A Novel User-Controlled Assisted Standing Control System for a Hybrid Neuroprosthesis

Spinal cord injury (SCI) is a serious condition with 17,000 new cases each year and an estimated total of 282,000 people in the United States who have SCI. Some people with SCI who have paraplegia suffer from paralysis, muscle spasticity, bone changes, chronic pain and other problems. Active orthoses such as the ReWalk, EXPOS, and Ekso have improved the quality of life of people with SCI. The hybrid neuroprosthesis is an active orthosis that uses functional electrical stimulation (FES) at the quadriceps and has two main purposes: restoring mobility in people with SCI and providing physical therapy for the user outside of a clinical setting. To mobilize people with SCI, the neuroprosthesis must provide assisted movement for a sitting to standing motion. A standing control system developed by the Pitt Neuromuscular Control and Robotics Laboratory (NCRL) before this proposed system did not give enough control of the movement to the user and FES alone did not provide enough torque at the knees for standing. The NCRL neuroprosthesis was modified to include a harmonic gearmotor at the knees, a thumb joystick for user control, and a force sensing walker. A control system using a finite state machine (FSM) was designed to perform hybrid standing in the neuroprosthesis. The FSM is divided into 3 states and uses 5 separate controllers: a tracking controller for forward leaning during sitting, a tracking controller to synchronize the knees, a tracking controller to lock the knees during standing, a hip tracking controller, and openloop FES. Four experiments were performed on subjects to analyze control performance, power usage, and energy consumption during motors only and hybrid standing. A subject with SCI successfully performed several trials of hybrid standing. The controllers performed sufficiently accurately, and several minor control problems were fixed. The highest average energy consumption at the knee motors was 88.4 joules during experiment 1. The hybrid standing experiment demonstrated a modest energy reduction of 15% in a subject with SCI. The hybrid standing demonstrated a high energy reduction of 74% in the right knee in experiment 2, through hybrid actuation and a slower standing speed

Down-Conditioning of Soleus Reflex Activity using Mechanical Stimuli and EMG Biofeedback

Spasticity is a common syndrome caused by various brain and neural injuries, which can severely impair walking ability and functional independence. To improve functional independence, conditioning protocols are available aimed at reducing spasticity by facilitating spinal neuroplasticity. This down-conditioning can be performed using different types of stimuli, electrical or mechanical, and reflex activity measures, EMG or impedance, used as biofeedback variable. Still, current results on effectiveness of these conditioning protocols are incomplete, making comparisons difficult. We aimed to show the within-session task- dependent and across-session long-term adaptation of a conditioning protocol based on mechanical stimuli and EMG biofeedback. However, in contrast to literature, preliminary results show that subjects were unable to successfully obtain task-dependent modulation of their soleus short-latency stretch reflex magnitude

Adaptive control for wearable robots in human-centered rehabilitation tasks

Robotic rehabilitation therapies have been improving by providing the needed assistance to the patient, in a human-centered environment, and also helping the therapist to choose the necessary procedure. This thesis presents an adaptive "Assistance-as-needed" strategy which adheres to the specific needs of the patient and with the inputs from the therapist, whenever needed. The exertion of assistive and responsive behavior of the lower limb wearable robot is dedicated for the rehabilitation of incomplete spinal cord injury (SCI) patients. The main objective is to propose and evaluate an adaptive control model on a wearable robot, assisting the user and adhering to their needs, with no or less combination of external devices. The adaptation must be more interactive to understand the user needs and their volitional orders. Similarly, by using the existing muscular strength, in incomplete SCI patients, as a motivation to pursue the movement and assist them, only when needed. The adaptive behavior of the wearable robot is proposed by monitoring the interaction and movement of the user. This adaptation is achieved by modulating the stiffness of the exoskeleton in function of joint parameters, such as positions and interaction torques. These joint parameters are measured from the user independently and then used to update the new stiffness value. The adaptive algorithm performs with no need of external sensors, making it simple in terms of usage. In terms of rehabilitation, it is also desirable to be compatible with combination of assistive devices such as muscle stimulation, neural activity (BMI) and body balance (Wii), to deliver a user friendly and effective therapy. Combination of two control approaches has been employed, to improve the efficiency of the adaptive control model and was evaluated using a wearable lower limb exoskeleton device, H1. The control approaches, Hierarchical and Task based approach have been used to assist the patient as needed and simultaneously motivate the patient to pursue the therapy. Hierarchical approach facilitates combination of multiple devices to deliver an effective therapy by categorizing the control architecture in two layers, Low level and High level control. Task-based approaches engage in each task individually and allow the possibility to combine them at any point of time. It is also necessary to provide an interaction based approach to ensure the complete involvement of the user and for an effective therapy. By means of this dissertation, a task based adaptive control is proposed, in function of human-orthosis interaction, which is applied on a hierarchical control scheme. This control scheme is employed in a wearable robot, with the intention to be applied or accommodated to different pathologies, with its adaptive capabilities. The adaptive control model for gait assistance provides a comprehensive solution through a single implementation: Adaptation inside a gait cycle, continuous support through gait training and in real time. The performance of this control model has been evaluated with healthy subjects, as a preliminary study, and with paraplegic patients. Results of the healthy subjects showed a significant change in the pattern of the interaction torques, elucidating a change in the effort and adaptation to the user movement. In case of patients, the adaptation showed a significant improvement in the joint performance (flexion/extension range) and change in interaction torques. The change in interaction torques (positive to negative) reflects the active participation of the patient, which also explained the adaptive performance. The patients also reported that the movement of the exoskeleton is flexible and the walking patterns were similar to their own distinct patterns. The presented work is performed as part of the project HYPER, funded by Ministerio de Ciencia y Innovación, Spain. (CSD2009 - 00067 CONSOLIDER INGENIOLas terapias de rehabilitación robóticas han sido mejoradas gracias a la inclusión de la asistencia bajo demanda, adaptada a las variaciones de las necesidades del paciente, así como a la inclusión de la ayuda al terapeuta en la elección del procedimiento necesario. Esta tesis presenta una estrategia adaptativa de asistencia bajo demanda, la cual se ajusta a las necesidades específicas del paciente junto a las aportaciones del terapeuta siempre que sea necesario. El esfuerzo del comportamiento asistencial y receptivo del robot personal portátil para extremidades inferiores está dedicado a la rehabilitación de pacientes con lesión de la médula espinal (LME) incompleta. El objetivo principal es proponer y evaluar un modelo de control adaptativo en un robot portátil, ayudando al usuario y cumpliendo con sus necesidades, en ausencia o con reducción de dispositivos externos. La adaptación debe ser más interactiva para entender las necesidades del usuario y sus intenciones u órdenes volitivas. De modo similar, usando la fuerza muscular existente (en pacientes con LME incompleta) como motivación para lograr el movimiento y asistirles solo cuando sea necesario. El comportamiento adaptativo del robot portátil se propone mediante la monitorización de la interacción y movimiento del usuario. Esta adaptación conjunta se consigue modulando la rigidez en función de los parámetros de la articulación, tales como posiciones y pares de torsión. Dichos parámetros se miden del usuario de forma independiente y posteriormente se usan para actualizar el nuevo valor de la rigidez. El desempeño del algoritmo adaptativo no requiere de sensores externos, lo que favorece la simplicidad de su uso. Para una adecuada rehabilitación, efectiva y accesible para el usuario, es necesaria la compatibilidad con diversos mecanismos de asistencia tales como estimulación muscular, actividad neuronal y equilibrio corporal. Para mejorar la eficiencia del modelo de control adaptativo se ha empleado una combinación de dos enfoques de control, y para su evaluación se ha utilizado un exoesqueleto robótico H1. Los enfoques de control Jerárquico y de Tarea se han utilizado para ayudar al usuario según sea necesario, y al mismo tiempo motivarle para continuar el tratamiento. Enfoque jerárquico facilita la combinación de múltiples dispositivos para ofrecer un tratamiento eficaz mediante la categorización de la arquitectura de control en dos niveles : el control de bajo nivel y de alto nivel. Los enfoques basados en tareas involucran a la persona en cada tarea individual, y ofrecen la posibilidad de combinarlas en cualquier momento. También es necesario proporcionar un enfoque basado en la interacción con el usuario, para asegurar su participación y lograr así una terapia eficaz. Mediante esta tesis, proponemos un control adaptativo basado en tareas y en función de la interacción persona-ortesis, que se aplica en un esquema de control jerárquico. Este esquema de control se emplea en un robot portátil, con la intención de ser aplicado o acomodado a diferentes patologías, con sus capacidades de adaptación. El modelo de control adaptativo propuesto proporciona una solución integral a través de una única aplicación: adaptación dentro de la marcha y apoyo continúo a través de ejercicios de movilidad en tiempo real. El rendimiento del modelo se ha evaluado en sujetos sanos según un estudio preliminar, y posteriormente también en pacientes parapléjicos. Los resultados en sujetos sanos mostraron un cambio significativo en el patrón de los pares de interacción, elucidando un cambio en la energía y la adaptación al movimiento del usuario. En el caso de los pacientes, la adaptación mostró una mejora significativa en la actuación conjunta (rango de flexión / extensión) y el cambio en pares de interacción. El cambio activo en pares de interacción (positivo a negativo) refleja la participación activa del paciente, lo que también explica el comportamiento adaptativo

A functional electrical stimulation (fes) control system for upper limb rehabilitation

Functional electrical stimulation (FES) is the controlled use of electrical pulses to produce contraction of muscles in such a way as to support functional movement. FES is now widely used to aid walking in stroke patients and research into using FES to support other tasks is growing. However, in the more complex applications, it is very challenging to achieve satisfactory levels of FES control.The overall aim of the author’s PhD thesis is to develop improved techniques for real-time Finite State Machine (FSM) control of upper limb FES, using multiple accelerometers for tracking upper limb movement and triggering state transitions. Specific achievements include: 1) Development of new methods for using accelerometers to capture body segment angle during performance of an upper limb task and use of that data to trigger state transitions (angle triggering); 2) Development of new methods to improve the robustness of angle triggering; 3) Development of a flexible finite state-machine controller for control of upper limb FES in real time; 4) In collaboration with a clinical PhD student, implementation of a graphical user interface (GUI) that allows clinical users (e.g. physiotherapists) to set up FSM controllers for FES-assisted upper limb functional tasks.Three alternative methods that use 3-axis accelerometer data to track body segment angle with respect to gravity have been reported. The first uncalibrated method calculates the change in angle during a rotation using the gravity vectors before and after the rotation. The second uncalibrated method calculates the angle between the accelerometer x-axis and the gravity vector. The third calibrated method uses a calibration rotation to define the measurement plane and the positive rotation direction. This method then calculates the component of rotation that is in the same plane as the calibration rotation. All three methods use an algorithm that switches between using sine and cosine, depending on the measured angle, which overcomes the poor sensitivity problem seen in previous methods.xviiiA number of methods can be included in the transition triggering algorithm to improve robustness and hence the usability of the system. The aim of such methods is to reduce the number of incorrect transition timings caused by signal noise, jerky arm movements and other negative effects, which lead to poor control of FES during reaching tasks. Those methods are: 1) Using the change in angle since entering a state rather than absolute angle; 2) Ignoring readings where the acceleration vector is significant in comparison to the gravity vector (i.e. the magnitude of the measured vector is significantly different from 9.81); and 3) Requiring a given number of consecutive or non-consecutive valid readings before triggering a transition. These have been implemented with the second uncalibrated angle tracking method and incorporated into a flexible FSM controller.The flexible FSM controller and the associated setup software are also presented in this thesis, for control of electrical stimulation to support upper limb functional task practice. In order to achieve varied functional task practice across a range of patients, the user should be able to set up a variety of different state machines, corresponding to different functional tasks, tailored to the individual patient. The goal of the work is to design a FSM controller and produce an interface that clinicians (even potentially patients) can use to design and set up their own task and patient-specific FSMs.The software has been implemented in the Matlab-Simulink environment, using the Hasomed RehaStim stimulator and Xsens MTx inertial sensors. The full system has been tested with stroke patients practicing a range of tasks in the laboratory environment, demonstrating the potential for further exploitation of the work