Research On Motion Planningand Control Of Swinging Leg Of The Hexapod Robot In Unstructured Environment

Hexapod robots have superior ability and potential to deal with unstructuredenvironment due to the redundancy of its structure and discreteness of its footholds.As the important link of the hexapod robot locomotion, the rationality of legswinging movement is directly related to the performance of the whole movementof the robot. Therefore, to study swinging movement of hexapod robot leg has boththeoretical and practical significance in terms of the further application of therobots.The purpose of this thesis is to analyze and study the swinging leg motionplanning and control on rugged terrain as well as a verification by simulationfocused on the completed hexapod robot HITCR-II, which is based on the terrainlocal features of the unstructured environment.Firstly, the study conducted a kinematic modeling of the legs using kinematictheories, derived the mathematical relationships of the motion between the end andthe joints of the legs, analyzed the workspace of the foot-end, laid the foundationfor sequence work which contains motion planning and control. The validity ofkinematic model has been established by simulation.On the basis of having analyzed the mechanism that how the robot select itsfootholds, the study proposed a method of feature extracting based on the shape ofthe foot-end which describes the local terrain more precisely and a footholdpossibility function which can proceed quantitative evaluation aimed at footholds.The foothold possibility function has improved the ability of terrain estimation andthe real-time locomotion of the robot efficiently, meanwhile a simulationexperiment has been conducted to confirm the validity of the terrain estimationstrategy.After adequate consideration about the impact of the terrain, the studyfocused on the method of trajectory planning and control for a hexapod robot whenits leg doing a swing movement. The study established a model of trajectoryplanning of a swing leg based on the optimal control theory and proposed anumerical solution based on steepest descent method. The study also devised a jointservo controller, the stability and feasibility of which has been verified theoreticallyby analyzing the stability of the controller based on Liapunov direct method.Finally, a simulation platform for the swing leg was set up based on ADAMSand Matlab, on which the simulation experiments about trajectory planning andcontrol method have been done and analyzed, verifying the validity of the algorithm mentioned above.