Date of Award

Fall 2000

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering - (Ph.D.)

Department

Mechanical Engineering

First Advisor

R. S. Sodhi

Second Advisor

Rong-Yaw Chen

Third Advisor

Sanchoy K. Das

Fourth Advisor

Zhiming Ji

Fifth Advisor

Bernard Koplik

Abstract

Although spatial mechanisms are more general in structure than planar mechanisms, their applications are few due to the limited number of practical design tools and the complexity of those available. It is in fact the task of the future to develop effective, but practical design tools for spatial mechanisms.

This research presents several new methods for synthesizing adjustable spatial mechanisms. The first method involves the kinematic synthesis of spatial mechanisms for multiphase motion generation. Using this method, spatial four and five-bar mechanisms can be synthesized to achieve different phases of prescribed rigid body positions. The theory of this approach has also been extended to incorporate rigid body tolerance problems. Using the tolerance problem method, spatial four-bar mechanisms can be synthesized to achieve the prescribed precise rigid body positions and also satisfy the rigid body positions within the prescribed tolerances. Both approaches use the R-R, S-S, R-S and C-S dyad displacement equations.

The second method involves the kinematic synthesis of spatial mechanisms for multiphase multiply separated positions. Using this method, spatial four and five-bar mechanisms can be synthesized to achieve different phases of prescribed rigid body positions, velocities and accelerations. The theory of this approach has also been extended to incorporate instantaneous screw axis (ISA) parameters. Using ISA parameters, spatial four-bar mechanisms can also be synthesized to achieve different phases of prescribed rigid body positions, velocities and accelerations. Both approaches use the R-R, S-S, R-S and C-S dyad displacement, velocity and acceleration equations.

For each method, the maximum number of prescribed rigid positions is determined for each mechanism for two and three phase problems. The spatial four and five-bar mechanisms considered in this research are the RRSS, RRSC, RSSR-SS and RSSR-SC.

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