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

Abstract

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. Key words: fuzzy logic controllerbiped robotvarying speed Notes Corresponding author. (Tel: 886–7–6011000 ext. 2810; Fax: 886–7–6011239; Email: tuky@ccms.nkfust.edu.tw)