The main objective of this dissertation is to understand how the humanoid organisms or machines use appropriate control strategies and reference motions to achieve the desirable collision responses such as the contact time, the contact forces, the departure velocities of two colliding subjects and the physical deformation. Thereby, the collision of a subject with a rigid object such as a flat ground or a soft object such as a soccer ball is modeled and studied. In particular, we are interested in the collision of a rigid humanoid organism with a rigid ground in the step stance. A complete model of a five-link subject standing on flat ground is considered in four phases: the take-off phase, the flight phase, the landing phase with impacts, and the standing-up phase. We project the joint space model onto the subspace consisting of the hip translational positions and the torso orientation. Inverse kinematics is used to map the Cartesian space to the joint space. Contact forces are formulated as a function of the state variables and controls. Collision of a subject with a soft object is studied by the interaction of a human rigid lower limb with a soccer ball. A general coupling model between the foot and the ball is obtained as a nonlinear spring in parallel with a nonlinear damper. Elasticity is obtained from experimentation. The nonlinear damping in proportion to a restitution-related constant eliminates impact discontinuity. Contact force is modeled as a function of the penetration and the penetration rate of the ball. Collision time we study is short and can be in the magnitude of milliseconds. The simulation requires fast tracking convergence and small steady state tracking error. Therefore, an integral sliding mode control strategy is designed to track the reference motion, obtained by experimental recording of humans executing the step stance leap. The sliding mode control algorithm is developed to track the preplanned trajectory against modeling uncertainties and impact disturbances for the ball-foot interaction.
|School:||The Ohio State University|
|School Location:||United States -- Ohio|
|Source:||DAI-B 79/10(E), Dissertation Abstracts International|
|Keywords:||Collision, Finite-time convergence, Integral sliding mode control, Projection, Step stance leap, Viscoelastic|
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