Dolphin-like propulsive mechanism based on an adjustable Scotch yoke

This paper addresses the design, construction, and motion control of an adjustable Scotch yoke mechanism generating desired kinematics for dolphin-like robots. Since dolphins propel themselves by dorsoventral oscillations following a sinusoidal path with alterable amplitudes, a two-motor-driven Scotch yoke mechanism is adopted as the primary propulsor to produce sinusoidal oscillations, where a certain combination of a leading screw mechanism and a rack and pinion mechanism driven by the slave motor are incorporated to independently change the length of the crank actuated by the master motor. Meanwhile, the output of the Scotch yoke, i.e., reciprocating motion, is converted into the up-and-down oscillations via a rack and gear transmission. A DSP-based built-in motion control scheme is then brought forth and applied to achieve dolphin-like propulsion. Preliminary tests, in a robotics context, confirm the feasibility of the devised mechanism severing as a dedicated propulsor for bio-inspired movements.