This paper presents a review on design issues and solutions found in active lower limb prostheses. This review is based on a systematic literature search with a methodical search strategy. The search was carried out across four major technical databases and the retrieved records were screened for their relevance. A total of 21 different active prostheses, including 8 above-knee, 9 below-knee and 4 combined knee-ankle prostheses were identified. While an active prosthesis may help to restore the functional performance of an amputee, the requirements regarding the actuation unit as well as for the control system are high and the development becomes a challenging task. Regarding mechanical design and the actuation unit high force/torque delivery, high efficiency, low size and low weight are conflicting goals. The actuation principle and variable impedance actuators are discussed. The control system is paramount for a “natural functioning” of the prosthesis. The control system has to enable locomotion and should react to the amputee’s intent. For this, multi-level control approaches are reviewed.

/pdf/active-lower-limb-prosthetics-a-systematic-review-of-design-1wltwzsyog.pdf

Active lower limb prosthetics: a systematic review of design issues and solutions.

Several studies have presented technological ensembles of active knee systems for transfemoral prosthesis. Other studies have examined the amputees' gait performance while wearing a specific active prosthesis. This paper combined both insights, that is, a technical examination of the components used, with an evaluation of how these improved the gait of respective users. This study aims to offer a quantitative understanding of the potential enhancement derived from strategic integration of core elements in developing an effective device. The study systematically discussed the current technology in active transfemoral prosthesis with respect to its functional walking performance amongst above-knee amputee users, to evaluate the system's efficacy in producing close-to-normal user performance. The performances of its actuator, sensory system, and control technique that are incorporated in each reported system were evaluated separately and numerical comparisons were conducted based on the percentage of amputees' gait deviation from normal gait profile points. The results identified particular components that contributed closest to normal gait parameters. However, the conclusion is limitedly extendable due to the small number of studies. Thus, more clinical validation of the active prosthetic knee technology is needed to better understand the extent of contribution of each component to the most functional development.

/pdf/technology-efficacy-in-active-prosthetic-knees-for-46v45jf109.pdf

Technology Efficacy in Active Prosthetic Knees for Transfemoral Amputees: A Quantitative Evaluation

People with lower limb loss or congenital limb absence require a technical substitute that restores biomechanical function and body integrity. In the last decades, mechatronic prostheses emerged and especially actuated ones increased the biomechanical functionality of their users. Yet, various open issues regarding the energy efficiency of powered systems and the impact of user-experience of the prosthesis on technical design remain. As tackeling the latter aspect urgently requires the consideration of user demands, this thesis proposes a novel human-machine-centered design (HMCD) approach for lower limb prosthetics. Further, it contributes to the design and control of elastic (prosthetic) actuation.

The HMCD approach describes a framework that equally considers technical and human factors. Therefore, seven human factors influencing lower limb prosthetic design are determined, analyzed, and modeled using human survey data: Satisfaction, Feeling of Security, Body Schema Integration, Support, Socket, Mobility, and Outer Appearance. Based on the application of quality function deployment (QFD), those factors can be considered as a HMCD focus in systems engineering. As an exemplary application, a powered prosthetic knee concept is elaborated with the HMCD approach. The comparison of the HMCD focus with a purely technical one, which is determined with a control group, reveals distinct differences in the weighting of requirements. Hence, the proposed method should lead to different prosthetic designs that might improve the subjective user-experience. To support this by integrating users throughout the systems engineering process, two concepts for human-in-the-loop experiments are suggested.

As an enabling technology of powered lower limb prostheses, variable (series) elastic actuation and especially such with variable torsion stiffness (VTS) is investigated. Inverse dynamics simulations with synthetic and human trajectories as well as experiments show that the consideration of the actuator inertia is crucial: Only by including it in advanced models, the whole range of natural dynamics and antiresonance can be exploited to minimize power consumption. A corresponding control strategy adapts the actuator to achieve energy efficiency over a wide range of operational states using these models.

The exemplary design of the powered prosthetic knee with respect to the HMCD prioritization of requirements confirms the fundamental suitability of VTS for integration in prosthetic components. In this, considering actuator inertia enables the determination of an optimal stiffness for serial elastic actuation of the human knee during walking that is not found in previous studies. A first simulation considering the changed dynamics of prosthetic gait indicates the potential to reveal lower design requirements. The designed knee concept combines promising biomechanical functionality and long operating time due to elastic actuation and energy recuperation.

Beyond lower limb prosthetics, the proposed HMCD framework can be used in other applications with distinct human-machine interrelations by adjusting the human and technical factors. Likewise, the insights into variable elastic actuation design and control can be transferred to other systems demanding energy-efficient performance of cyclic tasks.

Human-Machine-Centered Design and Actuation of Lower Limb Prosthetic Systems

A human-machine-centered design method for (powered) lower limb prosthetics

Understanding and defining the meaning of “action” is substantial for robotics research. This becomes utterly evident when aiming at equipping autonomous robots with robust manipulation skills for ...

https://journals.sagepub.com/doi/pdf/10.1177/0278364919835020

Action representations in robotics: a taxonomy and systematic classification

In recent years, there has been a worldwide interest in improvement of mobility of people with lower limb amputation. In spite of significant development of new technologies during the last decade, commercial below-knee and above-knee prostheses are still energetically passive devices. However, many locomotive functions, like walking up stairs and slopes, need significant power in knee and ankle joints. The additional power for doing previously mentioned activities needs to be achieved by means of external energy sources, which should be integral prosthetic components. This paper presents preliminary investigations towards an active robotic prosthesis that could potentially enable people with an above- or below-knee amputation to perform different types of motions that require power in lower limb joints. Our initial prototype, SmartLeg, integrates advanced prosthetic and robotic technology with the state-of-the-art machine learning algorithms capable of adapting the working of the prosthesis to the optimal gait and power consumption patterns, and which therefore provide means to customize the device to a particular user.

SmartLeg: An intelligent active robotic prosthesis for lower-limb amputees

Hankelet-based action classification for motor intention recognition

After above-knee amputation, amputees usually go under intense rehabilitation process in order to overcome their disadvantage and successfully reintegrate in the society. Passive prostheses, which are mostly used by amputees, enable performing of various activities such as walking on levelled and inclined ground, and even running, riding a bicycle and as of lately swimming. However, performing high power demanding tasks, such as stair ascent, presents a problem because the lack of muscles makes it impossible to produce required forces. This means, that in order for the prosthesis to be able to perform high demanding power activities it must be powered, primarily in its main joints – knee and ankle. In this paper, we are presenting hydraulic power system and control system for knee and ankle powered prosthesis which we are developing in order to achieve required kinematics and dynamics of the prosthesis which would enable it to perform high power demanding activities in more natural manner, especially stair ascent.

Power and Control System of Knee and Ankle Powered Above-Knee Prosthesis

The locomotion of people with amputation is slower, less stable and requires more metabolic energy than the locomotion of physically fit individuals. Individuals with amputation of the lower extremities fall more often than able individuals and often have difficulty moving on uneven terrain and stairs. These challenges can mostly be attributed to the use of passive mechanical prosthetic legs that do not react actively to perturbations. Latest submitted solutions for active prosthetic devices of the lower extremities can significantly improve mobility and quality of life for millions of people with lower limb amputation, but challenges in control mechanisms of such devices are currently limiting their clinical viability.

Matlab Simulation of Robust Control for Active Above-Knee Prosthetic Device

This paper presents research and development of hydraulically powered above-knee prosthesis (HAKP) and novel prosthetic foot, in order to enable transfemoral (TF) amputees perform stair ascent and other daily activities in as much as possible natural manner. Functions that need exertion of large forces and moments during locomotion such as walking up stairs and slopes cannot be naturally accomplished by commercially available microprocessor-controlled above-knee (AK) prostheses. Also, such prosthetic devices are expensive and unaffordable for major part of amputee population, so mostly used commercial prostheses are energetically passive devices. Deficiency of passive prosthetic devices is the lack of externally powered joints that could substitute a large number of missing muscles and provide a gait with the kinematics and dynamics similar to that of non-amputees.

Remzo Dedić

Papers

SmartLeg: An intelligent active robotic prosthesis for lower-limb amputees

Hankelet-based action classification for motor intention recognition

Power and Control System of Knee and Ankle Powered Above-Knee Prosthesis

Matlab Simulation of Robust Control for Active Above-Knee Prosthetic Device

Overview of the Development of Hydraulic Above Knee Prosthesis