Research On Biomimetic Gait Planning And Locomotion Control System For Hexapod Robots

Hexapod robot has the features of high motion efficiency, flexible locomotion, and strong adaptability in rough terrain. It is widely used in unstructured environments which require the robot to be autonomous, flexible, and reliable, such as post-disaster rescue, planetary exploration etc. It is one of the significant researches in the bio-inspired robot field. This paper mainly focuses on the gait planning and the motion control system which construct for the biomimetic locomotion of the hexapod robot. The hexapod robot is successfully designed and controlled through imitating the typical gaits and motion control mechanism of the six-legged insects in nature environment.Gait planning is the basis on which the hexapod robot implements the efficient and stable movement. Fristly, by analyzing the typical gaits of the six-legged insects, the tripod gait, the tetrapod gait, the wave gait and the spot turning gait of the hexapod robot are planned using the phase diagrams. The movement rules and applicability of each gait are analyzed. Based on the static stability criterion, the stability margin of each typical gait is calculated, and the stable performance of each typical gait is synthetically analyzed and compared.To implement the motion control of the hexapod robot, the biomimetic locomotion control system of the hexapod robot is designed based on the CPG (Central Pattern Generation, CPG). Firstly, the CPG network of the hexapod robot is constructed based on the nonlinear Kuramoto oscillators. The influences of the CPG parameters (including the coupled method, the frequency, the coupling strength, and the phase difference) on the period, the convergence speed and the phase relationship of the output signals of the CPG network are analyzed using the single parameter analysis method. The signal mapping mechanism between the output signals of the CPG network and the joint control signals of the hexapod robot is constructed. The CPG parameters including the frequency, the coupling strength and the phase difference matrix of each typical gait are proposed to implement the locomotion control of the hexapod robot. Finally, the gait transition mechanism of the hexapod robot is presented.Based on the Solidworks, ADAMS and Matlab, the virtual prototype and the CPG locomotion control network of the hexapod robot are constructed. The simulations of the typical gaits and the gait transition of the hexapod robot have been accomplished. The simulation results including the body displacement, the contact force and the joint control torque of the hexapod robot have been analyzed. Based on the hexapod robot platform, the corresponding experiments have been performed to test the performance of the proposed CPG locomotion control system. The results show that the proposed CPG-based locomotion control method can implement the typical gaits and the gait transition of the hexapod robot. The results of the simulations and the experiments verified the rationality of typical gaits planning and the feasibility of locomotion control for hexapod robot based on CPG network.