Gait-Assist Wearable Robot Using Interactive Rhythmic Stimulation to the Upper Limbs

Many power-assist wearable exoskeletons have been developed to provide walking support and gait rehabilitation for elderly subjects and gait-disorder patients. Most designers have focused on a direct power-assist to the wearer's lower limbs. However, gait is a coordinated rhythmic movement of four limbs controlled intrinsically by central pattern generators, with the upper limbs playing an important role in walking. Maintaining a normal gait can become difficult as a person ages, because of decreases in limb coordination, stride length, and gait speed. It is known that coordination mechanisms can be governed by the principle of mutual entrainment, in which synchronization develops through the interaction between nonlinear phase oscillators in biological systems. This principle led us to hypothesize that interactive rhythmic stimulation to upper-limb movements might compensate for the age-related decline in coordination, thereby improving the gait in the elderly. To investigate this hypothesis, we developed a gait-assist wearable exoskeleton that employs interactive rhythmic stimulation to the upper limbs. In particular, we investigated the effects on spatial (i.e., hip-swing amplitude) and temporal (i.e., hip-swing period) gait parameters by conducting walking experiments with 12 healthy elderly subjects under one control condition and five upper-limb-assist conditions, where the output motor torque was applied at five different upper-limb swing positions. The results showed a statistically significant increase in the mean hip-swing amplitude, with a mean increment of about 7% between the control and upper-limb-assist conditions. They also showed a statistically significant decrease in the mean hip-swing period, with a mean decrement of about 2.3% between the control and one of the upper-limb-assist conditions. Although the increase in the hip-swing amplitude and the decrease in the hip-swing period were both small, the results indicate the possibility that interactive rhythmic stimulation to the upper limbs might have a positive effect on the gait of the elderly

Powered knee orthosis for human gait rehabilitation: first advances

This paper presents a new system for a powered knee orthosis, that was designed to assist and improve the gait function of patients with gait pathologies. The system contains the orthotic device (embedded with sensors for angle and user-orthosis interaction torque measurements, and an electric actuator) and wearable sensors (inertial measurement unit, force sensitive resistors, and electromyography sensors), which allows the generation of smart rehabilitation tools and several motion assistive techniques. The main goal is to present a conceptual overview and functional description of the system and use scenarios of each component. The attachment mechanism of the orthosis to the limb is also highlighted, being composed of a straps system fixed in the mechanical links of the joint. It was noticed that users with distinct lower-limb morphologies can presents difficulties wearing the orthosis, since the device needs constant adjust to align the mechanical and human joints. The system was validated in ground-level walking on healthy subjects, with emphasis on the impact of the device in the user. The subjects reported that the orthosis is comfortable to use, easy to wear, and no issues were raised regarding the aesthetics of the device. Only the weight was assimilated as a possible hindrance (compensated in the future). Future challenges involve the inclusion of an ankle joint in the system and the use of the proposed tool in rehabilitation.This work is supported by the FCT - Fundacao para a Ciencia e Tecnologia - with the reference scholarship SFRH/BD/108309/2015, with the reference project UID/EEA/04436/2013, and by FEDER funds through the COMPETE 2020 - Programa Operacional Competitividade e Internacionalizacao (POCI) - with the reference project POCI-01-0145-FEDER-006941, and partially supported with grant RYC-2014-16613 by Spanish Ministry of Economy and Competitiveness

Biped locomotion control through a biologically-inspired closed-loop controller

Dissertação de mestrado integrado em Engenharia BiomédicaCurrently motor disability in industrialized countries due to neural and physical impairments is an increasingly worrying phenomenon and the percentage of patients is expected to be increasing continuously over the coming decades due to a process of ageing the world is undergoing. Additionally, rising retirement ages, higher demand of elderly people for an independent, dignified life and mobility, huge cost in the provision of health care are some other determinants that motivate the restoration of motor function as one of the main goals of rehabilitation. Modern concepts of motor learning favor a task-specific training in which all movements in daily life should be trained/assisted repetitively in a physically correct fashion. Considering the functional activity of the neuronal circuits within the spinal cord, namely the central pattern generator (CPG), as the foundation to human locomotion, motor relearning should be based on intensive training strategies directed to the stimulation and reorganization of such neural pathways through mechanisms addressed by neural plasticity. To this end, neuromodelings are required to simulate the human locomotion control to overcome the current technological challenges such as developing smaller, intelligent and cost-effective devices for home and work rehabilitation scenarios which can enable a continuous therapy/ assistance to guide the impaired limbs in a gentle manner, avoiding abrupt perturbations and providing as little assistance as necessary. Biomimetic models, taking neurological and biomechanical inspiration from biological animals, have been embracing these challenges and developing effective solutions on refining the locomotion models in terms of energy efficiency, simplicity in the structure and robust adaptability to environment changes and unexpected perturbations. Thus, the aim target of this work is to study the applicability of the CPG model for gait rehabilitation, either for assistance and/or therapy purposes. Focus is developed on the locomotion control to increase the knowledge of the underlying principles useful for gait restoration, exploring the brainstem-spinal-biomechanics interaction more fully. This study has great application in the project of autonomous robots and in the rehabilitation technology, not only in the project of prostheses and orthoses, but also in the searching of procedures that help to recuperate motor functions of human beings. Encouraging results were obtained which pave the way towards the simulation of more complex behaviors and principles of human locomotion, consequently contributing for improved automated motor rehabilitation adapted to the rehabilitation emerging needs.Actualmente a debilidade motora em países industrializados devido a deficiências neurais e físicas é um fenómeno crescente de apreensão sendo expectável um contínuo aumento do rácio de pacientes nas próximas décadas devido ao processo de envelhecimento. Inclusivé, o aumento da idade de reforma, a maior procura por parte dos idosos para uma mobilidade e vida autónoma e condigna, o elevado custo nos cuidados de saúde são incentivos para a restauração da função motora como um dos objectivos principais da reabilitação. Conceitos recentes de aprendizagem motora apoiam um treino de tarefas específicas no qual movimentos no quotidiano devem ser treinados/assistidos de forma repetitiva e fisicamente correcta. Considerando a actividade funcional dos circuitos neurais na medula, nomeadamente o gerador de padrão central (CPG), como a base da locomoção, a reaprendizagem motora deve-se basear em estratégias intensivas de treino visando a estimulação e reorganização desses vias neurais através de mecanismos abordados pela plasticidade neural. Assim, são necessários modelos neurais para simular o controlo da locomoção humana de modo a superar desafios tecnológicos actuais tais como o desenvolvimento de dispositivos mais compactos, inteligentes e económicos para os cenários de reabilitação domiciliar e laboral que podem permitir uma terapia/assistência contínua na guia dos membros debilitados de uma forma suave, evitando perturbações abruptas e fornecendo assistência na medida do necessário. Modelos biomiméticos, inspirando-se nos princípios neurológicos e biomecânicos dos animais, têm vindo a abraçar esses desafios e a desenvolver soluções eficazes na refinação de modelos de locomoção em termos da eficiência de energia, da simplicidade na estrutura e da adaptibilidade robusta face a alterações ambientais e perturbações inesperadas. Então, o objectivo principal do trabalho é estudar a aplicabilidade do modelo de CPG para a reabilitação da marcha, para efeitos de assistência e/ou terapia. É desenvolvido um foco no controlo da locomoção para maior entendimento dos princípios subjacentes úteis para a recuperação da marcha, explorando a interacção tronco cerebral-espinal medula-biomecânica de forma mais detalhada. Este estudo tem potencial aplicação no projecto de robôs autónomos e na tecnologia de reabilitação, não só no desenvolvimento de ortóteses e próteses, mas também na procura de procedimentos úteis para a recuperação da função motora. Foram obtidos resultados promissores susceptíveis de abrir caminho à simulação de comportamentos e princípios mais complexos da marcha, contribuindo consequentemente para uma aprimorada reabilitação motora automatizada adaptada às necessidades emergentes

Rehabilitative Soft Exoskeleton for Rodents

Robotic exoskeletons provide programmable, consistent and controllable active therapeutic assistance to patients with neurological disorders. Here we introduce a prototype and preliminary experimental evaluation of a rehabilitative gait exoskeleton that enables compliant yet effective manipulation of the fragile limbs of rats. To assist the displacements of the lower limbs without impeding natural gait movements, we designed and fabricated soft pneumatic actuators (SPAs). The exoskeleton integrates two customizable SPAs that are attached to a limb. This configuration enables a 1 N force load, a range of motion exceeding 80 mm in the major axis, and speed of actuation reaching two gait cycles/s. Preliminary experiments in rats with spinal cord injury validated the basic features of the exoskeleton. We propose strategies to improve the performance of the robot and discuss the potential of SPAs for the design of other wearable interfaces

A unilateral robotic knee exoskeleton to assess the role of natural gait assistance in hemiparetic patients.

Background: Hemiparetic gait is characterized by strong asymmetries that can severely affect the quality of life of stroke survivors. This type of asymmetry is due to motor deficits in the paretic leg and the resulting compensations in the nonparetic limb. In this study, we aimed to evaluate the effect of actively promoting gait symmetry in hemiparetic patients by assessing the behavior of both paretic and nonparetic lower limbs. This paper introduces the design and validation of the REFLEX prototype, a unilateral active knee–ankle–foot orthosis designed and developed to naturally assist the paretic limbs of hemiparetic patients during gait. Methods: REFLEX uses an adaptive frequency oscillator to estimate the continuous gait phase of the nonparetic limb. Based on this estimation, the device synchronically assists the paretic leg following two different control strategies: (1) replicating the movement of the nonparetic leg or (2) inducing a healthy gait pattern for the paretic leg. Technical validation of the system was implemented on three healthy subjects, while the effect of the generated assistance was assessed in three stroke patients. The effects of this assistance were evaluated in terms of interlimb symmetry with respect to spatiotemporal gait parameters such as step length or time, as well as the similarity between the joint’s motion in both legs. Results: Preliminary results proved the feasibility of the REFLEX prototype to assist gait by reinforcing symmetry. They also pointed out that the assistance of the paretic leg resulted in a decrease in the compensatory strategies developed by the nonparetic limb to achieve a functional gait. Notably, better results were attained when the assistance was provided according to a standard healthy pattern, which initially might suppose a lower symmetry but enabled a healthier evolution of the motion of the nonparetic limb. Conclusions: This work presents the preliminary validation of the REFLEX prototype, a unilateral knee exoskeleton for gait assistance in hemiparetic patients. The experimental results indicate that assisting the paretic leg of a hemiparetic patient based on the movement of their nonparetic leg is a valuable strategy for reducing the compensatory mechanisms developed by the nonparetic limb.post-print6406 K

Joint Trajectory Generation and High-level Control for Patient-tailored Robotic Gait Rehabilitation

This dissertation presents a group of novel methods for robot-based gait rehabilitation which were developed aiming to offer more individualized therapies based on the specific condition of each patient, as well as to improve the overall rehabilitation experience for both patient and therapist. A novel methodology for gait pattern generation is proposed, which offers estimated hip and knee joint trajectories corresponding to healthy walking, and allows the therapist to graphically adapt the reference trajectories in order to fit better the patient's needs and disabilities. Additionally, the motion controllers for the hip and knee joints, mobile platform, and pelvic mechanism of an over-ground gait rehabilitation robotic system are also presented, as well as some proposed methods for assist as needed therapy. Two robot-patient synchronization approaches are also included in this work, together with a novel algorithm for online hip trajectory adaptation developed to reduce obstructive forces applied to the patient during therapy with compliant robotic systems. Finally, a prototype graphical user interface for the therapist is also presented

DEVELOPMENT OF A ROBOTIC EXOSKELETON SYSTEM FOR GAIT REHABILITATION

Ph.DDOCTOR OF PHILOSOPH

A novel approach to user controlled ambulation of lower extremity exoskeletons using admittance control paradigm

The robotic lower extremity exoskeletons address the ambulatory problems confronting individuals with paraplegia. Paraplegia due to spinal cord injury (SCI) can cause motor deficit to the lower extremities leading to inability to walk. Though wheelchairs provide mobility to the user, they do not provide support to all activities of everyday living to individuals with paraplegia. Current research is addressing the issue of ambulation through the use of wearable exoskeletons that are pre-programmed. There are currently four exoskeletons in the U.S. market: Ekso, Rewalk, REX and Indego. All of the currently available exoskeletons have 2 active Degrees of Freedom (DOF) except for REX which has 5 active DOF. All of them have pre-programmed gait giving the user the ability to initiate a gait but not the ability to control the stride amplitude (height), stride frequency or stride length, and hence restricting users’ ability to navigate across different surfaces and obstacles that are commonly encountered in the community. Most current exoskeletons do not have motors for abduction or adduction to provide users with the option for movement in coronal plane, hence restricting user’s ability to effectively use the exoskeletons. These limitations of currently available pre-programmed exoskeleton models are sought to be overcome by an intuitive, real time user-controlled control mechanism employing admittance control by using hand-trajectory as a surrogate for foot trajectory. Preliminary study included subjects controlling the trajectory of the foot in a virtual environment using their contralateral hand. The study proved that hands could produce trajectories similar to human foot trajectories when provided with haptic and visual feedback. A 10 DOF 1/2 scale biped robot was built to test the control paradigm. The robot has 5 DOF on each leg with 2 DOF at the hip to provide flexion/extension and abduction/adduction, 1 DOF at the knee to provide flexion and 2 DOF at the ankle to provide flexion/extension and inversion/eversion. The control mechanism translates the trajectory of each hand into the trajectory of the ipsilateral foot in real time, thus providing the user with the ability to control each leg in both sagittal and coronal planes using the admittance control paradigm. The efficiency of the control mechanism was evaluated in a study using healthy subjects controlling the robot on a treadmill. A trekking pole was attached to each foot of the biped. The subjects controlled the trajectory of the foot of the biped by applying small forces in the direction of the required movement to the trekking pole through a force sensor. The algorithm converted the forces to Cartesian position of the foot in real time using admittance control; the Cartesian position was converted to joint angles of the hip and knee using inverse kinematics. The kinematics, synchrony and smoothness of the trajectory produced by the biped robot was evaluated at different speeds, with and without obstacles, and compared with typical walking by human subjects on the treadmill. Further, the cognitive load required to control the biped on the treadmill was evaluated and the effect of speed and obstacles with cognitive load on the kinematics, synchrony and smoothness was analyzed