Advances on mechanical designs for assistive ankle-foot orthoses

Assistive ankle-foot orthoses (AFOs) are powerful solutions to assist or rehabilitate gait on humans. Existing assistive AFO technologies include passive, quasi-passive, and active principles to provide assistance to the users, and their mechanical configuration and control depend on the eventual support they aim for within the gait pattern. In this research we analyze the state-of-the-art of assistive AFOs and classify the different approaches into clusters, describing their basis and working principles. Additionally, we reviewed the purpose and experimental validation of the devices, providing the reader with a better view of the technology readiness level. Finally, the reviewed designs, limitations, and future steps in the field are summarized and discussed.Comment: Figures appear at the end. Article submitted to Frontiers in Bioengineering and Biotechnology (currently under review

Dynamics analysis and simulation verification of a novel knee joint exoskeleton

A novel knee joint exoskeleton, is designed in this paper, including the mechanical structure and hydraulic damper. To determine the spring parameters of knee joint exoskeleton and verify its effectiveness, we conduct the following studies. Firstly, forward kinematics analysis of the swing phase is obtained and Lagrange dynamics analysis is carried out. Secondly, the 3D model of exoskeleton is set up and ADAMS simulation is conducted. Then the spring parameters of knee joint exoskeleton are selected, including the spring force, the spring stiffness coefficient and the spring expansion, according to the simulation results. Finally, there are three sets of moments on the non-wearable side, the moments resulted from ADAMS simulations, the moments from the CGA (Clinical gait analysis) and the moments calculated from the Lagrange equation are compared, results show they are in good agreement. The effectiveness of the ADAMS simulation proves that the parameters of the hydraulic damper can meet the actual requirements. The simulation analysis of the exoskeleton provides important parameters for the manufacture and it also provides theoretical basis for the later control theory

serial and parallel robotics: energy saving systems and rehabilitation devices

This thesis focuses on the design and discussion of robotic devices and their applications. Robotics is the branch of technology that deals with the design, construction, operation, and application of robots as well as computer systems for their control, sensory feedback, and information processing [1]. Nowadays, robotics has been an unprecedented increase in applications of industry, military, health, domestic service, exploration, commerce, etc. Different applications require robots with different structures and different functions. Robotics normally includes serial and parallel structures. To have contribution to two kinds of structures, this thesis consisting of two sections is devoted to the design and development of serial and parallel robotic structures, focused on applications in the two different fields: industry and health

Knee Exoskeletons Design Approaches to Boost Strength Capability: A Review

Exoesqueleto para incrementar la fuerza en las rodillasThere are different devices to increase the strength capacity of people with walking problems. These devices can be classified into exoskeletons, orthotics, and braces. This review aims to identify the state of the art in the design of these medical devices, based on an analysis of patents and literature. However, there are some difficulties in processing the records due to the lack of filters and standardization in the names, generating discrepancies between the search engines, among others. Concerning the patents, 74 patents were analyzed using search engines such as Google Patents, Derwent, The Lens, Patentscope, and Espacenet over the past ten years. A bibliometric analysis was performed using 63 scientific reports from Web of Science and The Lens in the same period for scientific communications. The results show a trend to use the mechanical design of exoskeletons based on articulated rigid structures and elements that provide force to move the structure. These are generally two types: (a) elastic elements and (b) electromechanical elements. The United States accounts for 32% of the technological patents reviewed. The results suggest that the use of exoskeletons or orthoses customized to the users’ needs will continue to increase over the years due to the worldwide growth in disability, particularly related to mobility difficulties and technologies related to the combined use of springs and actuators

A Simple Model to Estimate Plantarflexor Muscle–Tendon Mechanics and Energetics During Walking With Elastic Ankle Exoskeletons

A recent experiment demonstrated that when humans wear unpowered elastic ankle exoskeletons with intermediate spring stiffness they can reduce their metabolic energy cost to walk by ~7%. Springs that are too compliant or too stiff have little benefit. The purpose of this study was to use modeling and simulation to explore the muscle-level mechanisms for the ‘sweet-spot’ in stiffness during exoskeleton assisted walking

Design Feasibility of an Active Ankle-Foot Stabilizer

Walking is the most common form of mobility in humans. For lower limb mobility impairments, a common treatment is to prescribe an ankle-foot orthosis (AFO) or brace, which is a passive device designed to resist undesired ankle-foot motion. Recent advances in actuator technology have led to the development of active AFOs (AAFOs). However, these devices are generally too bulky for everyday use and are limited to applications such as gait training for rehabilitation. The aim of this research was to investigate the feasibility of developing a novel Active Ankle-Foot Stabilizer (AAFS). The design criteria were mainly based on the strengths and limitations of existing AFOs. The sagittal plane functional requirements were determined using simulated gait data for elderly individuals and drop foot patients; however, it is intended that the device would be suitable for a wider range of disabilities including ankle sprains. A model of the foot was introduced to modify the moment of a deficient ankle where young healthy adult kinematics and kinetics were assumed. A moment deficit analysis was performed for different gait periods resulting in an AAFS model with two components: a linear rotational spring to modify the ankle joint rotational stiffness, and a torque source. The frontal plane functional requirements for the AAFS were modeled as a linear rotational spring which responded to particular gait events. A novel Variable Rotational Stiffness Actuator (VSRA) AFO was also investigated. It consisted of an actuated spring medial and lateral to the ankle to control sagittal plane ankle stiffness and a passive leafspring posterior to the ankle to control frontal plane ankle stiffness. Due to high forces and profile limitations, a spring and rotation actuator that satisfied the design criteria could not be developed, resulting in an infeasible design. Considering the high forces and moments required by the AAFS, a pneumatic approach was adopted. A novel Airbeam AFO, which consisted of a shank cuff and a foot plate to which airbeams were attached proximally and distally to the ankle, was examined. The joint rotational stiffness of the ankle would be controlled by the inflation of these individual cylindrical airbeams. To satisfy the functional requirements, the airbeam diameters and pressures were too large to meet the design criteria and were unrealistic for a portable device. Finally, a Pneumatic Sock AFO, which proved to best satisfy the functional requirements within the design criteria, was examined. The design consisted of an inner sock worn on the ankle, surrounded by anterior, posterior, medial, and lateral bladders which inflate against outer fabric shells. Although promising, the Pneumatic Sock AFO requires further investigation in regards to manufacturing and behaviour characterization before a functional prototype can be developed. Mechanical test methods to characterize the behaviour of the Pneumatic Sock AFO in the sagittal and frontal planes were developed including the control components required, the configuration of a test rig, and test procedures.1 yea

Improving outcomes following complex foot and ankle injuries

Foot and ankle injuries are severely disabling for military personnel who are conditioned to undertake impact activities. Following injury, performance and patient-reported outcomes have been shown to improve for amputees compared to limb-salvage military patients. A novel custom-made ankle foot orthosis may provide improved outcomes for limb-salvage patients. Initial results with the orthosis demonstrate improved performance and patient-reported outcomes at 2-year follow-up and a reduction in the number of personnel pursuing amputation. The orthosis, however, does not work for all foot and ankle injuries. This work sought to define the indications for prescription and create a clinical decision tool to facilitate evidence-based prescription. The outcomes for UK military personnel with complex foot and ankle injuries who underwent rehabilitation prior to the introduction of the orthosis were investigated. Over 50% of the cohort underwent amputation with improved performance outcomes for amputees compared to limb-salvage patients. Following the introduction of the orthosis, a reduction in amputation and improvement in physical performance measures were seen. Patients with a pain-specialist diagnosis of chronic pain did not benefit from prescription of the orthosis, whereas patients with primarily a nerve injury diagnosis did. Using injury characteristics alone, however, was found to be unable to predict outcome for all injured personnel. Therefore, biomechanical measures were examined. Gait analysis of patients prior to prescription of an orthotic was conducted. Patients with a negative symmetry index of more than 20% for power generation at pre-swing were found to benefit from prescription of the orthosis in the absence of an ipsilateral injury. This is the most complete investigation of UK personnel prescribed a novel orthosis following foot and ankle injury. This analysis facilitated the production of a clinical decision tool. The tool now requires validation and can be used to counsel foot and ankle injury patients on whether they may benefit from prescription of this orthosis.Open Acces

Effectiveness of robot-assisted therapy on ankle rehabilitation – a systematic review

Objective The aim of this study was to provide a systematic review of studies that investigated the effectiveness of robot-assisted therapy on ankle motor and function recovery from musculoskeletal or neurologic ankle injuries. Methods Thirteen electronic databases of articles published from January, 1980 to June, 2012 were searched using keywords ‘ankle*’, ‘robot*’, ‘rehabilitat*’ or ‘treat*’ and a free search in Google Scholar based on effects of ankle rehabilitation robots was also conducted. References listed in relevant publications were further screened. Eventually, twenty-nine articles were selected for review and they focused on effects of robot-assisted ankle rehabilitation. Results Twenty-nine studies met the inclusion criteria and a total of 164 patients and 24 healthy subjects participated in these trials. Ankle performance and gait function were the main outcome measures used to assess the therapeutic effects of robot-assisted ankle rehabilitation. The protocols and therapy treatments were varied, which made comparison among different studies difficult or impossible. Few comparative trials were conducted among different devices or control strategies. Moreover, the majority of study designs met levels of evidence that were no higher than American Academy for Cerebral Palsy (CP) and Developmental Medicine (AACPDM) level IV. Only one study used a Randomized Control Trial (RCT) approach with the evidence level being II. Conclusion All the selected studies showed improvements in terms of ankle performance or gait function after a period of robot-assisted ankle rehabilitation training. The most effective robot-assisted intervention cannot be determined due to the lack of universal evaluation criteria for various devices and control strategies. Future research into the effects of robot-assisted ankle rehabilitation should be carried out based on universal evaluation criteria, which could determine the most effective method of intervention. It is also essential to conduct trials to analyse the differences among different devices or control strategies