Gait analysis for designing a new assistive knee brace

Assistive knee brace is a species of wearable lower extremity exoskeletons. In this research, an assistive knee brace was developed by integrating a multifunctional actuator with a custom-made knee-ankle-foot orthosis. In the study, the location of the actuator is moved up to the lateral side of the hip, instead of knee joint. Waist belt and shoulder belt are appended on the knee brace. This paper aimed to improve the design of the assistive knee braces through gait analysis. By walking with the knee braces, the spatial and temporal gait parameters, joint kinematics and joint kinetics parameters were evaluated, and the changes from normal walking were compared as well. The experimental results showed that walking with the developed knee brace provided minimal hindrance to the wearer. © 2011 IEEE

HyExo:A Novel Quasi-Passive Hydraulic Exoskeleton for Load-Carrying Augmentation

The development of assistive lower-limb exoskeletons gains prominence for human load-carrying augmentation. Hydraulic transmission has attractive hydrostatic features and lower inertia at the end of human limbs. However, few hydraulic lower-limb exoskeletons were developed with low energy consumption and light weight. In this article, we introduce HyExo, a quasi-passive hydraulic exoskeleton that is built on a lightweight rotary cage valve (RCV) block with a fast response and low energy consumption of 1.55&amp;#x00A0;W. Based on the RCV block, we propose an optimization-based regulator for joint energy distribution to harvest and release the hydraulic energy among joints during the stance phase. The interaction force model and control of the novel nonanthropomorphic structure are presented and evaluated. The load-supporting effect was investigated and validated through human subject experiments. The results show that with an assisting fluid pressure of 2.5&amp;#x00A0;MPa, HyExo can transfer a mean force of 237&amp;#x00A0;N to the ground. Meanwhile, the impact of wearing HyExo on gait is analyzed. The metabolic expenditure test shows that HyExo can slow the increasing rate in metabolic cost as load increases. Compared with a regular backpack, walking with HyExo to carry 30&amp;#x00A0;kg of weight reduces wearers&amp;#x0027; metabolic energy expenditure by 7.8&amp;#x0025;.</p

Experimental studies on kinematics and kinetics of walking with an assistive knee brace

Assistive knee brace is a species of wearable lower extremity exoskeletons. Such assistive equipment can enhance people's strength and provide desired locomotion to have advantages over wheelchairs, which are commonly used for patients with mobility disorders. However, the integration between the assistive knee brace and the user is challenging as inaccurate alignments may adversely affect the biomechanics of the knee joint. The goal of this study is to evaluate the changes between normal walking and walking with an assistive knee brace in "off" mode. The assistive knee brace was developed by integrating a multifunctional actuator with a custom-made knee-ankle-foot orthosis in order to minimize excessive shifting and to improve alignment to the knee joint. Spatial and temporal gait parameters, joint kinematics and joint kinetics parameters were compared. In general, the observed results showed that most of the gait parameters were not affected when walking with the knee brace. The only significant differences were found in knee flexion and knee rotational motions. These results indicated that walking with the developed knee brace provided minimal hindrance to the user and assured that assistive torque can be applied to the knee joint

Robotic design and modelling of medical lower extremity exoskeletons

This study aims to explain the development of the robotic Lower Extremity Exoskeleton (LEE) systems between 1960 and 2019 in chronological order. The scans performed in the exoskeleton system’s design have shown that a modeling program, such as AnyBody, and OpenSim, should be used first to observe the design and software animation, followed by the mechanical development of the system using sensors and motors. Also, the use of OpenSim and AnyBody musculoskeletal system software has been proven to play an essential role in designing the human-exoskeleton by eliminating the high costs and risks of the mechanical designs. Furthermore, these modeling systems can enable rapid optimization of the LEE design by detecting the forces and torques falling on the human muscles

Biomimetic design for an under-actuated leg exoskeleton for load-carrying augmentation

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaves 79-81).Metabolic studies have shown that there is a metabolic cost associated with carrying a load (Griffin et al, 2003). Further studies have shown that by applying forward propulsive forces a person can walk with a reduced metabolic rate (Farley & McMahon, 1992 and Gottschall & Kram, 2003). Previous work on exoskeleton design has not considered the passive dynamics of walking and has focused on fully actuated systems that are inefficient and heavy. In this thesis, an under-actuated exoskeleton is presented that runs parallel to the human leg. The exoskeleton component design is based on the kinematics and kinetics of human walking. The joint components of the exoskeleton in the sagittal plane consist of a force-controllable actuator at the hip, a variable-damper mechanism at the knee and a passive spring at the ankle. A state-machine control strategy is written based on joint angle and ground-exoskeleton force sensing. Positive, non-conservative power is added at the hip during the walking cycle to help propel the mass of the human and payload forward. At the knee, the damper mechanism is turned on at heel strike as the exoskeleton leg is loaded and turned off during terminal stance to allow knee flexion.(cont.) The spring at the ankle engages in controlled dorsiflexion to store energy that is later released to assist in powered plantarflexion. Kinetic and metabolic data are recorded from human subjects wearing the exoskeleton with a 751b payload. These data are compared to data recorded from subjects walking without the exoskeleton. It is demonstrated that the exoskeleton does transfer loads to the ground with a 90% and higher load transfer depending on the phase of gait. Further, exoskeleton wearers report that the exoskeleton greatly reduces the stress on the shoulders and back. However, although a significant fraction of the payload is transferred through the exoskeleton structure, the exoskeleton is found to increase metabolic economy by 74%. By comparing distinct exoskeleton configurations, the relative effect of each exoskeleton component is determined. Metabolic data show that the variable-damper knee and ankle spring mechanisms increase metabolism by only 32%, whereas a non-actuated exoskeleton (no motor, variable-damper, or spring) increases walking metabolism by 62%. These results highlight the benefit of ankle elastic energy storage and knee variable-damping in exoskeleton design, and further the need for a lighter, more efficient hip actuator.by Conor James Walsh.S.M

Design, control, and pilot study of a lightweight and modular robotic exoskeleton for walking assistance after spinal cord injury

Walking rehabilitation using exoskeletons is of high importance to maximize independence and improve the general well-being of spinal cord injured subjects. We present the design and control of a lightweight and modular robotic exoskeleton to assist walking in spinal cord injured subjects who can control hip flexion, but lack control of knee and ankle muscles. The developed prototype consists of two robotic orthoses, which are powered by a motor-harmonic drive actuation system that controls knee flexion–extension. This actuation module is assembled on standard passive orthoses. Regarding the control, the stance-to-swing transition is detected using two inertial measurement units mounted on the tibial supports, and then the corresponding motor performs a predefined flexion–extension cycle that is personalized to the specific patient’s motor function. The system is portable by means of a backpack that contains an embedded computer board, the motor drivers, and the battery. A preliminary biomechanical evaluation of the gait-assistive device used by a female patient with incomplete spinal cord injury at T11 is presented. Results show an increase of gait speed (+24.11%), stride length (+7.41%), and cadence (+15.56%) when wearing the robotic orthoses compared with the case with passive orthoses. Conversely, a decrease of lateral displacement of the center of mass (-19.31%) and step width (-13.37% right step, -8.81% left step) are also observed, indicating gain of balance. The biomechanical assessment also reports an overall increase of gait symmetry when wearing the developed assistive device.Peer ReviewedPostprint (published version

Transient Thermal Analysis of a Magnetorheological Knee for Prostheses and Exoskeletons during Over-Ground Walking

Proper knee movement is essential for accomplishing the mobility daily tasks such as walking, get up from a chair and going up and down stairs. Although the technological advances in active knee actuators for prostheses and exoskeletons to help impaired people in the last decade, they still present several usage limitations such as overweight or limited mechanical power and torque. To address such limitations, we developed the Active Magnetorheological Knee (AMRK) that comprises a Motor Unit (MU), which is a motor-reducer (EC motor and Harmonic Drive) and a MR clutch, that works in parallel to a magnetorheological (MR) brake. Magnetorheological fluids, employed in the MR clutch and brake, are smart materials that have their rheological properties controlled by an induced magnetic field and have been used for different purposes. With this configuration the actuator can work as a motor, clutch or brake and can perform similar movements than a healthy knee. However, the stability, control, and life of magnetorheological fluids critically depend on the working temperature. By reaching a certain temperature limit, the fluid additives quickly deteriorate, leading to irreversible changes of the MR fluid. In this study, we perform a transient thermal analysis of the AMRK, when it is used for walking over-ground, to access possible fluid degradation and user’s discomfort due overheating. The resulting shear stress in the MR clutch and brake generates heat, increasing the fluid temperature during the operation. However, to avoid overheating, we proposed a mode of operation for over-ground walking aiming to minimize the heat generation on the MR clutch and brake. Other heat sources inside the actuator are the coils, which generate the magnetic fields for the MR fluid, bearings, EC motor and harmonic drive. Results show that the MR fluid of the brake can reach up to 31°C after a 6.0 km walk, so the AMRK can be used for the proposed function without risks of fluid degradation or discomfort for the user

Non-linear actuators and simulation tools for rehabilitation devices

Mención Internacional en el título de doctorRehabilitation robotics is a field of research that investigates the applications of robotics in motor function therapy for recovering the motor control and motor capability. In general, this type of rehabilitation has been found effective in therapy for persons suffering motor disorders, especially due to stroke or spinal cord injuries. This type of devices generally are well tolerated by the patients also being a motivation in rehabilitation therapy. In the last years the rehabilitation robotics has become more popular, capturing the attention at various research centers. They focused on the development more effective devices in rehabilitation therapy, with a higher acceptance factor of patients tacking into account: the financial cost, weight and comfort of the device. Among the rehabilitation devices, an important category is represented by the rehabilitation exoskeletons, which in addition to the human skeletons help to protect and support the external human body. This became more popular between the rehabilitation devices due to the easily adapting with the dynamics of human body, possibility to use them such as wearable devices and low weight and dimensions which permit easy transportation. Nowadays, in the development of any robotic device the simulation tools play an important role due to their capacity to analyse the expected performance of the system designed prior to manufacture. In the development of the rehabilitation devices, the biomechanical software which is capable to simulate the behaviour interaction between the human body and the robotics devices, play an important role. This helps to choose suitable actuators for the rehabilitation device, to evaluate possible mechanical designs, and to analyse the necessary controls algorithms before being tested in real systems. This thesis presents a research proposing an alternative solution for the current systems of actuation on the exoskeletons for robotic rehabilitation. The proposed solution, has a direct impact, improving issues like device weight, noise, fabrication costs, size an patient comfort. In order to reach the desired results, a biomechanical software based on Biomechanics of Bodies (BoB) simulator where the behaviour of the human body and the rehabilitation device with his actuators can be analysed, was developed. In the context of the main objective of this research, a series of actuators have been analysed, including solutions between the non-linear actuation systems. Between these systems, two solutions have been analysed in detail: ultrasonic motors and Shape Memory Alloy material. Due to the force - weight characteristics of each device (in simulation with the human body), the Shape Memory Alloy material was chosen as principal actuator candidate for rehabilitation devices. The proposed control algorithm for the actuators based on Shape Memory Alloy, was tested over various configurations of actuators design and analysed in terms of energy eficiency, cooling deformation and movement. For the bioinspirated movements, such as the muscular group's biceps-triceps, a control algorithm capable to control two Shape Memory Alloy based actuators in antagonistic movement, has been developed. A segmented exoskeleton based on Shape Memory Alloy actuators for the upper limb evaluation and rehabilitation therapy was proposed to demosntrate the eligibility of the actuation system. This is divided in individual rehabilitation devices for the shoulder, elbow and wrist. The results of this research was tested and validated in the real elbow exoskeleton with two degrees of freedom developed during this thesis.Programa Oficial de Doctorado en Ingeniería Eléctrica, Electrónica y AutomáticaPresidente: Eduardo Rocón de Lima.- Secretario: Concepción Alicia Monje Micharet.- Vocal: Martin Stoele

Développement d'une unité de valves motorisées et algorithme de transition pour actionnement hydrostatique bimodal d'une jambe robotique

Les robots mobiles, tels que les exosquelettes et les robots marcheurs, utilisent des actionneurs qui doivent satisfaire à une large plage de requis de force et de vitesse. Par exemple, pour le cycle de marche d’une jambe robotique, la phase d’appui nécessite une force élevée tandis que la phase de balancement requiert une grande vitesse. Pour satisfaire ces requis opposés, le dimensionnement d’un système d’actionnement traditionnel à rapport de réduction unique conduit généralement à un moteur électrique lourd, surdimensionné et à une faible efficacité énergétique. Ainsi, l’alternative explorée est une architecture hydrostatique à deux vitesses où des valves motorisées sont utilisées pour reconfigurer dynamiquement le système entre deux modes de fonctionnement : fort ou rapide. La complexité réside dans le choix d’une technologie de valve légère ainsi que dans le développement d’un algorithme de contrôle permettant de réaliser les transitions de manière rapide et fluide. Un prototype d’une unité de valves motorisées est conçu et intégré dans l’architecture hydrostatique complète de l’actionneur et un banc d’essai d’une jambe robotique est fabriqué. Trois stratégies de contrôle des moteurs sont comparées lors du changement de mode : une vitesse constante, une diminution de vitesse et une réduction du courant. La méthode choisie, le contrôle en courant, est ensuite utilisée pour la démonstration des phases d’appui et de balancement de la jambe robotique. Par cette méthode, il est possible d’effectuer des transitions rapides, de maintenir une force suffisante et de minimiser les oscillations qui surviennent lors du contact avec le sol. Ces travaux offrent donc un premier point de comparaison au niveau du choix de valves, de la masse, de la vitesse d’actionnement et de la stratégie de contrôle