Design of a multi-layer fuzzy logic controller using pole assignment for bipedal walking at varying speeds

Abstract

When a biped robot detects obstacles along its path, it will reduce its walking speed to change direction for obstacle avoidance. It is essential for a biped robot to be able to vary its speed during walking. To control biped robots with variable walking speed capability, a Multi-Layer Fuzzy Logic Controller (MLFLC) is developed using the pole assignment technique in this paper. This method extends the previous result, that a switching surface, whose parameters are scaling factors, exists in a Multi-Layer Fuzzy Logic Controller (Tu et al., 2000). In this study, the poles of a closed-loop control system are derived relative to the switching surface parameters, i.e. the normalized scaling factors. Therefore, after choosing the appropriate poles, scaling factors are determined and then a Multi-Layer Fuzzy Logic Controller is designed. This design has two important features: (1) simplifying Fuzzy Logic Controller (FLC) design to select only the scaling factors; (2) pursuing the system performance requirement, based on the pole assignment. A three-link biped robot is used as the illustrative example. Simulation results are included.