Dynamic modeling and velocity control for limit cycle walking

摘要

Even though bipedal walking robots have been studied for decades, they still suffer from poor energy efficiency. Limit Cycle Walking (LCW) is a new paradigm that tries to minimize the energy usage by imitating the passivity-based walking method inherent to both humans and animals. Actuated robots based on LCW principles are still very immature and not very versatile. Many such robots are two-dimensional meaning that they are restricted to move only forward by using a supporting structure to prevent them from falling over, and only a few of them are able to adjust their walking speed or steer the heading. The aim of this thesis work is to increase the versatility of LCW robots by proposing several ideas to control their velocity. Most of the effort, however, has been paid to create a rigid-body simulator based on Open Dynamics Engine (ODE). The simulator is used for the study of the dynamics of a simple so called point-feet three-link model that consists only of a hip and a pair of legs. The simulation model is matched to an existing robot, GlMbiped, which has been developed at Automation Technology Laboratory in Aalto University. The simulator can then be utilized to make GlMbiped walk efficiently. The gait controller is based on a passive reference walker walking down a gentle slope which provides a Limit Cycle (LC) to follow. The results show that a method based on scaling the amplitude, or step length, of the reference or changing the reference slope angle results in an energy efficient and stable way to control the velocity. Both of these methods also provide continuous trajectories to standing pose and running gait.