Often a simple mechanism to trace a desired path is sought. Coupler curves of linkages are generally difficult to determine, especially in the case that a certain shape or a type of curve is required for a particular application. Precision point techniques do not guarantee that the desired path will be generated. The design methodology presented in this paper is an indirect synthesis approach to design four-bar linkages that trace (approximately) a given desired path. Simple and yet extremely useful design charts for the initial selection of four-bar linkage candidate designs are presented in this paper. This is based on our philosophy that an arbitrary path (desired) can be viewed as an approximation to a known symmetrical path. Four-bar linkages that generate symmetrical paths are easier to design and exhibit a definite pattern of changes in their shape as the linkage parameters are varied. The first step in automating the design-selection process requires a satisfactory means to quantitatively compare the desired with the known (symmetrical) coupler curves. This paper addresses various issues involved in the comparison of two arbitrary curves. Based on curve parametrization, an effective algorithm for quantitative shape evaluation of arbitrary curves is developed. Finally, the design charts and design examples are presented.

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