Walking Pattern Generation and Stabilization of Walking for Small Humanoid Robots

Declining birthrate and a growing proportion of elderly people are closed up as social issues in Japan. Especially, a growing proportion of elderly people is seen as an issue in nations of Europe and North America and so on as well as Japan. New labors engaging in the life support and the nursing for the elderly person will need in the future. To supplement the lack of the manpower, the research that applies the robot technology to the welfare field is important. Especially, because the shape of a humanoid robot looks like human, the person who receives nursing can be relieved. Besides, a humanoid robot can act under person's life environment, and can use the tool that the person uses. In addition, it is possible to avoid colliding with something put on the ground because the biped robot does not move with wheels. The biped robot can be used even in the environment including steps and ruggedness where robots with wheels cannot be used. In a word, the biped humanoid robot is extremely effective as the robot that acts in the environment where we live in daily life. However, it is necessary to prevent the robot from falling in the case of two-legged locomotion. Moreover, it is also necessary to keep controlling while the robot is only standing with stable posture. Various techniques about the walking of a humanoid robot have been devised up to now in recent years, and the walking pattern generation of a humanoid robot with complex dynamics has become possible. On the floor where information about the height of the small step was obtained beforehand, steady dynamic walking was achieved by using such as the technique of linear inverse pendulum model where the humanoid robot was expressed with an inverted pendulum of simple single-mass system, and truck model with preview control of ZMP trajectory (Kajita, 2005, 2009). However, in the case that the robot walks in a real environment, it is difficult to obtain the detailed information on the floor beforehand and give the information to the biped robot at any time. There are research examples (Kajita & Tani., 1996) of making the robot measure the shape of the road with sensors while walking. But, it is necessary to install the highly accurate sensor in the robot. The road where the robot walks is not only a smooth road. A small ruggedness and a gradual inclination are contained in many cases. However, it is impossible to record information of detailed shape on the ruggedness onto the robot beforehand. A biped robot KHR-2HV manufactured by Kondo Kagaku Co., Ltd. in Japan and HOAP-1 manufactured by Fujitsu Automation Ltd. in Japan were used in this study as humanoid robots. The basic walking experiment was conducted by using KHR-2HV. Then, another