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The Grashof characteristic of the mechanism is very clear in the animation. Most links do not rotate far from their original orientation to the horizontal. This Grashof motion is converted into a walking-like motion with the geometry of the couplers and the quadrilateral. Since the couplers are triangles, their shape has 0 DOF; they cannot change shape. So coupler BDE is essentially a big kneecap, and coupler GHI is the shin which simply serves to extend downwards. The location of coupler GHI (and thus the location of the foot at point HI) is driven directly by the quadrilateral CDFG. This quadrilateral is what converts the motion of the two four-bars to the motion of the foot. The top four-bar AMJB defines location of link B which, through coupler BDE, defines the position of joint link D. The second four-bar AMKC defines the position of link C. The known positions of link D and C allow for one interior angle of the quadrilateral to be found so, knowing the length of each side, its total shape can be determined. This angle of link C relative to link D is really the key that this mechanism uses to convert the Grashof motion of two dependent four-bar mechanisms into a specific foot path.
The MATLAB script also plotted that foot path , and said path which will be discussed in the next section.
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