Variable damping controller for a prosthetic knee during swing extension

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 39-40).Transfemoral amputees exhibit both increased metabolic consumption and gait asymmetry during level ground walking. A variable damping control strategy has been developed for swing extension in order to improve gait symmetry and reduce energy expenditure during level ground walking. Preliminary biomechanical studies suggest that the knee utilizes a variable damping control during swing extension. This thesis proposes a biologically inspired variable damping control strategy which can be simplified into a piecewise function with respect to the knee angle. The variable damping profile of the knee during swing extension has been modeled as an initial linear increase with respect to knee angle followed by a quadratic increase at the end of swing. A damping controller based on this proposed piecewise function has been implemented in a biomimetic, active, knee prosthesis (AAAKP) developed at MIT's Biomechatronics Lab. Preliminary studies on a unilateral, transfemoral amputee have shown that the AAAKP with the proposed damping control strategy is able to more closely emulate the damping profile of the unaffected leg, when compared to a conventional knee prosthesis (Otto Bock C-Leg®). This Initial study suggests that the proposed variable damping strategy for swing extension is able to more accurately emulate the joint mechanics of the unaffected knee. This work is intended to improve prosthetic knee behavior in order to reduce metabolic consumption and improve gait symmetry in transfemoral amputees during level ground walking.by Luke Matthewson Mooney.S.B

Estimation of Actuation System Parameters for Lower Limb Prostheses

This paper provides guidelines to estimate the kinematics, energy and torque requirements for lower limb prosthetic actuation systems during daily living activities. These parameters are estimated based on human biomechanical data from different sources to consider the variability due to the assumptions and errors in the analysis and data collection. The results showed that the powered actuation source is important at the ankle joint in the stance phase during level ground walking while it is more important at knee joint during stair ascending. These estimated parameters can be used as guidelines to design and select proper actuation systems

Development of a knee prosthesis powered by electro-hydrostatic actuation

L'abstract è presente nell'allegato / the abstract is in the attachmen

Motor Electrical Damping for Back-Drivable Prosthetic Knee

The paper presents a model and analysis of a backdrivable knee prosthesis. In this context, the investigation into the design, modelling and analysis of a back-drivable semiactive prosthetic knee is presented. A mathematical model has been developed for evaluating the electrical damping characteristics of the DC motor in passive mode. The analysis shows that a single actuator could be suitable to work in active mode to provide mechanical power and in passive mode as a damper dissipating energy

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

Dynamic Modeling, Parameter Estimation and Control of a Leg Prosthesis Test Robot

Robotic testing can facilitate the development of new concepts, designs and control systems for prosthetic limbs. Human subject test clearances, safety and the lack of repeatability associated with human trials can be reduced or eliminated with automated testing, and test modalities are possible which are dangerous or inconvenient to attempt with patients. This paper describes the development, modeling, parameter estimation and control of a robot capable of reproducing two degree-of-freedom hip motion in the sagittal plane. Hip vertical displacement and thigh angle motion profiles are applied to a transfemoral prosthesis attached to the robot. A treadmill is used as walking surface. Aside from tracking hip motion trajectories, the control system can be used to regulate the contact force between the treadmill and the prosthesis. The paper summarizes the overall development process, with emphasis on the generation of a dynamic model that can be used to design closed-loop motion and force control algorithms

Potential Optimal Gait Performance of Mauch S-N-S Prosthetic Knee Configurations as Predicted by Dynamic Modeling

Patients with prosthetic legs routinely suffer from abnormal gait patterns which can cause health issues and eventually lower the quality of their lives. Despite the half-century advance in the technology of prosthetic knees, from the purely mechanical to microprocessor controlled systems, patient testing suggests that very little progress has been made in the quality of the kinetics and kinematics of amputee gait. Moreover, the cost of microprocessor controlled prosthetic knees may be 10 times more than the purely mechanical knees. While prosthetic knees have become more complex and expensive, it is not proven that the prosthetic knee is a central factor limiting amputee patient gait. The goal of this project is to determine the degree to which the Mauch S-N-S prosthetic knee limits the ability of a subject to achieve a close to normal gait pattern. In this research, we developed dynamic models of the Mauch S-N-S prosthetic knee based on gait-like motion tests of a Mauch knee cylinder and used the dynamic models in computational simulations to determine the best achievable gait, on the basis of obtaining near-to-normal gait kinematics and kinetics. Idealized assumptions were made for patient performance capability and characteristics of the other prosthetic leg components, to obtain the desired focus on knee capabilities and limitations. The results indicate that even with this relatively old technology prosthetic knee, subjects have the potential to walk much more normally than the patient-test data indicates. An extension of the study showed the significant interaction of the prosthetic knee and ankle with respect to achieving optimal gait. The methodology of this study can be applied to evaluation other knees, prosthetic components and prosthetic systems combining these component

Potential Optimal Gait Performance of Mauch S-N-S Prosthetic Knee Configurations as Predicted by Dynamic Modeling

Patients with prosthetic legs routinely suffer from abnormal gait patterns which can cause health issues and eventually lower the quality of their lives. Despite the half-century advance in the technology of prosthetic knees, from the purely mechanical to microprocessor controlled systems, patient testing suggests that very little progress has been made in the quality of the kinetics and kinematics of amputee gait. Moreover, the cost of microprocessor controlled prosthetic knees may be 10 times more than the purely mechanical knees. While prosthetic knees have become more complex and expensive, it is not proven that the prosthetic knee is a central factor limiting amputee patient gait. The goal of this project is to determine the degree to which the Mauch S-N-S prosthetic knee limits the ability of a subject to achieve a close to normal gait pattern. In this research, we developed dynamic models of the Mauch S-N-S prosthetic knee based on gait-like motion tests of a Mauch knee cylinder and used the dynamic models in computational simulations to determine the best achievable gait, on the basis of obtaining near-to-normal gait kinematics and kinetics. Idealized assumptions were made for patient performance capability and characteristics of the other prosthetic leg components, to obtain the desired focus on knee capabilities and limitations. The results indicate that even with this relatively old technology prosthetic knee, subjects have the potential to walk much more normally than the patient-test data indicates. An extension of the study showed the significant interaction of the prosthetic knee and ankle with respect to achieving optimal gait. The methodology of this study can be applied to evaluation other knees, prosthetic components and prosthetic systems combining these component

Modular Design of a Passive, Low-Cost Prosthetic Knee Mechanism to Enable Able-Bodied Kinematics for Users With Transfemoral Amputation

There is a significant need for low-cost, high-performance prosthetic knee technology for transfemoral amputees in India. Replicating able-bodied gait in amputees is biomechanically necessary to reduce the metabolic cost, and it is equally important to mitigate the socio-economic discrimination faced by amputees in developing countries due to their conspicuous gait deviations. This paper improves upon a previous study of a fully passive knee mechanism, addressing the issues identified in its user testing in India. This paper presents the design, analysis and bench-level testing of the three major functional modules of the new prosthetic knee architecture: (i) a four-bar latch mechanism for achieving stability during stance phase of walking, (ii) an early stance flexion module designed by implementing a fully adjustable mechanism, and (iii) a hydraulic rotary damping system for achieving smooth and reliable swing-phase control