Simulation_Lab1 - Simulation Lab #1: Dynamic Simulation of...

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1 Simulation Lab #1: Dynamic Simulation of Jumping Professor B.J. Fregly Mechanics of the Human Locomotor System EML 5595 - Fall 2010 Lab and Jumping Software Developers: Jeff Reinbolt and B.J. Fregly Computational Biomechanics Lab, University of Florida Derived from a similar simulation lab developed at Stanford University by Clay Anderson, Allison Arnold, Silvia Blemker, Darryl Thelen, and Scott Delp I. Introduction In the study of human movement, experimental measurement is generally limited to the kinematics of the body segments, external reaction forces, and electromyographic (EMG) signals from the muscles. While these data are essential for characterizing movement, they do not help us understand how individual muscles or groups of muscles are coordinated to produce movement. However, knowledge of muscle coordination is essential for quantifying the stresses placed on bones and understanding the functional roles of muscles in normal and pathological movement. Dynamic simulation of the musculoskeletal system provides a means for understanding multijoint coordination as well as a framework for investigating how the various components of the musculoskeletal system interact to produce movement. The purpose of this lab is to introduce you to some basic issues involved in dynamic modeling and simulation of the human musculoskeletal system. You will use an interactive jumper model to perform repeated dynamic simulations of jumping with the goal of maximizing the jump height of the model. The interactive model gives you manual control over the initial joint angles in the model and the time histories of the net muscle joint torque actuators controlling the motion of each joint. These torque actuators represent the net control effect of all muscles spanning the toe, ankle, knee, and hip joints in the model. In addition, you can turn on and off passive joint torques that account for foot contact with the ground and ligament restraint of joint hyperextension. In both cases, if a joint goes beyond a physically realistic limit (e.g., the foot rotates through the ground or the knee hyperextends), a passive control torque is generated in the opposite direction to counteract the undesirable joint motion. Jumping was chosen as the activity for this lab because it possesses a well-defined objective (i.e., jump as high as possible) and, although still complex, its muscular coordination is relatively simple compared to walking. The musculoskeletal model used in this lab was taken from a study published by Pandy et al . (1990). While the joint angle definitions in the present model differ from those in that study (we use relative rather than absolute joint angles), the basic dynamical model is almost identical with two exceptions. First, we model the influence of muscles using net torque actuators instead of individual muscle forces, and second, we include the influence of passive ligamentous restraining torques. By working through this lab, you will get a feel for the computational cost of repeated dynamic simulation, develop an understanding of how passive torques can affect the
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This note was uploaded on 02/15/2012 for the course EML 5595 taught by Professor Staff during the Spring '08 term at University of Florida.

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Simulation_Lab1 - Simulation Lab #1: Dynamic Simulation of...

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