Integration of an Adaptive Ground Construct Model Into the Dynamic Simulation of Gait PDF Download
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Author: C. David Remy
Publisher:
ISBN:
Category :
Languages : en
Pages : 236
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Author: C. David Remy
Publisher:
ISBN:
Category :
Languages : en
Pages : 236
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Author: Matthew Millard
Publisher:
ISBN:
Category :
Languages : en
Pages : 145
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A predictive, forward-dynamic model and computer simulation of human gait has important medical and research applications. Most human simulation work has focused on inverse dynamics studies to quantify bone on bone forces and muscle loads. Inverse dynamics is not predictive - it works backwards from experimentally measured motions in an effort to find the forces that caused the motion. In contrast, forward dynamics determines how a mechanism will move without the need for experimentation. Most of the forward dynamic gait simulations reported consider only one step, foot contact is not modeled, and balance controllers are not used. This thesis addresses a few of the shortcomings of current human gait simulations by contributing an experimentally validated foot contact model, a model-based stance controller, and an experimentally validated model of the relationship between foot placement location and balance. The goal of a predictive human gait simulation is to determine how a human would walk under a condition of interest, such as walking across a slippery floor, using a new lower limb prosthesis, or with reduced leg strength. To achieve this goal, often many different gaits are simulated and the one that is the most human-like is chosen as the prediction for how a person would move. Thus it is necessary to quantify how `human-like' a candidate gait is. Human walking is very efficient, and so, the metabolic efficiency of the candidate gait is most often used to measure the performance of a candidate gait. Muscles consume metabolic energy as a function of the tension they develop and the rate at which they are contracting. Muscle tension is developed, and contractions are made in an effort generate torques about joints in order to make them move. To predict human gait, it is necessary for the simulation to be able to walk in such a way that the simulated leg joints use similar joint torques and kinematics as a human leg does, all while balancing the body. The joint torques that the legs must develop to propel the body forward, and balance it, are heavily influenced by the ground reaction forces developed between the simulated foot and the ground. A predictive gait simulation must be able to control the model so that it can walk, and remain balanced while generating ground reaction force profiles that are similar to experimentally observed human ground reaction force profiles. Ground reaction forces are shaped by the way the foot interacts with the ground, making it very important to model the human foot accurately. Most continuous foot contact models present in the literature have been experimentally validated using pendulum impact methods that have since been shown to produce inaccurate results. The planar foot contact model developed as part of this research was validated in-vivo using conventional force plates and optical tracking markers. The experimental data was also highly useful for developing a computationally efficient foot model by identifying the dominant contact properties of a real foot (during walking), without the complexity of modelling the 26 bones, 33 joints, over 90 ligaments, and the network of muscles that are in a real foot. Both ground reaction forces and the balance of the model are heavily influenced by the way the stance limb is controlled. Anthropomorphic multibody models typically have a fragile sense of balance, and ground reaction force profiles that do not look similar to experimentally measured human ground reaction force profiles. In contrast, the simple point-mass spring-loaded-inverted-pendulum (SLIP) can be made to walk or run in a balanced manner with center-of-mass (COM) kinematics and ground reaction force profiles that could be mistaken for the equivalent human data. A stance limb controller is proposed that uses a planar SLIP to compute a reference trajectory for a planar anthropomorphic multibody gait model. The torso of the anthropomorphic model is made to track the computed trajectory of the SLIP using a control system. The aim of this partitioned approach to gait simulation is to endow the anthropomorphic model with the human-like gait of the simpler SLIP model.
Author: Helena Blumen
Publisher: Frontiers Media SA
ISBN: 2889636267
Category :
Languages : en
Pages : 346
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Author: Matthew D. Furtney
Publisher:
ISBN:
Category :
Languages : en
Pages : 73
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In this thesis we present a novel approach to the computer simulation of forward dynamic gait models and the optimization of parameters that must be tuned for such models. This methodology is not limited to gait simulation, and could be useful for any situation in which a complex Simulink model requires variables to be tuned via machine learning to optimize all heuristic that can only be evaluated via simulation. Through the lens of Biomechatronic engineering research, we combine the fundamentals of software engineering with a refinement of the best practices of Matlab and Simulink programming and a working knowledge of inherent Matlab and Simulink constraints to construct a framework for rapid model development. Key features of this methodology include: the use of Simulink as an environment for rapidly prototyped models, the use of and construction of custom Simulink libraries, and use of the Matlab Optimization Toolbox. This methodology uses parallel evaluation of rapid acceleration Simulink executables to minimize optimization time, and allow research teams to take advantage of parallel processing and cloud computing. This methodology was applied to a bouncing gait model developed by Hartmut Geyer for evaluation. We demonstrate its effectiveness by simulating this model using a custom library of model components, such as ground contact model, Stateflow control, heuristic computation, and body segments.
Author: Olga Pätkau
Publisher:
ISBN:
Category :
Languages : en
Pages :
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In this thesis, two different control strategies are applied to the forward dynamic simulation of multibody systems in order to track a given reference motion. For this purpose, two different computational models are presented: a four-bar linkage model with one degree of freedom; and a two-dimensional human body model that consists of 12 segments with 14 degrees of freedom. The forward dynamic analysis of the two models is implemented using the matrix-R formulation and carried out by means of a variablestep integration solver. Furthermore, an analysis and comparison of different numerical integration methods are carried out. The joint forces and torques, which are applied to the multibody systems in order to drive their motion, are provided through an inverse dynamic analysis. In order to stabilize the simulation and to enable the tracking of a reference motion, two control methods are introduced: a proportional derivative control and a computed torque control using feedback linearization. The design of both control approaches is developed and applied to the forward dynamic simulation of both models. The system performance is evaluated by comparing the results with the reference motion. The reference human motion of a healthy subject was captured previously in a biomechanics laboratory. Moreover, the robustness of the computed torque control approach is analysed. In addition, environmental and social impacts of this thesis are outlined and an economical consideration is included.
Author: James Lanphier Patton
Publisher:
ISBN:
Category : Human locomotion
Languages : en
Pages : 308
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Author: Christopher L. Vaughan
Publisher: Human Kinetics
ISBN: 9780873223713
Category : Medical
Languages : en
Pages : 137
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Gait Analysis Laboratory is a comprehensive, interactive package for the study of human gait. It includes a text, IBM-compatible software, and an accompanying software manual. Everyone from undergraduate students to research professionals should find it easy to study over 250 variables involved in human gait with this package. And, this resource provides a study of gait in three dimensions instead of two. The book and software make the theory and tools of gait analysis available to anyone with a basic knowledge of mechanics and anatomy and with access to a personal computer, including researchers in biomechanics, kinesiology, biomedical engineering, and the movement sciences in general; students and teachers in physical education and physical therapy; and clinicians in orthopaedic surgery, physical therapy, podiatry, rehabilitation, neurology, and sports medicine. Dynamics of Human Gait text: the text - a theoretical introduction to human gait - contains five chapters. Chapter One explains the walking human as a series of interconnected systems that form the framework for detailed gait analysis. Chapter Two emphasizes the three-dimensional and cyclic nature of human gait.Chapter Three integrates anthropometric, kinematic, and force-plate data to form a 3D analysis of gait. Chapter Four describes the basics of electromyography. And Chapter Five contains a case study of the gait patterns of a person with a movement disability. GaitLab software: the GaitLab software contains three separate programs - Gaitmath, Gaitplot, and Animate - that help users apply the theoretical information in the text. Gaitmath allows users to input data to calculate five sets of parameters for gait - body segment parameters, linear kinematics, centres of gravity, angular kinematics, and dynamics of joints. Gaitplot plots these parameters graphically in many combinations. It also includes an animation program that models data from Gaitmath into a simple moving figure. Researchers and students can input the sample data provided - or, with the necessary gait analysis hardware, they can capture their own data and use the Gaitplot and Gaitmath programs to bring their data to life. The Animate program illustrates the gait patterns. Users can view colour-coded sequences of a nondisabled man walking on a treadmill.They can see how muscle activity, joint moments, and ground reaction forces are integrated. A freeze-frame function allows users to stop and look at any phase of the gait cycle. The accompanying software manual gives users all the information they need to run the software successfully. Hardware compatibility: the Gaitmath and Gaitplot programs can be run on any IBM or IBM-compatible personal computer equipped with a hard disk drive and a CGA monitor or a monochrome monitor with a graphics adapter. The Animate program requires an EGA or VGA card and monitor. This package should help everyone from student to professional understand the complexities of human gait.
Author: Chad Everett Joshua MacDonald
Publisher:
ISBN:
Category : Adaptation (Physiology)
Languages : en
Pages :
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Author: Ramanarayan Vasudevan
Publisher:
ISBN:
Category :
Languages : en
Pages : 282
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The empirical observation of human locomotion has found considerable utility in the diagnosis of numerous neuromuscular pathologies. Unfortunately without the construction of a dynamical system model of the measured gait, the effectualness of these observations is restricted to just the existing diagnostic variety rather than the prediction of potential instabilities in gait or guiding the construction of user specific prosthetics. In order to construct a dynamical system model of an observed gait in an automated fashion, one requires a family of representations rich enough to describe the dynamics of gait and an automated procedure to select a particular representation capable of describing a given observation from this family. The goal of this thesis is to address these two problems. First, a hybrid dynamical system representation is introduced that is shown to be capable of describing the discontinuities in dynamics that occur during locomotion. In particular, such a representation is constructible from observation given an unconstrained Lagrangian which is intrinsic to the biped after the identification of the sequence of contact points that are enforced during the observed motion. Second, a specific hybrid dynamical system representation is shown to be constructible from observed data by optimally switching between the set of vector fields corresponding to all possible combinations of contact point enforcements. At this point an algorithm for the computation of an optimal control of constrained nonlinear switched dynamical systems is devised. The control parameter for such systems include a continuous-valued input and discrete-valued input, where the latter corresponds to the mode of the switched system that is active at a particular instance in time. The presented approach, which this thesis proves converges to local minimizers of the constrained optimal control problem, first relaxes the discrete-valued input, performs traditional optimal control, and then projects the constructed relaxed discrete-valued input back to a pure discrete-valued input by employing an extension of the classical Chattering Lemma. This algorithm is extended by formulating a computationally implementable algorithm that works by discretizing the time interval over which the switched dynamical system is defined. Importantly, this thesis proves that the implementable algorithm constructs a sequence of points by recursive application that converge to the local minimizers of the original constrained optimal control problem. Four simulation experiments are included to validate the theoretical developments and illustrate its superiority when compared to standard mixed integer optimization techniques. The thesis concludes by applying the presented algorithm to perform the identification of a hybrid dynamical system representation of two classes of gaits. The first is a synthetic gait generated by the application of feedback linearization to a classical robotic bipedal model. For this synthetic observation, the presented identification scheme is able to correctly identify the correct model. The second set of gaits is one constructed from motion capture observations of 9 subjects during a flat ground walking experiment. For each subject, the presented identification scheme determines a distinct hybrid dynamical system representation. Surprisingly, the identified models for each participant share an identical discrete structure, or an identical sequence of contact point enforcements.
Author: Huseyin Celik
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Human locomotion is often assumed to be governed by optimality principles. To the extent that this is true, it should be possible to reproduce various human gaits (walking, running, sprinting) with a predictive approach employing some sort of optimality criterion in an optimization framework. While there are many instances of humans using aperiodic gaits in everyday life and sporting activities, previous simulations of bipedal locomotion have focused almost exclusively on periodic gaits. The main purpose of this dissertation is to implement model-based optimal controls approaches to create novel bipedal gait simulations that are both periodic and aperiodic. Those simulations are used to investigate new optimality criteria for normal human walking and to characterize relationships between musculoskeletal architecture and human sprinting performance.In our first study, a novel computational model and a simulation framework were developed to create the first simulation of aperiodic sprinting from rest. The model used was a modified spring-loaded inverted pendulum (SLIP) biped driven by torque actuators at the hip and force actuators on retracting legs. The direct multiple shooting method was used to formulate the optimization problem in which the time to traverse 20 m from rest was minimized. The initial guess to the simulation was a "jogging" simulation obtained using a proportional-derivative feedback to control trunk attitude, swing leg angle, and leg retraction and extension. Although the model was very simple, it exhibited a number of features characteristic of human sprinters, such as forward trunk lean at the start, straightening of the trunk during acceleration, and a dive at the finish.In our second study, a muscle driven computational model was developed to create simulations of normal bipedal walking using the direct multiple shooting method and evaluation of optimality criteria. We implemented a set of optimality measures derived from muscle activation, mechanical energy expenditure, or metabolic energy expenditure to represent effort; and trunk angle as well as vertical ground reaction force (GRF). Initial guesses to the optimizations were generated using a feedforward control that relied on muscle reflex loops. The simulations converged to distinct gait cycles for different optimality criteria. The additional trunk angle and vertical GRF terms helped to alleviate some undesired behaviors observed in predictive simulations of normal walking such as spikes in GRF and excessive trunk excursion. In our third study, maximum speed sprinting simulations were created with a muscle-actuated bipedal model and the direct multiple shooting method. The simulation framework and model successfully reproduced salient features of human sprinting once maximum speed has been attained. We perturbed several musculoskeletal architecture parameters of the plantarflexors in isolation (maximum isometric force, optimal fiber length, tendon stiffness, and moment arm) to investigate how variations in musculotendon architecture affect maximum speed bipedal sprinting performance. We found that increases in each parameter analyzed in the study enhanced maximum speed bipedal sprinting performance. In our fourth study, we used the computational model and simulation framework developed in the third study to investigate how variations in the maximum isometric force parameter of each major muscle group affect sprinting performance. The maximum isometric force parameter of each musculotendon actuator in the model was perturbed in isolation. The results showed that increasing each muscle's force-generating capacity enhanced sprinting performance, but hip flexors and quadriceps were found to have the most and least potential, respectively, to increase sprinting speed. The model employed mechanisms similar to those observed in human sprinters to attain higher speeds. Additional plantarflexor and hip flexor force increased speed primarily by enhancing stride length and stride frequency, respectively.In conclusion, this dissertation is the first study to create an aperiodic bipedal sprinting simulation from rest. We demonstrated that additional optimality criteria, vertical GRF and trunk angle, have the potential to eliminate some undesired behaviors and increase fidelity of predictive walking simulations. Contrary to the experimental findings showing that sprinters have smaller plantarflexor moment arms, we found that larger plantarflexor moment arms favor sprinting performance in the maximum speed sprinting phase. The results suggest that special attention should be given to strengthening hip flexor and plantarflexor muscles to increase maximum sprinting speed. The models and simulation frameworks described in this thesis can be used to simulate other bipedal gaits with only minor modifications.
