Synthesis of Four-bar Motion Generation Considering Worst Case Joint Tolerances
Abstract— Four-bar motion generation is used to synthesize a mechanism which passes through or approximate prescribed rigid-body positions. This work will discuss the motion generation of four-bar mechanism with position tolerance variations due to joint running clearance. The tolerance variations study will be based on the standards of American National Standard Institute (ANSI). The new design constraint introduced in this paper will consider the joint tolerances and incorporate it into the displacement position matrix of coupler points described in the conventional planar four-bar motion generation models. The synthesized planar four-bar mechanism will produce tolerance limits for moving pivots and link length from which any mechanism can be synthesized to satisfy the prescribed coupler points with their prescribed tolerances. The included example demonstrates the synthesis of a four-bar mechanism with joint tolerances. 1
Kinematic synthesis of RRSS mechanisms for multi-phase motion generation with tolerances
Abstract This paper presents a new technique for synthesizing spatial RRSS mechanisms to achieve phases of both precise rigid body positions and rigid body positions with tolerances. This method is an extension of the adjustable RRSS motion generation synthesis method developed by the authors [11]. By incorporating rigid body point tolerances in the rigid body displacement matrices and calculating mechanism solution loci for the prescribed rigid body positions under the tolerance limits, circle and center point regions can be calculated. R–R link solutions can then be selected from these regions. This paper considers two-phase fixed and moving pivot adjustment problems with fixed and adjustable crank and follower lengths.
Stochastic Linkage Modeling for Mechanical Error Analysis of Planar Mechanisms
This paper addresses stochastic linkage modeling for mechanical error analysis of planar mechanisms. Considering the effects of joint angle variations, the effective link length model is generalized. The generalized model produces more accurate predictions of mechanical errors than the effective link length model. However, the generalization requires more complicated mechanical error analysis. This paper proposes a stochastic model to intuitively consider the effects of tolerances and clearances, based on the clearance vector concept. Stochastic models are applied to typical mechanisms and their results are compared with those of Monte Carlo simulations. The comparison shows that the proposed stochastic model is effective for mechanical error analysis. The clearance vector model yields more accurate results and is easier to use than the generalized effective link length model.