Constrained Multi Body Dynamics Method To Study Musculoskeletal Disorders Due To Human Vibration

This dissertation presents a constrained multi-body dynamics method to study musculoskeletal disorders due to human vibration. The method uses Kanes equations to develop governing equations of a multi-body human-body model subjected to constraints. Kanes equations are modified to accommodate the constraint forces. It is observed that the resulting generalized constraint force array is proportional to the transpose of the matrix of coefficients of the constraint equations. This theoretical method is used to obtain a computational simulation of a heavy equipment operator subjected to whole body vibration due to multiple shocks in a working environment. The objective of this study is to determine the mechanism of shock inducing low back pain and disorder. To this end we develop a quantitative relation between vibration excitation and human response. The simulation model consists of a 17-segment system of bodies representing the bodies of the human frame. The bodies are connected by springs and dampers simulating the human joints. The model is validated by comparing computed head transmissibility response with experimental recorded data. The dissertation discusses a multi-body sitting human body model subjected to lower amplitude and high amplitude acceleration exposures containing multiple shocks. The simulation results are compared to published data. The dissertation presents a vibration analysis procedure to conduct time domain and frequency domain human body dynamics. Finally, the dissertation presents a means of predicting health risk under different vibration environments.

As mechanical systems become more complex so do the mathematical models and simulations used to describe the interactions of their parts. One area of multibody theory that has received a great deal of attention in recent years is the dynamics of multiple contact situations occurring in continuous joints and couplings. Despite the rapid gains in our understanding of what occurs when continuous joints and couplings interact, until now there were no books devoted exclusively to this intriguing phenomenon. Focusing on the concerns of practicing engineers, Multibody Dynamics with Unilateral Contacts presents all theoretical and applied aspects of this subject relevant to a practical understanding of multiple unilateral contact situations in multibody mechanical systems. In Part 1, Professor Pfeiffer and Dr. Glocker provide an exhaustive review of the laws and principles governing the dynamics of unilateral contacts in multibody mechanical and technical systems. Among the topics covered are multibody and contact kinematics, the dynamics of rigid body systems, multiple contact configurations, detachment and stick-slip transitions, frictionless impacts, impacts with friction, and the Corner law of contact dynamics. In Part 2, the authors present numerous applications of the theories presented in Part 1. Each chapter in this part is devoted to a different law, theory, or model, such as discontinuous force laws, classical impact theory, Coulomb's friction law, and mechanical and mathematical models of impacts and friction. In addition, each chapter features several practical examples that allow engineers to observe the concepts described in action. Examples are drawn from a broad array of fields and range from hammering in gears as occurring in a synchronous generator to impacts and friction as observed in a child's woodpecker toy, from a demonstration of classical impact theory using an automobile gear box example, to Coulomb's friction law as applied to a turbine blade damper. Multibody Dynamics with Unilateral Contacts is an indispensable resource for mechanical engineers working on all types of multibody systems and the friction and vibration problems that can occur in them. It is also a valuable reference for researchers studying nonlinear dynamics. The only book devoted entirely to the theory and applications of onE of the most crucial aspects of multibody system design. This is the first book to focus exclusively on the theory and applications of multiple contact situations occurring in continuous joints and couplings in multibody systems. As such, it is a valuable resource for engineers working on mechanical systems with interrelated multiple parts. Multibody Dynamics with Unilateral Contacts * Provides a comprehensive examination of the laws and principles governing the dynamics of unilateral contacts in multibody mechanical and technical systems. * Presents the latest mathematical models and simulation techniques for describing the interactions of joints and couplings in multibody systems. * Describes practical applications for all the concepts covered. * Includes numerous examples drawn from a wide range of fascinating and enlightening real-world demonstrations, including everything from an airplane's landing gear to a child's toy.

Every year workers' low-back, hand, and arm problems lead to time away from jobs and reduce the nation's economic productivity. The connection of these problems to workplace activities-from carrying boxes to lifting patients to pounding computer keyboards-is the subject of major disagreements among workers, employers, advocacy groups, and researchers. Musculoskeletal Disorders and the Workplace examines the scientific basis for connecting musculoskeletal disorders with the workplace, considering people, job tasks, and work environments. A multidisciplinary panel draws conclusions about the likelihood of causal links and the effectiveness of various intervention strategies. The panel also offers recommendations for what actions can be considered on the basis of current information and for closing information gaps. This book presents the latest information on the prevalence, incidence, and costs of musculoskeletal disorders and identifies factors that influence injury reporting. It reviews the broad scope of evidence: epidemiological studies of physical and psychosocial variables, basic biology, biomechanics, and physical and behavioral responses to stress. Given the magnitude of the problem-approximately 1 million people miss some work each year-and the current trends in workplace practices, this volume will be a must for advocates for workplace health, policy makers, employers, employees, medical professionals, engineers, lawyers, and labor officials.

Whole Body Vibrations: Physical and Biological Effects on the Human Body allows an understanding about the qualities and disadvantages of vibration exposure on the human body with a biomechanical and medical perspective. It offers a comprehensive range of principles, methods, techniques and tools to provide the reader with a clear knowledge of the impact of vibration on human tissues and physiological processes. The text considers physical, mechanical and biomechanical aspects and it is illustrated by key application domains such as sports and medicine. Consisting of 11 chapters in total, the first three chapters provide useful tools for measuring, generating, simulating and processing vibration signals. The following seven chapters are applications in different fields of expertise, from performance to health, with localized or global effects. Since unfortunately there are undesirable effects from the exposure to mechanical vibrations, a final chapter is dedicated to this issue. Engineers, researchers and students from biomedical engineering and health sciences, as well as industrial professionals can profit from this compendium of knowledge about mechanical vibration applied to the human body. Provides biomechanical and medical perspectives to understanding the qualities and disadvantages of vibration exposure on the human body Offers a range of principles, methods, techniques, and tools to evaluate the impact of vibration on human tissues and physiological processes Explores mechanical vibration techniques used to improve human performance Discusses the strong association between health and human well-being Explores physical, mechanical, and biomechanical aspects of vibration exposure in domains such as sports and medicine

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.

An introduction to multibody dynamics which emphasizes flexible body dynamics. The basic kinematics and dynamics of rigid and deformable bodies, modeling, and newer computational techniques are discussed, and examples and practical applications are given. The book is suitable for graduate students, researchers and practising engineers.

Dynamic Modeling of Musculoskeletal Motion introduces biomechanists to modern methods of modeling and analyzing dynamic biomechanical systems in three dimensions. Using vector kinematics, the reader is taught a systematic method which significantly reduces the complexity of working with multiple, moving limb segments in three dimensions. Operations which usually require the application of differential calculus are replaced by simple algebraic formulae. To derive dynamical equations of motion, a practical introduction to Kane's Method is given. Kane's Method builds upon the foundation of vector kinematics and represents one of the most exciting theoretical developments of the modern era. Together, these techniques enable biomechanists to decipher and model living systems with great realism, efficiency and accuracy. Interwoven with the theoretical presentation are chapters and examples which highlight the subtle differences between inanimate linkages and the biomechanical systems we seek to understand.

This textbook – a result of the author’s many years of research and teaching – brings together diverse concepts of the versatile tool of multibody dynamics, combining the efforts of many researchers in the field of mechanics.