24 research outputs found
Analysis and control of FES-assisted paraplegic walking with wheel walker.
The number of people with spinal cord injury (SCI) is increasing every year and
walking has been found to be the most exciting and important prospect to these
patients to improve their quality of life. Many individuals with incomplete SCI
have the potential to walk and everyone of them wants to try. Unfortunately up to
now, there is less than one third of patients could walk again after SCI. Residual
function, the orthotic support, energy expenditure, patient motivation and control
technique are some of the factors that influence the walking outcome of spinal cord
injured people. In this thesis, a series of studies are carried out to investigate the
possibility of enhancing the performance of the functional electrical stimulation
(PES) assisted paraplegic walking with wheel walker through the development and
implementation of intelligent control technique and spring brake orthosis (SBO)
with full utilization of the voluntary upper body effort. The main aim of this thesis
is to enable individuals with complete paraplegia to walk again with maximum
performance and the simplest approach as possible.
Firstly, before simulation of the system can be made, it is important to select the
right model to represent the actual plant. In this thesis, the development of a
humanoid and wheel walker models are carried out using MSC.visualNastran4D
(vN4D) software and this is integrated with Matlab Simulink® for simulation. The
newly developed quadriceps and hamstrings muscle models from the series of
experiments are used to represent subject muscles after comparison and validation
with other two well-known muscle models are performed.
Several experiments are conducted to investigate the effect of stimulation frequency
and pulse-width in intermittent stimulation with isometric measurement from
paraplegic subjects. The results from this work can serve as a guidance to determine
the optimum stimulation parameters such as frequency and pulse-width to reduce
muscle fatigue during PES application. The ability test is introduced to determine
the maximum leg force that can be applied to the specific paraplegic subject during
FES functional task with minimum chance of spasm and leg injury.
Investigations are carried out on the control techniques implemented for FES
walking with wheel walker. PID control and fuzzy logic control (FLC) are used to
regulate the electrical stimulation required by the quadriceps and hamstrings
muscles in order to perform the FES walking manoeuvre according to predefined
walking trajectory. The body weight transfer is introduced to increase the efficiency
of FES walking performance. The effectiveness of body weight transfer and control
strategy to enhance the performance of FES walking and reduce stimulation pulses
required is examined.
Investigations are carried out on the effectiveness of spring brake orthosis (SBO)
for FES assisted paraplegic walking with wheel walker. A new concept in hybrid
orthotics provides solutions to the problems that affect current 'hybrid orthosis,
including knee and hip flexion without relying on the withdrawal reflex or a
powered actuator and foot-ground clearance without extra upper body effort. The
use of SBO can also eliminate electrical stimulation pulses required by the
hamstrings muscle for the same FES walking system.
Further improvement of the FES walking system is achieved by introducing finite
state control (FSC) to control the switching time between springs, brakes and
electrical stimulation during FES assisted walking with wheel walker with the
combInation of FLC to regulate the electrical stimulation required for the knee
extension. The results show that FSC can be used to accurately control the
switching time and improve the system robustness and stability
Genetic Algorithms Based Approach for Designing Spring Brake Orthosis – Part Ii: Control of FES Induced Movement
Spring brake orthotic swing phase for paraplegic gait is initiated through releasing the brake on the knee mounted with a torsion spring. The stored potential energy in the spring, gained from the previous swing phase, is solely responsible for swing phase knee flexion. Hence the later part of the SBO operation, functional electrical stimulation (FES) assisted extension movement of the knee has to serve an additional purpose of restoring the spring potential energy on the fly. While control of FES induced movement as such is often a challenging task, a torsion spring, being antagonistically paired up with the muscle actuator, as in spring brake orthosis (SBO), only adds to the challenge. Two new schemes are proposed for the control of FES induced knee extension movement in SBO assisted swing phase. Even though the control schemes are closed-loop in nature, special attention is paid to accommodate the natural dynamics of the mechanical combination being controlled (the leg segment) as a major role playing feature. The schemes are thus found to be immune from some drawbacks associated with both closed-loop tracking as well as open-loop control of FES induced movement. A leg model including the FES knee joint model of the knee extensor muscle vasti along with the passive properties is used in the simulation. The optimized parameters for the SBO spring are obtained from the earlier part of this work. Genetic algorithm (GA) and multi-objective GA (MOGA) are used to optimize the parameters associated with the control schemes with minimum fatigue as one of the control objectives. The control schemes are evaluated in terms of three criteria based on their ability to cope with muscle fatigue
Online Assessment of Human-Robot Interaction for Hybrid Control of Walking
Restoration of walking ability of Spinal Cord Injury subjects can be achieved by different approaches, as the use of robotic exoskeletons or electrical stimulation of the user’s muscles. The combined (hybrid) approach has the potential to provide a solution to the drawback of each approach. Specific challenges must be addressed with specific sensory systems and control strategies. In this paper we present a system and a procedure to estimate muscle fatigue from online physical interaction assessment to provide hybrid control of walking, regarding the performances of the muscles under stimulation
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
Rehabilitation Engineering
Population ageing has major consequences and implications in all areas of our daily life as well as other important aspects, such as economic growth, savings, investment and consumption, labour markets, pensions, property and care from one generation to another. Additionally, health and related care, family composition and life-style, housing and migration are also affected. Given the rapid increase in the aging of the population and the further increase that is expected in the coming years, an important problem that has to be faced is the corresponding increase in chronic illness, disabilities, and loss of functional independence endemic to the elderly (WHO 2008). For this reason, novel methods of rehabilitation and care management are urgently needed. This book covers many rehabilitation support systems and robots developed for upper limbs, lower limbs as well as visually impaired condition. Other than upper limbs, the lower limb research works are also discussed like motorized foot rest for electric powered wheelchair and standing assistance device
Nonlinear robust control of functional electrical stimulation system for paraplegia
The study was directed towards enhancing Functional Electrical Stimulation (FES) for sit-to-stand movement restoration in paraplegia subjects. The scarcity of FES assistive devices was due to the inability of the developed equipment to attain clinical acceptance. Applications of control systems have shown fruitful results. And based on the literature, further improvements in model, trajectory and control systems are needed. Model with a higher level of accuracy and continuous as well as bump-free trajectories are essential ingredients for better control systems. The control systems can be enhanced by giving considering to changes in mass of the subject, disturbance rejection and stability. Hence, the comprehensive control scheme is necessary for this application as well as a better model and trajectory. In modelling an additional joint has been considered to improve the accuracy. In trajectory planning, the six-order polynomial has been used to refine the desired trajectory. The comprehensive control systems have been designed with consideration of robustness, disturbance rejection, and stability. Three nonlinear control approaches have been investigated; the Sliding Mode Control (SMC), Feedback Linearisation Control (FLC), and Back-Stepping Control (BSC). Results reveal improvements in the accuracy of the kinematic model by 24%, and the dynamic model by 47%. The trajectory planning parameters are continuous, and not susceptible to jerks or spikes. Execution time enhanced by 11%, the upper and lower terminal velocities improved by 16.9% and 20.9% respectively. The system response without disturbance shows good results with the SMC, FLC, and BSC. Revelations by robustness examination also maintain remarkable enhancements in the parameters with both 53% and 126% mass. The results for disturbance rejection examinations with fatigue, spasm, tremor, and combined disturbance effects showed sustenance of refinement in the response parameters. Therefore, indicating improvements despite the changes to the system. The BSC showed the best performance, followed by the FLC, and the SMC. Hence, the BSC is recommended for such systems