Simulation And Experimental Study On The Dynamics Of Passive Bipedal Walker

Passive dynamic walking is an interesting dynamic phenomenon. A pure passive walker can exhibit stable periodical gait on a gentle slope, only supplied by gravity. The study of this problem can be benefit for the design and manufacture of bipedal robots with actuators.The procedure of analyzing passive dynamic walking has been summarized first, and then, modeling, equations deriving, program coding, simulations, prototype production and experiment design are detailed presented. According to the procedure above, the effects of parameters on the gait descriptors, including step length, period and speed, has been discussed based on the results of simulations. These normalized parameters include the foot radius, the moment of inertia, the center of mass, and the slope angle. The effects of foot radius on the gait are validated by prototype experiments.Cell mapping method combined with Newton-Raphson iteration method has been used for obtaining the fixed points of the periodical gait of the models, and the basins of attraction of the fixed points have also been got. The effects of foot radius, moment of inertia and center of mass on the basins of attraction are summarized, and a model can endure large initial disturbance has been obtained. Through prototype experiments, the effects of foot radius on the basins of attraction have been validated, and the reason of exceptions has been analysedSurface of random stairs and random slope angles are designed for testing the robustness of the walkers. Five hundred simulations of 100 non-dimensional time units are implemented for the walker with each parameter combination, and falling ratio has been used for the measure. Enlarging foot radius and heightening the center of mass both are good for enhacing the robustness of the walkers. Larger moment of inertia is good for overcoming the random slope angle surface, but small moment of inertia is benifit for walking on random stairs. Experiments of walking on the surface with random slope angles are implemented, and the effects of enlarging foot radius are validated. The passive walkers with knees are studied through simulations. Parameter changing method is used for obtaining the fixed points, and the basins of attractions are obtained by cell mapping method. Walker with high walking speed has been obtained, and its Freude number is higher than any biped robot published.The period-doubling and chaotic gaits of passive dynamic walking have been analyzed. The effects of foot radius, moment of inertia and center of mass on the arising of period-doubling and chaotic gaits are summarized. The simulation results of period-doubling and chaos of kneed models have been presented. A straight leg model can walk stably with period-doubling gaits on the stairs with step length equal to 10% of the leg length has been presented in simulation. During experiment of walking on stairs, period-doubling has been recorded, and the records are accordant well with the simulation results.