Figure 11.

Typical measurements taken during trials of the first user using the tremor canceling (blue) and automatic position holding (red) features of the system. (a) Forces on the needle: mostly along the y-axis with a gradual rise during insertion and a sharp drop at the instant of puncture; (b) Position of the needle remains fixed with the position holding mode in contrast to the fluctuations with only tremor canceling; (c) The event of puncture: a positive peak in the inner product of needle velocity and force variation vectors; (d) Recorded needle tip trajectories for three representative trials of each mode. Position holding mode significantly reduced tool tip deviation from the puncture point [62].