The ability to quickly and accurately perform precise manual reaching tasks while riding in moving environments is a well recognized problem. Low frequency vibrations, typical of vehicle ride motions result in biodynamic perturbations to the extended arm, inhibiting the quick and accurate reaching movements that are necessary to operate control, navigation, and communication systems. Through this investigation, the effects of ride motions on movement time and endpoint accuracy have been systematically investigated with respect to the location and characteristics of targets, and vehicle ride motions. Vehicle motions were reproduced utilizing a Ride Motion Simulator, in which over 26,000 whole-body seated reaches were performed. Movements were recorded using a motion capture system for subsequent kinematics analyses.

Ride motions are shown to significantly affect the speed and accuracy of reaching tasks, performed with and without temporal constraints. For temporally unconstrained reaches, increases in vibration magnitude resulted in 6%, 10%, and 16.5% longer movement times for low, moderate, and rough vibrations, respectively. Compared to reaches performed in a stationary environment, reaches in directions that coincided with the direction of vibration resulted in 6.6% longer movement time, while reaches in directions perpendicular to the vibration direction were 11% longer in duration. For rapid reaches, whole-body ride motions contributed to approximately 13.5% longer reaction times, 3.6% shorter movement times, and a 56% increase in endpoint variability. Visual and proprioceptive feedbacks also were investigated, where endpoint variability was approximately 3.3 times larger without vision of the hand than visually-guided reaches, while ride motions contributed to an additional 30% increase in endpoint variability. Collectively, ride motion perturbations of visually-occluded reaches resulted in 4.5 times larger endpoint variability than visually-guided reaches performed in a stationary cab.

An active biodynamic human response algorithm is proposed to simulate seated reach trajectories under ride motion perturbations, incorporating trajectory planning, vibration feedthrough to the hand, and visual and proprioceptive feedbacks. This investigation and model development quantifies the performance degradation of in-vehicle reaching tasks when experiencing typical off-road vehicle motions. Direct extrapolation of these results to other vehicles or ride environments is not recommended.