人間を模擬した知覚系を持つ2足ヒューマノイドロボットの自己位置推定機能に対する歩行動作の影響に関する研究

早大学位記番号:新8279早稲田大

Dynamic Walking Models to Understand Asymmetric Gait Characteristics

Passive dynamic walking models remarkably predict gait behaviour such as walk-run transition speeds, preferred step length, stride frequencies and - with the inclusion of springs - ground reaction forces. Muscular or neurological conditions may lead to asymmetric walking characteristics that, in turn, come with long term health risks. Gait analysis may be used to understand an individual patient’s conditions to help rehabilitate them. However, people adapt their kinematic and kinetic walking patterns so it can be hard to distinguish the effects of gait alterations such as inertial imbalance or injury. In this thesis a compass walking model with no active controllers is explored to understand the dynamics of gait. To help us interpret the effects of mass imbalance with a prosthetic foot or orthotic device, asymmetric loading conditions are investigated. A simple spring-mass walking model is used to explore the effects of altered touch-down angles and effective leg stiffness to see if these are used as strategies to alter the characteristics of gait. Results show that an asymmetric touch-down angle alters step length while retaining a symmetric stance time. A hybrid model is then derived with springs to emulate human-like ground reaction forces and asymmetric inertial loading of the legs. Results support previous research that push-off from the trailing leg propels the leg mass more than the body mass. Higher rates of joint forces, larger step lengths and a longer stance time on the residual limb may be due to the prosthetic leg stiffness or the higher location of centre-of-mass. These results help us understand how the dynamic components affect gait characteristics such as step length, stance time and walking speeds. This work is motivated by the needs of persons with disabilities and by the desire to understand human walking

A Loosely-Coupled Passive Dynamics and Finite Element based Model for Minimising Biomechanically Driven Unhealthy Joint Loads during Walking in Transtibial Amputees

The primary objective of a prosthetic foot is to improve the quality of life for amputees by enabling them to walk in a similar way to healthy individuals. Amputees su˙er from health risks including joint pain, back pain and joint inflammation. The aim of this thesis is to develop a new computational approach to reduce the likelihood of biomechanically driven joint pain in transtibial amputees resulting from sustained exposure to Unhealthy Loads (ULs) during walking. This is achieved by developing a computational methodology to achieve a customisable sti˙ness design solution for prosthetic feet so that the occurrence of unhealthy joint loads during walking is minimised.It is assumed that the healthy population is able to spend energy most optimally during walking at all walking speeds. During walking, the force exerted by the body on the ground is measured by the ground reaction force (GRF). The GRF value is normalised with the body weight defining a dimensionless parameter . The values are similar for both legs in healthy populations but are di˙erent for the sound and a˙ected leg for amputees. A new hypothesis has been proposed in this thesis that walking is comfortable for an amputee when the di˙erence between values is minimal between the amputee and an equivalent healthy population. The values for healthy adults, as well as amputees, follow a finite number of patterns. The pattern of the values (or the GRF curve) depends on the walking speed of an individual, categorised as slow, fast or free walking. However, it is observed in the literature that free walking speed (FWS) varies over a wide range for healthy individuals (e.g. 1.1 m/s to 1.5 m/s). As a result, it was diÿcult to establish a relationship between walking speed and GRF pattern. A novel parametrised description of GRF curves for a healthy population and amputees is proposed so that a new dimensionless velocity ratio parameter and the corresponding value of the FWS can be predicted by observing the GRF pattern of a healthy adult or an amputee. A new classification approach based on the parametrised description of GRF curves, along with the dimensionless velocity ratio parameter, has been recommended for categorising very slow, slow, free, fast and very fast walking. The GRF result predictions are validated on healthy adults in an experiment conducted in a gait lab. A group of candidates who walk a lot in their daily life were specially selected for this experiment. This classification approach is used to develop a new measure of ULs based on the parametrised GRF description for healthy population and amputees. An innovative computational methodology is proposed to design an optimal sti˙ness response of a prosthetic foot that minimises the occurrence of ULs. This is achieved by transferring the roll-over shape (ROS) information of the prosthetic foot and the corresponding information for a given velocity ratio across a passive walking dynamic (PWD) and a finite element model via a newly defined form of loose coupling. A theoretical case study is presented in which an amputee walks in a gait lab with a representative C-shaped prosthetic foot. The thesis explains how the proposed novel computational methodology is able to redesign the prosthetic foot in a way that is better suited to minimising ULs. The redesign process of the prosthetic foot has led to the development of an innovative 3D printable double keel and double heel design. With the advancement of carbon reinforced polymers and additive manufacturing technology, the sti˙ness customisation methodology proposed in this thesis has the potential to create a new generation of energy-eÿcient prosthetic feet

Smart Technology for Telerehabilitation: A Smart Device Inertial-sensing Method for Gait Analysis

The aim of this work was to develop and validate an iPod Touch (4th generation) as a potential ambulatory monitoring system for clinical and non-clinical gait analysis. This thesis comprises four interrelated studies, the first overviews the current available literature on wearable accelerometry-based technology (AT) able to assess mobility-related functional activities in subjects with neurological conditions in home and community settings. The second study focuses on the detection of time-accurate and robust gait features from a single inertial measurement unit (IMU) on the lower back, establishing a reference framework in the process. The third study presents a simple step length algorithm for straight-line walking and the fourth and final study addresses the accuracy of an iPod’s inertial-sensing capabilities, more specifically, the validity of an inertial-sensing method (integrated in an iPod) to obtain time-accurate vertical lower trunk displacement measures. The systematic review revealed that present research primarily focuses on the development of accurate methods able to identify and distinguish different functional activities. While these are important aims, much of the conducted work remains in laboratory environments, with relatively little research moving from the “bench to the bedside.” This review only identified a few studies that explored AT’s potential outside of laboratory settings, indicating that clinical and real-world research significantly lags behind its engineering counterpart. In addition, AT methods are largely based on machine-learning algorithms that rely on a feature selection process. However, extracted features depend on the signal output being measured, which is seldom described. It is, therefore, difficult to determine the accuracy of AT methods without characterizing gait signals first. Furthermore, much variability exists among approaches (including the numbers of body-fixed sensors and sensor locations) to obtain useful data to analyze human movement. From an end-user’s perspective, reducing the amount of sensors to one instrument that is attached to a single location on the body would greatly simplify the design and use of the system. With this in mind, the accuracy of formerly identified or gait events from a single IMU attached to the lower trunk was explored. The study’s analysis of the trunk’s vertical and anterior-posterior acceleration pattern (and of their integrands) demonstrates, that a combination of both signals may provide more nuanced information regarding a person’s gait cycle, ultimately permitting more clinically relevant gait features to be extracted. Going one step further, a modified step length algorithm based on a pendulum model of the swing leg was proposed. By incorporating the trunk’s anterior-posterior displacement, more accurate predictions of mean step length can be made in healthy subjects at self-selected walking speeds. Experimental results indicate that the proposed algorithm estimates step length with errors less than 3% (mean error of 0.80 ± 2.01cm). The performance of this algorithm, however, still needs to be verified for those suffering from gait disturbances. Having established a referential framework for the extraction of temporal gait parameters as well as an algorithm for step length estimations from one instrument attached to the lower trunk, the fourth and final study explored the inertial-sensing capabilities of an iPod Touch. With the help of Dr. Ian Sheret and Oxford Brookes’ spin-off company ‘Wildknowledge’, a smart application for the iPod Touch was developed. The study results demonstrate that the proposed inertial-sensing method can reliably derive lower trunk vertical displacement (intraclass correlations ranging from .80 to .96) with similar agreement measurement levels to those gathered by a conventional inertial sensor (small systematic error of 2.2mm and a typical error of 3mm). By incorporating the aforementioned methods, an iPod Touch can potentially serve as a novel ambulatory monitor system capable of assessing gait in clinical and non-clinical environments

Biomechanical adaptations involved in ramp descent: Impact of microprocessor-controlled ankle-foot prothesis. Kinetic and kinematic responses to using microprocessor-controlled ankle-foot prosthesis in unilateral trans-tibial amputees during ramp descent

Ramp descent is a demanding task for trans-tibial amputees, due to the difficulty in controlling body weight progression over the prosthetic foot. A deeper understanding of the impact of foot function on ramp descent biomechanics is required to make recommendations for rehabilitation programs and prosthetic developments for lower-limb amputees. The thesis aim was to determine the biomechanical adaptations made by active unilateral trans-tibial amputees (TT) using a microprocessor-controlled ankle-foot prosthesis in active (MC-AF) compared to non-active mode (nonMC-AF) or elastically articulated ankle-foot device. A secondary aim was to determine the biomechanical adaptation made by able-bodied individuals when ankle motion was restricted using a custom made ankle-foot-orthosis and provide further insight into the importance of ankle dynamics when walking on ramps. Kinetic and kinematic data were recorded from nine TT’s and twenty able-bodied individuals. Able-bodied participants, ankle restriction, led to an increase in involved limb loading response knee flexion that is accompanied by the increased knee power generation during the single-limb-support phase that correlates to TTs results. TT’s use of an MC-AF reduced the ‘plantar-flexion’ resistance following foot contact allowing foot-flat to be attained more quickly. Followed by the increased ‘dorsi-flexion’ resistance which reduced the shank/pylon rotation velocity over the support foot, leading to an increase in negative work done by the prosthesis. These findings highlight the importance of having controlled ankle motion in ramp descent. Use of an MC-AF can provide TTs controlled motion for descending ramps and hence provide biomechanical benefits over using more conventional types of ankle-foot devices.Engineering and Physical Science Research Council (EPSRC) via Doctoral Training Account (DTA) (EP/P504821/1) Chas. A. Blatchford and Sons Ltd., Basingstoke, UK provided the prosthetic hardware, prosthetist support, and facilitated the attendance of the TT participants for this stud

Investigation of Optimization Targets for Predictive Simulation of Human Gait with Model Predictive Control

The design and development of gait-related treatments and devices is inhibited by anabsence of predictive gait models. Understanding of human gait and what motivates walkingpatterns is still limited, despite walking being one of the most routine human activities. While asignificant body of literature exists on gait modeling and optimization criteria to achievesimulated, normal gait, particularly with neuromuscular models, few studies have aimed to applyoptimization targets which approximate metabolic cost to mechanical gait models. Even fewerhave attempted this predictively, with no joint angle data specified a priori. The Sunmodel [31], [32] is one such mechanical framework which utilizes MPC to predict the dynamics ofhuman walking. This thesis expands the Sun model [31], [32] to simulate a full gait cycle (CG) andinvestigates the application of new optimization targets within an existing Model PredictiveControl (MPC) framework for predictive gait simulation developed by Sun [31], [32] .The Sun model [31], [32] was previously limited to a half gait cycle (GC) which assumedbilateral symmetry and optimized only according to characteristic constraints such as step lengthand velocity of the center of mass (COM). In this thesis, the Sun framework and MPC controlscheme were expanded to generate consecutive double support (DS), single support (SS), DS, andSS period simulations, which constitutes a full GC. The resulting GC simulation was not markedby GC events toe off (TO) and heel strike (HS), but did achieve continuity over the period whichwas not achieved by the Sun model [31], [32] . Additionally, new cost functions were developedconsistent with existing literature which suggests that the Central Nervous System (CNS) uses avariety of energy-related targets in generating gait. This thesis demonstrates that the applicationof optimization targets which approximate metabolic costs is possible with the proposed MPCframework for a mechanical gait model, but that the performance of resulting simulations shouldnot be evaluated until a full GC marked by TO and HS is achieved.While a continuous full GC simulation was achieved, the failure of the model to reliablymeet characteristic constraints, particularly in SS, prevents simulation of a GC marked by TO andHS. The work in this thesis points primarily to the failure of the optimization routine within theMPC framework to reliably find a solution that meets constraints as the cause of this problem. Ifthe optimization problem can be classified, an appropriate solution algorithm could be chosenwhich could reliably find a solution for any given set of constraints and initial conditions (IC).Identifying an appropriate solution algorithm could make the MPC framework proposed a viablemethod of gait prediction and simulation.This investigation provides researchers better understanding of the application ofenergy-based optimization in mechanical gait models and the current limitations of gaitprediction and simulation. In addition, direction is given to the future work necessary to establishMPC as a viable control method for gait simulation

Dynamic considerations of heel-strike impact in human gait

Based on the impulsive-dynamics formulation, this article presents the analysis of different strategies to regulate the energy dissipation at the heel-strike event in the context of human locomotion. For this purpose, a seven-link 2D human-like multibody model based on anthropometric data is used. The model captures the most relevant dynamic and energetic aspects of the heel-strike event in the sagittal plane. The pre-impact mechanical state of the system, around which the analysis of the heel impact contribution to energy dissipation is performed, is defined based on published data. In the context of the proposed impulsive-dynamics framework, different realistic strategies that the subject can apply to modify the impact dynamics are proposed and analyzed, namely, the trailing ankle push-off, the torso configuration and the degree of joint blocking in the colliding leg. Detailed numerical analysis and discussions are presented to quantify the effects of the mentioned strategies.Postprint (author's final draft

Review article: locomotion systems for ground mobile robots in unstructured environments

Abstract. The world market of mobile robotics is expected to increase substantially in the next 20 yr, surpassing the market of industrial robotics in terms of units and sales. Important fields of application are homeland security, surveillance, demining, reconnaissance in dangerous situations, and agriculture. The design of the locomotion systems of mobile robots for unstructured environments is generally complex, particularly when they are required to move on uneven or soft terrains, or to climb obstacles. This paper sets out to analyse the state-of-the-art of locomotion mechanisms for ground mobile robots, focussing on solutions for unstructured environments, in order to help designers to select the optimal solution for specific operating requirements. The three main categories of locomotion systems (wheeled - W, tracked - T and legged - L) and the four hybrid categories that can be derived by combining these main locomotion systems are discussed with reference to maximum speed, obstacle-crossing capability, step/stair climbing capability, slope climbing capability, walking capability on soft terrains, walking capability on uneven terrains, energy efficiency, mechanical complexity, control complexity and technology readiness. The current and future trends of mobile robotics are also outlined