Analysis of the Leg Motion: Part 1

For this analysis I assumed no compliance for the top part of the blue linkage, and that the cam is not tilted (the tilting contributes mostly on the rotation of the main body,and complicates analysis here)

I also modeled the green followers as points.

I separated the blue linkage into two links.  

My goal is ultimately to analyze the positions of the top green follower.  I approached this problem by separate it into two problems:

1. Get the motion of the lower link of the blue linkage
2. Get the motion of the upper link of the blue linkage

To obtain the motion of the lower link of the blue linkage,  apply vector loop analysis of the effective 4 bar linkage that exist between the lower green follower and the cam:

We usually can't do this easily due to effective length of R3 changes and is dependent of the cam shape, however I am fortunate that the cam is circular, so the length of R3 remains as the radius of the cam always.

This is a four bar mechanism and the results are:

Animation of the positions:  The blue point is the lower green follower that we are interested.

Angular positions and angular velocity of link 4: