499 research outputs found
Sci Robot
Robotic leg prostheses promise to improve the mobility and quality of life of millions of individuals with lower-limb amputations by imitating the biomechanics of the missing biological leg. Unfortunately, existing powered prostheses are much heavier and bigger and have shorter battery life than conventional passive prostheses, severely limiting their clinical viability and utility in the daily life of amputees. Here, we present a robotic leg prosthesis that replicates the key biomechanical functions of the biological knee, ankle, and toe in the sagittal plane while matching the weight, size, and battery life of conventional microprocessor-controlled prostheses. The powered knee joint uses a unique torque-sensitive mechanism combining the benefits of elastic actuators with that of variable transmissions. A single actuator powers the ankle and toe joints through a compliant, underactuated mechanism. Because the biological toe dissipates energy while the biological ankle injects energy into the gait cycle, this underactuated system regenerates substantial mechanical energy and replicates the key biomechanical functions of the ankle/foot complex during walking. A compact prosthesis frame encloses all mechanical and electrical components for increased robustness and efficiency. Preclinical tests with three individuals with above-knee amputation show that the proposed robotic leg prosthesis allows for common ambulation activities with close to normative kinematics and kinetics. Using an optional passive mode, users can walk on level ground indefinitely without charging the battery, which has not been shown with any other powered or microprocessor-controlled prostheses. A prosthesis with these characteristics has the potential to improve real-world mobility in individuals with above-knee amputation.R01 HD098154/HD/NICHD NIH HHSUnited States/T42 OH008414/OH/NIOSH CDC HHSUnited States
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
Biomechanics of Prosthetic Knee Systems : Role of Dampening and Energy Storage Systems
One significant drawback of the commercial passive and microprocessored prosthetic devices, the inability of delivering positive energy when needed, is due to the absence of the knee flexion during stance phase. Moreover, consequences such as circumduction and disturbed gait pattern take place due to the improper energy flow at the knee and the absence of the positive energy delivery during the swing phase. Current generation powered design has solved these problems by delivering the needed energy with heavy battery demanding motors, which increase the mass of the device significantly. Hence, the gait quality of transfemoral amputees has not improved significantly in the last 50 years due to the inefficient energy flow distribution causing the patient to hike his/her pelvis, which leads to back pain in the long run. In this context, state-of-art prosthetics technology is trending toward creating energy regenerative devices, which are able to harvest/ return energy during ambulation by a spring mechanism, since a spring not only permits significant power demand reduction but also provides high power-to-weight ratio. This study will examine the sagittal plane knee moment versus knee flexion angle properties robotically, clinically and theoretically to explore the functional stiffness of a healthy knee as well as a prosthetic knee during the energy return and harvest phases of gait. With this intention, a prosthetic knee test method will be developed for investigating the torque-angle properties of the knee by iteratively modifying the hip trajectory until achieving the closest to healthy knee biomechanics by a 3-Degree of Freedom (DOF) Simulator. This research reveals that constant spring stiffness is suboptimal to varying gait requirements for different types of activity, due to the variability of the power requirements of the knee caused by the passive, viscous and elastic characteristics and the activation dependent properties of the muscles. Exploring this variation is crucial for the design of tran
Biomechanics of Prosthetic Knee Systems : Role of Dampening and Energy Storage Systems
One significant drawback of the commercial passive and microprocessored prosthetic devices, the inability of delivering positive energy when needed, is due to the absence of the knee flexion during stance phase. Moreover, consequences such as circumduction and disturbed gait pattern take place due to the improper energy flow at the knee and the absence of the positive energy delivery during the swing phase. Current generation powered design has solved these problems by delivering the needed energy with heavy battery demanding motors, which increase the mass of the device significantly. Hence, the gait quality of transfemoral amputees has not improved significantly in the last 50 years due to the inefficient energy flow distribution causing the patient to hike his/her pelvis, which leads to back pain in the long run. In this context, state-of-art prosthetics technology is trending toward creating energy regenerative devices, which are able to harvest/ return energy during ambulation by a spring mechanism, since a spring not only permits significant power demand reduction but also provides high power-to-weight ratio. This study will examine the sagittal plane knee moment versus knee flexion angle properties robotically, clinically and theoretically to explore the functional stiffness of a healthy knee as well as a prosthetic knee during the energy return and harvest phases of gait. With this intention, a prosthetic knee test method will be developed for investigating the torque-angle properties of the knee by iteratively modifying the hip trajectory until achieving the closest to healthy knee biomechanics by a 3-Degree of Freedom (DOF) Simulator. This research reveals that constant spring stiffness is suboptimal to varying gait requirements for different types of activity, due to the variability of the power requirements of the knee caused by the passive, viscous and elastic characteristics and the activation dependent properties of the muscles. Exploring this variation is crucial for the design of tran
An Overview on Principles for Energy Efficient Robot Locomotion
Despite enhancements in the development of robotic systems, the energy economy of today's robots lags far behind that of biological systems. This is in particular critical for untethered legged robot locomotion. To elucidate the current stage of energy efficiency in legged robotic systems, this paper provides an overview on recent advancements in development of such platforms. The covered different perspectives include actuation, leg structure, control and locomotion principles. We review various robotic actuators exploiting compliance in series and in parallel with the drive-train to permit energy recycling during locomotion. We discuss the importance of limb segmentation under efficiency aspects and with respect to design, dynamics analysis and control of legged robots. This paper also reviews a number of control approaches allowing for energy efficient locomotion of robots by exploiting the natural dynamics of the system, and by utilizing optimal control approaches targeting locomotion expenditure. To this end, a set of locomotion principles elaborating on models for energetics, dynamics, and of the systems is studied
Design, Control, and Optimization of Robots with Advanced Energy Regenerative Drive Systems
We investigate the control and optimization of robots with ultracapacitor based regenerative drive systems. A subset of the robot joints are conventional, in the sense that external power is used for actuation. Other joints are energetically self-contained passive systems that use ultracapacitors for energy storage. An electrical interconnection known as the star configuration is considered for the regenerative drives that allows for direct electric energy redistribution among joints, and enables higher energy utilization efficiencies. A semi-active virtual control strategy is used to achieve control objectives. We find closed-form expressions for the optimal robot and actuator parameters (link lengths, gear ratios, etc.) that maximize energy regeneration between any two times, given motion trajectories. In addition, we solve several trajectory optimization problems for maximizing energy regeneration that admit closed-form solutions, given system parameters. Optimal solutions are shown to be global and unique. In addition, closed-form expressions are provided for the maximum attainable energy. This theoretical maximum places limits on the amount of energy that can be recovered. Numerical examples are provided in each case to demonstrate the results. For problems that don\u27t admit analytical solutions, we formulate the general nonlinear optimal control problem, and solve it numerically, based on the direct collocation method. The optimization problem, its numerical solution and an experimental evaluation are demonstrated using a PUMA manipulator with custom regenerative drives. Power flows, stored regenerative energy and efficiency are evaluated. Experimental results show that when following optimal trajectories, a reduction of about 10-22% in energy consumption can be achieved. Furthermore, we present the design, control, and experimental evaluation of an energy regenerative powered transfemoral prosthesis. Our prosthesis prototype is comprised of a passive ankle, and an active regenerative knee joint. A novel varying impedance control approach controls the prosthesis in both the stance and swing phase of the gait cycle, while explicitly considering energy regeneration. Experimental evaluation is done with an amputee test subject walking at different speeds on a treadmill. The results validate the effectiveness of the control method. In addition, net energy regeneration is achieved while walking with near-natural gait across all speeds
Modeling and Control of Adjustable Articulated Parallel Compliant Actuation Arrangements in Articulated Robots
Considerable advances in robotic actuation technology have been made in recent years. Particularly the use of compliance has increased, both as series elastic elements as well as in parallel to the main actuation drives. This work focuses on the model formulation and control of compliant actuation structures including multiple branches and multi-articulation, and significantly contributes by proposing an elegant modular formulation that describes the energy exchange between the compliant elements and articulated multi-body robot dynamics using the concept of power flows, and a single matrix that describes the entire actuation topology. Using this formulation, a novel gradient descent based control law is derived for torque control of compliant actuation structures with adjustable pretension, with proven convexity for arbitrary actuation topologies. Extensions towards handling unidirectionality of elastic elements and joint motion compensation are also presented. A simulation study is performed on a 3-DoF leg model, where series-elastic main drives are augmented by parallel elastic tendons with adjustable pretension. Two actuation topologies are considered, one of which includes a biarticulated tendon. The data demonstrate the effectiveness of the proposed modelling and control methods. Furthermore, it is shown the biarticulated topology provides significant benefits over the monoarticulated arrangement
Biomimetic agonist-antagonist active knee prosthesis
Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 92-96).The loss of a limb is extremely debilitating. Unfortunately, today's assistive technologies are still far from providing fully functional artificial limb replacements. Although lower extremity prostheses are currently better able to give assistance than their upper-extremity counterparts, important locomotion problems still remain for leg amputees. Instability, gait asymmetry, decreased walking speeds and high metabolic energy costs are some of the main challenges requiring the development of a new kind of prosthetic device. These challenges point to the need for highly versatile, fully integrated lower-extremity powered prostheses that can replicate the biological behavior of the intact human leg. This thesis presents the design and evaluation of a novel biomimetic active knee prosthesis capable of emulating intact knee biomechanics during level-ground walking. The knee design is motivated by a mono-articular prosthetic knee model comprised of a variable damper and two series elastic clutch units spanning the knee joint. The powered knee system is comprised of two series-elastic actuators positioned in parallel in an agonist-antagonist configuration. This investigation hypothesizes that the biomimetic active-knee prosthesis, with a variable impedance control, can improve unilateral transfemoral amputee locomotion in level-ground walking, reducing the metabolic cost of walking at selfselected speeds. To evaluate this hypothesis, a preliminary study investigated the clinical impact of the active knee prosthesis on the metabolic cost of walking of four unilateral above-knee amputees. This preliminary study compared the antagonistic active knee prosthesis with subjects' prescribed knee prostheses. The subjects' prescribed prostheses encompass four of the leading prosthetic knee technologies commercially available, including passive and electronically controlled variable-damping prosthetic systems. Use of the novel biomimetic active knee prosthesis resulted in a metabolic cost reduction for all four subjects by an average of 5.8%. Kinematic and kinetic analyses indicate that the active knee can increase self-selected walking speed in addition to reducing upper body vertical displacement during walking by an average of 16%. The results of this investigation report for the first time a metabolic cost reduction when walking with a prosthetic system comprised of an electrically powered active knee and passive foot-ankle prostheses, as compared to walking with a conventional transfemoral prosthesis. With this work I aim to advance the field of biomechatronics, contributing to the development of integral assistive technologies that adapt to the needs of the physically challenged.by Ernesto Carlos Martinez-Villalpando.Ph.D
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
- …