https://arxiv.org/abs/2005.14250
https://sites.google.com/view/fiducialforcesensor
Consumer webcams and a printed fiducial can be used to create a six-axis force-torque sensor. We used four springs to build a platform free to move in all angular directions. We affixed a two printed fiducial markers to the platform, and then aimed a consumer camera up at the marker. To the right, a different view of the sensor reveals the tag location. The tags are glued to the light shield, which is removable. This allows for easy design changes. (Green bottle cap for size comparison only).