Sci Robot

Robotic leg prostheses promise to improve the mobility and quality of life of millions of individuals with lower-limb amputations by imitating the biomechanics of the missing biological leg. Unfortunately, existing powered prostheses are much heavier and bigger and have shorter battery life than conventional passive prostheses, severely limiting their clinical viability and utility in the daily life of amputees. Here, we present a robotic leg prosthesis that replicates the key biomechanical functions of the biological knee, ankle, and toe in the sagittal plane while matching the weight, size, and battery life of conventional microprocessor-controlled prostheses. The powered knee joint uses a unique torque-sensitive mechanism combining the benefits of elastic actuators with that of variable transmissions. A single actuator powers the ankle and toe joints through a compliant, underactuated mechanism. Because the biological toe dissipates energy while the biological ankle injects energy into the gait cycle, this underactuated system regenerates substantial mechanical energy and replicates the key biomechanical functions of the ankle/foot complex during walking. A compact prosthesis frame encloses all mechanical and electrical components for increased robustness and efficiency. Preclinical tests with three individuals with above-knee amputation show that the proposed robotic leg prosthesis allows for common ambulation activities with close to normative kinematics and kinetics. Using an optional passive mode, users can walk on level ground indefinitely without charging the battery, which has not been shown with any other powered or microprocessor-controlled prostheses. A prosthesis with these characteristics has the potential to improve real-world mobility in individuals with above-knee amputation.R01 HD098154/HD/NICHD NIH HHSUnited States/T42 OH008414/OH/NIOSH CDC HHSUnited States

Design, Control, and Perception of Bionic Legs and Exoskeletons

Bionic systems---wearable robots designed to replace, augment, or interact with the human body---have the potential to meaningfully impact quality of life; in particular, lower-limb prostheses and exoskeletons can help people walk faster, better, and safer. From a technical standpoint, there is a high barrier-to-entry to conduct research with bionic systems, limiting the quantity of research done; additionally, the constraints introduced by bionic systems often prohibit accurate measurement of the robot's output dynamics, limiting the quality of research done. From a scientific standpoint, we have begun to understand how people regulate lower-limb joint impedance (stiffness and damping), but not how they sense and perceive changes in joint impedance. To address these issues, I first present an open-source bionic leg prosthesis; I describe the design and testing process, and demonstrate patients meeting clinical ambulation goals in a rehabilitation hospital. Second, I develop tools to characterize open-loop impedance control systems and show how to achieve accurate impedance control without a torque feedback signal; additionally, I evaluate the efficiency of multiple bionic systems. Finally, I investigate how well people can perceive changes in the damping properties of a robot, similar to an exoskeleton. With this dissertation, I provide technical and scientific advances aimed at accelerating the field of bionics, with the ultimate goal of enabling meaningful impact with bionic systems.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163108/1/afazocar_1.pd

The Functionality Verification through Pilot Human Subject Testing of MyFlex-δ: An ESR Foot Prosthesis with Spherical Ankle Joint

Most biomechanical research has focused on level-ground walking giving less attention to other conditions. As a result, most lower limb prosthesis studies have focused on sagittal plane movements. In this paper, an ESR foot is presented, of which five different stiffnesses were optimized for as many weight categories of users. It is characterized by a spherical ankle joint, with which, combined with the elastic elements, the authors wanted to create a prosthesis that gives the desired stiffness in the sagittal plane but at the same time, gives flexibility in the other planes to allow the adaptation of the foot prosthesis to the ground conditions. The ESR foot was preliminarily tested by participants with transfemoral amputation. After a brief familiarization with the device, each participant was asked to wear markers and to walk on a sensorized treadmill to measure their kinematics and kinetics. Then, each participant was asked to leave feedback via an evaluation questionnaire. The measurements and feedback allowed us to evaluate the performance of the prosthesis quantitatively and qualitatively. Although there were no significant improvements on the symmetry of the gait, due also to very limited familiarization time, the participants perceived an improvement brought by the spherical ankle joint

The Functionality Verification through Pilot Human Subject Testing of MyFlex-δ: An ESR Foot Prosthesis with Spherical Ankle Joint

Most biomechanical research has focused on level-ground walking giving less attention to other conditions. As a result, most lower limb prosthesis studies have focused on sagittal plane movements. In this paper, an ESR foot is presented, of which five different stiffnesses were optimized for as many weight categories of users. It is characterized by a spherical ankle joint, with which, combined with the elastic elements, the authors wanted to create a prosthesis that gives the desired stiffness in the sagittal plane but at the same time, gives flexibility in the other planes to allow the adaptation of the foot prosthesis to the ground conditions. The ESR foot was preliminarily tested by participants with transfemoral amputation. After a brief familiarization with the device, each participant was asked to wear markers and to walk on a sensorized treadmill to measure their kinematics and kinetics. Then, each participant was asked to leave feedback via an evaluation questionnaire. The measurements and feedback allowed us to evaluate the performance of the prosthesis quantitatively and qualitatively. Although there were no significant improvements on the symmetry of the gait, due also to very limited familiarization time, the participants perceived an improvement brought by the spherical ankle joint

Foot/Ankle Prostheses Design Approach Based on Scientometric and Patentometric Analyses

There are different alternatives when selecting removable prostheses for below the knee amputated patients. The designs of these prostheses vary according to their different functions. These prostheses designs can be classified into Energy Storing and Return (ESAR), Controlled Energy Storing and Return (CESR), active, and hybrid. This paper aims to identify the state of the art related to the design of these prostheses of which ESAR prostheses are grouped into five types, and active and CESR are categorized into four groups. Regarding patent analysis, 324 were analyzed over the last six years. For scientific communications, a bibliometric analysis was performed using 104 scientific reports from the Web of Science in the same period. The results show a tendency of ESAR prostheses designs for patents (68%) and active prostheses designs for scientific documentation (40%).Beca Conacyt Doctorad

Study of composite elastic elements for transfemoral prostheses: the MyLeg Project

In this thesis, the work on the design and realization of a semi-active foot prosthesis with variable stiffness system is presented. The final prosthesis was the result of a path started by the design of the elastic composite elements of an ESR prosthesis, a passive prosthetic device, generally prescribed to amputees with K3 and K4 of level of ambulation. The design of both the ESR prosthesis and the final variable stiffness prosthesis was carried out using a new systematic methodology of prosthesis design. This methodology has been developed and then presented in the same thesis by the author. Modelling and simulation techniques are illustrated step by step. With the variable stiffness prosthesis, the aim is to allow future users to perform more daily activities without being restricted by the conditions of the ground. It has been chosen to develop a semi-active prosthesis rather than a bionic foot for two main reasons: a bionic foot may be too expensive for most future users; and a bionic foot may be undesirable for too much weight; the much weight can be due to the motor and batteries, in addition to the structure that will certainly be much more complex than the structure of a semi-active prosthesis. To investigate the effectiveness of the variable stiffness, human subjects with amputees will be carried out

Electromyography-Based Control of Lower Limb Prostheses: A Systematic Review

Most amputations occur in lower limbs and despite improvements in prosthetic technology, no commercially available prosthetic leg uses electromyography (EMG) information as an input for control. Efforts to integrate EMG signals as part of the control strategy have increased in the last decade. In this systematic review, we summarize the research in the field of lower limb prosthetic control using EMG. Four different online databases were searched until June 2022: Web of Science, Scopus, PubMed, and Science Direct. We included articles that reported systems for controlling a prosthetic leg (with an ankle and/or knee actuator) by decoding gait intent using EMG signals alone or in combination with other sensors. A total of 1,331 papers were initially assessed and 121 were finally included in this systematic review. The literature showed that despite the burgeoning interest in research, controlling a leg prosthesis using EMG signals remains challenging. Specifically, regarding EMG signal quality and stability, electrode placement, prosthetic hardware, and control algorithms, all of which need to be more robust for everyday use. In the studies that were investigated, large variations were found between the control methodologies, type of research participant, recording protocols, assessments, and prosthetic hardware

Proportional EMG Control of Ankle Plantar Flexion in a Powered Transtibial Prosthesis

The human calf muscle generates 80% of the mechanical work to walk throughout stance-phase, powered plantar flexion. Powered plantar flexion is not only important for walking energetics, but also to minimize the impact on the leading leg at heel-strike. For unilateral transtibial amputees, it has recently been shown that knee load on the leading, intact limb decreases as powered plantar flexion in the trailing prosthetic ankle increases. Not surprisingly, excessive loads on the leading, intact knee are believed to be causative of knee osteoarthritis, a leading secondary impairment in lowerextremity amputees. In this study, we hypothesize that a transtibial amputee can learn how to control a powered anklefoot prosthesis using a volitional electromyographic (EMG) control to directly modulate ankle powered plantar flexion. We here present preliminary data, and find that an amputee participant is able to modulate toe-off angle, net ankle work and peak power across a broad range of walking speeds by volitionally modulating calf EMG activity. The modulation of these key gait parameters is shown to be comparable to the dynamical response of the same powered prosthesis controlled intrinsically (No EMG), suggesting that transtibial amputees can achieve an adequate level of powered plantar flexion controllability using direct volitional EMG control.United States. Dept. of Defense (award number 6920559)United States. Dept. of Defense (award number 6920877)Swiss National Science Foundation (grant PBELP3_140656