-- DanielSantos? - 18 Apr 2006

---

• Planar Model with 2 Contact Points, Stride Length symmetric about COM
• Mass = 50 grams
• COM Height = 2cm
• Stride Length = 10cm

---

• Isotropic Embedded Cone Model (mu, a)
• Mu = 1
• a -> chosen so that over 0 to 180 degrees, some angle is critically stable

---

• Anisotropic Frictional Adhesion Model (mu, alpha, Fmax)
• Mu = 1
• Alpha = 30 degrees
• Fmax -> chosen so that over 0 to 180 degrees, some angle is critically stable

---

• GP1.jpg:
  

This plot shows the internal forces and the measure of stability for all three cases:

• Anisotropic & Aligned
• Anisotropic & Opposed
• Isotropic

We see that the internal forces are always compressive in the anisotropic case and always tensile in the isotropic case. In the isotropic case, the rear foot applies more shear force. The front foot is favore in this case and applies less shear force due to the contact constraints. In the anistropic case, the opposite is desired. In order to generate adhesion, the front foot must apply shear force.

---

• GP2.jpg:
  

This plot condenses the anisotropic cases to whichever is the best for the current angle of inclination. At shallow angles it is best to have front and rear feet opposed. As inclination increases, it is best to have both front and rear feet aligned with gravity. In this case, gravity loads the feet in the direction that will allow them to generate adhesion. However, as we begin to overhang, gravity will have less and less affect in the shear direction and eventually the system will be more stable with the feet opposed again. This will allow the feet to pull against each other and generate adhesion as we tend towards the inverted case.

---