversion. Preliminary evaluation of the device was conducted, validating the system mass of 1292 grams, build height of 250 mm, joint velocity of 2.18 radians/second, settling time of 120 milliseconds, and steady state error of 0.008 radians. Clinical evaluation of the device was performed during a preliminary study with one subject with transtibial amputation. Joint angles of the ankle-Foot, knee, and hip were measured during rock climbing with the robotic Prosthesis and with a traditional passive Prosthesis. We found that the robotic Prosthesis increases the range of achieved ankle and subtalar positions compared to a standard passive Prosthesis. In addition, maximum knee flexion and hip flexion angles are decreased while climbing with the robotic Prosthesis. These results suggest that a lightweight, actuated, 2-DOF EMG-controlled robotic ankle-Foot Prosthesis can improve ankle and subtalar range of motion and climbing biomechanical function.

  • development and evaluation of a powered artificial gastrocnemius for transtibial amputee gait
    Journal of Robotics, 2018
    Co-Authors: Michael Frederick Eilenberg, Jiunyih Kuan, Hugh M Herr
    Abstract:

    Existing robotic transtibial prostheses provide only ankle joint actuation and do not restore biarticular function of the gastrocnemius muscle. This paper presents the first powered biarticular transtibial Prosthesis, which is a combination of a commercial powered ankle-Foot Prosthesis and a motorized robotic knee orthosis. The orthosis is controlled to emulate the human gastrocnemius based on neuromuscular models of matched nonamputees. Together with the ankle-Foot Prosthesis, the devices provide biarticular actuation. We evaluate differences between this biarticular condition and a monoarticular condition with the orthosis behaving as a free-joint. Six participants with transtibial amputation walk with the Prosthesis on a treadmill while motion, force, and metabolic data are collected and analyzed for differences between conditions. The biarticular Prosthesis reduces affected-side biological knee flexion moment impulse and hip positive work during late-stance knee flexion, compared to the monoarticular condition. The data do not support our hypothesis that metabolism decreases for all participants, but some participants demonstrate large metabolic reductions with the biarticular condition. These preliminary results suggest that a powered artificial gastrocnemius may be capable of providing large metabolic reductions compared to a monoarticular Prosthesis, but further study is warranted to determine an appropriate controller for achieving more consistent metabolic benefits.

  • ICORR - Effects of a powered ankle-Foot Prosthesis on kinetic loading of the contralateral limb: A case series
    IEEE ... International Conference on Rehabilitation Robotics : [proceedings], 2013
    Co-Authors: David Hill, Hugh M Herr
    Abstract:

    Lower-extremity amputees encounter a series of stress-related challenges. Among them is an increased risk of chronic joint disorders. For unilateral, transtibial amputees, we hypothesize that increasing the power output of the trailing, ankle-Foot Prosthesis during powered plantar flexion could mitigate kinetic loading applied to the leading, contralateral leg during walking. Here, we present a case series that analyzes kinetic factors of unilateral, transtibial amputee gait and forms a comparison between two types of ankle prostheses with varying power outputs. The factors examined here are impact resultant force, peak Foot pressure at heel-strike, step-to-step transition work, and knee external adduction moment. The two prostheses are the amputee participant's daily-use passive ankle-Foot Prosthesis and the BiOM powered ankle-Foot Prosthesis capable of biologically accurate powered plantar flexion during late stance. In a preliminary study on two transtibial amputees walking over level terrain at a controlled speed (1.25 m/s), we observed average reductions of 8% in peak impact resultant force, 18% in impact resultant force loading rate, 8% in peak heel-strike Foot pressure, and 15% in the 1st peak knee external adduction moment when the powered ankle-Foot Prosthesis was compared to the conventional passive Prosthesis. Overall, our preliminary results suggest that more biomimetic prosthetic ankle-Foot push-off during late stance may limit leading-leg musculoskeletal stress in walking.

  • powered ankle Foot Prosthesis improves walking metabolic economy
    IEEE Transactions on Robotics, 2009
    Co-Authors: Jeff Anthony Weber, Hugh M Herr
    Abstract:

    At moderate to fast walking speeds, the human ankle provides net positive work at high-mechanical-power output to propel the body upward and forward during the stance period. On the contrary, conventional ankle-Foot prostheses exhibit a passive-elastic response during stance, and consequently, cannot provide net work. Clinical studies indicate that transtibial amputees using conventional prostheses have higher gait metabolic rates than normal. Researchers believe that the main cause for these higher rates is due to the inability of conventional prostheses to provide sufficient positive power at terminal stance in the trailing leg to limit heel strike losses of the adjacent leading leg. In this investigation, we evaluate the hypothesis that a powered ankle-Foot Prosthesis, capable of providing human-like ankle work and power during stance, can decrease the metabolic cost of transport (COT) compared to a conventional passive-elastic Prosthesis. To test the hypothesis, a powered Prosthesis is built that comprises a unidirectional spring, configured in parallel with a force-controllable actuator with series elasticity. The Prosthesis is shown to deliver the high mechanical power and net positive work observed in normal human walking. The rate of oxygen consumption and carbon dioxide production is measured as a determinant of metabolic rate on three unilateral transtibial amputees walking at self-selected speeds. We find that the powered Prosthesis decreases the amputee's metabolic COT on average by 14% compared to the conventional passive-elastic prostheses evaluated (Flex-Foot Ceterusreg and Freedom Innovations Sierra), even though the powered system is over twofold heavier than the conventional devices. These results highlight the clinical importance of prosthetic interventions that closely mimic the mass distribution, kinetics, and kinematics of the missing limb.

  • 2008 special issue powered ankle Foot Prosthesis to assist level ground and stair descent gaits
    Neural Networks, 2008
    Co-Authors: Max Berniker, Hugh M Herr
    Abstract:

    The human ankle varies impedance and delivers net positive work during the stance period of walking. In contrast, commercially available ankle-Foot prostheses are passive during stance, causing many clinical problems for transtibial amputees, including non-symmetric gait patterns, higher gait metabolism, and poorer shock absorption. In this investigation, we develop and evaluate a myoelectric-driven, finite state controller for a powered ankle-Foot Prosthesis that modulates both impedance and power output during stance. The system employs both sensory inputs measured local to the external Prosthesis, and myoelectric inputs measured from residual limb muscles. Using local prosthetic sensing, we first develop two finite state controllers to produce biomimetic movement patterns for level-ground and stair-descent gaits. We then employ myoelectric signals as control commands to manage the transition between these finite state controllers. To transition from level-ground to stairs, the amputee flexes the gastrocnemius muscle, triggering the prosthetic ankle to plantar flex at terminal swing, and initiating the stair-descent state machine algorithm. To transition back to level-ground walking, the amputee flexes the tibialis anterior muscle, triggering the ankle to remain dorsiflexed at terminal swing, and initiating the level-ground state machine algorithm. As a preliminary evaluation of clinical efficacy, we test the device on a transtibial amputee with both the proposed controller and a conventional passive-elastic control. We find that the amputee can robustly transition between the finite state controllers through direct muscle activation, allowing rapid transitioning from level-ground to stair walking patterns. Additionally, we find that the proposed finite state controllers result in a more biomimetic ankle response, producing net propulsive work during level-ground walking and greater shock absorption during stair descent. The results of this study highlight the potential of prosthetic leg controllers that exploit neural signals to trigger terrain-appropriate, local prosthetic leg behaviors.

Elliot J. Rouse - One of the best experts on this subject based on the ideXlab platform.

  • Development of a Passive Ankle Foot Prosthesis with Manually Adjustable Ankle Stiffness
    2019
    Co-Authors: Tafadzwa Dongo, Benard W. Ikua, Daniel Nyamongo Sagwe, Elliot J. Rouse
    Abstract:

    Major advancements have been made in the field of prosthetics, but devices remain largely out of reach for the amputee population domiciled in the developing nations, which makes up 80% of the entire amputee population of the world. The amputees are left to contend with low function prosthetics that do not mimic the behavior of the natural lost limb, with the long-term use of such devices leading to physical injury to the user. This work was aimed at developing a low-cost ankle-Foot Prosthesis that affords the user the opportunity to manually alter the stiffness of the ankle, as well storing energy in a foreFoot section to aid push-off in late stance. In this paper, the design and results of structural analysis performed on critical parts of the Prosthesis are presented, as well as the future direction of the work.

  • The VSPA Foot: A Quasi-Passive Ankle-Foot Prosthesis With Continuously Variable Stiffness
    IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society, 2017
    Co-Authors: Max K Shepherd, Elliot J. Rouse
    Abstract:

    Most commercially available prosthetic feet do not exhibit a biomimetic torque-angle relationship, and are unable to modulate their mechanics to assist with other mobility tasks, such as stairs and ramps. In this paper, we present a quasi-passive ankle-Foot Prosthesis with a customizable torque-angle curve and an ability to quickly modulate ankle stiffness between tasks. The customizable torque-angle curve is obtained with a cam-based transmission and a fiberglass leaf spring. To achieve variable stiffness, the leaf spring’s support conditions can be actively modulated by a small motor, shifting the torque-angle curve to be more or less stiff. We introduce the design, characterize the available torque-angle curves, and present kinematics from a transtibial amputee subject performing level-ground walking, stair ascent/descent, and ramp ascent/descent. The subject exhibited a more normative range of motion on stairs and ramps at lower stiffness levels, and preferred different stiffness levels for each task. Paired with an appropriate intent recognition system, our novel ankle Prosthesis could improve gait biomechanics during walking and many other mobility tasks.

  • design of a quasi passive ankle Foot Prosthesis with biomimetic variable stiffness
    International Conference on Robotics and Automation, 2017
    Co-Authors: Max K Shepherd, Elliot J. Rouse
    Abstract:

    Modern passive ankle-Foot prostheses do not exhibit appropriate biomechanics during walking, and are unable to adjust their mechanics for other mobility tasks, such as stair traversal or quiet standing. In this paper, we introduce a quasi-passive ankle-Foot Prosthesis that addresses these challenges; the ankle has a customizable, nonlinear torque-angle curve, and the overall stiffness can be varied continuously between mobility tasks. The variation in mechanics is accomplished by integrating two mechanisms: a cam-based transmission, in which rotation of the ankle joint causes deflection of a leaf spring, and an active sliding support beneath the leaf spring, which can modify the spring's effective stiffness. In addition to introducing the design, we present the mathematics to calculate the cam profile for any arbitrary torque-angle curve, and experimentally characterize the system for a desired curve based on human walking. Lastly, we demonstrate the full range of stiffness levels available and stiffness transition time.

  • ICRA - Design of a quasi-passive ankle-Foot Prosthesis with biomimetic, variable stiffness
    2017 IEEE International Conference on Robotics and Automation (ICRA), 2017
    Co-Authors: Max K Shepherd, Elliot J. Rouse
    Abstract:

    Modern passive ankle-Foot prostheses do not exhibit appropriate biomechanics during walking, and are unable to adjust their mechanics for other mobility tasks, such as stair traversal or quiet standing. In this paper, we introduce a quasi-passive ankle-Foot Prosthesis that addresses these challenges; the ankle has a customizable, nonlinear torque-angle curve, and the overall stiffness can be varied continuously between mobility tasks. The variation in mechanics is accomplished by integrating two mechanisms: a cam-based transmission, in which rotation of the ankle joint causes deflection of a leaf spring, and an active sliding support beneath the leaf spring, which can modify the spring's effective stiffness. In addition to introducing the design, we present the mathematics to calculate the cam profile for any arbitrary torque-angle curve, and experimentally characterize the system for a desired curve based on human walking. Lastly, we demonstrate the full range of stiffness levels available and stiffness transition time.

Andrew H. Hansen - One of the best experts on this subject based on the ideXlab platform.

  • Development of an Ankle-Foot Prosthesis for Physical Therapy
    2019 Design of Medical Devices Conference, 2019
    Co-Authors: Eric Nickel, Andrew H. Hansen, Gregory O. Voss, Sara R. Koehler-mcnicholas
    Abstract:

    A novel ankle-Foot Prosthesis with adjustable range-of-motion limits was developed to support implementation of gradual training protocols in the physical therapy of new amputees. Stakeholder interviews drove design requirements that guided the development. Our first prototype did not pass structural strength testing, but with minor revisions to some components, our second prototype was able to pass structural strength testing to the P6 load level (125kg user) of the ISO 10328 standard for prosthetic feet. The system is ready for laboratory testing with Prosthesis users and clinicians to generate further insight for future design iterations.

  • Bimodal ankle-Foot Prosthesis for enhanced standing stability
    PloS one, 2018
    Co-Authors: Sara R. Koehler-mcnicholas, Eric Nickel, Karl Koester, Billie C. S. Slater, John Ferguson, Andrew H. Hansen
    Abstract:

    Previous work suggests that to restore postural stability for individuals with lower-limb amputation, ankle-Foot prostheses should be designed with a flat effective rocker shape for standing. However, most commercially available ankle-Foot prostheses are designed with a curved effective rocker shape for walking. To address the demands of both standing and walking, we designed a novel bimodal ankle-Foot Prosthesis that can accommodate both functional modes using a rigid Foot plate and an ankle that can lock and unlock. The primary objective of this study was to determine if the bimodal ankle-Foot system could improve various aspects of standing balance (static, dynamic, and functional) and mobility in a group of Veterans with lower-limb amputation (n = 18). Standing balance was assessed while subjects completed a series of tests on a NeuroCom Clinical Research System (NeuroCom, a Division of Natus, Clackamas, OR), including a Sensory Organization Test, a Limits of Stability Test, and a modified Motor Control Test. Few statistically significant differences were observed between the locked and unlocked ankle conditions while subjects completed these tests. However, in the absence of visual feedback, the locked bimodal ankle appeared to improve static balance in a group of experienced lower-limb Prosthesis users whose PLUS-M mobility rating was higher than approximately 73% of the sample population used to develop the PLUS-M survey. Given the statistically significant increase in mean equilibrium scores between the unlocked and locked conditions (p = 0.004), future testing of this system should focus on new amputees and lower mobility users (e.g., Medicare Functional Classification Level K1 and K2 Prosthesis users). Furthermore, commercial implementation of the bimodal ankle-Foot system should include a robust control system that can automatically switch between modes based on the user’s activity.

  • Bimodal ankle-Foot Prosthesis for enhanced standing stability - Fig 2
    2018
    Co-Authors: Sara R. Koehler-mcnicholas, Billie Savvas C. Slater, Karl Koester, Eric A. Nickel, John E. Ferguson, Andrew H. Hansen
    Abstract:

    CAD renderings of the ankle-Foot Prosthesis in the unlocked mode (top) and locked mode (bottom). Mode switching is controlled by a slider (green) that is pushed and pulled by an actuator (not shown). The durometer of rubber bumpers (red and purple) located on the anterior and posterior portions of the ankle block are selected according to the weight and activity level of the user.

  • The influence of a hydraulic prosthetic ankle on residual limb loading during sloped walking.
    PloS one, 2017
    Co-Authors: Sara R. Koehler-mcnicholas, Eric Nickel, Joseph Medvec, Kyle Barrons, Spencer Mion, Andrew H. Hansen
    Abstract:

    In recent years, numerous prosthetic ankle-Foot devices have been developed to address the demands of sloped walking for individuals with lower-limb amputation. The goal of this study was to compare the performance of a passive, hydraulic ankle-Foot Prosthesis to two related, non-hydraulic ankles based on their ability to minimize the socket reaction moments of individuals with transtibial amputation during a range of sloped walking tasks. After a two-week accommodation period, kinematic data were collected on seven subjects with a transtibial amputation walking on an instrumented treadmill set at various slopes. Overall, this study was unable to find significant differences in the torque at the distal end of the prosthetic socket between an ankle-Foot Prosthesis with a hydraulic range-of-motion and other related ankle-Foot Prosthesis designs (rigid ankle, multiaxial ankle) during the single-support phase of walking. In addition, socket comfort and perceived exertion were not significantly different for any of the ankle-Foot prostheses tested in this study. These results suggest the need for further work to determine if more advanced designs (e.g., those with microprocessor control of hydraulic features, powered ankle-Foot designs) can provide more biomimetic function to Prosthesis users.

  • development of a bimodal ankle Foot Prosthesis for walking and standing swaying
    Journal of Medical Devices-transactions of The Asme, 2013
    Co-Authors: Andrew H. Hansen, Eric Nickel
    Abstract:

    The human ankle-Foot system conforms to a circular effective rocker shape for walking, but to a much flatter effective shape for standing and swaying. Many persons with lower limb amputations have impaired balance and reduced balance confidence, and may benefit from prostheses designed to provide flatter effective rocker shapes during standing and swaying tasks. This paper describes the development and testing of an ankle-Foot Prosthesis prototype that provides distinctly different mechanical properties for walking and standing/swaying. The prototype developed was a single-axis prosthetic Foot with a lockable ankle for added stability during standing and swaying. The bimodal ankle-Foot Prosthesis prototype was tested on pseudoprostheses (walking boots with prosthetic feet beneath) for walking and standing/swaying loads, and was compared to an Otto Bock single-axis prosthetic Foot and to able-bodied data collected in a previous study. The height-normalized radius of the effective rocker shape for walking with the bimodal ankle-Foot prototype was equal to that found earlier for able-bodied persons (0.17); the standing and swaying effective shape had a lower height-normalized radius (0.70) compared with that previously found for able-bodied persons (1.11). The bimodal ankle-Foot Prosthesis prototype had a similar radius as the Otto Bock single-axis prosthetic Foot for the effective rocker shape for walking (0.17 for both), but had a much larger radius for standing and swaying (0.70 for bimodal, 0.34 for single-axis). The results suggest that the bimodal ankle-Foot Prosthesis prototype provides two distinct modes, including a biomimetic effective rocker shape for walking and an inherently stable base for standing and swaying. The radius of the prototype's effective rocker shape for standing/swaying suggests that it may provide inherent mechanical stability to a Prosthesis user, since the radius is larger than the typical body center of mass’s distance from the floor (between 50–60% of height). Future testing is warranted to determine if the bimodal ankle-Foot Prosthesis will increase balance and balance confidence in Prosthesis users.