FIG. 1.

Experimental setup. Thumb and finger sensors (shown as white cylinders) were attached to vertical aluminum bars, and a movable load (shown as a black cylinder) was attached to the long horizontal aluminum beam. A transmitter (the small black cube) of a magnetic tracking device was attached to a Plexiglas base affixed to the top of the handle. $\overrightarrow{{\mathrm{F}}^{\mathrm{th}}}$, $\overrightarrow{{\mathrm{F}}^{\mathrm{i}}}$, $\overrightarrow{{\mathrm{F}}^{\mathrm{m}}}$, $\overrightarrow{{\mathrm{F}}^{\mathrm{r}}}$, and $\overrightarrow{{\mathrm{F}}^{\mathrm{l}}}$ are the force vectors of the thumb, index, middle, ring, and little fingers and $\overrightarrow{{\mathrm{d}}^{\mathrm{th}}}$, $\overrightarrow{{\mathrm{d}}^{\mathrm{i}}}$, $\overrightarrow{{\mathrm{d}}^{\mathrm{m}}}$, $\overrightarrow{{\mathrm{d}}^{\mathrm{r}}}$, and $\overrightarrow{{\mathrm{d}}^{\mathrm{l}}}$ are the force application point vectors of the thumb, index, middle, ring, and little fingers, respectively. M_X, M_Y, and M_Z are the global moments with respect to the global X-, Y-, and Z-axes; m_x, m_y, and m_z are the local moments with respect to the local x-, y-, and z-axes on each sensor, respectively; th, i, m, r, and l stand for the thumb, index, middle, ring, and little fingers.