Optimal Gait Generation in Biped Locomotion of Humanoid Robot to Improve Walking Speed

Abstract

Humanoid robot is a type of robot that the overall appearance is based on that of the human body. Humanoid robots include a rich diversity of projects where perception, processing and action are embodied in a recognizably anthropomorphic form in order to emulate some subset of the physical, cognitive and social dimensions of the human body and experience. The research on humanoid robots spans from stability to optimal control, gait generation, human-robot and robot-robot communication (Konno et al., 1997) (Hirai et al, 1998) (Cheng et al., 2001). In addition, humanoid robots have been also used to understand better human motion and establish working coexistence of human and humanoid robot (Althaus et al., 2004). Humanoid robot with two legs usually have problem to stabilize its biped walk motions. In fact, one of the most sophisticated forms of legged motion is that of biped gait locomotion. Human locomotion stands out among other forms of biped locomotion chiefly in terms of the dynamic systems point of view. This is due to the fact that during a significant part of the human walking motion, the moving body is not in static equilibrium. Biped walking robot can be classified by its gait. There are two major research areas in biped walking robot: the static gait and dynamic gait. For a biped robot, two different situations arise in sequence during the walking motion: the statically stable double-support phase in which the whole structure of the robot is supported on both feet simultaneously, and the statically unstable single-support phase when only one foot is in contact with the ground, while the other foot is being transferred from back to front. Eventually, this type of walking pattern delays the walking speed. Moreover, joint structure design in robots does not permit flexible movement like that of human being. Indeed, one motor only can rotate in one direction. Even by reducing reduction-ratio can increase the motor rotation, it will eventually reduce the torque output which is not desirable for real-time operation. Therefore, a method to control sufficient walking speed in conjunction with the biped gait trajectory is inevitably important. This is because in real-time application, the robots are likely to be required to walk faster or slower according to situation that occurred during the operation.