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This angle was then used as the "input" for conducting the rest of the position analysis.
Figure 7: Sketch of the handle input.
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Figure 9: Sketch of the gear mechanism. R4 and θ4 belong to the input gear, R5 and θ5 belong to the intermediate gear that turns the wheels. R6 and θ6 are the distance and angle of the vector from the center of the front wheel to the "foot".
The following animations show the position of the gear assembly for constant (left) and variable (right) inputs over a simulated 20 seconds.
Four-bar Linkage Position
The input link for the four-bar linkage is the "link" from the center of the front wheel to the foot, R6 (Figure 9). θ6 is known, because it is the same gear as Gear 5, and therefore θ6 = θ5 + 90º (because it has an offset start position). Since R6 and θ6 are known, and Llleg, Luleg, L0, and θ1 are measured, θlleg and θuleg can be found using the vector loop equation (Figure 10).
Figure 10: Sketch of the four-bar linkage that makes up the leg segments.
The following animations show the position of the gear assembly for constant (left) and variable (right) inputs over a simulated 20 seconds.
Additional plots from the position analysis can be found in the Appendix.