The basic haptic paddle design (Figure 1) consists of an acrylic handle coupled to a single motor
through a capstan drive. As with prior haptic paddles, ours (Figure 2) is designed to be low-costand easy to manufacture, consisting of laser-cut acrylic. All prior haptic paddle designs have used
capstan drives, with the exception of the Michigan haptic paddle (iTouch Motor), which uses a
direct drive device without a transmission (Gillespie, Hoffman, and Freudenberg 2003). While
there is nothing intrinsically disadvantageous with capstan drives (indeed, they are preferred in
many commercial haptic devices for their low friction and smoothness), several years of experience in the laboratory have illustrated that they can be a source of significant frustration for students and
teaching assistants (TAs) as implemented on haptic paddles. For example, when students cause
paddle instability (which they often do when learning about control, and occasionally at other
times in the lab) the string will pop off of the motor drive wheel. It then requires several hands
working in a small space to re-wrap and tension the string, while tightening screws and nuts to fix
both ends of the string to the capstan. This process takes anywhere from 2-10 minutes, depending
on student experience and frustration level. If done incorrectly, the string may be too loose and
slip around the motor spool.