Martín A. Pucheta

Synthesis of Planar Multiloop Linkages Starting from Existing Parts or Mechanisms: Enumeration and Initial Sizing

Abstract We present a methodology for dealing with mechanism synthesis problems in which the initial parts to move can have the form of either open-, closed-, or mixed-chain mechanisms, isolated points, or bodies to guide. We use a finite element method-like description of the initial kinematics problem, a graph representation to solve the number synthesis, and the precision-point method to solve the initial dimensions of the linkages. A preliminary analysis of the structural parts in conjunction with the imposed motion constraints is considered just after the initial description to distinguish those analyzable parts from the unknowns of the synthesis problem. A nonstandard example for function generation is illustrated throughout the paper.

Topological Synthesis of Planar Metamorphic Mechanisms for Low-Voltage Circuit Breakers

This article presents a systematic graph theory-based method for the topological synthesis of planar metamorphic mechanisms including metamorphic transformations of links and changes in the degrees-of-freedom. The parts to move, with input and output motion defined, and the topological design space, are represented by graphs of simple-jointed mechanisms. The topological requirements involving link transformations are expressed in terms of subgraphs with a given degrees-of-freedom containing prescribed input and output parts. The algorithm executes two subgraph searches inside atlases of mechanisms with different degrees-of-freedom. An application to the design of a family of low-voltage circuit-breaker mechanisms is shown.

Combined Graph Layout Algorithms for Automated Sketching of Kinematic Chains

The graph layout problem arises frequently in the conceptual stage of mechanism design, specially in the enumeration process where a large number of topological solutions must be analyzed. Two main objectives of graph layout are the avoidance or minimization of edge crossings and the aesthetics. Edge crossings cannot be always avoided by force-directed algorithms since they reach a minimum of the energy in dependence with the initial position of the vertices, often randomly generated. Combinatorial algorithms based on the properties of the graph representation of the kinematic chain can be used to find an adequate initial position of the vertices with minimal edge crossings. To select an initial layout, the minimal independent loops of the graph can be drawn as circles followed by arcs, in all forms. The computational cost of this algorithm grows as factorial with the number of independent loops. This paper presents a combination of two algorithms: a combinatorial algorithm followed by a force-directed algorithm based on spring repulsion and electrical attraction, including a new concept of vertex-to-edge repulsion to improve aesthetics and minimize crossings. Atlases of graphs of complex kinematic chains are used to validate the results. The layouts obtained have good quality in terms of minimization of edge crossings and maximization of aesthetic characteristics.Copyright

Synthesis and Optimization of Flexible Mechanisms

This paper resumes researches done in two European projects: SYNAMEC and SYNCOMECS. As a result of this activity, an integrated computer-aided tool for the synthesis and design of flexible mechanisms has been developed. Within the SYNAMEC project, a software system for the mechanism type synthesis (choice of topology), the integration into existing mechanism and the preliminary dimensional synthesis (choice of sizes and physical properties) was developed. This tool was improved in the SYNCOMECS project to include compliance in its components library. Once preliminary design is achieved, the combined use of SAMCEF-Mecano, SAMCEF-Field and BOSS-Quattro software allows optimizing detailed models of the system taking into account all mechanical effects. Aeronautical applications are shown, where starting from an initial configuration suggested by the integrated type synthesis tool, the users can optimize and design its system from early pre-design sizing to detailed stress analysis using a single software in a GUI environment.

Automated Type and Modular Dimensional Synthesis of Planar Linkages

We present an automated method for type and dimensional synthesis of planar linkage mechanisms. In the kinematic problem, a graph representation called initial graph is given to the parts to move. The type synthesis stage consists of an exhaustive subgraph search of the initial graph inside the graphs taken from a previously enumerated atlas of mechanisms. Each alternative resulting from the type synthesis is dimensioned using the Precision Position Method and Genetic Algorithms: the closed-chain topology is decomposed into single-open chains of two and three links programmed as dyad and triad modules; these modules are executed to compute all the significant dimensions of the linkage. Using this type and dimensional synthesis method, a fast generation and evaluation of many mechanisms can be done in few minutes using a desktop personal computer. The enumeration of mechanisms for a path following task, including eight-bar solutions, illustrates the whole design process.Copyright