Screw Shaft-Driven Underactuated Hand

For fall 2012 Introduction to Mechanical Prototyping at Olin College, I collaborated on a team of four to create an underactuated robotic hand. Throughout the semester, we researched systems that use fewer actuators than the number of degrees of freedom (i.e. are underactuated). We designed and built two prototypes and one final working product that could pick up a grain rice, a a towel, an ice cube, balls ranging in size from a ping pong to a softball, and many others. The final product was built with laser cut MDF pieces, waterjet aluminum sheet parts, 3D-printed thermoplastics, two variety polymers, and three screw shafts. For transmission, we used a belt system sandwiched between two MDF parts. 

The fingers are four-bar linkages with a polymer joint in the driven linkage. The polymers in the finger were selected with care. The joint in the linkage was constructed with a stiffer and harder polymer. We adjusted the length and width of the joint so that the polymer worked as a spring in the finger. We used this polymer on the finger pads as well as it had sufficient grip for our purposes. 

I learned about the process of effective prototypes that can answer specific question in this project. It was my first experience with a belt drive which was fantastic. It was exciting to research, design, and create a system that works better than expected.

Please see the write-up here and videos of the final product here.