Fuzzy Logic Control Design for a Stair-Climbing Robot

legs to assist walking and moving up-and-down stairs [1]. A control bar is attached to the robot waist to assist the aged person by stepping onto the feet of the robot. The robot “Zero Walker-1” [2] focused on ascending and descending stairs. An electric wheelchair named “iBOT” [3], capable of ascending and descending stairs and slopes was released by a Japanese company. In [4], a bipedal robot was developed to provide only lower-limbs and a waist, named “WL-16RII”, which can walk independently and allow users to build the upper body based on their requirements. This biped locomotor would be applicable as a walking wheelchair or as a walking support machine that is able to walk up and down stairs carrying or assisting an elder. The developed biped locomotor with Stewart Platform Legs successfully achieved walking up and down on stairs for 250 mm continuously and carrying 60-kg man on it. Additionally, Nishiwaki, et al. [5] successfully controlled their robot “H6” to walk up stairs for 250 mm by utilizing toe joints; and the robot “HRP-2” from Harada successfully climbed up 280 mm stairs by grasping the stair rail [6]. A self-standing type eight-wheeled robot in [7] is able to climb up and down stairs and is supported by a mechanism with a planetary gear without an inner gear to eliminate the disadvantages of a wheeled system. However, the height of climbing an obstacle generally is the same as the diameter of the robot's wheel. The aforementioned robots generally need tremendous effect on expense and time. Furthermore, it is very difficult to lift an aged person by human force; and it is not very easy to have a large and heavy-weight lift machine in a normal house. In the paper, a robot is designed to move up-and-down stairs for providing service. This robot consists of a main body, actuating system, roller chains, a front arm and a rear arm for assisting in moving up and down stairs. The actuating system includes two brushless DC motors for locomotion, two worm gears for torque magnification, and two DC motors to control arms. A DSP-based board acts as control center. Some rubber blocks attached to the roller chains are used to generate friction with ground and stairs for moving. A fuzzy logic controller integrates the outputs of DC bus current sensor and an inclinometer to steer the robot. Two walking experiments of moving up and down stairs with the rise/depth of 120/400 mm and 175/280 mm are shown in the taped pictures from videos to verify the proposed design.