Research On Walking Mechanism Analysis And Control System Of A Crab-liked Biologically Inspired Robot

The robot, with the advantages of high dependability, good adaptability and powerful performance, is now regarded as a kind of ideal platform for performing dangerous military missions. In addition, the research on amphibious military robot has become a hotspot all over the world.The research is supported by project of 'Biologically Inspired Crab-liked Amphibious Robot Study', which is funded by NSFC (National Natural Science Foundation of China). Contents of this paper include scheme design of crab-liked robot, control system design, and research on walking mechanism and control methodology of octopod walking machine.The author has reviewed relative researches concerning multi-legged walking machine domestically and abroad and summarized literature of researches on multi-legged gait of walking machine.Crab leg mechanism model is made by abstracting walking leg structure of a crab. Based on geometry parameter optimizing of the legs, a mechanical prototype of biologically inspired machine crab is designed. To meet the general demand of machine crab control system, a multilayer multi-object hierarchical distributing control architecture is presented based on behavior decomposition of crab-liked biologically inspired robot. By adopting DSP as a central processor, hardware structure of the system is set up and the whole control system is designed.In this paper, single leg trajectory planning problem is discussed and trajectory planning algorithm of polynomial approximation is presented. In addition to that, leg tip trajectory's polynomial expressions about time is derived corresponding to swing and supporting phase respectively. Expressions of joint angle variables' inverse kinematics are derived for the geometry configuration of the machine crab. Single leg control experimental system is established, and by experimenting on the system, feasibility of control method and leg tip's trajectory planning algorithm were proven.Based on observation on crab's gait, octopod gait states is defined and categorized by using Porta methodology, and gait states transition topology is sketched as well. Wave gait for octopod is categorized, and conclusion of R=4for any octopod wave gait is drawn through gait state transition analysis. Transition among wave gaits is discussed, octopod wave gait transition graph is drawn and method of transition among wave gait is presented in the paper. Acquisition of quadripod gait problem is studied, the conclusion that quadripod gait can always be obtained for gait states in any initial conditions of R=4 through executing finite constant swing phase time alternative steps is drawn.Based on the anatomy fact that the rhythmic motor pattern is controlled by CPG function modular, the conception of CPG control in multi-legged gait is presented. Aided by computer simulation, neuraxon's nonlinear oscillation model given by Lakshmanan and Murali is analyzed, Hopf bifurcation phenomenon and effects of parameters on its oscillation behavior are discussed in detail. A CPG model for machine crab's octopod gait control is made by adopting the neuron oscillator, and some gaits are generated using this model by simulation. Simulation result proved that the constructed CPG model can be used as gait generation and control module of crab-liked biologically inspired robot.The machine crab prototype designed in this paper provides a test bench for theoretical research on multi-legged walking machines. The results of gait analysis and gait generation theory are of universally significance and will definitely play an important role in walking machine studying.