Figures for Frictional Adhesion Paper.

Example 1 - Planar Model with 2 Contact Points on Vertical (90 degree) Flat Surface.

• Mass = 50 grams
• COM Height = 2cm
• Stride Length = 10cm
• Mu = 1
• Alpha = 30 degrees
• Fmax = m*g

• GP_Vert1.jpg:
  

This plot shows the contact forces at the front and rear foot, as a function of internal body force. Optimal forces (best internal force) are shown as black squares. The angle of inclination is 90 degrees. Due to the geometry of this example, the internal body force has no effect on the normal forces. Internal Force is taken to be postive compressive in this case (feet squeezing). Increasing internal force results in front foot taking more shear load.

• GP_Vert2.jpg:
  

This plot shows the safety margin as a function of internal body force. Note how safety margin decreases as you move away from optimal internal force in either direction.

• GP_Vert3.jpg:
  

This plot shows the contact forces in the contact constraint space. The optimal force is shown as a black square. The internal body force can change the amount of shear load taken by each foot. Note that in this example, front foot causes failiure in both cases (increasing or decreasing internal force). With increasing internal force, front foot would eventually hit Fmax and start to slip/slide. With decreasing internal force, front foot would eventually hit Adhesion limit and peel/pop off.