Characterization of whip targeting kinematics in discrete and rhythmic tasks

Abstract

Robotic control of complex objects is inferior to that of humans despite superior communication, sensors and actuators. Therefore, studying human control of complex dynamic objects, in particular a bullwhip, should reveal how humans may achieve superior dexterity. An expert whip-cracker performing two distinct targeting tasks, discrete and rhythmic, was observed using the Qualisys 3D motion capture software. The objective was to investigate the kinematics of the whip, the kinematics of the subject's arm while controlling the whip and the differences between discrete and rhythmic tasks. The subject was able to expertly perform both targeting tasks with excellent targeting accuracy. The study confirmed the existence of a wave propagating down the whip as stated in prior work. Furthermore, a distinct difference between discrete and rhythmic tasks was observed in the reproducibility of position profiles, reproducibility of phase profiles, and the waveforms of elbow and wrist angles. Finally, the whip trajectory was substantially confined to a plane. In contrast with claims made in prior work, this plane was found to be distinct from the parasagittal plane and slanted with respect to it.