Design and Analysis of the HCCC, RCCC, and PCCC Spatial Mechanisms for Function Generation

Abstract

A computer aided design technique for the synthesis of spatial function generating mechanisms is presented. The Selective Precision Synthesis technique has been extended for the synthesis of the spatial HCCC, RCCC, and PCCC function generating mechanisms. These mechanisms consist of three cylindrical joints (C) and one each of a helical (H), revolute (R), and prismatic (P) joint, respectively. A closed form displacement analysis of the HCCC mechanism has also been presented. In this synthesis technique, for each input position the user specifies accuracy neighborhoods around the desired output rather than exact points. Nonlinear inequality constraints relating the desired output displacement to the actual output displacements are then iteratively solved using the generalized reduced gradient method of optimization, until a good mechanism solution is reached. The analysis uses spatial rotation matrices to solve for the displacement variables.