Development of Fuzzy Logic Controllers for Controlling Bipedal Robot Locomotion on Uneven Terrains with IMU Feedbacks

Locomotion controller is an important and essential aspect for bipedal robots. Typically, a Linear Inverted Pendulum Model (LIPM) is a mathematical approach to generate the Center of Mass (CoM) trajectory of a bipedal robot. By combining the swing foot trajectory, the omni-directional walking command is capable of generating joint angle control commands in terms of Inverse Kinematics (IK). To improve bipedal locomotion stability on uneven terrain situations, an Inertia Measurement Unit (IMU) was desired to place on the robot's chest was used to measure the body's tilt posture on uneven terrains. The robot body's tilt posture provided an indication of locomotion stability. The body's tilt posture information was further evaluated with a Fuzzy Logic Controller (FLC) to generate appropriate offset angles to be applied on the corresponding joints so that the body's tilt posture can be adjusted accordingly to meet a stable situation. Finally, a kid-size bipedal robot, named Huro Evolution JR, was used as the experiment platform. The proposed FLC can be applicable to the terrain conditions of maximum 25° slope in Double Support Phased (DSP) stand cases. With the walking cases, the FLC is capable of walking on maximum 12° slope, 1 cm stair height and the combined terrain situation well. In the future, the Center of Pressure (CoP) information will be accompanied with the IMU information to further improved the locomotion stability in a high dynamic environment.