A new method is presented for the modification of the output motion of linkage mechanisms with closed-loop chains using cams positioned at one or more of its joints. As an example and to present the basic concept, the method is applied to a four-bar linkage mechanism that is synthesized for function generation for the purpose of eliminating the high harmonic component of the output link motion. By eliminating the high harmonic component of the output motion of a mechanism, the potential vibrational excitation that the mechanism can impart on the overall system, including its own structure, is greatly reduced. The resulting system should therefore be capable of operating at higher speeds and with increased precision. For mechanisms with rigid links, the primary source of high harmonics in the output motion is the nonlinearity of the kinematics of their closed-loop chains. With the present method, a selected range or ranges of high harmonic motions generated due to such nonlinearities may be eliminated by integrating appropriately designed cams that are used to vary the effective length of one or more of the links during the motion. A numerical example is provided together with a discussion of the related topics of interest.

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