  Commercial six-axis force-torque sensors suffer from being some combination
of expensive, fragile, and hard-to-use. We propose a new fiducial-based design
which addresses all three points. The sensor uses an inexpensive webcam and can
be fabricated using a consumer-grade 3D printer. Open-source software is used
to estimate the 3D pose of the fiducials on the sensor, which is then used to
calculate the applied force-torque. A browser-based (installation free)
interface demonstrates ease-of-use. The sensor is very light and can be dropped
or thrown with little concern. We characterize our prototype in dynamic
conditions under compound loading, finding a mean $R^2$ of over 0.99 for the
$F_x, F_y, M_x$, and $M_y$ axes, and over 0.87 and 0.90 for the $F_z$ and $M_z$
axes respectively. The open source design files allow the sensor to be adapted
for diverse applications ranging from robot fingers to human-computer
interfaces, while the sdesign principle allows for quick changes with minimal
technical expertise. This approach promises to bring six-axis force-torque
sensing to new applications where the precision, cost, and fragility of
traditional strain-gauge based sensors are not appropriate. The open-source
sensor design can be viewed at
http://sites.google.com/view/fiducialforcesensor.
