Tracking Performance During Whole-Body Vibration with Side-Mounted and Center-Mounted Control Sticks.

Abstract : To compare the relative susceptibility to vibration interference of a side-mounted control stick and a center-mounted control stick (both force-type, or isometric, controllers), pitch axis tracking performance was measured during sinusoidal whole-body Z-axis vibration. The tracking task had a dynamically unstable controlled element, which became increasingly unstable until the subject lost control. The tracking score was the highest level of instability at which control could be maintained. Subjects were seated upright and vibrated at plus or minus 0.4 g along the z axis at frequencies of 2 Hz, 6 Hz, and 10 Hz. Results indicated that with either stick all frequencies of vibration produced significant decrements in tracking performance, compared to the no-vibration control condition. There was no clear cut superiority of one stick location over the other, but which stick produced better performance was dependent upon the frequency of the vibration. The side stick was slightly better at 2 Hz, but the center stick was slightly better at 6 Hz and significantly better at 10 Hz. The large difference between the sticks at 10 Hz was attributed to the fact that for the side stick the input vibration is transmitted directly to the arm and hand via the arm rest, but for the center stick the input is from the seat, and at 10 Hz the amount transmitted to the hand is attenuated by the body. (Author)