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

Design and simulation analysis of an improved wearable power knee exoskeleton

The wearable lower limb power robotic exoskeleton is a device that can improve the human walking ability. In this paper, an improved exoskeleton device for knee joint is designed, including the improvement of mechanical structure and hydraulic cylinder. In order to verify the effectiveness of the improvement of the hydraulic cylinder, we have carried out the following studies. Firstly, in terms of mechanical structure, length adjusting device is added to meet the needs of different people. At the same time, a limit device is added to the knee joint to improve the safety performance and comfort. Secondly, the dynamics of the model is carried out by Lagrange, and the exoskeleton model is established for ADAMS motion simulation. The force of ADAMS simulation, the calculated by Lagrange equation and the force of the first edition of hydraulic cylinder are compared, and the force selection of hydraulic cylinder is analyzed. By comparison with the first edition, the optimization rate of the improved hydraulic cylinder reaches 8 %. Finally, in order to verify the rationality of ADAMS simulation and the effectiveness of hydraulic cylinder improvement, the wear test is carried out, the average errors of leg centroid in normal walking, wearing exoskeleton walking and ADAMS simulation data are compared. The average error rate is less than 10 %. The results show that the simulation model design is reasonable, and the effectiveness of the hydraulic cylinder improvement is verified. The exoskeleton device designed can well follow the human motion. The simulation analysis of the exoskeleton provides important parameters for the manufacture and it also provides theoretical basis for the later control theory

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

AVALIAÇÃO Biomecânica da Marcha Com Exoesqueleto Robótico em Sujeitos Com Avc Crônico

Objetivo: Avaliar o efeito do uso de um exoesqueleto robótico de joelho esquerdo na cinética e cinemática de pacientes com disfunção neuromotora decorrente de Acidente Vascular Cerebral (AVC). Metodologia: Foram comparados os padrões biomecânicos angulares (inerciais) e eletromiográficos (sEMG) durante marcha livre e com o exoesqueleto robótico desenvolvido na UFES, em um percurso de 10 metros. Previamente, houve a avaliação da Máxima Contração Voluntária (MCV) dos músculos a serem avaliados para a normalização dos dados. Resultados: Houve um protocolo piloto onde foram avaliados onze sujeitos saudáveis e posteriormente dois sujeitos com AVC crônico participaram dos experimentos, sendo que em um sujeito foi detectado um coeficiente de correlação de concordância (pc) > 0,80 nos padrões de flexão de joelho e de quadril direitos, e em outro sujeito foi detectada moderada correlação no padrão (pc > 0,80) de flexão dos quadris. Foi detectado coeficiente de correlação de Pearson (r) 70% em flexão de quadril, flexão de joelho direito e planti/dorsiflexão, já o segundo sujeito apresentou Cb 0,05) nos picos de ativação muscular. Conclusões: Os resultados referentes à análise biomecânica de pessoas com AVC crônico foram satisfatórios. Há a necessidade da implementação do protocolo experimental em um maior número de sujeitos com AVC ou com outras complicações neuromotoras

DEVELOPMENT OF A ROBOTIC EXOSKELETON SYSTEM FOR GAIT REHABILITATION

Ph.DDOCTOR OF PHILOSOPH

The effects of ankle-foot orthoses on gait deviations associated with untreated developmental dysplasia of the hip during walking: case study

Developmental dysplasia of the hip (DDH) is considered to be one of the most common orthopaedic disorders, referring to a range of conditions from mild to severe dislocation of the hip joint. Knowledge of ankle-foot orthosis (AFO) use in patients with severe developmental dysplasia of the hip bone is crucial and may help improve the gait cycle during walking. The plantar pressure sensing mat and insole plantar sensor pad are ideal low cost alternatives to the force plate for capturing plantar centre pressure excursion during gait. Acquired centre of pressure (COP) traces are favoured by many medical clinicians and allied health professionals evaluating foot loading and body balance with respect to foot biomechanics, foot injury, foot deformation and foot ulceration. Researchers have recommended the use of COP traces for the study of the deformed foot and deformed lower limb to improve orthosis assessment and orthosis performance testing. Knowledge of the COP and plantar pressure characteristics such as peak pressure, contact pressure and pressure time integral during walking can help identify possible foot pathology, help determine the most effective foot orthosis, and allow for the appropriate calculation of balance control and joint kinetics and kinematics during gait. However, there are unclear gait alterations in individuals with DDH which have clinical implications such as the investigation of AFOs and their effect on lower limb kinematics and kinetics, and their impact on the plantar pressure characteristics of the joints during walking and running. This research aimed to provide a better understanding of the gait characteristics of patients with severe DDH. The first set of objectives was to study and evaluate the kinematics and kinetics of the ankle, knee and hip joints during walking in the sagittal plane for a patient aged 27 years (the author of this research) with severe dysplasia of the left hip, using two different types of ankle-foot orthosis (custom-made, and leaf-AFO). The data were collected using ten cameras and one force plate under four conditions: barefoot, custom-made AFO, leaf AFO, and shoes only. The angles between every two segments were calculated using the Euler rotation sequence. An inverse dynamic approach was used to calculate sagittal joint moments and power. The results showed that the planter flexion angle reached its maximum during the time between the toes-off, the ground phase and the initial swing phase with a mean difference of 21.1° and 14°, respectively. Moreover, the results indicated that the fabricated orthosis decreased both the right and left extensor moments significantly during the load-bearing phase in comparison to barefoot by a mean difference of 0.29, and 0.43 Nm/kg respectively for both limbs. Results showed that the custom-orthosis had a higher moment during the late stance of the gait cycle compared to barefoot, with the data showing significant change by a mean difference of 0.1604 Nm/kg. However, the Leaf Spring AFO had little impact on the flexion moment during the late stance phase. The second set of objectives of this study was to evaluate the effect of wearing the two ankle-foot orthosis on the plantar pressure distribution of specific foot regions for the patient with DDH. These objectives were achieved by developing a correlation technique between the COP trajectory and the lower limb trajectory during the three main phases of gait (heel strike, midstance and push off). The lower limb trajectory data were collected using a new close-range photogrammetry system that employed six HD video cameras to capture the lower limb trajectory. The COP trace and pressure data were collected using 3000E F-scan in-shoe sensors sampling at 100 Hz inserted inside the patient’s shoes. Six walking trials (ten steps per trial) were recorded for each condition (barefoot, custom-made orthosis, and Leaf-AFO). The average of the three middle steps was taken out of the ten steps for each trial under each condition. The corresponding results showed that the highest values of the pressure time integral for the left foot barefoot condition were registered under the lateral heel (LH) 115.92±2.91 kPa.sec, medial heel (MH) 101.66±2.55 kPa.sec, first toe (T1) 73.79±1.85 kPa.sec, fourth and fifth toes (T45) 49.90±1.25 kPa.sec and second toe (T2) 42.94±1.08 kPa.sec. The research concluded that the kinematics and kinetics of the ankle and hip joint were improved by the custom-made orthosis more than that of the Leaf AFO-Spring Orthoses. The current work also concluded that both AFOs did not much change the kinematics of the knee joint however, there were some improvements in the moments and power generated. Finally, the researcher concluded that both orthoses enhanced body stability, minimized foot pain, and minimizing the risk of injury beneath specific foot regions. More investigations are required in the future, such as the investigation of the customized Knee-Ankle-Foot Orthosis (KAFOs) and increasing the number of samples

Biyomimetik Bir Alt Uzuv Dış Iskelet Robotun Tasarımı Ve Denetimi

TÜBİTAK MAG Proje15.04.2017Dış iskelet robotlar, insan uzuvları ile etkileşim halinde çalışan, giyilebilir elektromekanikyapılardır. Bu robotlar, yürüme engeli olan ya da yaşlı kişilerde yardımcı uzuv, felçli kişilerderehabilitasyon ve sağlıklı insanlarda güç artırımı amacı ile kullanılmaktadır. Bu projede, insanvücudu eklemlerinin biyomekanik davranışlarından esinlenilerek enerji verimli, kararlı, güvenli,esnek ve kullanıcı ile uyumlu bir alt uzuv dış iskelet robotun biyomimetik tasarımı ve denetimigerçekleştirilmiştir.İnsan vücudunun kas-iskelet sistemi, bağlı bulundukları eklemlerde sertlik ve sönümlemeyidevamlı değiştirerek esnek ve kararlı bir hareket kabiliyeti sağlamaktadır. Bu projedegeliştirilen dış iskelet robotun bilek eklemlerinde hem sertlik hem de sönümleme değerlerinibağımsız değiştirebilen karma eyleyici tasarımı, diz ve kalça eklemlerinde ise seri elastikeyleyici ile sönümlemesi değiştirilebilir eyleyici içeren karma eyleyici tasarımları kullanılmıştır.Böylece, bütün eklemlerde mekanik olarak ayarlanabilir empedans (sertlik ve sönümleme)değerleri ile çalışabilen biyomimetik esnek bir dış iskelet robot literatüre kazandırılmıştır. Dışiskelet robotun geliştirilmesi aşamasında, sertliği değiştirilebilir eyleyiciler, sönümlemesideğiştirilebilir eyleyiciler ve dış iskelet robotun bütünü için benzetim çalışmalarıgerçekleştirilmiştir ve dış iskelet robotun bir bütün olarak üretimi yapılmıştır. Bu dış iskeletrobotun kontrol performansını denemek için de bir dizi deneysel kontrol çalışmalarıgerçekleştirilmiştir. Gerçekleştirilen bu deneysel çalışmalar; sertliği değiştirilebilir eyleyicininkuvvet kontrol ve pozisyon kontrol deneyleri, insan bilek sertliğinin EMG sinyalleri tabanlıgerçek zamanlı olarak kestirimi, bunun sertliği değiştirilebilir eyleyiciye uygulanması,sönümlemesi değiştirilebilir eyleyicinin istenen sönümleme torklarının kontrolü deneyleri, buiki eyleyicinin birleşiminden oluşan karma eyleyicinin deneysel performans çalışmaları vedaha sonrada geliştirilen dış iskelet robotun kullanıcı-baskın ve robot-baskın kontroldeneylerdir. Böylelikle, bu projede biyomimetik bir dış iskelet robotun tasarımı ve üretimigerçekleştirilmiş, kontrol çalışmaları deneysel olarak denenerek robotun temel performansdeğerlendirmeleri yapılmıştır.Exoskeleton robots are wearable electromechanical structures which can work interacting withhuman limbs. These robots are used as assistive limb, rehabilitation and power augmentationpurposes for elderly or disabled person, paralyzed person and healthy person respectively. Thisproject aims at designing and controlling of a lower limb exoskeleton robot which is energyefficient, stable, safe and user compatible by the inspiration of the human body jointbiomechanical behaviors and neuro-muscular control.Human body neuro-muscular system varies stiffness and damping of the human joints regularlyand thus provides flexible and stable movement capability. An hybrid actuator design variyingstiffness and damping independently in the ankle joints and another hybrid actuator designincluding series eleastic actuator and variable damping actuator in the knee and hip joints wereused in the exoskeleton robot developed in this project. Hence, a biomimetic compliantexoskeleton robot operating with mechanically adjustable impedance coefficients (stiffness anddamping) is contributed to the literature. During the development stage of the exoskeleton robot,some simulation studies were carried out for all variable stiffness, variable damping actuatorsand whole exoskleton robot. In addition, a set of experimental control studies was conducted toevaulate the control performance of this exoskeleton robot. These experimental studies areimpedans force control experiments of the varaible stiffness actuators, position controlexperiments of the varaible stiffness actuators, real time estimation experiments of human anklejoint stiffness based on EMG signals, applying those on the varaible stiffness actuators, desiredtork and damping experiments of the varaible damping actuators, experimental performancestudies of the hybrid actuators including these two types and then user in charge and robot incharge experiments of the whole exosekeleton robot. In this way, a biomimetic lower limbexoskeleton robot was designed and manufactured, and its performance was evaluated with aset of experimental control studies