| How to make the robot walk efficiently, naturally and stably is always animportant field of robot research, for which the concept of passive walking providesa new idea. Compared to inefficient, complicated and unnatural active walking,passive walking is closer to efficient, simple and natural human walking. Throughstudy on passive walking, researchers can learn more about how the dynamics act onhuman walking, which would provide some useful suggestion on design of robots. Inthis article, a3D biped-robot dynamic model with knees is presented. By analyzingkinetic characteristic and stability of the model, its motion principle is studied.Firstly, the physical model of a3D biped-robot is presented based on analysis ofthe existing models. Refer to the characteristic of human walking, the3D motion ofthe model is breaked into two2D motion: coronal motion and sagittal motion. WithLagrange euqation and the law of angular momentum conservation, their dynamicalequations and nondimensionalized dynamical model of the robot is obtained.Secondly, by combining Poincare mapping method, local linearization and theNewton-Raphson iteration method, fixed point of the dynamical model on sagittalplane is obtained using Matlab simulation. Based on the methods, the influence ofparameter variation on kinetic characteristic of the sagittal model including steplength, periodic time, average speed and the minimum foot-groud space and kineticcharacteristic of the coronal model including periodic time and range of the swingphase is analyzed in detail.Then, a new cell mapping method (ZPCM) is presented, with which theattractor of the model and its domain of attraction can be obtained more efficientlyand more precisely. With ZPCM and Floquet theorem, the influence of parameter(mass and mass distribution of the legs, angle of the slope, etc) variation on localstability and global stability of the model is analyzed, based on which the optimizedparameters range is obtained.Finally, the optimal parameter group is obtained based on the theoreticalanalysis above. Refer to the group, the prototype of the model is designed, of whichthe reliable knee-locking mechanism is the key.2D and3D virtual simulations areperformed using ADAMS, which very the theoretical analysis on the stability of therobot’s3D walking. The interaction between coronal motion and sagittal motion isalso analyzed via the simulations. Experiments under diferent slope angle and massdistribution are performed to verify the correctness of the theoretical analysis. |
