Fereshte Tohidi - MSc Student, Amirkabir University of Technology, Tehran;
Ali Tehrani Safa - Research Assistant, Amirkabir University of Technology, Tehran;
Mahyar Naraghi - Associate Professor, Amirkabir University of Technology, Tehran;

Assigning when and where to put a foot for achieving a specific goal is the foot placement control that adjusts the step length and step velocity of a walker or enables to track the desired trajectory. However, the robustness analysis of foot placement is essential before any applications. In this paper, the robustness of the simplest limit cycle walker driven by an impulsive push-off, and controlled by foot placement is studied. In this regard, we propose different third-order walking trajectories designed based on the average step length and the step velocity of the human gait. The walking trajectory is implemented by the open -loop hip torque control strategy. Furthermore, to measure the robustness of the system, the well-known single step-down and single step-up tests are engaged. Simulation results demonstrate, while the step length and the step period of the gait are kept unvaried, the leg retraction speed has positive effects on the gait stability and robustness.

The simplest walker, Foot placement, Push-off, Robustness