I'm interested in printing a working two degree of freedom planetary gear set. I searched around and found a paper from University of Maryland in 1988 (source). I am having difficulty translating the information into a real-world model.
The goal is to make a system that allows two independent inputs to affect the speed and torque of a single output. As the paper points out, a differential system doesn't quite make this possible.
Although mechanical systems with multiple inputs or multiple outputs have existed for many years, generally, they have been used as a series of one-DOF devices rather than as true multi-DOF mechanisms. For example, the automotive bevel-gear differential, a two-DOF mechanism with one input and two outputs, is made-up of a one-DOF gear train in series with its gear box.
I tried analyzing a standard differential system but I don't believe you can alter it to use two independent inputs. The six link systems described in the paper seem to be the right direction, and so I would like to understand the graph.
Here is the figure from the paper:
And here is my attempt to interpret graph 6-1-1:
I think this is clearly incorrect because elements 5 and 6 have no effect on the system. Could anyone help me interpret the graph?