On Robust Mechanical Design of PAR2 Delta-Like Parallel Kinematic Manipulator

Sensitivity analysis of manipulators aims at studying the influence of variations in its own geometric parameters on its performance. This information is useful for evaluating the position error of the end-effector as well as for the synthesis of tolerances. Indeed, the synthesis of tolerances is a very important issue in the design and manufacturing of robot manipulators. In this paper, a sequential procedure for modeling, dimensioning and tolerance synthesis of the parallel kinematic manipulator PAR2 is proposed. For optimal dimensional design, an approach based on the optimization of the workspace is proposed, taking into account several constraints; followed by a numerical matrix analysis based deterministic method for sensitivity analysis whose performance is studied in terms of accuracy. To calculate the optimal dimensional tolerances, a new tolerance synthesis method is used. The effect of geometric tolerance on accuracy is analyzed.

Information Architecture for Design Tolerancing: From Conceptual to the Detail Design

Tolerance design is the process of deriving a description of geometric tolerance specifications for a product from a set of specifications on the desired properties of the product. Existing approaches to tolerance analysis and synthesis entail detailed knowledge of geometry of assemblies and are mostly applicable during advanced stages of design, leading to a less than optimal design process. During the design process of assemblies, both assembly structure and associated tolerance information evolve continuously and significant gains can be achieved by effectively using this information to influence the design of an assembly. Any pro-active approach to the assembly or tolerance analysis in the early design stages will involve decision making with incomplete information models. In order to carry out early tolerance synthesis and analysis in the conceptual stages of the product design, we need to devise techniques for representing function-behavior-assembly models that will allow analysis and synthesis of tolerances, even with the incomplete data set. A ‘function’ (what the system is for) is associated with the transformation of an input physical entity into an output physical entity by the system. The problem or customer’s need, initially described by functional requirements on an assembly, and associated constraints on the functional requirements derives the concept of an assembly. This specification of functional requirements and constraints define a functional model for the assembly. Many researchers have studied functional representation (function based taxonomy and ontology), function to form mapping, and behavior representation (behavior means how the system/product works). However, there is no comprehensive function-assembly-behavior (FAB) integrated model. In this paper, we discuss the integration of function, assembly, and behavior representation into a comprehensive information model (FAB models). To do this, we need to develop appropriate assembly models and tolerance models that would enable the designer to incrementally understand the build-up or propagation of tolerances (i.e., constraints) and optimize the layout, features, or assembly realizations. This will ensure ease of tolerance delivery.