Mimicking human walking with 5-link model using HZD controller

Abstract

Walking with 5-link model has been achieved by HZD (Hybrid Zero Dynamics) controller based on virtual constraints. These holonomic constraints are obtained by optimizing a set of virtual relations (e.g., Bezier polynomial) between system states which mostly do not have physical interpretations. In this paper, the virtual constraints are designed using human walking experiment data. Inspiring from human locomotion, different polynomials are extracted to mimic human joint angles patterns during walking. The virtual leg angle is the increasing variable which synchronize the joints angles and defines the virtual constraints. Simulation results show that stable locomotion with leg and upper-body behavior similar to human experiment data is achieved for a wide range of speeds and body configuration parameters. VPP (Virtual Pivot Point) concept, a significant balancing feature found in human/animal locomotion, is investigated for different gait speeds as a performance index to compare the kinetic behavior of the simulated and human walking. Hence, we present humanlike posture control as an outcome of motion control achieved by HZD with human inspired virtual constraints.