BIPEDAL HUMANOID ROBOT CONTROL BY FUZZY ADJUSTMENT OF THE REFERENCE WALKING PLANE
Mechatronics, Ph.D. Dissertation, 2012
Assoc. Prof. Kemalettin Erbatur (Thesis Supervisor), Prof. Dr. Hakan Temeltaş, Prof. Dr. Mustafa Ünel, Assoc. Prof. Erkay Savaş, Asst. Prof. Güllü Kızıltaş Şendur
Date &Time: August 6th, 2012 - 14:30
The two-legged humanoid structure has advantages for an assistive robot in the human living and working environment. A bipedal humanoid robot can avoid typical obstacles at homes and offices, reach consoles and appliances designed for human use and can be carried in human transport vehicles. Also, it is speculated that the absorption of robots in the human shape into the human society can be easier than that of other artificial forms.
However, the control of bipedal walk is a challenge. Walking performance on solely even floor is not satisfactory. The complications of obtaining a balanced walk are dramatically more pronounced on uneven surfaces like inclined planes, which are quite commonly encountered in human surroundings. The difficulties lie in a variety of tasks ranging from sensor and data fusion to the design of adaptation systems which respond to changing surface conditions.
This thesis presents a study on bipedal walk on inclined planes with changing slopes. A Zero Moment Point (ZMP) based gait synthesis technique is employed. The pitch angle reference for the foot sole plane as expressed in a coordinate frame attached at the robot body is adjusted online by a fuzzy logic system to adapt to different walking surface slopes. Average ankle pitch torques and the average value of the body pitch angle, computed over a history of a predetermined number of sampling instants, are used as the inputs to this system.
The proposed control method is tested via walking experiments with the 29 degrees-of-freedom (DOF) human-sized full-body humanoid robot SURALP (Sabanci University Robotics Research Laboratory Platform). Experiments are performed on even floor and inclined planes with different slopes. The results indicate that the approach presented is successful in enabling the robot to stably enter, ascend and leave inclined planes with 15 percent (8.5 degrees) grade. This, to the best knowledge of the author, constitutes the steepest ascend reported to date, with a transition from even floor, by a blind walking biped robot.
The thesis starts with a terminology section on bipedal walking and introduces a number of successful humanoid robot projects. A survey of control techniques for the walk on uneven surfaces is presented. The design and construction of the experimental robotic platform SURALP is discussed with the mechanical, electronic, walking reference generation and control aspects. The fuzzy reference adjustment system proposed for the walk on inclined planes is detailed and experimental results are presented.