Design and Evaluation of the LOPES Exoskeleton Robot for Interactive Gait Rehabilitation

This paper introduces a newly developed gait rehabilitation device. The device, called LOPES, combines a freely translatable and 2-D-actuated pelvis segment with a leg exoskeleton containing three actuated rotational joints: two at the hip and one at the knee. The joints are impedance controlled to allow bidirectional mechanical interaction between the robot and the training subject. Evaluation measurements show that the device allows both a "pa- tient-in-charge" and "robot-in-charge" mode, in which the robot is controlled either to follow or to guide a patient, respectively. Electromyography (EMG) measurements (one subject) on eight important leg muscles, show that free walking in the device strongly resembles free treadmill walking; an indication that the device can offer task-specific gait training. The possibilities and limitations to using the device as gait measurement tool are also shown at the moment position measurements are not accurate enough for inverse-dynamical gait analysis

Design of an Elastic Actuation System for a Gait-Assistive Active Orthosis for Incomplete Spinal Cord Injured Subjects

A spinal cord injury severely reduces the quality of life of affected people. Following the injury, limitations of the ability to move may occur due to the disruption of the motor and sensory functions of the nervous system depending on the severity of the lesion. An active stance-control knee-ankle-foot orthosis was developed and tested in earlier works to aid incomplete SCI subjects by increasing their mobility and independence. This thesis aims at the incorporation of elastic actuation into the active orthosis to utilise advantages of the compliant system regarding efficiency and human-robot interaction as well as the reproduction of the phyisological compliance of the human joints. Therefore, a model-based procedure is adapted to the design of an elastic actuation system for a gait-assisitve active orthosis. A determination of the optimal structure and parameters is undertaken via optimisation of models representing compliant actuators with increasing level of detail. The minimisation of the energy calculated from the positive amount of power or from the absolute power of the actuator generating one human-like gait cycle yields an optimal series stiffness, which is similar to the physiological stiffness of the human knee during the stance phase. Including efficiency factors for components, especially the consideration of the electric model of an electric motor yields additional information. A human-like gait cycle contains high torque and low velocities in the stance phase and lower torque combined with high velocities during the swing. Hence, the efficiency of an electric motor with a gear unit is only high in one of the phases. This yields a conceptual design of a series elastic actuator with locking of the actuator position during the stance phase. The locked position combined with the series compliance allows a reproduction of the characteristics of the human gait cycle during the stance phase. Unlocking the actuator position for the swing phase enables the selection of an optimal gear ratio to maximise the recuperable energy. To evaluate the developed concept, a laboratory specimen based on an electric motor, a harmonic drive gearbox, a torsional series spring and an electromagnetic brake is designed and appropriate components are selected. A control strategy, based on impedance control, is investigated and extended with a finite state machine to activate the locking mechanism. The control scheme and the laboratory specimen are implemented at a test bench, modelling the foot and shank as a pendulum articulated at the knee. An identification of parameters yields high and nonlinear friction as a problem of the system, which reduces the energy efficiency of the system and requires appropriate compensation. A comparison between direct and elastic actuation shows similar results for both systems at the test bench, showing that the increased complexity due to the second degree of freedom and the elastic behaviour of the actuator is treated properly. The final proof of concept requires the implementation at the active orthosis to emulate uncertainties and variations occurring during the human gait

Design of a Lightweight Modular Powered Transfemoral Prosthesis

Rehabilitation options for transfemoral amputees are limited, and no product today can mimic the full functionality of a human limb. Powered prosthetics have potential to close this gap but contain major drawbacks which ultimately increase the energy expenditure of the user. This thesis explores the viability of new designs and methods to reduce energy expenditure. In doing so a prototype containing many of the explored concepts is also being constructed to replace the laboratory’s current powered prosthetic, AMPRO II. This goal is accomplished by reducing weight through optimizing structural components, using lightweight motors and gearing, and reducing the energy requirements through novel passive spring sub-assemblies. Adjustable and modular components also enable a wider range of use and are explored. The main objective of this thesis is to investigate these design improvements and create the next-generation prosthetic for the Human Rehabilitation Lab. This thesis explores using a combination of passive and powered components to reduce the need for heavy actuators. Methods involve coding walking simulations based on an inverse dynamics study. By simulating design concepts with elastic elements the resulting power requirements of the motors have been estimated to evaluate each concept. Motors and gearing options have also been investigated with an optimization-based approach; gearing ratio was minimized in a test comparing discrete off-the-shelf motor options to biomechanical requirements. For the structural components, the mass of each part has been minimized through an iterative approach in FEA. Elements selected for further investigation from this thesis are being constructed with a prototype. Improvements over AMPRO II include adjustable height, functionality on both legs, a flexible foot, modularity, capabilities of passive elastic elements, and a mass estimated to be 20% lighter. Components include flat motors with harmonic drives, adjustable pylons for height, a low-profile mounting frame, passive pre-loaded springs, and a rotary series elastic actuator (RSEA). Unproven concepts such as the springs and RSEA have been designed as modular and optional to reduce risk. Moving forward, the first prototype is currently being built without the optional components to test the biomechanics. Future tests will incorporate the designed elastic elements to validate simulation concepts

An Underactuated Active Transfemoral Prosthesis With Series Elastic Actuators Enables Multiple Locomotion Tasks

Robotic lower limb prostheses have the power to revolutionize mobility by enhancing gait efficiency and facilitating movement. While several design approaches have been explored to create lightweight and energy-efficient devices, the potential of underactuation remains largely untapped in lower limb prosthetics. Taking inspiration from the natural harmony of walking, in this article, we have developed an innovative active transfemoral prosthesis. By incorporating underactuation, our design uses a single power actuator placed near the knee joint and connected to a differential mechanism to drive both the knee and ankle joints. We conduct comprehensive benchtop tests and evaluate the prosthesis with three individuals who have above-knee amputations, assessing its performance in walking, stair climbing, and transitions between sitting and standing. Our evaluation focuses on gathering position and torque data recorded from sensors integrated into the prosthesis and comparing these measurements to biomechanical data of able-bodied locomotion. Our findings highlight the promise of underactuation in advancing lower limb prosthetics and demonstrate the feasibility of our knee–ankle underactuated design in various tasks, showcasing its ability to replicate natural movement

Simulación del modelo de actuador serial elástico para prótesis Tobillo-Pie en Matlab

The ankle - foot set plays a very important role for human displacement, such as walking or running, giving vertical support and propulsion to the human walking progression by using the muscle extension and contraction. Many designs have been developed to replicate the function of normal gait, lost by injuries or diseases affecting the limb below the knee [1]. Motor rehabilitation has become a field of growing interest, due to the large number of cases of people with injuries or mutilation in its members or in other cases by cerebrovascular accidents and spinal cord damage that cause paralysis or any kind of disability. [2], [3]. This paper shows the process to get the model of SEA mechanism in Matlab, linking VR-World of Simulink from 3D Solidworks Model to test the model and finally checking the characteristic curves of normal gait to 1.5 m/s with this SEA prosthesis.El conjunto tobillo-pie desempeña un papel muy importante para el movimiento humano, como caminar o correr, ya que proporciona apoyo vertical y propulsión de la progresión de la marcha humana mediante la extensión y contracción muscular. Se han desarrollado muchos diseños para replicar la función de la marcha normal, perdida por lesiones o enfermedades que afectan la extremidad debajo de la rodilla [1]. La rehabilitación motora se ha convertido en un campo de amplio interés, ya que en Colombia hay gran cantidad de casos de personas con lesiones o mutilaciones en sus miembros o en otros casos por accidentes cerebrovasculares y daño medular que provocan parálisis o cualquier tipo de discapacidad. [2], [3]. Este artículo muestra el proceso para obtener el modelo del mecanismo SEA en Matlab, vinculando el VR-World de Simulink con un modelo 3D en Solidworks de la prótesis para validarlo y finalmente verificar las curvas características de la marcha normal a 1,5 m / s con esta prótesis SEA

Advancements in Prosthetics and Joint Mechanisms

abstract: Robotic joints can be either powered or passive. This work will discuss the creation of a passive and a powered joint system as well as the combination system being both powered and passive along with its benefits. A novel approach of analysis and control of the combination system is presented. A passive and a powered ankle joint system is developed and fit to the field of prosthetics, specifically ankle joint replacement for able bodied gait. The general 1 DOF robotic joint designs are examined and the results from testing are discussed. Achievements in this area include the able bodied gait like behavior of passive systems for slow walking speeds. For higher walking speeds the powered ankle system is capable of adding the necessary energy to propel the user forward and remain similar to able bodied gait, effectively replacing the calf muscle. While running has not fully been achieved through past powered ankle devices the full power necessary is reached in this work for running and sprinting while achieving 4x’s power amplification through the powered ankle mechanism. A theoretical approach to robotic joints is then analyzed in order to combine the advantages of both passive and powered systems. Energy methods are shown to provide a correct behavioral analysis of any robotic joint system. Manipulation of the energy curves and mechanism coupler curves allows real time joint behavioral adjustment. Such a powered joint can be adjusted to passively achieve desired behavior for different speeds and environmental needs. The effects on joint moment and stiffness from adjusting one type of mechanism is presented.Dissertation/ThesisDoctoral Dissertation Mechanical Engineering 201