Contact Modelling For Forward Dynamics Of Human Motion
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Contact Modelling For Forward Dynamics Of Human Motion
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Author : Peter Brown
language : en
Publisher:
Release Date : 2017
Contact Modelling For Forward Dynamics Of Human Motion written by Peter Brown and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Biomechanics categories.
Multibody forward dynamics models of the human body are often used in predictive simulations of human motion. An important component of these models is contact modelling. For example, foot-ground contact plays a crucial role in obtaining accurate results from a walking or running simulation and contact models of joints are necessary to determine accurate joint pressures. Contact models increase multibody system equation complexity (often dramatically) and can introduce nonlinearities and discontinuities into the system equations. This is particularly problematic in predictive simulations, which may determine optimal performance by running a model simulation thousands of times. A desirable contact model should be accurate enough to recreate physiological motion and contact pressures yet still efficient enough to use in an optimisation. A suitable contact model for multibody biomechanics is volumetric contact modelling. Volumetric contact modelling is ideally suited for large, conforming contacts, as is found in biomechanic applications, and has relatively simple, analytical equations (provided the contact surfaces can be approximated as simplified shapes). Another advantage is that volumetric contact can be used to calculate contact pressure, which is difficult to do with simpler point-contact models. In this thesis, volumetric contact was used in two biomechanics models to test its applicability: an anatomical knee model with tibiofemoral contact and a foot-ground contact model. The volumetric knee model was based on another knee model in the literature, with the contact model replaced with volumetric contact. The volumetric model ran faster than real-time and had similar contact forces to the original model. Further improvements are possible by using medical images to determine the contact geometry and including muscles in the model. A friction model is an important part of some biomechanic contact models, particularly the foot-ground contact model. A literature review revealed that many current friction models introduce discontinuities into system equations or are unnecessarily complex. A novel continuous friction model was developed which uses a minimum number of parameters for easy parametrisation. A novel, three-dimensional foot-ground contact model was developed and validated, for future use in a human gait simulation. The foot model used volumetric contact equations for ellipsoidal geometry (which were derived in this thesis, as an improvement on previous sphere-plane contact models). A gait experiment was used to parametrise and validate the model (except for the friction parameters). The model ran over 100 times faster than real-time (in an inverse simulation) and matched experimental normal force and centre of pressure location (with less than 7% root-mean-square error). It was discovered that the designed gait experiment could not be used to determine the friction parameters for the foot-ground model. A possible alternative was suggested, and the validation of the friction portion of the model was left to a future study. In conclusion, volumetric contact can be used to produce a computationally efficient and accurate contact model.
Contributions To Contact Simulation And Human Motion Analysis
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Author : Farnood Gholami
language : en
Publisher:
Release Date : 2016
Contributions To Contact Simulation And Human Motion Analysis written by Farnood Gholami and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
"This thesis contains contributions to contact simulation and human motion analysis. Effects of the foot and ankle modelling techniques on the foot kinematics and dynamics are investigated. The analyses are carried out based on experimental data obtained using a motion capture system. The appropriateness of modelling the human ankle joint based on a stationary axis of rotation is investigated and a technique is also proposed which is capable of predicting the directional changes of the ankle axis during the foot flexion. Furthermore, two main modelling assumptions related to the number of the foot segments and the dimension of the foot model were the subject of the foot dynamics analyses. Effects of these modelling assumptions on the ankle joint torque and power are determined. A framework was developed which quantifies the gait abnormality of multiple sclerosis (MS) patients using a Kinect camera. The reliability of such a framework in assessing gait parameters in MS patients is evaluated based on captured data by Kinect. Also, a novel set of MS gait indices based on the concept of dynamic time warping is introduced whichcan characterize a patient's gait pattern and quantify the subject's gait deviation from the healthy population. In the second part of the thesis, two algorithms, namely, the accelerated-box and the generalized inverse-based algorithms, were developed for contact dynamics simulation. The accelerated-box algorithm improves the simulation of rigid body contact problems, in particular when the system under consideration has redundant constraints. The mathematical formulation is expressed in terms of a mixed linear complementarity problem (MLCP). The accelerated-box approach is partly motivated by the box friction model which is one of the existing approaches to solve contact problems. The original box friction model suffers from certain drawbacks in the presence of a large number of contact points such as long computational time, divergence problems, and instability. On the other hand, the accelerated-box approach developed in this thesis overcomes such drawbacks by taking advantage of the sparse structure of the lead matrix of the MLCP. This new method reduces the sensitivity of the solution to the constraint relaxation terms and decreases the number of required pivots to obtain the solution, and hence, shorter computational times result. This approach accordingly suggests a more reliable method for real-time simulation of multibody systems. A method based on the use of the Moore-Penrose generalized inverse was developed to deal with systems with redundant contacts. This approach omits the necessity of relaxing the constraints when redundancy exists in the system. To develop such a method, the generalized inverse is incorporated inside the pivoting steps of the MLCP solver. The method is very stable and robust, and its computational time is considerably smaller than the counterpartmethods, specially for highly redundant systems. Finally, a novel complementarity problem formulation is introduced. In this formulation, contacts are characterized based on constraints for normal direction while friction forces are simultaneously regularized and incorporated into the formulation. The dimension of such a formulation is significantly lower in comparison with counterpart formulations in the literature. Redundant constraints can be handled via relaxing the constraints. The proposed regularized formulation is examined for benchmark examples and results show acceptable agreement with the expected behaviours, while the computational time is considerably reduced in comparison with other formulations in the literature. This formulation could be a useful and practical choice for real-time simulation of complex mechanical systems." --
Simulating And Generating Motions Of Human Figures
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Author : Katsu Yamane
language : en
Publisher: Springer Science & Business Media
Release Date : 2004-01-15
Simulating And Generating Motions Of Human Figures written by Katsu Yamane and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004-01-15 with Computers categories.
This book focuses on two issues related to human figures: realtime dynamics computation and interactive motion generation. In spite of the growing interest in human figures as both physical robots and virtual characters, standard algorithms and tools for their kinematics and dynamics computation have not been investigated very much. "Simulating and Generating Motions of Human Figures" presents original algorithms to simulate, analyze, generate and control motions of human figures, all focusing on realtime and interactive computation. The book provides both practical methods for contact/collision simulation essential for the simulation of humanoid robots and virtual characters and a general framework for online, interactive motion generation of human figures based on the dynamics simulation algorithms.
Forward Dynamic Modeling Of Human Locomotion
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Author : James Lanphier Patton
language : en
Publisher:
Release Date : 1993
Forward Dynamic Modeling Of Human Locomotion written by James Lanphier Patton and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with Human locomotion categories.
Optimal Control And Multibody Dynamic Modelling Of Human Musculoskeletal Systems
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Author : Mohammad Sharif Shourijeh
language : en
Publisher:
Release Date : 2013
Optimal Control And Multibody Dynamic Modelling Of Human Musculoskeletal Systems written by Mohammad Sharif Shourijeh and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Musculoskeletal dynamics is a branch of biomechanics that takes advantage of interdisciplinary models to describe the relation between muscle actuators and the corresponding motions of the human body. Muscle forces play a principal role in musculoskeletal dynamics. Unfortunately, these forces cannot be measured non-invasively. Measuring surface EMGs as a non-invasive technique is recognized as a surrogate to invasive muscle force measurement; however, these signals do not reflect the muscle forces accurately. Instead of measurement, mathematical modelling of the musculoskeletal dynamics is a well established tool to simulate, predict and analyse human movements. Computer simulations have been used to estimate a variety of variables that are difficult or impossible to measure directly, such as joint reaction forces, muscle forces, metabolic energy consumption, and muscle recruitment patterns. Musculoskeletal dynamic simulations can be divided into two branches: inverse and forward dynamics. Inverse dynamics is the approach in which net joint moments and/or muscle forces are calculated given the measured or specified kinematics. It is the most popular simulation technique used to study human musculoskeletal dynamics. The major disadvantage of inverse dynamics is that it is not predictive and can rarely be used in the cause-effect interpretations. In contrast with inverse dynamics, forward dynamics can be used to determine the human body movement when it is driven by known muscle forces. The musculoskeletal system (MSS) is dynamically under-determinate, i.e., the number of muscles is more than the degrees of freedom (dof) of the system. This redundancy will lead to infinite solutions of muscle force sets, which implies that there are infinite ways of recruiting different muscles for a specific motion. Therefore, there needs to be an extra criterion in order to resolve this issue. Optimization has been widely used for solving the redundancy of the force-sharing problem. Optimization is considered as the missing consideration in the dynamics of the MSS such that, once appended to the under-determinate problem, \human-like" movements will be acquired. \Human-like" implies that the human body tends to minimize a criterion during a movement, e.g., muscle fatigue or metabolic energy. It is commonly accepted that using those criteria, within the optimization necessary in the forward dynamic simulations, leads to a reasonable representation of real human motions. In this thesis, optimal control and forward dynamic simulation of human musculoskeletal systems are targeted. Forward dynamics requires integration of the differential equations of motion of the system, which takes a considerable time, especially within an optimization framework. Therefore, computationally efficient models are required. Musculoskeletal models in this thesis are implemented in the symbolic multibody package MapleSim that uses Maple as the leverage. MapleSim generates the equations of motion governing a multibody system automatically using linear graph theory. These equations will be simplified and highly optimized for further simulations taking advantage of symbolic techniques in Maple. The output codes are the best form for the equations to be applied in optimization-based simulation fields, such as the research area of this thesis. The specific objectives of this thesis were to develop frameworks for such predictive simulations and validate the estimations. Simulating human gait motion is set as the end goal of this research. To successfully achieve that, several intermediate steps are taken prior to gait modelling. One big step was to choose an efficient strategy to solve the optimal control and muscle redundancy problems. The optimal control techniques are benchmarked on simpler models, such as forearm flexion/extension, to study the efficacy of the proposed approaches more easily. Another major step to modelling gait is to create a high-fidelity foot-ground contact model. The foot contact model in this thesis is based on a nonlinear volumetric approach, which is able to generate the experimental ground reaction forces more effectively than the previously used models. Although the proposed models and approaches showed strong potential and capability, there is still room for improvement in both modelling and validation aspects. These cutting-edge future works can be followed by any researcher working in the optimal control and forward dynamic modelling of human musculoskeletal systems.
Human Motion Simulation
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Author : Karim Abdel-Malek
language : en
Publisher: Academic Press
Release Date : 2013-05-30
Human Motion Simulation written by Karim Abdel-Malek and has been published by Academic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-05-30 with Computers categories.
Simulate realistic human motion in a virtual world with an optimization-based approach to motion prediction. With this approach, motion is governed by human performance measures, such as speed and energy, which act as objective functions to be optimized. Constraints on joint torques and angles are imposed quite easily. Predicting motion in this way allows one to use avatars to study how and why humans move the way they do, given specific scenarios. It also enables avatars to react to infinitely many scenarios with substantial autonomy. With this approach it is possible to predict dynamic motion without having to integrate equations of motion -- rather than solving equations of motion, this approach solves for a continuous time-dependent curve characterizing joint variables (also called joint profiles) for every degree of freedom. Introduces rigorous mathematical methods for digital human modelling and simulation Focuses on understanding and representing spatial relationships (3D) of biomechanics Develops an innovative optimization-based approach to predicting human movement Extensively illustrated with 3D images of simulated human motion (full color in the ebook version)
Mathematical Modeling And Simulation Of Human Motion Using 3 Dimensional Multi Segment Coupled Pendulum System
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Author : Loay Ahmed-Wasfe Al-Zube
language : en
Publisher:
Release Date : 2004
Mathematical Modeling And Simulation Of Human Motion Using 3 Dimensional Multi Segment Coupled Pendulum System written by Loay Ahmed-Wasfe Al-Zube and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.
The use of mathematical models to investigate the dynamics of human movement relies on two approaches: forward dynamics and inverse dynamics. In this investigation a new modeling approach called the Boundary Method is outlined. This method addresses some of the disadvantages of both the forward and the inverse approach. The method yields as output both a set of potential movement solutions to a given motor task and the net muscular impulses required to produce those movements. The input to the boundary method is a finite and adjustable number of critical target body configurations. In each phase of the motion that occurs between two contiguous target configurations the equations of motion are solved in the forward direction as a two point ballistic boundary value problem. In the limit as the number of specified target configurations increases the boundary method approaches a stable algorithm for doing inverse dynamics. A 3-Dimensional, multi-segment coupled pendulum system, that mathematically models human motion, will be presented along with a derivation of a generalized formula that constructs the equations of motion for this model. The suggested model is developed to utilize the boundary method. The model developed in this thesis will lead to a long rang goal, which is the development of a diagnostic tool for any motion analysis laboratory that will answer the question of finding optimal movement patterns, to prevent injury and improve performance in human subjects.
A Study Of Optimization Based Predictive Dynamics Method For Digital Human Modeling
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Author : Mahdiar Hariri
language : en
Publisher:
Release Date : 2012
A Study Of Optimization Based Predictive Dynamics Method For Digital Human Modeling written by Mahdiar Hariri and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Human body categories.
Here, kinematics of the motion is assumed to be known. It is shown that this approach leads to more realistic values for the contact forces and moments for a human motion task as opposed to the ZMP based approach. The proposed approach appears to be quite promising and needs to be fully integrated into the predictive dynamics approach of human motion simulation. Some other insights are obtained for the predictive dynamics approach of human motion simulation. For example, it is mathematically proved and also validated that there is a need for an individual constraint to ensure that the normal component of the resultant global forces remains compressive for non-adhesive contacts between the body and the environment. Also, the ZMP constraints and stability margins are applicable for the problems where all the contacts between the environment and the body are in one plane; however, the NCM constraints and stability margins are applicable for all types of arbitrary contacts between the body and the environment. The ZMP and NCM methods are used to model the motion of a human (soldier) performing several military tasks: Aiming, Kneeling, Going Prone and Aiming in Prone Position. New collision avoidance theorems are also presented and used in these simulations.
Mechanics And Control Of Human Balance
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Author : Matthew Millard
language : en
Publisher:
Release Date : 2011
Mechanics And Control Of Human Balance written by Matthew Millard and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
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.
Multibody Dynamics
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Author : Juan Carlo Garcia Orden
language : en
Publisher: Springer Science & Business Media
Release Date : 2007-04-05
Multibody Dynamics written by Juan Carlo Garcia Orden and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007-04-05 with Technology & Engineering categories.
The ECCOMAS Thematic Conference Multibody Dynamics 2005 was held in Madrid, representing the second edition of a series which began in Lisbon 2003. This book contains the revised and extended versions of selected conference communications, representing the state-of-the-art in the advances on computational multibody models, from the most abstract mathematical developments to practical engineering applications.