In a recent study, Rastegar, et al. (2003), presented a special class of planar and spatial linkage mechanisms in which for a continuous full rotation or continuous rocking motion of the input link, the output link undergoes two continuous rocking motions. In a special case of such mechanisms, for periodic motions of the input link, the output motion is periodic with a doubled fundamental frequency. The above class of linkage mechanisms were referred to as “speed-doubling” linkage mechanisms. Such mechanisms can be cascaded to further double the fundamental frequency (rocking motion) of the output motion. They can also be cascaded with other linkage mechanisms to obtain crank-rocker or crank-crank type of mechanisms. The conditions for the existence of “speed-doubling” linkage mechanisms were also provided. In this paper, a study of the dynamics of a “speed-doubling” linkage mechanism is presented. It is shown that such mechanisms have dynamic advantage over regular mechanisms designed to achieve similar output motions. The main advantage of such mechanisms is shown to be their lower peak input torque requirement, and that the required torque generally has lower amplitude high-frequency components. The speed-doubling mechanisms have practical applications, particularly when higher output speeds are desired, since higher output motions can be achieved with lower input speeds and smaller motors.

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