To get the upper green follower motion, we can form the 5 bar linkage problem:

Link 5 motion is known from the analysis I have done in Part 1. Link 2 and Link 5 motions are thus inputs representing 2 DOF so we can solve this 5 bar mechanism.

We are interested ultimately in the motion of link 4, where the flap which connects with the robot leg is located above B and moves with Link 4.

The results are:

The velocity close to 0 angle has the largest magnitude, which represents the backward returning motion of the leg due to the coin pulling it back.

Animation (Positions): Green point is the flap/leg that sits directly above the joint B. We see a flat ellipsoid like motion only because of assumption of no compliance between link 5 and link 4 (The paper model link 4 doesn't falls but rather keep an angle around 80 degrees with respect to link 5)

Another video that summarizes the motion of both green followers to see if consistent with the cam motion.

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