Dynamics and control of open- and closed-chained multibody systems

 
 
 
 

Dynamics and control of open- and closed-chained multibody systems

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Title: Dynamics and control of open- and closed-chained multibody systems
Author: Lin, Nanjou
Description: Locally optimal trajectory management (LOTM) performance for kinematically-redundant open-chained manipulators is improved, by using a low order polynomial Rayleigh-Ritz expansion to reduce the base reaction fluctuations and by adding a kinetic energy term into the cost function to cause joint motions to come to a full stop without extra effort at the end of the manipulation period. The LOTM approach may be used for operating robots in space station laboratories without disturbing the micro-gravity environment or for managing the joint motions of the legs of walking vehicles. The dynamics of a walking hexapod with each leg having two segments and two revolute joints for a total of three degrees of freedom is investigated. Both a complete model and a simplified model are formulated using Lagrange's equations for quasi-coordinates. The simplified model is based on the assumption that the inertia of each leg is much less than the inertia of the central body. The simplified model is shown to have superior computational efficiency in performing dynamic simulation of a hexapod. Using the simplified model, a dynamic simulation with closed-loop feedback control is introduced. In the dynamic model of a walking machine, the closed-loop kinematic constraints yield infinite solutions of the feedforward joint moment calculation. Hence, the feedforward joint moments are neglected and a closed-loop control is used. The output of the dynamic simulation provides the ground reaction forces and active joint moments. Numerical results show that this method is useful for the study of the mechanics of legged locomotion. It provides an alternative to analytical techniques such as the optimal force distribution method and can be used in conjunction with experimental techniques using force-plates and high-speed cameras.
Permanent Link: http://rave.ohiolink.edu/etdc/view?acc_num=case1056555546
http://hdl.handle.net/2374.OX/16258
Date: 1992

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