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A controller for a powered transfemoral prosthesis is presented, which can coordinate power delivery at the knee with the motion of the crankshaft on a bicycle. The controller continuously estimates the lengths of a four-bar linkage model through the application of a recursive least squares algorithm. The link lengths are used to estimate the angle of the bicycle crankshaft. With this measure, the delivery of knee torque is coordinated with the motion of the user. The controller is implemented on a prosthesis prototype and assessed on a transfemoral amputee subject ( N = 1). The subject exhibited a bilateral work asymmetry of 83.5% when cycling with his daily use prosthesis in a free-swing mode. When 60-N·m peak assistance was provided by the powered prosthesis, the bilateral work asymmetry was reduced to 11.4%. The subject's metabolic energy rate was measured for speed and power-matched cycling while the powered prosthesis provided zero assistance (i.e., turned off and providing its back-drive resistance) or 30-N·m peak assistance. Subject's metabolic energy rate decreased by 16.5% when receiving powered assistance relative to the zero-assistance condition. [ABSTRACT FROM PUBLISHER]

It is 8 a.m. on a December morning in Jaipur, Rajasthan, India. The day has just begun at Bhagawan Mahavir Vikalanga Sahayata Samithi (BMVSS), a nonprofit organization dedicated to fitting the disabled with artificial limbs (Figure 1). Slowly, patients from across India and neighboring countries gather in the center?s front yard. By the end of the day, more than 35 people will make a long journey back to their homes and communities outfitted with a new prosthetic leg or arm that will promise them a more active and functional future. The entire treatment is free. [ABSTRACT FROM PUBLISHER]

Hand amputation is a traumatic event that dramatically and permanently changes the life of any person who undergoes one. After surgery, the amputee requires a prosthetic device to perform activities of daily living-in particular, tasks requiring grasping and manipulation functions. According to the Washington, D.C.-based Amputee Coalition, there are 1.9 million amputees who use limb prosthetic services and products, and it is estimated that, among them, 500,000 are upper-limb amputees, with approximately 185,000 new amputations every year (www.amputee-coalition.org). The Center for Orthotic and Prosthetic Care, a consortium of providers in Kentucky, Indiana, North Carolina, and New York, says that upper-limb amputations represent 14% of all amputations (www.centeropcare.com). Based on these statistics, we can estimate that, in the European Union, there are a total of 3 million amputees, with 290,000 new cases each year; among these, 40,000 are upperlimb amputations. [ABSTRACT FROM PUBLISHER]

Lower limb amputees can use electrical activity from their residual muscles for myoelectric control of a powered prosthesis. The most common approach for myoelectric control is a finite state controller that identifies behavioral states and discrete changes in motor tasks. An alternative approach to state-based myoelectric control is continuous proportional myoelectric control where ongoing electrical activity has a proportional relationship to the prosthetic joint torque or power. To test the potential of continuous proportional myoelectric control for powered lower limb prostheses, we recruited five unilateral transtibial amputees to walk on a treadmill with an experimental powered prosthesis. Subjects walked using the powered prosthesis with and without visual feedback of their control signal in real time. Amputee subjects were able to adapt their residual muscle activation patterns to alter prosthetic ankle mechanics when we provided visual feedback of their myoelectric control signal in real time. During walking with visual feedback, subjects significantly increased their peak prosthetic ankle power (p = 0.02, ANOVA) and positive work (p = 0.02, ANOVA) during gait above their prescribed prosthesis values. However, without visual feedback, the subjects did not increase their peak ankle power during push off. These results show that amputee users were able to volitionally alter their prosthesis mechanics during walking, but only when given an explicit goal for their residual muscle motor commands. Future studies that examine the motor and learning capabilities of lower limb amputees using their residual muscles for continuous proportional myoelectric control are needed to determine the viability of integrating continuous high-level control with existing finite state prosthetic controllers. [ABSTRACT FROM PUBLISHER]

This paper describes a control approach that provides walking and standing functionality for a powered ankle prosthesis, and demonstrates the efficacy of the approach in experiments with a unilateral transtibial amputee subject. Both controllers incorporate a finite-state structure that emulates healthy ankle joint behavior via a series of piecewise passive impedance functions. The walking controller additionally modifies impedance parameters based on estimated cadence, while the standing controller modulates the ankle equilibrium angle in order to adapt to the ground slope and user posture, and the supervisory controller selects between the walking and standing controllers. The system is shown to reproduce several essential biomechanical features of the healthy joint during walking, particularly relative to a passive prosthesis, and is shown to adapt to various cadences. The system is also shown to adapt to slopes over a range of \pm 15^\circ, providing support to the user, as validated by quasi-static stiffness measurements recorded by the prosthesis. The subject is shown to place more weight on the powered prosthesis than on his passive prosthesis when standing on sloped surfaces, particularly at angles of 10^\circ or greater. The authors also demonstrated that the prosthesis typically began providing support within 1 s of initial ground contact. Further, the supervisory controller was shown to effectively switch between walking and standing, as well as determine ground slope just prior to the transition from the standing controller to the walking controller, where the estimated ground slope was accurate to within 1.25^\circ for all trials. [ABSTRACT FROM PUBLISHER]

Recent powered (or robotic) prosthetic legs independently control different joints and time periods of the gait cycle, resulting in control parameters and switching rules that can be difficult to tune by clinicians. This challenge might be addressed by a unifying control model used by recent bipedal robots, in which virtual constraints define joint patterns as functions of a monotonic variable that continuously represents the gait cycle phase. In the first application of virtual constraints to amputee locomotion, this paper derives exact and approximate control laws for a partial feedback linearization to enforce virtual constraints on a prosthetic leg. We then encode a human-inspired invariance property called effective shape into virtual constraints for the stance period. After simulating the robustness of the partial feedback linearization to clinically meaningful conditions, we experimentally implement this control strategy on a powered transfemoral leg. We report the results of three amputee subjects walking overground and at variable cadences on a treadmill, demonstrating the clinical viability of this novel control approach. [ABSTRACT FROM PUBLISHER]

C5/C6 tetraplegic patients and transhumeral amputees may be able to use voluntary shoulder motion as command signals for a functional electrical stimulation system or transhumeral prosthesis. Stereotyped relationships, termed “postural synergies,” among the shoulder, forearm, and wrist joints emerge during goal-oriented reaching and transport movements as performed by able-bodied subjects. Thus, the posture of the shoulder can potentially be used to infer the desired posture of the elbow and forearm joints during reaching and transporting movements. We investigated how well able-bodied subjects could learn to use a noninvasive command scheme based on inferences from these postural synergies to control a simulated transhumeral prosthesis in a virtual reality task. We compared the performance of subjects using the inferential command scheme (ICS) with subjects operating the simulated prosthesis in virtual reality according to complete motion tracking of their actual arm and hand movements. Initially, subjects performed poorly with the ICS but improved rapidly with modest amounts of practice, eventually achieving performance only slightly less than subjects using complete motion tracking. Thus, inferring the desired movement of distal joints from voluntary shoulder movements appears to be an intuitive and noninvasive approach for obtaining command signals for prostheses to restore reaching and grasping functions. [ABSTRACT FROM PUBLISHER]

In this study, we hypothesized that haptic feedback would enhance grip force control of surface electromyography (sEMG)-controlled prosthetic hands for targeted reinnervation (TR) amputees. A new miniature haptic device, a tactor, that can deliver touch, pressure, shear, and temperature sensation, allows modality-matching haptic feedback. TR surgery that creates sensory regions on the patient's skin that refer to the surface of the missing limb allows somatotopic-matching haptic feedback. This paper evaluates the hypothesis via an sEMG-controlled virtual prosthetic arm operated by TR amputees under diverse haptic feedback conditions. The results indicate that the grip force control is significantly enhanced via the haptic feedback. However, the simultaneous display of two haptic channels (pressure and shear) does not enhance, but instead degrades, grip force control. [ABSTRACT FROM AUTHOR]

In order to better rehabilitate lower limb amputees, prosthetic technology needs to facilitate turning gait by providing torsional control in the transverse plane. This paper characterizes biological ankle function in the transverse plane during turning gait with simple mechanical elements to assist in the design of a biomimetic prosthetic ankle joint. Motion capture data was collected from ten subjects performing left and right turns through a 900 hallway corner. The Initiation, Apex, and Termination steps of the turn were investigated. The data for each step was separated into several states, and passive elements were chosen to model the ankle in each state. During the first state of each turning step, the ankle behaved similarly to straight steps by limiting the kinetic energy of the foot prior to foot flat. During the subsequent states of each turning step, the ankle altered its characteristic properties to accommodate the curved trajectory of the body center of mass. The results suggest controlling transverse plane stiffness with a finite state control system will suffice to mimic biological function during a turn. [ABSTRACT FROM AUTHOR]