Many planar manipulators are composed of a basic four-bar mechanism. The output delivered by the mechanism deviates from desired one due to factors like link tolerances. The performance needs to be characterized for satisfactory application. This article presents investigation of mechanical error in four-bar mechanism with revolute joints (4R) under the influence of link tolerance. The classical partial derivative formulation (PDA) in uncertainty analysis technique is primarily used for estimating the mechanical error. The error estimation is carried out with proposed modification in PDA formulation. A geometric approach is also developed to estimate the mechanical error for 4R configuration. The mechanical error obtained through PDA is verified using geometric approach. The generalized formulation is demonstrated, and comparative estimation is presented. The methods and conclusions proposed herewith are adaptable for other planar configurations.
This article incorporates formulation and application for the varying position of output link of P3R and 4R manipulator configuration and estimation of mechanical error. The behavior of the output link is analyzed for linear and rotary inputs for both the type of configurations. The variation in link tolerance is introduced as input for estimating the mechanical error for P3R and 4R manipulator with the derived formula. Comparison of the errors provides the basis of selecting the best manipulator with the minimum mechanical error. Sample case is illustrated for the identical operational features in these P3R and 4R manipulators and the performance of these manipulators is quantified in this paper. The methodology is successful in considering the effect of source of mechanical errors in general; the proposed methodology is going to be helpful for the analysis of spatial and parallel manipulator.
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