Synthesis and design automation of rigid body and compliant mechanisms.

摘要

This dissertation presents a set of design tools and approaches for synthesis of both rigid body and compliant mechanisms. The research goal is to achieve design automation for articulated mechanical systems. It is comprised of two parts.;The focus of the first part is on synthesis and design of planar rigid body linkages for path generation problems. The solution approach includes an off-line linkage library and the on-line computer aided design framework. The former introduces curve characterization, type-P Fourier descriptor normalization that a digital library that characterizes the motion curves of variety of planar linkages. And the latter brings a new computer-aided linkage design and simulation system that integrates a curve matching algorithm and design optimization routines. This computer-aided design system is built to achieve design automation and interactive design. To enable the design automation framework, first a pre-built library of open and closed planar curves is generated according to commonly used planar linkages. Then the classical linkage path generation problem is translated into a database-searching problem together with a local optimization problem, which embeds a rapid search algorithm that compares the Fourier descriptors of the task path against those of the linkage samples in the library, and retrieves a design candidate from them. To enable the interactive design framework, a set of design interfaces are implemented that facilitate designers intervene and steer the design process.;The second part of this dissertation focuses on type synthesis of compliant mechanisms with screw theory. Here a systematic synthesis procedure for flexure elements and general compliant mechanisms is proposed. In this approach, we first categorize a list of commonly used atomic flexure primitives, and through which, basic R-joints and P-joints that allow a single rotation or a single translation are defined. By using parallel structures of these flexure primitives, eleven designs of R-joints and eight designs of P-joints are systematically synthesized. In contract to freedom elements, we synthesize serial chains of flexure primitives and obtained six designs of P-constraints and three designs of R-constraints. These freedom and constraint elements are basic building blocks for designing more complex flexure mechanisms. To demonstrate our theory, hybrid structures with a serial and parallel combination of compliant elements are designed, and also parallel compliant mechanisms with three translational degrees of freedom are synthesized.