|M.Sc Student||Gamus Benny|
|Subject||Analysis of Dynamic Bipedal Robot Walking with Contact|
|Department||Department of Mechanical Engineering||Supervisor||Professor Yizhar Or|
|Full Thesis text|
In the study of dynamic legged locomotion, foot slippage is common but often neglected. The purpose of this work is to analyze the hybrid dynamics of simple bipedal robot models under possible stick-slip transitions and harness the passive dynamics into new control laws.
A systematic generalized formulation of the dynamics is introduced. This formulation takes into account the possibility of foot slippage due to low friction using Coulomb’s model.
The formulation is numerically implemented on simple models of passive dynamic walkers. For sufficiently high friction, the results agree with those of existing studies. Furthermore, this work studies the influence of low friction (which induces foot slippage) on the existence and stability of passive periodic gaits. Stable periodic solutions that involve stick-slip transitions are numerically revealed.
Open- and closed-loop passivity-based control laws are evaluated for a biped with joint torque actuation. The influence of friction on the stability, average speed and energetic efficiency of an actuated biped is numerically analyzed. Moreover, while most studies seek to avoid slippage, this paper proposes a control law that induces and stabilizes stick-slip gaits, even for terrains with high friction. Remarkably, this law significantly reduces the energetic cost of walking.
This study sheds light on the dynamics of foot slippage in legged locomotion. More importantly, the somewhat unexpected results provide motivation for further research.